Sexually dimorphic gene expression in mouse brain precedes gonadal differentiation

Area of Science:

• Neuroscience
• Developmental Biology
• Genetics

Background:

• The traditional view posits gonadal steroid hormones as the primary drivers of sex differences in brain development and behavior.
• Testosterone and its metabolites are thought to masculinize the brain and inhibit feminine differentiation patterns.
• Emerging evidence suggests hormones may not be the sole determinants of sexual dimorphism in the brain.

Purpose of the Study:

• To investigate the hypothesis that genes directly induce sexually dimorphic neural development patterns.
• To identify candidate genes influencing sex differences in the brain independent of gonadal hormones.

Main Methods:

• Utilized microarrays and reverse transcription polymerase chain reaction (RT-PCR) to detect gene expression.
• Analyzed gene expression in developing murine brains at 10.5 days post coitum (dpc).

Main Results:

• Over 50 candidate genes with differential sex expression were identified.
• At least seven murine genes confirmed to show differential expression between male and female brains before gonadal hormone influence.
• These expression differences were observed at 10.5 dpc, a stage preceding significant gonadal hormone activity.

Conclusions:

• The identification of sex-differentially expressed genes prior to gonadal hormone exposure supports a significant role for genetic factors in brain sexual differentiation.
• These findings challenge the exclusive role of hormones and highlight the importance of intrinsic genetic programming in establishing sex differences in the brain.