Detección de mutaciones del gen de HNF1B en niños con malformaciones congénitas renales y del tracto urinario / Detection of mutations of the HNF1B gene in children with congenital anomalies of the kidney and urinary tract

Resumen: Introducción: Las anomalías congénitas del riñón y del tracto urinario se originan de alteraciones genéticas, en su mayoría desconocidas. Las mutaciones en el gen que codifica para el factor hepatocitario nuclear 1B (HNF1B), son la causa monogénica más frecuentemente descrita. Se desconocen datos en Chile y Latinoamérica. Objetivo: Determinar la presencia de variantes del gen HNF1B en niños chilenos con anomalías congénitas del riñón y/o tracto urinario y sus características clínicas. Pacientes y Mé todo: Estudio descriptivo con pacientes entre 10 meses y 17 años, consultantes en Unidad de Nefrología Hospital Luis Calvo Mackenna, período abril - diciembre 2016, portadores de displasia renal quística, displasia/hipoplasia renal no quística y/o riñón en herradura. Se determinaron variantes de HNF1B mediante secuenciación de exones 1, 2, 3 y 4; previa extracción y amplificación de DNA. Se utilizaron enzimas de restricción para definir si variantes eran homo o heterocigotas. Familiares di rectos de casos índices se estudiaron con secuenciación del exón afectado. Resultados: Se incluyeron 32 pacientes, 43,75% varones, mediana edad 11 años. El 65,6% displasia/hipoplasia renal no quística, 31,25% displasia renal quística y 3,15% riñón en herradura. En 2 pacientes (6,25%) se detectó una misma variante genética heterocigota en exón 4, posición 1027 (C1027T), no descrita anteriormente. El estudio de familiares determinó la variante en 3 de 5 individuos, todos sin anomalías nefrouro- lógicas congénitas. Conclusiones: Confirmamos la presencia de una variante genética heterocigota del gen HNF1B, no descrita previamente, dando inicio a la búsqueda de este tipo de mutaciones en nuestro medio, lo cual nos permite aproximarnos al conocimiento de causalidad, determinación de compromiso extrarrenal y consejo genético.

Abstract Introduction: Congenital anomalies of the kidney and urinary tract are caused by genetic alterations mostly unknown. Mutations in the gene that codes for hepatocyte nuclear factor 1B (HNF1B) are the most frequently described monogenic causes. Data are unknown in Chile and Latin America. Objective: To determine the presence of variants of the HNF1B gene in Chilean children with conge nital anomalies of the kidney and/or the urinary tract and their clinical characteristics. Patients and Method: Descriptive study with children aged 10 months to 17 years, patients of the Calvo Mackenna Hospital Nephrology Unit, with cystic renal dysplasia, non cystic renal dysplasia/hypoplasia, horses hoe kidney between April and December 2016. HNF1B variants were determined by sequencing of exons 1, 2, 3 and 4 after DNA extraction and amplification. Restriction enzymes were used to define if the variants were homo or heterozygous. Direct family members of index cases were studied with sequencing of the affected exon. Results: 32 patients were included, 43.75% males, median age 11 years. 65.6% of them had non-cystic renal dysplasia, 31.25% cystic renal dysplasia, and 3.15% hor seshoe kidney. In two patients (6.25%) the same heterozygous genetic variant was detected in exon 4, position 1027 (C1027T), not previously described. The study of relatives found the same variant in three out of five individuals, all without congenital nephro-urological anomalies. Conclusions: We confirmed the presence of a not previously described heterozygous genetic variant of the HNF1B gene. This work initiates the search for this type of mutations in our region which allows us to ap proach the knowledge of causality, determination of extrarenal involvement, and genetic counseling.

[Detection of mutations of the HNF1B gene in children with congenital anomalies of the kidney and urinary tract]. / Detección de mutaciones del gen de HNF1B en niños con malformaciones congénitas renales y del tracto urinario.

INTRODUCTION: Congenital anomalies of the kidney and urinary tract are caused by genetic alterations mostly unknown. Mutations in the gene that codes for hepatocyte nuclear factor 1B (HNF1B) are the most frequently described monogenic causes. Data are unknown in Chile and Latin America. OBJECTIVE: To determine the presence of variants of the HNF1B gene in Chilean children with conge nital anomalies of the kidney and/or the urinary tract and their clinical characteristics. PATIENTS AND METHOD: Descriptive study with children aged 10 months to 17 years, patients of the Calvo Mackenna Hospital Nephrology Unit, with cystic renal dysplasia, non cystic renal dysplasia/hypoplasia, horses hoe kidney between April and December 2016. HNF1B variants were determined by sequencing of exons 1, 2, 3 and 4 after DNA extraction and amplification. Restriction enzymes were used to define if the variants were homo or heterozygous. Direct family members of index cases were studied with sequencing of the affected exon. RESULTS: 32 patients were included, 43.75% males, median age 11 years. 65.6% of them had non-cystic renal dysplasia, 31.25% cystic renal dysplasia, and 3.15% hor seshoe kidney. In two patients (6.25%) the same heterozygous genetic variant was detected in exon 4, position 1027 (C1027T), not previously described. The study of relatives found the same variant in three out of five individuals, all without congenital nephro-urological anomalies. CONCLUSIONS: We confirmed the presence of a not previously described heterozygous genetic variant of the HNF1B gene. This work initiates the search for this type of mutations in our region which allows us to ap proach the knowledge of causality, determination of extrarenal involvement, and genetic counseling.