Role of the x-linked histone demethylase Kdm6a in sex-specific differentiation of hypothalamic neurons

CABRERA ZAPATA, L.E.; CISTERNAS, C.D.; SOSA, C.; GARCIA-SEGURA, L.M.; AREVALO, M.A.; CAMBIASSO, M.J.

Congreso; XI (Virtual) Meeting Steroids and Nervous System; 2022

Currently it is well known that the sex chromosome complement (XY/XX) contribution tobrain sexual differentiation is not just limited to the determination of a gonadal type in utero(testes for XY, ovaries for XX), but continues playing a role in the development andexpression of sex dimorphisms at morphological, physiological, and behavioral levelsthroughout life. However, little is known about the identity of particular X or Y-linked genesinvolved and the mechanisms by which these genes participate in the process. Several Xlinkedgenes are involved in neuronal differentiation and may contribute to the generationof sex dimorphisms in brain. Previous results showed that XX hypothalamic neurons growfaster, have longer axons, and exhibit higher expression of the neuritogenic gene neurogenin3 (Ngn3) than XY before perinatal masculinization. Here we evaluated the participation ofcandidate X-linked genes in the development of these sex differences, focusing mainly onKdm6a, a gene encoding for an H3K27 demethylase with genome-wide gene expressioncontrol functions. We established hypothalamic neuronal cultures from wild-type ortransgenic Four Core Genotypes mice, a model that allows evaluating the effect of sexchromosomes independently of gonadal type. X-linked genes Kdm6a, Eif2s3x and Ddx3xshowed higher expression in XX compared to XY neurons, regardless of gonadal sex.Moreover, Kdm6a expression pattern with higher mRNA levels in XX than XY did notchange with age at E14, P0, and P60 in hypothalamus or under 17β-estradiol treatment inculture. Kdm6a pharmacological blockade by GSK-J4 reduced axonal length only in femaleneurons and decreased the expression of neuritogenic genes Neurod1, Neurod2 and Cdk5r1in both sexes equally, while a sex-specific effect was observed in Ngn3. Finally, Kdm6adownregulation using siRNA reduced axonal length and Ngn3 expression only in femaleneurons, abolishing the sex differences observed in control conditions. Altogether, theseresults point to Kdm6a as a key mediator of the higher axogenesis and Ngn3 expressionobserved in XX neurons before the critical period of brain masculinization.