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. Overall design: 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.