Identification of a regulatory domain controlling the Nppa-Nppb gene cluster during heart development and stress.

The paralogous genes Nppa and Nppb are organized in an evolutionary conserved cluster and are a valuable model to study coregulation and regulatory landscape organization during heart development and disease. Here, we analyzed the chromatin conformation, epigenetic status and enhancer potential of sequences of the Nppa-Nppb cluster in vivo . Our data indicate that the regulatory landscape of the cluster is present within a 60 kbp domain centered around Nppb . Both promoters and several potential regulatory elements interact with each other in a similar manner in different tissues and developmental stages. The distribution of H3K27ac and the association of Pol2 across the locus changed during cardiac hypertrophy, revealing their potential involvement in stress-mediated gene regulation. Functional analysis of double reporter transgenic mice revealed that Nppa and Nppb share developmental, but not stress-response enhancers, responsible for their co-regulation. Moreover, the Nppb promoter was required, but not sufficient, for hypertrophy-induced Nppa expression. In summary, the developmental regulation and stress-response of the Nppa-Nppb cluster involve the concerted action of multiple enhancers and epigenetic changes distributed across a structurally rigid regulatory domain.