The ARX problem – how an epilepsy gene escapes exome sequencing

Silence. You might wonder why you hear very little about ARX in exome studies these days. The X-chromosomal aristaless related homeobox gene was one of the first genes for epilepsies and brain malformations to be discovered. Mutations in ARX can be identified in male patients with a variety of neurodevelopmental disorders including idiopathic West Syndrome – accordingly, it’s on the differential list for patients with Infantile Spasms without a known cause. Let me tell you about the problems that the ARX gene poses for exome sequencing. Continue reading

Exploring samtools – Green Eggs and Ham (*.bam)

That Sam I Am.  The entire field of high-throughput genomics appears to be inspired by the American children’s book author Dr. Seuss. Given that we are currently reading through the original books almost on a daily basis due to the presence of a toddler in our home, mentioning *.sam files, *.bam files or sam2bam routines always makes me smile. However, this is not a post about children’s books; it’s about a likely 2013 trend in genomic research, the redefinition of the boundary between genome center and end user and the laptopification of life sciences. Continue reading

The exome fallacy

Are you fully covered? My experience with a phenomenon I shall call exome fallacy began in 2011. While browsing the exomes of a few patients with epileptic encephalopathies, we wanted to have a quick look at whether we could exclude mutations in the epilepsy gene SCN1A in our patients through exome data. As some of you might already guess, the words “exome” and “exclude” don’t go well together and we learned the hard way that each individual exome covers certain parts of the gene quite well. However, if you expect your exome data to have sufficient quality to cover an entire gene in several individuals, you end up disappointed. But there is even more to the exome fallacy than you might think… Continue reading