title: The transcription factors Nkx6.1 and Nkx6.2 possess equivalent activities in promoting beta-cell fate specification in Pdx1+ pancreatic progenitor cells.
abstract: Despite much progress in identifying transcriptional regulators that control the specification of the different pancreatic endocrine cell types, the spatiotemporal aspects of endocrine subtype specification have remained largely elusive. Here, we address the mechanism by which the transcription factors Nkx6.1 (Nkx6-1) and Nkx6.2 (Nkx6-2) orchestrate development of the endocrine alpha- and beta-cell lineages. Specifically, we assayed for the rescue of insulin-producing beta-cells in Nkx6.1 mutant mice upon restoring Nkx6 activity in select progenitor cell populations with different Nkx6-expressing transgenes. Beta-cell formation and maturation was restored when Nkx6.1 was expressed in multipotential Pdx1(+) pancreatic progenitors, whereas no rescue was observed upon expression in committed Ngn3(+) (Neurog3(+)) endocrine progenitors. Although not excluding additional roles downstream of Ngn3, this finding suggests a first requirement for Nkx6.1 in specifying beta-cell progenitors prior to Ngn3 activation. Surprisingly, although Nkx6.2 only compensates for Nkx6.1 in alpha-but not in beta-cell development in Nkx6.1(-/-) mice, a Pdx1-promoter-driven Nkx6.2 transgene had the same ability to rescue beta-cells as the Pdx1-Nkx6.1 transgene. This demonstrates that the distinct requirements for Nkx6.1 and Nkx6.2 in endocrine differentiation are a consequence of their divergent spatiotemporal expression domains rather than their biochemical activities and implies that both Nkx6.1 and Nkx6.2 possess alpha- and beta-cell-specifying activities.
authors.affiliation: Department of Developmental and Cell Biology, University of California at Irvine, 4203 McGaugh Hall, Irvine, CA 92697-2300, USA.
authors.forename: Shelley B
authors.initials: SB
authors.lastname: Nelson
authors.forename: Ashleigh E
authors.initials: AE
authors.lastname: Schaffer
authors.forename: Maike
authors.initials: M
authors.lastname: Sander
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D015415:Biomarkers; D002454:Cell Differentiation; D004268:DNA-Binding Proteins / Q000378:metabolism; D004622:Embryo, Mammalian / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010179:Pancreas / Q000166:cytology* / Q000378:metabolism*; D013234:Stem Cells / Q000166:cytology* / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D015415:Biomarkers; D004268:DNA-Binding Proteins; D018398:Homeodomain Proteins; D007328:Insulin; D009419:Nerve Tissue Proteins; D015534:Trans-Activators; D014157:Transcription Factors; C489726:Myt1 protein, mouse; C407737:Neurog3 protein, mouse; C491328:Nkx6-1 protein, mouse; C117745:Nkx6-2 protein, mouse; C084010:pancreatic and duodenal homeobox 1 protein