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Gene. 2019 Mar 20;689:227-234. doi: 10.1016/j.gene.2018.12.024. Epub 2018 Dec 18.

Characterization of two novel mutations in the claudin-16 and claudin-19 genes that cause familial hypomagnesemia with hypercalciuria and nephrocalcinosis.

Author information

1
Unidad de Investigacion, Hospital Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain.
2
Nefrologia Pediatrica, Hospital de Cruces, Baracaldo, Spain.
3
Paediatric Nephrology, M. Iashvili Childrens Hospital, Tbilisi, Georgia.
4
Nefrologia Pediatrica, Hospital Vall d' Hebron, Barcelona, Spain.
5
Unidad de Investigacion, Hospital Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain. Electronic address: fclamar@gobiernodecanarias.org.

Abstract

Familial hypomagnesemia with hypercalciuria and nephrocalcinosis is an autosomal-recessive renal tubular disorder characterized by excessive urinary losses of magnesium and calcium, bilateral nephrocalcinosis and progressive chronic renal failure in childhood or adolescence. The disease is caused by mutations in the tight-junction proteins claudin-16 and claudin-19 that are encoded by the CLDN16 and CLDN19 genes, respectively. Patients with CLDN19 mutations also are affected with severe ocular abnormalities. The aim of our study was to identify and characterize the molecular defects causing this disease in a Georgian girl and two Spanish siblings. Clinical and biochemical parameters were studied. The CLDN16 and CLDN19 genes were analyzed by DNA sequencing. The functional consequences of the identified mutations on pre-mRNA splicing were investigated using a minigene assay. Sequence analysis revealed that the patient from Georgia was homozygous for a novel mutation, c.602G > A; p.(G201E), in exon 4 of the CLDN16 gene. The two Spanish siblings were homozygous for a new CLDN19 mutation, c.388G > T; p.(G130C), located in exon 2, and both parents were heterozygous carriers of the mutation. Bioinformatics analysis predicted that the amino acid substitutions generated by these mutations were pathogenic. Functional studies showed that mutation c.388G > T also results in partial skipping of CLDN19 exon 2, which would imply significant alterations in the claudin-19 protein structure. Conversely, CLDN16 mutation c.602G > A had no effect on pre-mRNA splicing. Our study expands the genotypic classification of this rare disease and provides the first report of a CLDN19 mutation affecting splicing.

KEYWORDS:

CLDN16; CLDN19; Claudin; Exon skipping; Hypercalciuria; Hypomagnesemia; Minigene; Mutation; Nephrocalcinosis; Pre-mRNA splicing

PMID:
30576809
DOI:
10.1016/j.gene.2018.12.024
[Indexed for MEDLINE]

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