title: Novel CYP27B1 Gene Mutations in Patients with Vitamin D-Dependent Rickets Type 1A.
abstract: 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 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 D1α-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.
authors.affiliation: Division of Pediatric Endocrinology, Dr. Behçet Uz Children's Hospital, İzmir, Turkey.
authors.forename: Korcan
authors.initials: K
authors.lastname: Demir
authors.affiliation: College of Science and General Studies, Alfaisal University, Riyadh, Saudi Arabia; Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia.
authors.forename: Walaa E
authors.initials: WE
authors.lastname: Kattan
authors.affiliation: Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia.
authors.forename: Minjing
authors.initials: M
authors.lastname: Zou
authors.affiliation: Department of Pediatric Endocrinology, Sifa University, Bornova Health Application and Research Center, İzmir, Turkey.
authors.forename: Erdem
authors.initials: E
authors.lastname: Durmaz
authors.affiliation: Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia.
authors.forename: Huda
authors.initials: H
authors.lastname: BinEssa
authors.affiliation: Division of Pediatric Endocrinology, Dr. Behçet Uz Children's Hospital, İzmir, Turkey.
authors.forename: Özlem
authors.initials: Ö
authors.lastname: Nalbantoğlu
authors.affiliation: Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia.
authors.forename: Roua A
authors.initials: RA
authors.lastname: Al-Rijjal
authors.affiliation: Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia.
authors.forename: Brian
authors.initials: B
authors.lastname: Meyer
authors.affiliation: Division of Pediatric Endocrinology, Dr. Behçet Uz Children's Hospital, İzmir, Turkey.
authors.forename: Behzat
authors.initials: B
authors.lastname: Özkan
authors.affiliation: Department of Genetics, King Faisal Specialist Hospital & Research Centre, Riyadh, Saudi Arabia.
authors.forename: Yufei
authors.initials: Y
authors.lastname: Shi
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000235:genetics*; D002648:Child; D002675:Child, Preschool; D005091:Exons; D053098:Familial Hypophosphatemic Rickets / Q000235:genetics*; D005260:Female; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D007223:Infant; D007438:Introns; D008297:Male; D009154:Mutation; D016133:Polymerase Chain Reaction; D020641:Polymorphism, Single Nucleotide; D017384:Sequence Deletion
chemical_list: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; C000600378:CYP27B1 protein, human