Human Ad4BP/SF-1 and its related nuclear receptor

Embryological and molecular development of the adrenal glands

In this mini review, the embryological and functional development of the adrenal glands is presented from a molecular perspective. While acknowledging that this is a highly complex series of events, the processes are described in simple and broad strokes in a single text for the reader who is interested in this field but is not an active researcher. The origin of the adrenal glands is in the mesodermal ridge as early as the fourth week of gestation. Between the eighth and ninth weeks of gestation, the adrenal glands are encapsulated and this results in the presence of a distinct organ. There have been great strides in deciphering the very complicated molecular aspects of adrenal gland development in which multiple transcription factors have been identified, directing the adrenogonadal primordium into the adrenal cortex, kidney, or bipotential gonad. Adrenocorticotrophic hormone is critical for early development of the hypothalamic-pituitary adrenal axis. Several mutations in transcription factors, responsible for normal adrenal gland development have been found to induce the familial syndrome of congenital adrenal hypoplasia or neoplasia.

Sexually dimorphic expression of steroidogenic factor 1 (SF-1) in developing gonads of the American bullfrog, Rana catesbeiana

Genetic sex determination leads to gonadal differentiation and ultimately the differences between the sexes in steroid hormone secretion. Gonadal steroidogenesis is critical for the development of a sexually dimorphic phenotype and adult reproductive function. Control of gonadal development and steroidogenesis is under the regulation, at least in part, of steroidogenic factor-1 (SF-1). We have begun to characterize SF-1 expression in an amphibian to determine the role of this protein in development and reproduction. We have detected a putative SF-1 protein from several tissues in the American bullfrog, Rana catesbeiana, that co-migrates with mouse SF-1 on a Western blot. Our results show that bullfrog SF-1 protein is expressed in steroidogenic and other reproductive tissues in a manner similar to that reported for other species, with high expression in the brain, pituitary, gonad, liver, and interrenal, but little or no expression in non-reproductive tissues such as skin and intestine. Using a quantitative Western blot analysis system, we documented changes in SF-1 protein in the gonads of developing tadpoles. Our results indicate that there is sexually dimorphic expression of SF-1 protein that becomes evident at the time of sexual differentiation of the gonads. In males, the expression of SF-1 decreases following testicular formation and in females the expression increases with the formation of ovaries. This is the first study to investigate changes in SF-1 during development at the protein level. The expression is similar to that reported for changes in SF-1 mRNA expression in chickens and alligators, however, opposite to that seen in mammals and turtles. These results indicate that SF-1 may play a pivotal role in development of the reproductive system in amphibians as it does in other vertebrate groups.

The mouse fetoprotein transcription factor (FTF) gene promoter is regulated by three GATA elements with tandem E box and Nkx motifs, and FTF in turn activates the Hnf3beta, Hnf4alpha, and Hnf1alpha gene promoters

Fetoprotein transcription factor (FTF) is an orphan nuclear receptor that activates the alpha(1)-fetoprotein gene during early liver developmental growth. Here we sought to define better the position of FTF in transcriptional cascades leading to hepatic differentiation. The mouse FTF gene was isolated and assigned to chromosome 1 band E4 (one mFTF pseudogene was also found). Exon/intron mapping shows an mFTF gene structure similar to that of its close homologue SF1, with two more N-terminal exons in the mFTF gene; exon mapping also delimits several FTF mRNA 5'- and 3'-splice variants. The mFTF transcription initiation site was located in adult liver at 238 nucleotides from the first translation initiator codon, with six canonical GATA, E box, and Nkx motifs clustered between -50/-140 base pairs (bp) from the cap site; DNA/protein binding assays also pinpointed an HNF4-binding element at +36 bp and an FTF-binding element at -257 bp. Transfection assays and point mutations showed that the mFTF promoter is activated by GATA, HNF4alpha, FTF, Nkx, and basic helix-loop-helix factors, with marked cooperativity between GATA and HNF4alpha. A tandem GATA/E box activatory motif in the proximal mFTF promoter is strikingly similar to a composite motif coactivated by differentiation inducers in the hematopoietic lineage; a tandem GATA-Nkx motif in the distal mFTF promoter is also similar to a composite motif transducing differentiation signals from transforming growth factor-beta-like receptors in the cardiogenic lineage. Three genes encoding transcription factors critical to early hepatic differentiation, Hnf3beta, Hnf4alpha, and Hnf1alpha, each contain dual FTF-binding elements in their proximal promoters, and all three promoters are activated by FTF in transfection assays. Direct DNA binding action and cooperativity was demonstrated between FTF and HNF3beta on the Hnf3beta promoter and between FTF and HNF4alpha on the Hnf1alpha promoter. These combined results suggest that FTF is an early intermediary between endodermal specification signals and downstream genes that establish and amplify the hepatic phenotype.