Humans are characterized by the advanced cognitive functions empowered by their elaborated brains. Although the molecular mechanisms that differentiate humans from non-human primates remain mostly unresolved, human-specific mechanisms involved in fetal brain development have become resolved. We recently found that some human-specific genes, which have been newly acquired in the course of human evolution, regulate brain development to expand brain volume. However, there has been no systematic search for the total number of human-specific genes in the human genome and functional screening of those involved in brain development.
　In this study, we comprehensively searched for human-specific genes by focusing on the generation mechanisms. Novel genes are obtained mainly by two mechanisms during vertebrate evolution, the duplication of preexisting genes and de novo emergence of genes from non-genic sequences. We conducted a systematic search and successfully identified both types of human-specific genes including novel ones, which are not annotated in the public databases. Expression analysis on various human organs in the adult and fetal stages revealed that some are specifically expressed during brain development. Currently, we are optimizing the technical details for functional screening of candidate genes to identify those significantly affecting neural stem cell dynamics to expand neuronal numbers in the brain.