title: Identification and functional analysis of c.422_423InsT, a novel mutation of theHNF1Agene in a patient with diabetes.
abstract: BACKGROUND
  HNF1Agene regulates liver-specific genes, and genes that have a role in glucose metabolism, transport, and secretion of insulin.HNF1Agene mutations are frequently associated with type 2 diabetes. HNF1A protein has three domains: the dimerization domain, the DNA-binding domain, and the trans-activation domain. Some mutations in the dimerization or DNA-binding domains have no influence on the normal allele, while others have dominant negative effects. The I27L, A98V, and S487N polymorphisms are common variants of theHNF1Agene; they have been found in T2D and non-diabetic subjects.
  
  
  RESULTS
  We searched for mutations in the first three exons of theHNF1Agen in an Amerindian population of 71 diabetic patients. DNA sequencing revealed the previously reported I27L polymorphism (c.79A>C) in 53% of diabetic patients and in 67% of the control group. Thus, the I27L/L27L polymorphism might be a marker of Amerindians. In addition, we found the c.422_423InsT mutation in theHNF1Agene of one patient, which had not been previously reported. This mutation resulted in a frame shift of the open reading frame and a new translation stop in codon 187, leading to a truncated polypeptide of 186 amino acids (Q141Hfs*47). This novel mutation affects the DNA-binding capacity of the mutant HNF1A protein by EMSA; its intracellular localization by fluorescence and confocal microscopy, and a dominant-negative effect affecting the DNA-binding capacity of the normal HNF1A by EMSA. We also studied the homology modeling structure to understand the effect of this mutation on its DNA-binding capacity and its dominant negative effect.
  
  
  CONCLUSIONS
  The HNF1A Q141Hfs*47 mutant polypeptide has no DNA-binding capacity and exerts a dominant negative effect on the HNF1A protein. Therefore, it might produce severe phenotypic effects on the expression levels of a set ofβ-cell genes. Consequently, its screening should be included in the genetic analysis of diabetic patients after more functional studies are performed.
authors.affiliation: Centro de Investigación y Posgrado Laboratorio de Diagnóstico Molecular División Académica de Ciencias de la Salud (DACS) Universidad Juárez Autónoma de Tabasco (UJAT) Ave. Gregorio Méndez Magaña. No 2838-A, Col. Tamulté de las Barrancas Villahermosa C.P. 86150 México.
authors.forename: Jesús Miguel
authors.initials: JM
authors.lastname: Magaña-Cerino
authors.affiliation: Departamento de Biología Celular Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN) Ave. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco Ciudad de México C.P. 07360 México.
authors.forename: Juan P
authors.initials: JP
authors.lastname: Luna-Arias
authors.affiliation: Departamento de Biología Celular Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN) Ave. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco Ciudad de México C.P. 07360 México.
authors.forename: María Luisa
authors.initials: ML
authors.lastname: Labra-Barrios
authors.affiliation: Departamento de Biología Celular Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV-IPN) Ave. Instituto Politécnico Nacional 2508, Col. San Pedro Zacatenco Ciudad de México C.P. 07360 México.
authors.forename: Bartolo
authors.initials: B
authors.lastname: Avendaño-Borromeo
authors.affiliation: Centro de Investigación y Posgrado Laboratorio de Diagnóstico Molecular División Académica de Ciencias de la Salud (DACS) Universidad Juárez Autónoma de Tabasco (UJAT) Ave. Gregorio Méndez Magaña. No 2838-A, Col. Tamulté de las Barrancas Villahermosa C.P. 86150 México.
authors.forename: Xavier Miguel
authors.initials: XM
authors.lastname: Boldo-León
authors.affiliation: Centro de Investigación y Posgrado Laboratorio de Diagnóstico Molecular División Académica de Ciencias de la Salud (DACS) Universidad Juárez Autónoma de Tabasco (UJAT) Ave. Gregorio Méndez Magaña. No 2838-A, Col. Tamulté de las Barrancas Villahermosa C.P. 86150 México.
authors.forename: Mirian Carolina
authors.initials: MC
authors.lastname: Martínez-López
keywords: Dominant‐negative effect; HNF1A; I27L; MODY3; Q141Hfs*47