castanyes blaves

Random ramblings about some random stuff, and things; but more stuff than things -- all in a mesmerizing and kaleidoscopic soapbox-like flow of words.

7/02/2009

 

What a NGS IT person should be skilled in

PLoS Computational Biology: Managing and Analyzing Next-Generation Sequence Data
The skills necessary within the Facility include the following.

1.

An intimate knowledge of UNIX-based operating systems.
2.

Understanding of a scripting language such as Perl.
3.

An understanding of parallel computing environments for UNIX clusters.
4.

Knowledge of network-based data storage.
5.

General knowledge of biology and genome sciences.
6.

Ability to derive data analysis and software requirements from investigators who do not have a sophisticated understanding of information technology.
7.

Ability to develop software encapsulating new analysis methods.
8.

Understanding of relational databases and database architecture.
9.

Ability to seek out and test novel bioinformatics software and analysis routines.


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6/24/2009

 

Lamprey Genome rearrangements

DNA Jettisoned From Lamprey Genome During Development | GenomeWeb Daily News | Sequencing | GenomeWeb
Amemiya and his co-workers became suspicious that the lamprey's genome structure and composition was changing during development when they heard rumors lamprey genome sequences efforts were being complicated by genome fragmentation. They speculated that this might be due to genome rearrangements similar to those described for the hagfish, a chordate and superficially similar organism.

To test this, the researchers compared germ line and somatic tissues from sea lamprey caught in Lake Michigan.

Indeed, they found that the genome was larger in sperm (germ line cells) than in adult blood nuclei (somatic cells), even within the same individual. The sperm cells also contained more DNA than kidney and liver cells, which both had similar DNA content to red blood cells. Overall, the researchers noted, sperm genomes contained some 20 percent more DNA than adult cells such as red blood cells.


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5/21/2009

 

Gene by gene turns genome-by-genome

This is a good example of the kind of paper we are probably going to see more and more often in the future:

Gene discovery using massively parallel pyrosequencing to develop ESTs for the flesh fly Sarcophaga crassipalpis
http://www.ncbi.nlm.nih.gov/pubmed/19454017

Get (a) a certain amount of RNAseq reads for your species "X", (b) build as many full-length cDNAs as possible from the fragments and (c) compare against close species in terms of:
  • New interesting cDNAs that don't have hits against existing public cDNAs -- What do they do?
  • Expression patterns -- Are these different to the patterns in other close species?
  • Protein coding evolution -- run pairwise dNdS against closest genome or tree-based dNdS against an existing phylogeny [1,2] -- Does anything show up in a Gene Ontology enrichment analysis?
Then the data is published and stored in a publicly available database, and can be added to the pool to compare against for the next project. Iterate :-)

It used to be gene-by-gene sequencing and it's now transcriptome by transcriptome sequencing. There are still sequence error and sequence coverage issues: one of my first scientific mentors, Prof. Montserrat Aguade was one of the first to do gene sequencing on the Adh gene in Drosophila when doing her PhD in Harvard. People then extended Adh sequencing and analysis to other Drosophila species, then other clades, then other genes, then some gene families like odorant binding proteins for a bunch of Drosophila species or populations, or gene pathways like the insulin pathway, etc.

But now we have a much broader picture with a rather complete transcriptome. And most of the sequencing issues are going to be corrected across the phylogeny in pretty much the same way as allele imputation is filling the gaps at the population genomics level (e.g. 1000 Genomes Project).

I am very excited about all this!

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5/01/2009

 

NCBI SRA blastn service

Never easier before to check your sequence against the NCBI Short Read Archive database:

