A major surprise emerging from genome sequencing projects is that humans have a comparable number of protein-coding genes as significantly less complex organisms such as the minute nematode worm Caenorhabditis elegans. Clearly something other than gene count is behind the genetic differences between simpler and more complex life forms.
Increased functional and cellular complexity can be explained, in large part, by how genes and the products of genes are regulated. A University of Toronto-led study published in the latest issue of Genome Biology reveals that a step in gene expression (referred to as alternative splicing) is more highly regulated in a cell and tissue-specific manner than previously appreciated and much of this additional regulation occurs in the nervous system. The alternative splicing step allows a single gene to specify multiple protein products by processing the RNA transcripts made from genes (which are translated to make protein).
We are finding that a significant number of genes operating in the same biological processes and pathways are regulated by alternative splicing differently in nervous system tissues compared to other mammalian tissues, says lead investigator Professor Benjamin Blencowe of the Banting and Best Department of Medical Research and Centre for Cellular and Biomolecular Research (CCBR) at the University of Toronto
According to Blencowe, it is particularly interesting that many of the genes have important and specific functions in the nervous system, including roles associated with memory and learning. However, in most cases the investigators working on these genes were not aware that their favorite genes are regulated at the level of splicing. Blencowe believes that the data his group has generated provides a valuable basis for understanding molecular mechanisms by which genes can function differently in different parts of the body.