Cloning of androgen-inducible gene 1 (AIG1) from human dermal papilla cells.

Cultured human dermal papilla cells are useful for studying the androgen-dependent growth of hair follicles. We cloned the human homolog of FAR-17a, a gene identified from the hamster flank organ as one of the androgen inducible genes, by degenerative PCR and human dermal papilla cDNA library screening. We isolated a novel cDNA clone, designated as AIG1 (Androgen-inducible Gene 1), whose expression was found to be inducible by androgen. AIG1 cDNA consists of 1,398 nucleotides in length, which encodes a protein of 238 amino acids (27 kDa). The deduced protein sequence showed 35% overall homology with FAR-17a. RT-PCR of human dermal papilla cDNA revealed two mRNA transcripts, which differed by 156 nucleotides. This results in an in-frame deletion of 52 amino acids. A computer analysis of hydropathy indicated five hydrophobic domains are present in the large protein sequence, while four hydrophobic portions are in the smaller protein sequence. In a Northern blot analysis, the major 1.5 kb and minor 1.2 kb bands of AIG1 mRNA were detected. AIG1 mRNA was expressed at a relatively high level in the heart, ovary, testis, liver, and kidney. However, they were expressed at a low level in the spleen, prostate, brain, skeletal muscle, pancreas, small intestine, and colon. When dermal sheath cells were stimulated with DHT, the level of AIG1 mRNA expression was increased at 30 ng/ml. The level of expression was higher in males than females. In this study, we cloned and initially characterized AIG1. Further study will be needed to understand the functions of AIG1 in the androgen-regulated hair cycle.