Study in birds finds distinctions between male and female brain development

Findings provide new insight about genetic differences in brain development

New research in a small songbird reveals differences in how the brain develops between male and female early in the bird’s life.

The study, published today in the journal Cell Reports, identifies thousands of genes that are differentially expressed during development in the part of the zebra finch’s brain that controls singing among males. The study by researchers at Oregon Health & Science University and the Federal University of Rio Grande do Norte in Brazil provides new insights about how genes and hormones differentiate the brains of males and females.

Sami Friedrich, a crab, and the Oregon Coast
Friedrich, pictured with a crab at the Oregon Coast. (Courtesy) Read the Research News interview with Friedrich.

“The literature is full of studies documenting various kinds of sex differences in the brain, but we have limited understanding of how those differences come about during development,” said lead author Samantha R. Friedrich, Ph.D., an OHSU behavioral neuroscience researcher. “This work moves us one step closer to teasing apart the molecular ballet underneath sex-specific neurodevelopment.”

The authors write that they found few distinctions between males and females early in development, most of them in sex chromosome genes, but starting 20 days after hatching the two sexes “undergo two massively gene-rich and functionally distinct developmental programs,” likely driven by factors like gonadal hormones.

The new study zeroed in on an area of the zebra finch brain known to be associated with singing, which is only done by males in this species.

“In spite of much research, the role that sex plays in brain development is still unclear,” said senior author Claudio V. Mello, M.D., Ph.D., professor of behavioral neuroscience in the OHSU School of Medicine.

In the song-control circuitry of the brain, the researchers found that thousands of genes were expressed differently in males and females. Many of these genes have been linked to cell survival and to differences in the growth of cells and axons forming connections within the brain.

“The zebra finch song control system is highly dimorphic, an extreme example of how nature has modified male and female differences in the brain,” Mello said. “From the standpoint of human health, it’s important to improve our understanding of sex differences in brain development, and how genetic and hormonal factors lead to sex differences in brain structure and function.”

The research was supported by the National Institutes of Health, awards R21OD028774, R03NS115145 and R24GM120464 and the National Science Foundation, graduate research fellowship DGE-1448072.



Emergence of sex-specific transcriptomes in a sexually dimorphic brain nucleus