ANXA11 expression in human smooth muscle aortic cells post-ILb1 exposure
About a year ago, I did a little work on a very interesting project which was trying to identify blood-based biomarkers for the early detection of stroke. The data included gene expression measurements using microarrays at various time points after the onset of ischemia (reduced blood supply). I had not worked with timecourse data before, so I went looking for methods and found a Bioconductor package, maSigPro, which did exactly what I was looking for. In combination with ggplot2, it generated some very attractive and informative plots of gene expression over time.
I was very impressed by maSigPro and meant to get around to writing a short guide showing how to use it. So I did finally, using RMarkdown to create the document and here it is. The document also illustrates how to retrieve datasets from GEO using GEOquery and annotate microarray probesets using biomaRt. Hopefully it’s useful to some of you.
I’ll probably do more of this in the future, since publishing RMarkdown to RPubs is far easier than copying, pasting and formatting at WordPress.
Location of BLAST (tblastn) hits Mya arenaria GagPol (AIE48224.1) vs GOS contigs
Last week, I was listening to episode 337 of the podcast This Week in Virology. It concerned a retrovirus-like sequence element named Steamer, which is associated with a transmissible leukaemia in soft shell clams.
At one point the host and guests discussed the idea of searching for Steamer-like sequences in the data from ocean metagenomics projects, such as the Global Ocean Sampling expedition. Sounds like fun. So I made an initial attempt, using R/ggplot2 to visualise the results.
To make a long story short: the initial BLAST results are not super-convincing, the visualisation could use some work (click image, right, for larger version) and the code/data are all public at Github, summarised in this report. It made for a fun, relatively-quick side project.
One of the commonest bioinformatics questions, at Biostars and elsewhere, takes the form: “I have a list of identifiers (X); I want to relate them to a second set of identifiers (Y)”. HGNC gene symbols to Ensembl Gene IDs, for example.
When this occurs I have been known to tweet “the answer is BioMart” (there are often other solutions too) and I’ve written a couple of blog posts about the R package biomaRt in the past. However, I’ve realised that we need to take a step back and ask some basic questions that new users might have. How do I find what marts and datasets are available? How do I know what attributes and filters to use? How do I specify different genome build versions? Continue reading →
I guess I’ve been around bioinformatics for the best part of 15 years. In that time, I’ve seen almost no improvement in the way biologists handle and use data. If anything I’ve seen a decline, perhaps because the data have become larger and more complex with no improvement in the skills base.
It strikes me when I read questions at Biostars that the problem faced by many students and researchers is deeper than “not knowing what to do.” It’s having no idea how to figure out what they need to know in order to do what they want to do. In essence, this is about how to get people into a problem-solving mindset so as they’re aware, for example that:
it’s extremely unlikely that you are the first person to encounter this problem
it’s likely that the solution is documented somewhere
effective search will lead you to a solution even if you don’t fully understand it at first
the tool(s) that you know are not necessarily the right ones for the job (and Excel is never the right tool for the job)
implementing the solution may require that you (shudder) learn new skills
time spent on those skills now is almost certainly time saved later because…
…with a very little self-education in programming, tasks that took hours or days can be automated and take seconds or minutes
It’s good (and bad) to know that these issues are not confined to Australian researchers: here is It’s time to reboot bioinformatics education by Todd Harris. It is excellent and you should go and read it as soon as possible.
Unfortunately, but for good reasons, it’s an internal event this year, but I’m putting my presentations online. I’ll be speaking twice; the first for Thursday is called “Online bioinformatics forums: why do we keep asking the same questions?” It’s an informal, subjective survey of the questions that come up again and again at bioinformatics Q&A forums such as Biostars and my attempt to understand why this is the case. Of course one simple answer might be selection bias – we don’t observe the users who came, found that their question already had an answer and so did not ask it again. I’ll also try to articulate my concern that many people view bioinformatics as a collection of recipe-style solutions to specific tasks, rather than a philosophy of how to do biological data analysis.
My second talk on Friday is called “Should I be dead? a very personal genomics.” It’s a more practical talk, outlining how I converted my own 23andMe raw data to VCF format, for use with the Ensembl Variant Effect Predictor. The question for the end – which I’ve left open – is this: as personal genomics becomes commonplace, we’re going to need simple but effective reporting tools that patients and their clinicians can use. What are those tools going to look like?
Looking forward to spending some time in Melbourne and hopefully catching up with this awesome lady.
Here’s a new way to abuse biological information: take a list of gene IDs and use them to create a completely fictitious, but very convincing set of microarray probeset IDs.
This one begins with a question at BioStars, concerning the conversion of Affymetrix probeset IDs to gene names. Being a “convert ID X to ID Y” question, the obvious answer is “try BioMart” and indeed the microarray platform ([MoGene-1_0-st] Affymetrix Mouse Gene 1.0 ST) is available in the Ensembl database.
However, things get weird when we examine some example probeset IDs: 73649_at, 17921_at, 18174_at. One of the answers to the question notes that these do not map to mouse.
The data are from GEO series GSE56257. The microarray platform is GPL17777. Description: “This is identical to GPL6246 but a custom cdf environment was used to extract data. The cdf can be found at the link below.”