Novel steroidogenic factor‐1 homolog (ff1d) is coexpressed with anti‐Mullerian hormone (AMH) in zebrafish

ff1d is a novel zebrafish FTZ‐F1 gene with sequence characteristics indicating similar basic regulatory mechanisms as the previously characterized ff1 based on the presence of an FTZ‐F1 box in the DNA binding domain and an interactive domain (I‐Box) and an AF‐2 in the ligand binding domain. The highest sequence similarity was found between ff1d and ff1b (NR5A4), a gene previously shown to be a functional homolog to the steroidogenic factor 1 (SF‐1). The expression pattern of ff1d was comparable to ff1b both in brain and gonads in adults and in the pituitary and interrenal cells in embryos. SF‐1 is crucial in mammalian steroidogenesis and in sex determination by regulating the anti‐Mullerian hormone (AMH). In fish, AMH has not been described previously. In this study, we cloned a partial zebrafish AMH. AMH was detected in growing oocytes, the ovarian follicular layer and testicular Sertoli cells, similar to the mammalian pattern, suggesting a conserved role between zebrafish and mammalian AMH. Teleosts lack a gene homolog to SRY, which constitute the universal testis‐determining factor in mammalian sex determination. Comparison of sequences and expression patterns indicate that ff1d is a new candidate for sex determination and differentiation in a way similar to SF‐1, possibly involving AMH. Developmental Dynamics 233:595–604, 2005. © 2005 Wiley‐Liss, Inc.