High resolution methylation analysis of the HoxA5 regulatory region in different somatic tissues of laboratory mouse during development.

Homeobox genes encode a group of DNA binding regulatory proteins whose key function occurs in the spatial-temporal organization of genome during embryonic development and differentiation. The role of these Hox genes during ontogenesis makes it an important model for research. HoxA5 is a member of Hox gene family playing a central role during axial body patterning and morphogenesis. DNA modification studies have shown that the function of Hox genes is partly governed by the methylation-mediated gene expression regulation. Therefore the study aimed to investigate the role of epigenetic events in regulation of tissue-specific expression pattern of HoxA5 gene during mammalian development. The methodology adopted were sodium bisulfite genomic DNA sequencing, quantitative real-time PCR and chromatin-immunoprecipitation (ChIP). Methylation profiling of HoxA5 gene promoter shows higher methylation in adult as compared to fetus in various somatic tissues of mouse being highest in adult spleen. However q-PCR results show higher expression during fetal stages being highest in fetal intestine followed by brain, liver and spleen. These results clearly indicate a strict correlation between DNA methylation and tissue-specific gene expression. The findings of chromatin-immunoprecipitation (ChIP) have also reinforced that epigenetic event like DNA methylation plays important role in the regulation of tissue specific expression of HoxA5.