Localisation of lanosterol 14 alpha-demethylase in round and elongated spermatids of the mouse testis: an immunoelectron microscopic and stereological study

Lanosterol 14 alpha -demethylase (CYP51) is a microsomal cytochrome P450 en zyme involved in the postsqualene cholesterol biosynthetic pathway. CYP51 r emoves 14 alpha -methyl group from lanosterol], forming FF-MAS (folicular f luid meiosis activating sterol) which accumulates in gonads. The goal of ou r study is to determine the expression of CYP51 protein in the male gonad. Using electron microscopic immunogold techniques, CYP51 is localised on inn er and outer acrosomal membranes of male germ cells, the round and elongate d spermatids. Significance of CYP51 localization on the acrosome which is a Golgi-derived organelle is not known, but we propose that CYP51-formed FF- MAS can function as a signalling sterol during fertilisation.