Evolutionary Rate and Gene Expression Across Different Brain Regions

Tamir Tuller,Martin Kupiec,Eytan Ruppin

doi:10.1186/gb-2008-9-9-r142

Abstract

Cortically expressed genes are more conserved than sub-cortical ones and gene expression levels exert stronger constraints on sequence evolution in cortical than in sub-cortical regions.

Highlights

The evolutionary rate of a protein is a basic measure of evolution at the molecular level
The evolutionary rate (ER) of a protein, the ratio between the rate of its nonsynonymous to the rate of its synonymous mutations, rate of nonsynonymous substitutions (dN)/rate of synonymous substitutions (dS), is a basic measure of evolution at the molecular level. (Throughout the report, when we talk about the ER of a gene we refer to the ER of its corresponding protein.) It is affected by many systemic factors, including gene dispensability, expression level, the number of protein interactions, and the recombination rate [3,4,5,6,7]
These brain regions can be broadly divided into two major phylogenetic classes: cortical regions, which are primarily characteristic of the mammalian lineage; and subcortical brain regions, which have a broad phyletic distribution [24]. (No other vertebrates have a structure that clearly resembles the isocortical regions studied here [25].) Second, the brain regions are divided into four major developmental classes, including those that develop from the embryonic forebrain, midbrain, hindbrain, and spinal cord [26]

Summary

Introduction

The evolutionary rate of a protein is a basic measure of evolution at the molecular level. Previous studies have shown that genes expressed in the brain have significantly lower evolutionary rates than those expressed in somatic tissues. Genome Biology 2008, Volume 9, Issue 9, Article R142 Tuller et al R142.2 their ER [5,10], even when controlling for the dispensability of the genes [4]. This inverse relation extends to other eukaryotes (including humans and other vertebrates) [11]. A general principle arising from such studies has been that tissue-specific genes have higher ERs than 'housekeeping' genes, which are broadly expressed in most tissues [16,17,18]

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