Why (and how) is there sexual dimorphism?

3 December 2021

Josie Clowney
Department of Molecular, Celluar and Developmental Biology
University of Michigan, Ann Arbor

zoom recording

Abstract

Sexual reproduction is pervasive among multicellular organisms. Combining gametes increases genetic diversity and thus species resilience by mixing alleles. In most organisms, distinct morphs – sexes – produce a large gamete (the egg) or a small gamete (the sperm). Egg and sperm are able to come together via the evolution of physical systems of mating; because the gametes are different, the different sexes that make them have different anatomies and perform distinct mating behaviors to unite them. The sexual morphs of a species develop via distinct transcriptional regulation of a common genome. I will focus on the logical principles by which concise gene regulatory systems that determine sex result in remarkably complex sexual dimorphisms in the brain.

In insects, the presence of a Y chromosome in males sparks a cascade of sex-specific splicing events. This sex differentiation system uses only five genes. Two of these, doublesex and fruitless, are ultimately produced in distinct male and female versions that sex the body (doublesex) and the brain (fruitless). fruitless plays the remarkable role of exerting sex differences in the anatomy, connectivity, or physiology of dozens of disparate groups of neurons. Many or all of these neurons control sex-typical behaviors including mating, aggression, and egg-laying. I will discuss our on-going work on neuronal transcriptional regulation by fruitless and consider models by which just one factor can generate both female-specific and male-specific neurons, neural circuits, and behaviors.

current theory lunch schedule