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Novel CYP27B1 Gene Mutations in Patients with Vitamin D-Dependent Rickets Type 1A.

ABSTRACT: The CYP27B1 gene encodes 25-hydroxyvitamin D-1?-hydroxylase. Mutations of this gene cause vitamin D-dependent rickets type 1A (VDDR-IA, OMIM 264700), which is a rare autosomal recessive disorder. To investigate CYP27B1 mutations, we studied 8 patients from 7 unrelated families. All coding exons and intron-exon boundaries of CYP27B1 gene were amplified by PCR from peripheral leukocyte DNA and subsequently sequenced. Homozygous mutations in the CYP27B1 gene were found in all the patients and heterozygous mutations were present in their normal parents. One novel single nucleotide variation (SNV, c.1215 T>C, p.R379R in the last nucleotide of exon 7) and three novel mutations were identified:, a splice donor site mutation (c.1215+2T>A) in intron 7, a 16-bp deletion in exon 6 (c.1022-1037del16), and a 2-bp deletion in exon 5 (c.934_935delAC). Both c.1215 T>C and c.1215+2T>A were present together in homozygous form in two unrelated patients, and caused exon 7 skipping. However, c.1215 T>C alone has no effect on pre-mRNA splicing. The skipping of exon 7 resulted in a shift of downstream reading frame and a premature stop codon 57 amino acids from L380 (p.L380Afs*57). The intra-exon deletions of c.1022-1037del16 and c.934_935delAC also resulted in a frameshift and the creation of premature stop codons at p.T341Rfs*5, and p.T312Rfs*19, respectively, leading to the functional inactivation of the CYP27B1 gene. Clinically, all the patients required continued calcitriol treatment and the clinical presentations were consistent with the complete loss of vitamin D1?-hydroxylase activity. In conclusion, three novel mutations have been identified. All of them caused frameshift and truncated proteins. The silent c.1215 T>C SNV has no effect on pre-mRNA splicing and it is likely a novel SNP. The current study further expands the CYP27B1 mutation spectrum.

SUBMITTER: Demir K

PROVIDER: S-EPMC4489500 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Novel CYP27B1 Gene Mutations in Patients with Vitamin D-Dependent Rickets Type 1A.

Demir Korcan K Kattan Walaa E WE Zou Minjing M Durmaz Erdem E BinEssa Huda H Nalbantoğlu Özlem Ö Al-Rijjal Roua A RA Meyer Brian B Özkan Behzat B Shi Yufei Y

PloS one 20150701 7

The CYP27B1 gene encodes 25-hydroxyvitamin D-1α-hydroxylase. Mutations of this gene cause vitamin D-dependent rickets type 1A (VDDR-IA, OMIM 264700), which is a rare autosomal recessive disorder. To investigate CYP27B1 mutations, we studied 8 patients from 7 unrelated families. All coding exons and intron-exon boundaries of CYP27B1 gene were amplified by PCR from peripheral leukocyte DNA and subsequently sequenced. Homozygous mutations in the CYP27B1 gene were found in all the patients and heter ...[more]

PMID: 26132292

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Project description:ContextVitamin D-dependent rickets type 1A (VDDR1A) is a rare autosomal recessively inherited disorder due to loss-of-function mutations in the CYP27B1 gene. CYP27B1 encodes an enzyme of 25-hydroxyvitamin D-1α-hydroxylase for converting inactive 25-OHD to biologically active 1,25-(OH)2D.ObjectiveTo identify underlying genetic defects in patients with VDDR1A.MethodsTwelve patients from 7 Turkish and 2 Saudi families were investigated. The coding exons and intron-exon boundaries of the CYP27B1 gene were amplified by Polymerase Chain Reaction (PCR) from peripheral lymphocyte DNA. PCR products were directly sequenced. The consequences of c.590G > A mutation were analyzed by in silico and functional analysis.ResultsCYP27B1 mutations were identified in all the patients. Two novel mutations were identified in two separate families: c.171delG (family 7) and c.398_400dupAAT (family 8). The intra-exon deletion of c.171delG resulted in a frameshift and premature stop codon 20 amino acids downstream from the mutation (p.L58Cfs∗20). The intra-exon duplication of c.398_400dupAAT generated a premature stop codon at the mutation site (p.W134∗). A missense c.590G > A (p.G197D) mutation was found in a patient from family 4 and caused a defect in pre-mRNA splicing. As a result, two populations of transcripts were detected: the majority of them with intron 3 retention (83%), and the minority (17%) being properly spliced transcripts with about 16% of wild-type enzymatic activity. The remaining nine patients from six families carried a previously reported c.1319_1325dupCCCACCC (F443Pfs∗24) mutation. Clinically, all the patients need continued calcitriol treatment, which was consistent with inactivation of 25-hydroxy vitamin D1α-hydroxylase activity.ConclusionTwo novel frameshift CYP27B1 mutations were identified and predicted to inactivate 25-hydroxyvitamin D-1α-hydroxylase. The loss of enzymatic activity by c.590G > A missense mutation was mainly caused by aberrant pre-mRNA splicing.

Dataset Information

Novel CYP27B1 Gene Mutations in Patients with Vitamin D-Dependent Rickets Type 1A.

Publications

Novel CYP27B1 Gene Mutations in Patients with Vitamin D-Dependent Rickets Type 1A.

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