Dimorphic regulation of the MafB gene by sex steroids in hamsters (Mesocricetus auratus)

Background MafB is a transcription factor that regulates macrophage differentiation. Macrophages are a traditional feature of the hamster Harderian gland (HG); however, studies pertaining to MafB expression in the HG are scant. Here, I cloned and sequenced the full-length cDNA of the MafB gene in adult hamsters. Results Molecular characterization revealed that MafB encodes a protein containing 323 amino acids with a DNA-binding domain, a transactivation domain, and a leucine zipper domain. Bioinformatic analysis of the hamster MafB sequence demonstrated 98% consistency with the mammalian group, and quantitative real-time polymerase chain reaction assays indicated that MafB was expressed in different tissues of both sexes. The highest expression levels in endocrine tissues were identified in the pancreas. Gonadectomy in male hamsters was correlated with significantly higher mRNA levels in the HG; replacement with dihydrotestosterone (DHT) restored mRNA expression. The HG in male hamsters contained two-fold more MafB mRNA than the HG of female hamsters. Adrenals revealed similar mRNA expression levels during the estrous cycle. The estrous phase was correlated with higher mRNA levels in the ovary. Significantly up-regulated expression and sexual dimorphism of MafB was found in the pancreas. Conclusions MafB in the HG may play an active role in the macrophage differentiation required for phagocytosis activity and intraocular repair. Additionally, sex steroids appear to strongly influence the HG and MafB in the pancreas.