Global profiling of Nkx2.2 SD-domain mutant pancreas during development and adulthood compared to transcriptional profiling of SD-domain mutant expressing neural progenitors.

The consolidation of unambiguous cell fate commitment relies on the ability of transcription factors (TFs) to exert tissue-specific regulation of complex genetic networks. The mechanisms by which TFs establish such precise control over gene expression, however, have remained elusive—especially in instances where a single TF operates in two or more discrete cellular systems. In this study, we demonstrate that  cell specific functions of NKX2.2 are driven by the highly conserved NK2-Specific Domain (SD). Mutation of the endogenous NKX2.2 SD domain prevents the developmental progression of beta cell precursors into mature, insulin-expressing beta cells, resulting in overt neonatal diabetes. Within the adult beta cell, the SD domain stimulates beta cell performance through the activation and repression of a subset of NKX2.2-regulated transcripts critical for beta cell function. These irregularities in beta cell gene expression may be mediated via SD domain-contingent interactions with components of the nuclear pore complex. In stark contrast to these pancreatic phenotypes, however, the SD domain is entirely dispensable for the development of NKX2.2-dependent cell types within the CNS. Together, these results reveal a previously undetermined mechanism through which NKX2.2 directs disparate transcriptional programs in the pancreas vs. neuroepithelium. Examination of total RNA profiles of E15.5 pancreata of wildtype and Nkx2.2SDmut animals, of wildtype and beta-specific Nkx2.2SDmut adult islets, and of mouse ES cell-derived spinal motor neuron progenitors expressing a wildtype copy of Nkx2.2 tagged by FLAG under the control of a doxycycline (DOX) inducible promotor (iNkx2.2), an SD-domain mutant copy of Nkx2.2 tagged by FLAG under the control of a doxycycline (DOX) inducible promotor (iSDmut), or no Nkx2.2 (pMN). Examination of the global DNA binding profile of Nkx2.2 in MIN6 cells. 2-4 replicates are provided for all samples.