CONICET | Buscador de Institutos y Recursos Humanos

To identify the evolutionary genetic novelties that contributed to shape human-specific traits such as the use of acomplex language, long-term planning and exceptional learning abilities is one of the ultimate frontiers of modernbiology. Evolutionary signatures of functional shifts could be detected by comparing noncoding regions that are highlyconserved across mammals or primates and rapidly accumulated nucleotide substitutions only in the lineage leading tohumans. As gene loci densely populated with human-accelerated elements (HAEs) are more likely to have contributed tohuman-specific novelties, we sought to identify the transcriptional units and genomic 1 Mb intervals of the entire humangenome carrying the highest number of HAEs. To this end, we took advantage of four available data sets of humangenomic accelerated regions obtained through different comparisons and algorithms and performed a meta-analysis ofthe combined data. We found that the brain developmental transcription factor neuronal PAS domain-containing protein3 (NPAS3) contains the largest cluster of noncoding-accelerated regions in the human genome with up to 14 elementsthat are highly conserved in mammals, including primates, but carry human-specific nucleotide substitutions. We thentested the ability of the 14 HAEs identified at the NPAS3 locus to act as transcriptional regulatory sequences in a reporterexpression assay performed in transgenic zebrafish. We found that 11 out of the 14 HAEs present in NPAS3 act astranscriptional enhancers during development, particularly within the nervous system. As NPAS3 is known to play acrucial role during mammalian brain development, our results indicate that the high density of HAEs present in thehuman NPAS3 locus could have modified the spatiotemporal expression pattern of NPAS3 in the developing human brainand, therefore, contributed to human brain evolution.