Conserved synteny between the chicken Z sex chromosome and human chromosome 9 includes the male regulatory gene DMRT1: a comparative (re)view on avian sex determination

Sex-determination mechanisms in birds and mammals evolved independently for more than 300 million years. Unlike mammals, sex determination in birds op erates through a ZZ/ZW sex chromosome system, in which the female is the he terogametic sex. However, the molecular mechanism remains to be elucidated. Comparative gene mapping revealed that several genes on human chromosome 9 (HSA 9) have homologs on the chicken Z chromosome (GGA Z), indicating the common ancestry of large parts of GGA Z and HSA 9. Based on chromosome homo logy maps, we isolated a Z-linked chicken ortholog of DMRT1, which has been implicated in XY sex reversal in humans. Its location on the avian Z and w ithin the sex-reversal region on HSA 9p suggests that DMRT1 represents an a ncestral dosage-sensitive gene for vertebrate sex-determination. Z dosage m ay be crucial for male sexual differentiation/determination in birds. Copyr ight (C) 2000 S. Karger AG. Basel.