NCBI SRA BLAST

First thoughts:
  • Transcriptome coverage is hugely biased to the 3' end (or 5' depending on library preparation). A lot more than I suspected.
  • Would be great to do queries for phylogenetic subclades: e.g. my human sequence against all SRA data for primates.
  • A lot of the 454 data has homopolymer issues, mostly TTT[...]TTTs but also some others:
Query  465  GGGCCTTGACAAAGTGTAAACCGCATGGATGGGCTTCCCC-AAGGATTTATTGACATTGC  523<br /><font color="#ff0000"><b>Sbjct</b></font>  249  ........................................<font color="#ff0000"><b>C</b></font>...................  190<br /><br /></pre><ul><li>Some of these (unless they are real variations) get picked up as mismatches, some as indels:<pre>Query  1    CGGCAAGGTATGTGCGTGATTTTGGGCCCACGTGTATTTCCATTAATTTT-AAGCCGTAA  59<br /><font color="#ff0000"><b>Sbjct</b></font>  224  ..................................................<font color="#ff0000"><b>T</b></font>.........  165<br /><br />Query  60   TTGTCGTTTTTGGCGGTTTCGAGTTGAACTGCGTTAGTCCGTGCGCTGTTCGCAAGTGTG  119<br /><font color="#ff0000"><b>Sbjct</b></font>  164  ..........<font color="#ff0000"><b>C</b></font>.................................................  105<br /></pre></li></ul><pre><br />Query  61   TGTCGTTTTTGGCGGTTTCGAGTTGAACTGCGTTAGTCCGTGCGCTGTTCGCAAGTGTGC  120<br /><font color="#ff0000"><b>Sbjct</b></font>  118  .....<font color="#ff0000"><b>C</b></font>......................................................  177<br />Query  61   TGTCG-TTTTTGGCGGTTTCGAGTTGAACTGCGTTAGTCCGTGCGCTGTTCGCAAGTGTG  119<br /><font color="#ff0000"><b>Sbjct</b></font>  160  .....<font color="#ff0000"><b>T</b></font>...............................<font color="#ff0000"><b>-</b></font>......................  102<br />Query  61   TTAATTTTAAGCCGTAATTGTCGTTTTTGGCGGTTTCGAGTTGAACTGCGTTAGTCCGTG  120<br /><font color="#ff0000"><b>Sbjct</b></font>  181  ...........................<font color="#ff0000"><b>C</b></font>................................  122<br /><br /><br /><br />


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A customized and versatile high-density genotyping array for the mouse -- Gary Churchill, The Jackson Laboratory, USA

Microarray based genotyping is an inexpensive and powerful tool to characterize genetic variation. High-density genotyping microarrays are commercially available for humans, economically important livestock and model organisms. However, they have not been available previously for the laboratory mouse, the premier mammalian model organism for biomedical research. Here we describe a custom high-density mouse genotyping array. The Mouse Diversity array was designed to capture the known genetic variation present in the laboratory mouse. It contains 623,124 SNPs distributed across the 19 mouse autosomes, the sex chromosomes, and the mitochondria with a median spacing of one SNP every 1,411 bp in the nuclear genome. The array also contains 916,269 invariant probes that are targeted to functional elements and regions of the genome known to harbor segmental duplications. The nature of the probes opens the door to a variety of novel applications including the characterization of copy number variation, allele specific gene expression and DNA methylation. Performance of the array based on call rate, replication and concordance with previously known genotypes is exceptional. The content-rich Mouse Diversity array provides a critical new tool for mouse genetics including the possibility of extending the successes of genome-wide association studies in humans to the mouse.

Funny comment -- This may be the last chip we do. The economics tell us the line is still below for chips, but sequencing is getting cheaper.

History: people catching mice, trading them, etc. Bottlenecks and all sort of artificial effects.

Diversity 11 classical inbred strains: some chromosomal regions with extremely low diversity. Is this petness? Longevity/Fecundity?

Problem with ascertainment bias: 623124 phylogenetically informative SNPs with known ascertainment

Collaborative Cross -- 8 M. musculus lines -- each contributing equally to the final "line". All inbred by now.

Phenotypes of intermediate CCs: e.g. voluntary exercise goes from 0 miles per day to 18 miles per day.

With 2 different inbred parents, we get complex children but with theoretically predictable phenotype, which means doing GWAS with phenotypes "a la carte".

Also, just by mixing genomes, creating diversity that was not in the parents: very useful novel phenotypic diversity.

Resolution is 7x better. CC will not be GWAS-level, but on the order of 10 genes or MB level resolution. Possibly gene level resolution in 10 generations. Always a mapping resolution panel and a validation panel, going back to the inbred lines.

Selection strictly by random number. Maintaining the diversity is good, lucky because natural selection already took a toll on the original strains.

Done in a way to maximise diversity, not to mimic human population structure. Deep reservoir of diversity for studying phenotypes.

A-Male/B-female crosses and compare to A-Female/B-Male in terms of sex-related epigenetics and other studies.

Some strains will die out along the way, but in 5-10 years should get a lot of info out of it.

Hyuna Yang a lot of array work.
David Aylor pop.struct.

