cDNA cloning and mRNA expression of a FTZ-F1 homologue from the pituitary of the orange-spotted grouper, epinephelus coioides.

A FTZ-F1 homologue was cloned from the pituitary cDNA library of the orange-spotted grouper. The full-length cDNA of the orange-spotted grouper FTZ-F1 spanned 1735 bp including a poly (A) tail. The open reading frame encodes a protein of 468 amino acids. Sequence analysis indicated that it had a structure typical of the orphan nuclear receptor superfamily, and the FTZ-F1 box, a characteristic of the FTZ-F1 family. Phylogenetic analysis indicated that the orange-spotted grouper FTZ-F1 was closely related to medaka FTZ-F1 and did not belong to either the SF-1/Ad4BP group or the LRH-1/FTF group. Virtual Northern Blot detected a major transcript of about 1.7 kb and a minor transcript of 2.2 kb of FTZ-F1 in the orange-spotted grouper pituitary gland. The expression of FTZ-F1 homologue gene in different tissues and during embryonic development of the orange-spotted grouper was determined using one-step RT-PCR coupled with Southern blot analysis. In addition to the pituitary gland, the orange-spotted grouper FTZ-F1 was also expressed in the hypothalamus, forebrain, heart, liver, kidney, and ovary. The stronger signal from the gel image indicated that the expression level of FTZ-F1 homologue gene was higher in the ovary of stage 3 than stage 2. During embryonic development, mRNA for the orange-spotted grouper FTZ-F1 homologue was present in newly fertilized eggs, but disappeared in embryos at 50 min post fertilization. The orange-spotted grouper FTZ-F1 homologue mRNA reappeared in embryos at 1.5 hr post fertilization. Its expression level was increased from late blastula to neurula stages. Taken together, results of the current study suggest that the orange-spotted grouper FTZ-F1 homologue exhibits characteristics indicative of both the LRH-1/FTF- and the SF-1/Ad4BP-like genes, and may also play important roles in the hypothalamus-pituitary-gonadal axis, cholesterol metabolism, and embryogenesis.