Epigenetic switch turns on genetic behavioral variations.

What roles do environmental factors, genes, and heredity play in shaping the behaviors of individuals? In his 1963 article entitled “Behavior genetics and individuality understood,” the pioneering behavioral geneticist Jerry Hirsch (1) eloquently articulated that “Individual differences are no accident. They are generated by properties of organisms as fundamental to behavioral science and biology as thermodynamic properties are to physical science.” In the era of molecular genetics and genomics, understanding neuronal activity and organismal behavior at the cellular and molecular levels has rapidly progressed, primarily via studies of behavior in genetically tractable organisms, such as the fruit fly, the worm, the laboratory mouse, and others. Nonetheless, over 50 y after Hirsch’s seminal article, and despite the aforementioned scientific advances in cellular and molecular neurobiology, understanding the specific contributions of natural genetic variations to phenotypic diversity between individuals and across populations remains a major research challenge. The reasons for why identifying the actual genetic elements that underlie natural behavioral variations between individuals is difficult are deeply embedded in the polygenic nature of the majority of complex phenotypes, including behavior (2, 3), and the often complex, nonlinear relationship betweenplastic primary geneproducts, RNAs and proteins, and the organismal phenotypes they influence. Now in PNAS, Anreiter et al. (4) elegantly demonstrate that the previously identified (5), naturally occurring allele-specific effects of foraging (for) on individual behavioral foraging decisions of larval and adult Drosophila depends on the epigenetic action of the dG9a gene (4).