Published mouse distances:

Mus cervicolor - Mus crociduroides = 7.60 MYA
Mus cervicolor - Mus haussa = 6.60 MYA
Mus cervicolor - Mus indutus = 6.60 MYA
Mus cervicolor - Mus mattheyi = 6.60 MYA
Mus cervicolor - Mus minutoides = 6.60 MYA
Mus cervicolor - Mus musculoides = 6.60 MYA
Mus cervicolor - Mus musculus = 4.80 MYA
Mus cervicolor - Mus pahari = 7.60 MYA
Mus cervicolor - Mus platythrix = 7.10 MYA
Mus cervicolor - Mus setulosus = 6.60 MYA
Mus cervicolor - Mus spretus = 4.80 MYA
Mus crociduroides - Mus haussa = 7.60 MYA
Mus crociduroides - Mus indutus = 7.60 MYA
Mus crociduroides - Mus mattheyi = 7.60 MYA
Mus crociduroides - Mus minutoides = 7.60 MYA
Mus crociduroides - Mus musculoides = 7.60 MYA
Mus crociduroides - Mus musculus = 7.60 MYA
Mus crociduroides - Mus pahari = 3.40 MYA
Mus crociduroides - Mus platythrix = 7.60 MYA
Mus crociduroides - Mus setulosus = 7.60 MYA
Mus crociduroides - Mus spretus = 7.60 MYA
Mus haussa - Mus indutus = 3.20 MYA
Mus haussa - Mus mattheyi = 2.60 MYA
Mus haussa - Mus minutoides = 3.20 MYA
Mus haussa - Mus musculoides = 3.20 MYA
Mus haussa - Mus musculus = 6.60 MYA
Mus haussa - Mus pahari = 7.60 MYA
Mus haussa - Mus platythrix = 7.10 MYA
Mus haussa - Mus setulosus = 4.00 MYA
Mus haussa - Mus spretus = 6.60 MYA
Mus indutus - Mus mattheyi = 3.20 MYA
Mus indutus - Mus minutoides = 2.50 MYA
Mus indutus - Mus musculoides = 2.50 MYA
Mus indutus - Mus musculus = 6.60 MYA
Mus indutus - Mus pahari = 7.60 MYA
Mus indutus - Mus platythrix = 7.10 MYA
Mus indutus - Mus setulosus = 4.00 MYA
Mus indutus - Mus spretus = 6.60 MYA
Mus mattheyi - Mus minutoides = 3.20 MYA
Mus mattheyi - Mus musculoides = 3.20 MYA
Mus mattheyi - Mus musculus = 6.60 MYA
Mus mattheyi - Mus pahari = 7.60 MYA
Mus mattheyi - Mus platythrix = 7.10 MYA
Mus mattheyi - Mus setulosus = 4.00 MYA
Mus mattheyi - Mus spretus = 6.60 MYA
Mus minutoides - Mus musculoides = 1.60 MYA
Mus minutoides - Mus musculus = 6.60 MYA
Mus minutoides - Mus pahari = 7.60 MYA
Mus minutoides - Mus platythrix = 7.10 MYA
Mus minutoides - Mus setulosus = 4.00 MYA
Mus minutoides - Mus spretus = 6.60 MYA
Mus musculoides - Mus musculus = 6.60 MYA
Mus musculoides - Mus pahari = 7.60 MYA
Mus musculoides - Mus platythrix = 7.10 MYA
Mus musculoides - Mus setulosus = 4.00 MYA
Mus musculoides - Mus spretus = 6.60 MYA
Mus musculus - Mus pahari = 7.60 MYA
Mus musculus - Mus platythrix = 7.10 MYA
Mus musculus - Mus setulosus = 6.60 MYA
Mus musculus - Mus spretus = 2.30 MYA
Mus pahari - Mus platythrix = 7.60 MYA
Mus pahari - Mus setulosus = 7.60 MYA
Mus pahari - Mus spretus = 7.60 MYA
Mus platythrix - Mus setulosus = 7.10 MYA
Mus platythrix - Mus spretus = 7.10 MYA
Mus setulosus - Mus spretus = 6.60 MYA


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4/30/2009

 

RNAseq in the worm -- Gary Williams

Illumina Short-read transcriptome data has the potential to help solve many problems with curating gene models and the genomic sequence in C. elegans. This is an initial look at the data and some examples of how it can be used.

So far, C. elegans gene predictions:

36% - fully confirmed by ESTs
48% - partially confirmed
14% - no transcript confirmation

RNAseq data -- different worms than the genome, so some polymorphisms expected -- 200bp inserts, 36bp paired end reads

MAQ or cross-match to genomic or transcript sequences

6137 new splice junctions (6% increase)

Jumped from 70000 to 98000 splice junctions.
3x as many polyA sites
80 possible new coding genes

V-shaped coverages -- validation against traces, then:
  • Detected sequencing error, correction needed for the reference
  • Detected alternative haplotype
Moving towards single-cell sequencing -- not sequencing in tiny cells but sequencing each cell in each developmental state in the worm. Moving towards RNA sequencing C. briggsae and C. remanei.

