title: The functional role of the Meis/Prep-binding elements in Pax6 locus during pancreas and eye development.
abstract: Pax6 is an essential transcription factor for lens, lacrimal gland and pancreas development. Previous transgenic analyses have identified several Pax6 regulatory elements, but their functional significance and binding factors remain largely unknown. In this study, we generated two genomic truncations to delete three elements that were previously shown to bind to the Meis/Prep family homeoproteins. One 3.1 kb deletion (Pax6(∆DP/∆DP)) removed two putative pancreatic enhancers and a previously identified ectodermal enhancer, while a 450 bp sub-deletion (Pax6(∆PE/∆PE)) eliminated only the promoter-proximal pancreatic enhancer. Immunohistochemistry and quantitative RT-PCR showed that the Pax6(∆PE/∆PE) pancreata had a significant decrease in Pax6, glucagon, and insulin expression, while no further reductions were observed in the Pax6(∆DP/∆DP) mice, indicating that only the 450 bp region is required for pancreatic development. In contrast, Pax6(∆DP/∆DP), but not Pax6(∆PE/∆PE) mice, developed stunted lacrimal gland and lens hypoplasia which was significantly more severe than that reported when only the ectodermal enhancer was deleted. This result suggested that the ectodermal enhancer must cooperate with its neighboring sequences to regulate the Pax6 ectodermal expression. Finally, we generated conditional knockouts of Prep1 in the lens and pancreas, but surprisingly, did not observe any developmental defects. Together, these results provide functional evidence for the independent and synergistic roles of the Pax6 upstream enhancers, and they suggest the potential redundancy of Meis/Prep protein in Pax6 regulation.
authors.affiliation: Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Carbe
authors.forename: Kristina
authors.initials: K
authors.lastname: Hertzler-Schaefer
authors.forename: Xin
authors.initials: X
authors.lastname: Zhang
mesh_terms: D000818:Animals; D001665:Binding Sites / Q000235:genetics / Q000502:physiology; D015153:Blotting, Western; D004622:Embryo, Mammalian / Q000196:embryology / Q000378:metabolism; D004742:Enhancer Elements, Genetic / Q000235:genetics* / Q000502:physiology; D005123:Eye / Q000196:embryology / Q000378:metabolism*; D005136:Eye Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D007765:Lacrimal Apparatus / Q000196:embryology / Q000378:metabolism; D007908:Lens, Crystalline / Q000196:embryology / Q000378:metabolism; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors / Q000235:genetics* / Q000378:metabolism; D010179:Pancreas / Q000196:embryology / Q000378:metabolism*; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D005136:Eye Proteins; D018398:Homeodomain Proteins; D000075064:Myeloid Ecotropic Viral Integration Site 1 Protein; D009363:Neoplasm Proteins; D000071841:PAX6 Transcription Factor; D051761:Paired Box Transcription Factors; C000605732:Pax6 protein, mouse; C491412:Pknox1 protein, mouse; D012097:Repressor Proteins