Chicken LRH-1 gene is transcribed from multiple promoters in steroidogenic organs

Liver receptor homolog-1 (LRH-1) is a homolog of FTZ-F1, a transcription factor of the fruit fly, and belongs to the orphan nuclear receptor family. LRH-1 is expressed in organs derived from the endoderm, including intestine, liver and exocrine pancreas and plays a predominant role in development, bile-acid homeostasis, and reverse cholesterol transport. Recent research has revealed that mammalian LRH-1 is also expressed in the steroidogenic organs and has suggested that LRH-1 shares a role in steroidogenesis with steroidogenic factor-1 (SF-1), which is a paralog of LRH-1. In this study, we determined transcription initiation sites of chicken LRH-1 and showed that LRH-1 is expressed as several splicing variants in chicken steroidogenic organs. From three steroidogenic organs, the adrenal glands, ovaries, and testes, several cDNA fragments including different lengths and sequences were amplified by 5′-RACE and these were mainly classified into five types. Using these sequences, chicken genomic database was searched and four types of first exons were identified in chromosome 8. However, the database sequence of these regions included several gaps. So we cloned gap regions by PCR cloning from chicken genomic DNA and found the other type of first exons in the gaps. Moreover, RT-PCR showed the expression of LRH-1 in chicken steroidogenic organs as many splicing variants. We concluded that the chicken LRH-1 gene is transcribed from at least five different transcription initiation sites and alternative splicing produces several types of mRNA in steroidogenic organs.