Elevated gene expression levels distinguish human from non-human primate brains

TLDR

Little is known about how the human brain differs from that of our closest relatives. The study investigates the genetic basis of human brain specialization by comparing cortical gene expression in humans, chimpanzees, and rhesus macaques using multiple techniques. Gene expression profiles of the cerebral cortex were compared across humans, chimpanzees, and rhesus macaques using several independent techniques. The study identified 169 genes differentially expressed between human and chimpanzee cortex, 91 of which are human‑lineage specific, with ~90% up‑regulated in humans, indicating a distinctive pattern of elevated expression that may underlie enhanced neuronal activity and cerebral function.

Abstract

Little is known about how the human brain differs from that of our closest relatives. To investigate the genetic basis of human specializations in brain organization and cognition, we compared gene expression profiles for the cerebral cortex of humans, chimpanzees, and rhesus macaques by using several independent techniques. We identified 169 genes that exhibited expression differences between human and chimpanzee cortex, and 91 were ascribed to the human lineage by using macaques as an outgroup. Surprisingly, most differences between the brains of humans and non-human primates involved up-regulation, with ≈90% of the genes being more highly expressed in humans. By contrast, in the comparison of human and chimpanzee heart and liver, the numbers of up- and down-regulated genes were nearly identical. Our results indicate that the human brain displays a distinctive pattern of gene expression relative to non-human primates, with higher expression levels for many genes belonging to a wide variety of functional classes. The increased expression of these genes could provide the basis for extensive modifications of cerebral physiology and function in humans and suggests that the human brain is characterized by elevated levels of neuronal activity.