CONICET | Buscador de Institutos y Recursos Humanos

The sexual differentiation of mammalian central nervous system is the result of gonadal steroid action during the critical period (Embryonic day 18-Posnatal day 10, E18-P10). Conversion of androgens to estrogens by neural aromatase is a prerequisite for brain sexual differentiation. Studies of other laboratories have demonstrated a sexual dimorphism in aromatase (ARO) expression and activity in hypothalamic areas before the organizational effects of gonadal steroids. Recent evidences have shown that sex chromosomes genes contribute directly to the development of some sex differences in the brain. The aim of this study is to evaluate the contribution of sex chromosome complement (SCC) on the sexually dimorphic expression of ARO in the mouse forebrain at E16. To this end, we used the four core genotype mouse model (FCG) in which gonadal sex and SCC are dissociated. This mouse model combines a deletion of the testis-determining gene Sry from the Y chromosome with the subsequent insertion of a Sry transgene onto an autosome, thus the Y chromosome and the Sry transgene segregate independently. The FCG mice comprise XX and XY gonadal males (XXM and XYM) and XX and XY gonadal females (XXF and XYF). The regional distribution of ARO was immunohistochemically evaluated in brain sections of E16 mice of the FCG using a specific anti-ARO antiserum. ImageJ software was used to quantified the percentage of covered area in one entire field (0.035 mm2) placed in a standardized manner within the neuroanatomical region of interest. Specific immunoreactivity for aromatase (AROir) was found in neuronal perikarya and fibers in the Stria Terminalis, Anterior Amygdaloid Area, and Medial and Central nuclei of the Amygdala. The AROir in the Stria Terminalis and in the Anterior Amygdaloid Area was statistically higher in mice with SCC XY (p