Unmasking a role for sex chromosomes in gene silencing

摘要

Several sexually dimorphic phenotypes correlate withsex-chromosome dosage rather than with phenotypicsex. New research suggests that sex chromosomedimorphism helps to regulate gene silencing. During mammalian development, sexual development isinitiated in the embryonic gonad. Male gonadal cellsexpress the Sry gene (sex determining region Y), a Ylinkedgene which triggers differentiation of the testis.Steroidogenic Leydig cells, within the testis, producetestosterone, masculinizing non-gonadal tissues includingthe sex ducts, the external genitalia and parts of thebrain. The dominant role of hormones in masculinizingthe brain was shown about 50 years ago by Alfred Jost. Bytreating female guinea pigs with testosterone prenatally,he demonstrated irreversible male-type behavioralchanges. This early research suggested that XX and XYcells were equivalent and that sexual dimorphismsresulted from exposure to male or female gonadalhormones [1]. However, the question of whether sexualdimorphism is completely reliant on hormones orwhether there is also a genetic component has remainedan area of interest.