Tasty Tidbits: The Horse Y Chromosome

I am  particularly interested in anything about the Y chromosome because, as far as sex chromosomes go, it is often overlooked, or intentionally ignored. In genetic sex determination (meaning there is a gene or chromosome that determines whether an individual is genetically male or female), the Y determines maleness. However, it also does not recombine, and is often very small and degenerated relative to its partner, the X chromosome. The Y chromosome also often contains lots of repeated sequences (that may or may not be functional). These repeated regions make it difficult to sequence. The regions of the Y chromosome that are easy to sequence are those that are similar to the X, but, because they are similar to the X, these regions can sometimes be mis-assigned.

So, now we come to the horse Y chromosome. The paper summarized here by Paria et al (2011) is really pretty cool. Without getting into the dirty details I'll say that they do a lot of work making sure the sequence they're analyzing is male-specific.

What they find (and why it's important):

• There are some Y-linked genes that are shared across the mammals studied (confirming the shared evolutionary origin of the Y chromosome).
• There are some horse Y-linked genes that have been acquired only along this lineage (showing how species-specific gene movements can shape the future of the Y chromosome).
• Some of these genes are expressed in many tissues (these tend to be the ones conserved over long evolutionary distances and argue for their importance).
• The genes that have tissue-specific expression are expressed in male-specific tissues, like testis (highlighting how male-specific functions can easily accumulate on the Y, the male-specific chromosome). 

I should go into more detail, but I'm off to relieve my better half of a yelling baby who thinks she's grown too big for bedtime.

For more, please see the original paper:

Paria N, Raudsepp T, Pearks Wilkerson AJ, O'Brien PCM, Ferguson-Smith MA, et al. (2011) A Gene Catalogue of the Euchromatic Male-Specific Region of the Horse Y Chromosome: Comparison with Human and Other Mammals. PLoS ONE 6(7): e21374. doi:10.1371/journal.pone.0021374

(link to paper)