Updated gene builds will be given to other projects. Next Ensembl Metazoa comparative genomics build may already have the modENCODE-updated C. elegans and D. melanogaster builds.

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4/27/2009

 

Giving functional genomics a REST -- Alex Bruce

http://www.ensembl.org/Homo_sapiens/Transcript/ProteinSummary?db=core;g=ENSG00000084093;r=4:57468799-57493097;t=ENST00000309042

interesting case where a small skipping exon generates an extra copy for the Znf-C2H2 domain.

REST is an essential vertebrate transcription factor with very diverse roles. It has an important role in regulatory secretory pathway. Independently confirmed by 2 other groups.

RE1 array used to identify misregulated REST target genes in diseases like Huntington's.

RE1 "half" sites. Canonical/Transfac/Discovered motifs.

Different evolutionary pressures over RE1 sites seem to be associating with different function subsets: common sites are less well conserved than unique sites. Unique sites need to be tissue specific, so they are bound to keep a general binding weakness to turn off binding in non-specific tissue (if I correctly understand?).

Solexa sequencing quite good in identifying high affinity motifs, but poor at low affinity motifs.

There is an in vivo hierarchy between RE1 for REST binding and it can be discriminated at the DNA sequence level.

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4/23/2009

 

Phenotype data in Ensembl -- Fiona Cunningham

European Genotype Archive: Genome Wide Association Studies (GWAS) like WTCCC data and others. Only public information is public available under very strict rules.

NHGRI GWAS will be imported in Ensembl: it's got manually curated data of high quality.

Links in Variation view: link "Phenotype Data (n)"

http://www.ensembl.org/Homo_sapiens/Variation/Phenotype?source=dbSNP;v=rs420259

Diagnostic testing: situation will now improve in Ensembl

Locus specific databases (LSDBs): p53, ABO, collagen, albinism, cystic
fibrosis, Altzheimer's disease, ... >700

The main aim is to be able to link the reference CDS sequence used by the biomedical community to the most up-to-date reference sequence in the genomics community. This mapping will allow clinicians to link all phenotype data on their end to the genomic data in the genomic community.

Political pros and cons have to be carefully handled and continuously explained. Ensembl openness, existing infrastructure and visibility is the biggest selling point to have these dbs linked in a common LSDB resource.

Website here will have LRG XML files and prettified HTML reports soon.

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Ensembl Quality Checking -- Michael Schuster

All Ensembl gene predictions for all vertebrate species are based on experimental evidence:

  1. UniprotKB/Swiss-Prot
  2. NCBI RefSeq proteins and mRNAs
  3. UniprotKB/TrEMBL
  4. EMBL Nucleotide Sequence Archive

Aligning the evidences back to the gene prediction with Exonerate. Types of alignment results:

  • perfect
  • added start
  • longer region
  • missing start
  • non-matching start
  • non-matching region
  • shorter region
  • ...

Exonerate has an exhaustive mode that takes a lot more time but fixes some of the mini-intron and
mini-exon issues that sometimes occur. Exonerate cdna2genome is very useful for quality checking.

Genebuild now uses head-to-head alignments of genewise and exonerate, and takes the best in each case.

Some cases are still difficult to get right with algorithmic solutions: this is were the curators are needed.

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4/07/2009

 

EnsemblCompara "Back to the future": using phylogenetic information to help gene annotation

Here is an example success story of using phylogenetic information to improve human gene annotation. What do you see wrong in this EnsemblCompara GeneTree?


The human gene prediction has been split into one third to the left and two thirds to the right. Some of the other species have the full length prediction, but some of the 2x and projected genomes also have this issue. This case was reported to the Havana team at the Sanger and they have now built a human and mouse full-length prediction for the gene (notice the Havana_genes blue and dark green model):

The next Ensembl/Havana merge will hopefully reflect this change but, right now, you need to activate the Havana_genes DAS track to see the most up-to-date Havana annotation. There is a good number of these fixed now in the highly loved genomes, aka human, mouse and zebrafish. But there is a second level of genomes that are not getting any manual annotation here but may be annotated somewhere else...



