A recent study published in the journal Cell has identified a major genetic component of human brain development, with implications for research into autism and schizophrenia. Scientists at The Scripps Research Institute have found that the gene SRGAP2, the protein product of which is responsible for forming neuronal connections in neocortical development, has undergone two human-specific truncated duplications.
One of the duplicates has been named SRGAP2C, and appeared in the genome about 2.4 million years ago, during the time in which human lineage separated from nonhuman primates (a related paper published in the same issue of Cell covers the recent evolution of SRGAP2). SRGAP2C interacts with the original SRGAP2 to inhibit its functions, delaying the maturation of dendritic spines on pyramidal neurons. Dendritic spines are crucial for integrating synaptic signals from other neurons.
Far from having a negative effect on brain development, SRGAP2C ultimately results in a higher density of dendritic spines on the neurons when they mature – a human-specific trait. Conditions like schizophrenia and autism in humans feature atypical neuronal connectivity; studying human-specific gene duplications like SRGAP2C may allow such diseases to be effectively modelled in mice, and unravel some of the mysteries surrounding these and other neurodevelopmental conditions.