X-linked hypophosphatemia (XLH), the most common form of inherited rickets, is a dominant disorder that is characterized by renal phosphate wasting with hypophosphatemia, abnormal bone mineralization, short stature, and rachitic manifestations. The related gene with inactivating mutations associated with XLH has been identified as PHEX, which is a phosphate-regulating gene with homologies to endopeptidases on the X chromosome. In this study, a variety of PHEX mutations were identified in four Chinese families with XLH.
We investigated four unrelated Chinese families who exhibited typical features of XLH by using PCR to analyze mutations that were then sequenced. The laboratory and radiological investigations were conducted simultaneously.
Three novel mutations were found in these four families: one frameshift mutation, c.2033dupT in exon 20, resulting in p.T679H; one nonsense mutation, c.1294A>T in exon 11, resulting in p.K432X; and one missense mutation, c.2192T>C in exon 22, resulting in p.F731S.
We found that the PHEX gene mutations were responsible for XLH in these Chinese families. Our findings are useful for understanding the genetic basis of Chinese patients with XLH.
"Detailed medical and family histories were collected and recorded (Table 1). The diagnosis of familial HR was made based on positive family history of rickets, clinical manifestations, biochemical findings , and radiological evidence (Dixon et al., 1998; Gaucher et al., 2009; Kang et al., 2012). Blood samples were also collected from 100 unrelated ethnically-matched normal controls (male/female: 50/50; age 39.2 ± 8.3 years). "
[Show abstract][Hide abstract] ABSTRACT: Abstract Familial hypophosphatemic rickets (HR), the most common inherited form of rickets, is a group of inherited renal phosphate wasting disorders characterized by growth retardation, rickets with bone deformities, osteomalacia, poor dental development, and hypophosphatemia. The purpose of this study was to identify the genetic defect responsible for familial HR in a 4-generation Chinese Han pedigree by exome sequencing and Sanger sequencing. Clinical features include skeletal deformities, teeth abnormalities, hearing impairments and variable serum phosphate level in patients of this family. A novel deletion mutation, c.1553delT (p.F518Sfs*4), was identified in the X-linked phosphate regulating endopeptidase homolog gene (PHEX). The mutation is predicted to result in prematurely truncated and loss-of-function PHEX protein. Our data suggest that exome sequencing is a powerful tool to discover mutation(s) in HR, a disorder with genetic and clinical heterogeneity. The findings may also provide new insights into the cause and diagnosis of HR, and have implications for genetic counseling and clinical management.
"the mRNA Accession Number: NM_000444.5.). The PCR and sequencing primers were the same as we used in our previous study . All 22 exons and exon-intron boundaries in the PHEX gene were amplified by polymerase chain reaction (PCR). "
[Show abstract][Hide abstract] ABSTRACT: Objective
X-linked dominant hypophosphatemia (XLH) is the most prevalent form of inherited rickets/osteomalacia in humans. The aim of this study was to identify PHEX gene mutations and describe the clinical features observed in 6 unrelated Chinese families and 3 sporadic patients with hypophosphatemic rickets/osteomalacia.
For this study, 45 individuals from 9 unrelated families of Chinese Han ethnicity (including 16 patients and 29 normal phenotype subjects), and 250 healthy donors were recruited. All 22 exons and exon-intron boundaries of the PHEX gene were amplified by polymerase chain reaction (PCR) and directly sequenced.
The PHEX mutations were detected in 6 familial and 3 sporadic hypophosphatemic rickets/osteomalacia. Altogether, 2 novel mutations were detected: 1 missense mutation c.1183G>C in exon 11, resulting in p.Gly395Arg and 1 missense mutation c.1751A>C in exon 17, resulting in p.His584Pro. No mutations were found in the 250 healthy controls.
Our study increases knowledge of the PHEX gene mutation types and clinical phenotypes found in Chinese patients with XLH, which is important for understanding the genetic basis of XLH. The molecular diagnosis of a PHEX genetic mutation is of great importance for confirming the clinical diagnosis of XLH, conducting genetic counseling, and facilitating prenatal intervention, especially in the case of sporadic patients.
PLoS ONE 05/2014; 9(5):e97830. DOI:10.1371/journal.pone.0097830 · 3.23 Impact Factor
"Laboratory findings of the disease include low serum phosphorus levels, normal serum calcium levels, increased activity of serum alkaline phosphatases, normal or increased parathyroid hormone (PTH) levels, and inappropriately normal or decreased levels of 1,25-dihydroxyvitamin D35,6). The PHEX gene, located on Xp22.1, consists of 22 exons that translate into a 749 amino acid protein, which is a member of the peptidase M13 family of membrane-bound metalloproteases7,8). "
[Show abstract][Hide abstract] ABSTRACT: X-linked hypophosphatemia (XLH) is the most common form of familial hypophosphatemic rickets and it is caused by loss-of-function mutations in the PHEX gene. Recently, a wide variety of PHEX gene defects in XLH have been revealed; these include missense mutations, nonsense mutations, splice site mutations, insertions, and deletions. Recently, we encountered a 2-year-9-month-old female with sporadic hypophosphatemic rickets. She underwent osteotomy, dental abscess was evident, and there was severe bowing of the legs. A low serum phosphorus level in combination with elevated serum alkaline phosphatase activity and normal serum calcium is suggestive of hypophosphatemic rickets. PHEX gene analysis revealed a splice acceptor site mutation, c.934-1G>T (IVS8(-1)G>T), at the intron8 and exon9 junction. To the best of our knowledge, this mutation is novel and has not been reported. The results of this study expand and improve our understanding of the clinical and molecular characteristics and the global pool of patients with sporadic hypophosphatemic rickets.
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