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Promoting Open Source Bioinformatics

Interesting to see all the buzz that the Benjamin Franklin Award has generated in the blogosphere, twittersphere, facebooksphere and any of the other spheres out there... I still think there is something we should try and resolve in open source bioinformatics, which is promoting Open Source software to create more awareness in the scientific community. We need to reconcile the promotion of modularity and generality with the fact that giving credit to the scientists who contribute to Open Source Bioinformatics software is still important. Projects that have built very modular and generic components may be doing a lot for the bioinformatics community at large but, at the same time, the less atomic and single-purpose your software is, the more difficult it is to publish it in a prominent scientific journal. The same goes for citing it in the downstream publications: very atomic programs are very successful in citation metrics, but infrastructure code is not. This means that well-designed, well-implemented and well-tested software is often not prominent enough for new people to notice, and too many bioinformaticians resort to their own glue code for building their bioinformatics infrastructure.

There wouldn't be anything wrong with rewriting your own code over and over again if it weren't because: (a) people spend too much time writing scaffolding code that will let them access what is really new and interesting in their project and (b) that code tends to be used and tested only internally and almost never reused for any other party unless it has been very well designed and documented --- hence the name scaffolding code.

There is a really good chance now to build an infrastructure that brings up a terminal next to the next generation Petabyte-size data sources, using emerging "cloud" technologies. These technologies are already advanced in other fields other than bioinformatics, so we can leverage what it has already been done for us and make extensive use of it. These terminals don't need to be silly, and the community should provide in them as much prebuilt code as possible so that the new breed of bioinformaticians get used to have this software at their fingertips.

A few years ago all the effort was in building packages for different Linux distributions, so that people could easily install Open Source software on their in-house CPU clusters. I think we need to shift gears now to cloud software accessibility. The good news is that it seems everybody is happy with the common Ubuntu system as a start. I fear the proliferation of iPhone-like SDKs around that will make the existing bioinformatics software useless. In an era where everybody is acutely aware about governments having to pour our taxes into infrastructure that was already paid for, noone will like to see all existing bioinformatics software become a "toxic" or "legacy asset"!

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4/06/2009

 

Genomes to come: wallaby

Tammar Wallaby - Wikipedia, the free encyclopedia

The Tammar Wallaby (Macropus eugenii), also known as the Dama Wallaby or Darma Wallaby, is a small member of the kangaroo family and is the type species for research on kangaroos and marsupials.

It is found on offshore islands on the South Australian and Western Australian coast. It is classified as vermin on Kangaroo Island, where it seasonally breeds in large numbers and damages the echidna habitat on the island.



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4/02/2009

 

Quarterly Activity Report -- Hinxton Sequence Forum Wellcome Trust Genome Campus

A quarterly activity report for the different activities that take place under what can be considered "sequence" at the WTGC in Hinxton, Cambridge, UK:

  • HGNC has made great progress in solving nomenclatures for 130 cases where the community has a diversity of opinions and it's difficult to agree on something. Very good point in saying that in the Internet era it's better to give a gene a name that is distinctive to common words that would clobber your Google search results. There is now a forum set up for different communities to use in discussions for gene family names.
  • Havana now has started using RNAseq data to confirm new genes found in human and zebrafish that didn't have evidence before. One new feature is a "confirmed intron" for when paired Solexa reads bridge two exons, with an associated score for read depth. Confident this type of data will bring out many interesting new annotations that couldn't be found before, e.g. genes expressed in a given tissue during a lapse of a few hours in the development. There are already a few examples in zebrafish.
  • Wormbase has been working hard on compiling more data from the modENCODE. Small but cool infrastructure achievement in having VMware images running for old releases that investigators can just pull and bring up on demand.
  • Ensembl Genomes has been successfully testing the beta sites for Bacteria, Protists and the first Metazoa build. Another Metazoa build is in progress, with all the phylogenetics goodness of the 12 Drosophila genomes plus the vectors plus C.elegans and a few other outgroups. The modENCODE project is about to complete the re-annotation of gene models using CAGE data that will bring more precise gene starts for melano and elegans. Ensembl Genomes is still working together with Manchester and now the US to put together an Aspergillus resource that provides the best value for money to researchers. PombBase is also being pursued, lots of labs interested in having it Ensemblified and ready to use.
* This is a personal blog. Things said here are not to be taken as official reports.

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3/31/2009

 

ape

dechronization: Hey R Users! Time to Update ape
The ape package written by Emmanuel Paradis is the foundation for phylogenetic analyses in R. Yesterday, Paradis and his coauthors posted a new version (3.2) on the CRAN archive yesterday. There don't seem to be too many new functions, but there are some important bug fixes. One these - preventing calculation of negative state probabilities when reconstructing discrete character states - solves one of the more vexing problems I've had with the ace function. You should definitely get the update if you're doing ancestral reconstruction of discretely coded traits! Now we just need to hope the April 17th upgrade to R 2.9 goes smoothly...


