09-P087 FGF signaling is required for the specification of GnRH neurons

like) exhibit a pleiotropic phenotype including abnormalities of cardiac, skeletal and limb development, in addition to renal agenesis. Here we report abnormalities of gonad development in homozygous mutants. From early stages, Vcc/Vcc embryos contain gonads longer than controls and by 13.5 dpc this increased length is evidenced by an increase in the number of testis cords. The gene mutated in Vcc, Pcsk5, encodes a proprotein convertase that is thought to co-ordinately regulate the expression of several paralogous Hox genes. Utilising a variety of approaches, we are investigating the possibility that abnormal HOX-dependent patterning of the urogenital ridge in Vcc/Vcc embryos expands the gonadal field, resulting in the striking lengthening of the mutant gonads. Studies of this mutation may shed light on the cellular processes underlying gonad formation and subsequent testis cord formation in males, and their genetic regulation.