Mutational analysis of PHEX, FGF-23, and DMP-1 genes in 4 families patients with familial hypophosphatemic vitamin D resistant rickets

Abstract

Objective To evaluate the frequency of mutations that occur in PHEX, FGF-23 and DMP-1 genes associated with familial hypophosphatemic vitamin D resistant rickets among 6 patients from 4 families in China. Methods The peripheral blood samples from 4 families were collected and other 10 persons from different families were selected as normal controls, and then the total gene DNA was extracted from the whole blood.Using polymerase chain reaction(PCR) amplication, sequences of the exons and flanking zones in PHEX, FGF-23 and DMP-1 genes were sequenced by direct DNA sequencing and TA cloning, and then the mutations found were analyzed. Results In exon 6 of DMP-1 gene, c1218 C>T and c1230 G>A mutations were detected in lineage 1, as same sense mutation(propositus and its sister: homozygous mutation; mother: heterozygous mutation); c1333-1334 GC>TT mutation, as missense mutation, was found in exon 12 of PHEX gene on the propositus of lineage 2, determined as heterozygous mutation, but the same mutation was not found from their parents.In exon 3 of FGF-23 gene, c716 C>T, p.T239M heterozygous mutation was found on the propositus and its mother.In exon 6 of the DMP-1 gene, c205 A>T homozygous mutation was detected in lineage 3.In lineage 3, c716 C>T mutation of the FGF-23 gene was detected, and the propositus and their father had the same mutation.No disease causing mutations of the PHEX, FGF-23 and DMP-1 genes were detected in the family members of lineage 1, 3 and 4. Conclusions The mutation c1333-1334 GC>TT detected in exon 12 of PHEX gene might be the cause of disease for the propositus of lineage 2, as missense mutation, which needs further verification; c716 C>T, p.T239M mutation of the FGF-23 gene detected in lineage 2 and 3 might not be the causes of the hypophosphatemic rickets and abnormal phenotype. Key words: Familial hypophosphatemic vitamin D resistant rickets; PHEX gene; FGF-23 gene; DMP-1 gene