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3/26/2009

 

Jalview Google Summer of Code 2009

(Shameless plug of the day)

There is an opportunity for students to propose a Jalview
related software development project as part of the Google Summer of
Code this year, with an stipend of $4500. This project would be
supported by the NESCent mentor organisation, and ideally improve
Jalview's phylogenetic analysis capabilities, enhance the applet's use
as an AJAX web gui component, and/or extend its visualization and
editing capabilities for use as a curation tool.

The application period for student proposals is rapidly approaching, and
its important to discuss proposals with mentors before submission. If
you or anyone you know are interested, please read and/or forward the
message below, and look at the jalview project section on the following
(huge) URL:

http://www.nescent.org/wg/phyloinformatics/index.php?title=Phyloinformatics_Summer_of_Code_2009#Extend_Jalview_Alignment_visualization_tool


Regards.
Albert Vilella.
----

PHYLOINFORMATICS SUMMER OF CODE 2009

http://hackathon.nescent.org/Phyloinformatics_Summer_of_Code_2009

The Phyloinformatics Summer of Code program provides a unique
opportunity for undergraduate, masters, and PhD students to obtain
hands-on experience writing and extending open-source software for
evolutionary informatics under the mentorship of experienced
developers from around the world. The program is the participation of
the US National Evolutionary Synthesis Center (NESCent) as a
mentoring organization in the Google Summer of Code(tm) (http://
code.google.com/soc/).

Students in the program will receive a stipend from Google (and
possibly more importantly, a T-shirt solely available to successful
participants), and may work from their home, or home institution, for
the duration of the 3 month program. Each student will have at least
one dedicated mentor to show them the ropes and help them complete
their project.

NESCent is particularly targeting students interested in both
evolutionary biology and software development. Initial project ideas
are listed on the website. These range from hardware accerelation for
phylogenetic inference, to tree visualization within a wiki, to
alignment of next-gen sequencing data, to development of a reusable
ontology term markup module for biocuration. All project ideas are
flexible and many can be adjusted in scope to match the skills of the
student.  We also welcome novel project ideas that dovetail with
student interests.

TO APPLY: Apply online at the Google Summer of Code website (http://
socghop.appspot.com/), where you will also find GSoC  program
rules and eligibility requirements.  The 12-day application period
for students opens on Monday March 23rd and runs through Friday,
April 3rd, 2009.

INQUIRIES: phylosoc {at} nescent {dot} org. We strongly encourage all
interested students to get in touch with us with their ideas as early
on as possible.

2009 NESCent Phyloinformatics Summer of Code:
http://hackathon.nescent.net/Phyloinformatics_Summer_of_Code_2009

Google Summer of Code FAQ:
http://socghop.appspot.com/document/show/program/google/gsoc2009/faqs

Cyberinfrastructure Traineeships (managed separately from GSoC;
postdocs also eligible):
http://hackathon.nescent.org/
Cyberinfrastructure_Summer_Traineeships_2009

To sign up for quarterly NESCent newsletters: http://www.nescent.org/
about/contact.php

---------

Todd Vision and Hilmar Lapp
National Evolutionary Synthesis Center
http://nescent.org

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3/24/2009

 

Sugarcane sugar content

Sugarcane genes associated with sucrose content. [BMC Genomics. 2009] - PubMed Result
Sugarcane genes associated with sucrose content.

Papini-Terzi FS, Rocha FR, Vencio RZ, Felix JM, Branco DS, Waclawovsky AJ, Del Bem LE, Lembke CG, Costa MD, Nishiyama MY Jr, Vicentini R, Vincentz MG, Ulian EC, Menossi M, Souza GM.

