Genetic Basis of Human Brain Evolution: Bioinformatics and Expression Analysis of Human Accelerated Regions in Transgenic Mice

GRETEL B. KAMM; RODRIGO LÓPEZ-LEAL; MARCELO RUBINSTEIN; LUCÍA F. FRANCHINI

Huerta Grande

Congreso; Second Joint Meeting of the Argentine Society for Neurociences; 2010

It has been hypothesized that variation in gene regulation is responsible for much of the phenotypic diversity within and between species. In particular, it was proposed a few decades ago that the phenotypic divergence between human and chimpanzees is largely due to changes in gene regulation rather than changes in the protein-coding sequences of genes. We hypnotize that the unparalleled explosion in human cognitive capacities and behavioral repertoire is due the acquisition of new temporal and spatial expression patterns of preexisting genes. Using bioinformatic tools previously developed in our lab, we described noncoding DNA elements that show evidence of rapid evolution in the human lineage (increase in the rate of nucleotide substitution). Further analysis of all described regions with an accelerated human substitution rate (termed human accelerated regions [HARs]) allowed us to identify the largest cluster of HARs located within 648 kb of the neuronal PAS domain protein 3 (NPAS3) gene. NPAS3 encodes a bHLH-PAS transcription factor that is broadly expressed in the developing mouse nervous system, and its dysfunction has been associated with schizophrenia in humans. In order to explore the participation of NPAS3 HARs on this gene regulation we generated transgenic mice carrying HAR mouse or human ortholog sequences upstream of Hsp68 minimal promoter and the reporter gene lacZ. Two Npas3 HARs were able to partially recapitulate the embryonic expression pattern of the endogenous gene suggesting their participation as Npas3 developmental enhancers. The identification of these HARs as functional NPAS3 enhancers will allow us to perform a comparative expression analysis of the human and mouse orthologs and to investigate their potential role in human brain evolution.