Determination of the expression pattern of the dual promoter of zebrafish fushi tarazu factor-1a following microinjections into zebrafish one cell stage embryos.

The zebrafish fushi tarazu factor-1a (ff1a) is a transcription factor belonging to the NR5A subgroup of nuclear receptors. The NR5A receptors bind DNA as monomers and are considered to be orphans due to their ability to promote transcription of downstream genes without ligands. In zebrafish, four ff1 homologues (Ff1a, Ff1b, Ff1c, and Ff1d) have been identified so far. The gene coding for Ff1a is driven by two separate promoters, and give rise to four splice variants. Ff1a is expressed in the somites and pronephric ducts during somitogenesis and in the brain, liver, and mandibular arch during later embryonic stages. In adults the gene is highly expressed in gonads, liver, and intestine, but can be detected in most tissues. The broad variety of embryonic expression domains indicates several important developmental features. One of the mammalian fushi tarazu factor-1 genes, steroidogenic factor-1 (SF-1), is essential for the development of gonads and adrenals. SF-1 is together with Sox9, WT1, and GATA4 a positive transcriptional regulator of human anti-mullerian hormone (AMH) and thereby linked to the male sex-determining pathway. The zebrafish ff1a dual promoter contains several GATA binding sites and E-boxes, a site for DR4, XFD2, MyoD, Snail, HNF3, S8, and an HMG-box recognition site for Sox9. In a first attempt to dissect the ff1a promoter in vivo we have produced first generation transgenes in order to determine the correlation between the expression of the endogenous ff1a gene and the microinjected ff1a dual promoter coupled to the pEGFP reporter vector. Our results show that the microinjected constructs are expressed in the correct tissues.