ABSTRACT: BACKGROUND: Sucrose content is a highly desirable trait in sugarcane as the worldwide demand for cost-effective biofuels surges. Sugarcane cultivars differ in their capacity to accumulate sucrose and breeding programs routinely perform crosses to identify genotypes able to produce more sucrose. Sucrose content in the mature internodes reach around 20% of the culms dry weight. Genotypes in the populations reflect their genetic program and may display contrasting growth, development, and physiology, all of which affect carbohydrate metabolism. Few studies have profiled gene expression related to sugarcanes sugar content. The identification of signal transduction components and transcription factors that might regulate sugar accumulation is highly desirable if we are to improve this characteristic of sugarcane plants. RESULTS: We have evaluated thirty genotypes that have different Brix (sugar) levels and identified genes differentially expressed in internodes using cDNA microarrays. These genes were compared to existing gene expression data for sugarcane plants subjected to diverse stress and hormone treatments. The comparisons revealed a strong overlap between the drought and sucrose-content datasets and a limited overlap with ABA signaling. Genes associated with sucrose content were extensively validated by qRT-PCR, which highlighted several protein kinases and transcription factors that are likely to be regulators of sucrose accumulation. The data also indicate that aquaporins, as well as lignin biosynthesis and cell wall metabolism genes, are strongly related to sucrose accumulation. Moreover, sucrose-associated genes were shown to be directly responsive to short term sucrose stimuli, confirming their role in sugar-related pathways. CONCLUSION: Gene expression analysis of sugarcane populations contrasting for sucrose content indicated a possible overlap with drought and cell wall metabolism processes and suggested signaling and transcriptional regulators to be used as molecular markers in breeding programs. Transgenic research is necessary to further clarify the role of the genes and define targets useful for sugarcane improvement programs based on transgenic plants.


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3/20/2009

 

Next Generation community resources for Next Generation Sequencing

I've been looking at SEQanswers lately to try and discern where is people drawing the "Here be dragons" of their research. A lot of it is about wet lab protocols, which is great news, because it means the discoveries in different labs are shortcutting publication delays and being adopted as soon as possible. But there is also a lot of data analysis discussions which is great to identify the needs for specific bioinformatics tools in the outside world. It is becoming increasingly important in new emerging IT fields to know what *not* to work on other than what to work on, and forums like SEQanswers are great for this.

Great seeing people using this forum and not being afraid of showing results --- which is also showing muscle sometimes, but all good and fair. I wonder how much of this is known by lab bosses and how much of potentially old generation bosses understand of these Internet open community practices...

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3/18/2009

 

The blurring line between protein alignments and genomic alignments

As more and more data is being poured into the public sequence databases, an increasingly detailed map is being drawn that relates sequences from different individuals or different species, mainly into what has been known in the field as protein or genomic (DNA) alignments. This is what one can call twenty-first century molecular cartography.


All references to molecular evolution this year should be accompanied with an analogy to Darwin's work, so here is how it works in this case: Darwin's next generation machine, the Beagle, went on a journey to accumulate an enormous variety of specimens that, when compared all together, allowed Darwin to draw the first phylogenetic tree.


Contrary to what one would think, alignments with more sequences are easier to resolve than ones with less sequences, at least when the phylogenetic tree relating the sequences increases in detail, which is almost always. And this is allowing researchers to generate genomic alignments for phylogenetically dense groups of genomes while, in parallel, the protein alignments for the corresponding protein coding genes in these genomes are combined together with more distantly related species. This dense taxon sampling is making the distinction between protein alignments and genomic alignments less and less obvious.


As an example, one can use the highly conserved protein coding exons to anchor the points in the different chromosomes that define stretches of conserved synteny among the genomes, and then align these DNA stretches all together with a genomic aligner. At the same time, one can use the exon boundaries defined in the DNA sequences of the coding genes to help infer the right protein alignment at the aminoacidic level.


A new opportunity is now arising in exploiting the information that is contained separately in the genomic and protein alignments to combine them into a single object representing both. New methods are being developed that will exploit the landmarks that both genomic and protein alignments have correctly place to converge into a single intertwined alignment object. This new type of alignment has in a way already been represented in closely related prokaryotic genomes. But prokaryotic genomes are less interesting for some topics, like alternative splicing, repetitive elements or recombination hotspots. Combined genomic and protein alignments will bring new elements of detail together that have been scattered so far for researchers to study and hopefully some new and brilliant mechanistic explanations of the innards of molecular evolution will arise from them, in the same way that Darwin did two centuries ago.


So a deluge of sequencing data is not really a problem but an opportunity.



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3/16/2009

 

How much should you stretch HMM classification?

There are ongoing discussions in our Campus regarding the use of de novo clustering or HMM classification to update the family models in an Orthology database from one release to the other.

One trend that I don't favour is to use the HMM models from the previous build and classify the current protein sets to it. Then re-run the alignment and tree-building steps after that.

The other trend that I favour is to re-run the new blasts/phmmers for the new proteins, re-cluster with the other hits in the updated graph, and then re-run the alignment and tree-building steps in the new set of family models.

