Yi Xing's Alternative Splicing and Computational Genomics Blog

Nonsense Mediated Decay and Evolution

Given that NMD is a widespread phenomenon in many eukaryotic organisms, one might wonder what is its role in genome evolution. Michael Lynch published a seminal paper which discussed this topic. Click to see the paper:

Debate over the mechanisms responsible for the phylogenetic and genomic distribution of introns has proceeded largely without consideration of the population-genetic forces influencing the establishment and retention of novel genetic elements. However, a simple model incorporating random genetic drift and weak mutation pressure against intron-containing alleles yields predictions consistent with a diversity of observations: (i) the rarity of introns in unicellular organisms with large population sizes, and their expansion after the origin of multicellular organisms with reduced population sizes; (ii) the relationship between intron abundance and the stringency of splice-site requirements; (iii) the tendency for introns to be more numerous and longer in regions of low recombination; and (iv) the bias toward phase-0 introns. This study provides a second example of a mechanism whereby genomic complexity originates passively as a "pathological" response to small population size, and raises difficulties for the idea that ancient introns played a major role in the origin of genes by exon shuffling.

Lynch suggests NMD offers protection for mildly deleterious introns and therefore facilitates their evolution. See another article by him and colleagues on this subject.

Posted by yxing at January 28, 2005 12:09 PM