title: Aberrant mRNA splicing of paired box 4 (PAX4) IVS7-1G>A mutation causing maturity-onset diabetes of the young, type 9.
abstract: OBJECTIVE
  Paired box 4 (PAX4) mutations cause maturity-onset diabetes of the young, type 9 (MODY9). The molecular defect and alteration of PAX4 function associated with the mutation PAX4 IVS7-1G>A in a family with MODY9 and severe diabetic complications were studied.
  
  
  METHODS
  We investigated the functional consequences of PAX4 IVS7-1G>A on mRNA splicing using minigene assays. Wild-type and mutant PAX4 were expressed in mouse pancreatic β- and α-cell lines, and protein levels and translocation of PAX4 into the nucleus were determined. We also examined transcriptional repression of PAX4 target-gene promoters and β-cell viability under diabetic-like (high-glucose) conditions.
  
  
  RESULTS
  PAX4 IVS7-1G>A disrupts an acceptor splice site, causing an adjacent cryptic splice site within exon 8 to be used, resulting in a three-nucleotide deletion and glutamine deletion at position 250 (p.Q250del). Wild-type and PAX4 Q250del proteins were expressed at similar levels and could translocate normally into the nucleus in βTC3 and αTC1.9 cells. However, the repressor functions of PAX4 Q250del on human insulin and glucagon promoters in INS-1 832/13 and αTC1.9 cells were significantly decreased, compared with that of wild-type PAX4. Moreover, the rate of apoptosis was increased in INS-1 cells over-expressing PAX4 Q250del when cultured in high-glucose conditions.
  
  
  CONCLUSIONS
  PAX4 IVS7-1G>A caused aberrant mRNA splicing and PAX4 Q250 deletion. The mutation impaired PAX4 repressor functions on target-gene promoters and increased susceptibility to apoptosis upon high glucose exposure. Thus, PAX4 IVS7-1G>A contributes to the pathogenesis of diabetes in this MODY9 family through β-cell dysfunction.
authors.affiliation: Division of Molecular Medicine, Department of Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, 10700, Thailand.|Graduate Program in Immunology, Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, 10700, Thailand.
authors.forename: Jatuporn
authors.initials: J
authors.lastname: Sujjitjoon
authors.affiliation: Department of Physiology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, 10700, Thailand.
authors.forename: Suwattanee
authors.initials: S
authors.lastname: Kooptiwut
authors.affiliation: Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, 10700, Thailand.
authors.forename: Nalinee
authors.initials: N
authors.lastname: Chongjaroen
authors.affiliation: Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, 10700, Thailand.
authors.forename: Watip
authors.initials: W
authors.lastname: Tangjittipokin
authors.affiliation: Division of Endocrinology and Metabolism, Department of Medicine, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, 10700, Thailand. sinpv.natpl@gmail.com.
authors.forename: Nattachet
authors.initials: N
authors.lastname: Plengvidhya
authors.affiliation: Division of Molecular Medicine, Department of Research and Development, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, 10700, Thailand. ptyench@gmail.com.
authors.forename: Pa-Thai
authors.initials: PT
authors.lastname: Yenchitsomanus
mesh_terms: D000328:Adult; D017398:Alternative Splicing / Q000235:genetics*; D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics*; D005260:Female; D017353:Gene Deletion; D005947:Glucose / Q000494:pharmacology; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D050417:Insulin-Secreting Cells / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D009154:Mutation / Q000235:genetics; D051761:Paired Box Transcription Factors / Q000235:genetics*; D012097:Repressor Proteins / Q000187:drug effects; D014178:Translocation, Genetic
chemical_list: D018398:Homeodomain Proteins; C491709:PAX4 protein, human; D051761:Paired Box Transcription Factors; D012097:Repressor Proteins; D005947:Glucose
keywords: MODY; Minigene assay; PAX4; Splice site mutation; mRNA splicing defect; β-Cell survival