People who argue in favour of the HMM classification procedure and want to convince me of their feasibility show give convincing answers to these questions:

Let's say you only have a few complete genomes sequences with provisional gene predictions from your clade but expect to have 20% more extra finished genomes with better gene predictions every two months. Over the course of a year your will have more than doubled the number of genomes. Do you trust the HMMs you are doing today to represent the family models in two month, four-month, six-month, eight-month, ten-month, twelve-month time?

Let's say that you have answered the previous question with a 'yes' then, where do you draw the line to update your HMM by rebuilding them from updated genome sets? Why don't you take Human, S.cerevisiae, A.thaliana, E.coli and P.furiosus and call that the ultimate representation of all family models on Earth? Do you think those families would be as good as than the ones obtained using 80 genomes instead?

If so, then it's very easy for you, just use those 5 genomes as your family model set. But I don't think that is the way to go.

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3/15/2009

 

Fish Genomes to come

We hosted the International Fish Genomes meeting once more this weekend,
bringing researchers from Europe, America and Asia to give talks about their
current scientific progresses and also to discuss possible collaborations.

The amount of work reported by the zebrafish people at the Sange, leaded by
Dr. Derek Stemple, was a surprise to me, only because I wasn't closely
following their efforts before (a quick summary at the bottom). They are in
some ways ahead of the human genetics people in developing methods and
protocols to take full advantage of the NextGen sequencing technologies. The
ZFIN consortium has recently released Zv8, the latest version of the Danio
rerio assembly, which will be present, with brand new gene prediction build,
in the upcoming Ensembl v54 in April.

One recurring theme in most talks was how to deal with heterozigosity and
polyploidization issues when trying to assemble fish genomes. Different
techniques to create artificial individuals with double haplotype genome sets
have been developed that make this task easier. Another recurring theme was
that the NextGen sequencing was focused on assembly, but there are a lot of
hanging fruits to be picked up for SNP and cDNA analyses that will squeeze
more biological results out of the same data. Squeezing data doesn't seem
very trendy nowadays with the second deluge we are facing, but I don't think
it's something we should feel to personal about, because in essence is only a
change in the scale of data set size, but with the same imagination and
ingenuity at hand as before.

One of the most interesting talks to me was Dr. Hugues Roest Crollius demo of
their Dyogen Synteny Browser, which complements a lot what we have in the
EnsemblCompara GeneTrees in terms of visualization and predictions errors
discovery. This browser is specially relevant for the fish clade, by bringing
out very clear patterns of gene conservation and loss after the whole genome
duplication in the Teleosts.

The extraterrestrial talk about skate cell biology and development brought
pictures of baby skates resembling very much the alien stuck onto the face of
the guy on Alien, the film. Cool and disturbing in equal amounts.


Another conclusion from the meeting is that we probably need to gather
efforts in writing a strong proposal to NHGRI for a 2x-mammalian-like sequencing
spree in the fish clade. As the mammalian genomics study is now showing, you
get a more complete picture by sequencing lots of ``millions of years'' than
getting stuck in repetitive and haplotypic knots in one single genome. Still,
no one stepped forward on Saturday to coordinate the proposal, and a bit more
haggling and ambushing may be needed :-).

----
Derek Stemple -- Zebrafish Genome Project

Heterozigosity and haplotype issues in the six related individuals
used first

Better DNA to make libraries --> Fertilized eggs with UV-inactivated
sperm -- melt the spindle in the first division -- doubled haploid
fish (DH)

Better genetic maps -- radiation hybrid, heat shock, meotic map

Gene Annotation using Solexa Sequencing -- how to do it

Q: SNPs from the Solexa data?

A: Not focusing on that now, reference already has 0.6M, 6M with other
line

Q: 3UTR repetitive element problems in Solexa?

A: Use read pairs, filter out in the alignment, it's difficult. Will
probably do bigger library inserts soon.

Q: Depth and false 5prime ends?

A: A third of reads cross a boundary, 5prime ends there is a bias
towards one strand in the sequencing

Matthew Clark

SJD is homozigous but nobody uses it because of reproduction issues in
the lab

Doing CNV analyses, comparing with repeats using a HMM (Jared Simpson)

Read pair abberrations -- lots of deletions found -- badly assembled
bits of the genome? (Klaudia Walter)

Doing a WGSA Affy for SNP chip -- will help BAC mapping

De novo map -- mapmaker, joinmap, RECORD, SMOOTH, Combin, MSTmap

MSTmap works on Turing -- combine genetic map with sequencing

Zebrafish and Danio genus polymorphism rates -- conserved elements



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