Genetic mechanism underlying primate brain evolution 
The enlarged brain and highly developed cognitive skills are the most significant characteristics that set us apart from our relatives, the non-human primates. The brains of modern humans are more than 20 times larger than those of Old World monkeys, and more than four times larger than those of great apes. This evolutionary expansion is believed to be crucial to the highly developed cognitive abilities in humans, yet its genetic basis remains unsolved. To understand the genetic basis shaping up the phenotypic characteristics  such as enlarged brain as well as highly developed cognitive skills of humans comparing to its relative, Chimpanzee, we analyzed  sequence variation and  gene expression of human brain-expressed genes in diverse non-human primate species, we identified 47 candidate genes showing strong evidence of positive selection in the human lineage. Genes with maximal expression in the brain showed a higher evolutionary rate in human than in chimpanzee. We observed that many immune-defense-related genes were under strong positive selection, and this trend was more prominent in chimpanzee than in human.
Neuropsin (kallikrein 8, KLK8) is a secreted-type serine protease preferentially expressed in the central nervous system and involved in learning and memory. Its splicing pattern is different in human and mouse, with the longer form (type II) only expressed in human. Sequence analysis suggested a recent origin of type II during primate evolution. Here we demonstrate that the type II form is absent in nonhuman primates, and is thus a human-specific splice form. With the use of an in vitro splicing assay, we show that a human-specific T to A mutation (c.71–127T4A) triggers the change of splicing pattern, leading to the origin of a novel splice form in the human brain. Using mutation assay, we prove that this mutation is not only necessary but also sufficient for type II expression. Our results demonstrate a molecular mechanism for the creation of novel proteins through alternative splicing in the central nervous system during human evolution .
MicroRNAs (miRNAs) are a growing class of small RNAs (about 22 nt) that play crucial regulatory roles in the genome by targeting mRNAs for cleavage or translational repression. We analyzed two miRNA clusters located on chromosome X and 19, respectively. Our data indicate rapid evolution of this cluster in primates including frequent tandem duplications and nucleotide substitutions. We propose that, like protein-coding genes, miRNA genes involved in male reproduction are subject to rapid adaptive changes that may contribute to functional novelties during evolution. Our results also showed an evidence of an Alu-mediated rapid expansion of miRNA genes in a previously identified primate-specific miRNA family, drawn from sequencing and comparative analysis of 9 diverse primate species. Evolutionary analysis reveals similar divergence among miRNA copies whether they are within or between species, lineage-specific gain and loss of miRNAs, and gene pseudolization in multiple species. These observations support a birth-and-death process of miRNA genes in this family, implicating functional diversification during primate evolution.

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