Characterization and functional evaluation of goat PDX1 regulatory modules through comparative analysis of conserved interspecies homologs

PDX1 is a crucial transcription factor in pancreas development and mature β-cell function. However, the regulation of PDX1 expression in larger animals mirroring human pancreas morphogenesis and endocrine maturation remains poorly understood. Therefore, we conducted a comparative analysis to characterize regulatory regions of goat PDX1 gene and assessed their transcriptional activity by transient transfection of several transgenic EGFP constructs in β- and non-β cell lines. We recognized several highly conserved regions encompassing the promoter and cis-regulatory elements (Area I-IV) at 5’ flanking sequence of the genes. Within the promoter, we identified that a key E-box and nearby CAAT element synergistically drive transcription, constituting the basal promoter of goat PDX1 gene. Furthermore, each recognized regulatory area separately enhances this basal promoter activity in β-cells compared to non-β cells; however, cooperatively, they exhibit a bifunctional regulatory effect on transcription. Additionally, the intact ~ 3 kb upstream region (Area I-III) functions as the most efficient reporter transgene in vitro and shows islet-specific expression in native rat pancreas. Together, our findings suggest that the regulation of goat PDX1 gene is governed by conserved regions similar to other mammals, while both structurally and functionally, these regions exhibit a closer resemblance to those found in humans.