title: Novel Compound Heterozygous Mutations in the CYP27B1 Gene Lead to Pseudovitamin D-Deficient Rickets.
abstract: Pseudovitamin D deficiency is the consequence of a genetic defect in the CYP27B1 gene resulting in diminished or absent conversion of 25-hydroxyvitamin D3 (25-(OH)D3) into 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3) and leads to growth retardation and rickets, usually in the first 2 years of life. DNA obtained from human leucocytes from a patient suspected of pseudovitamin D deficiency and her healthy parents was sequenced for a genetic defect in the CYP27B1 gene. In silico analyses on the mutations were performed using online available software. The 1α-hydroxylase activity of the patient, her parents, and a sample derived from a mixed buffy coat of healthy blood donors was measured by culturing peripheral blood mononuclear cells with 25-(OH)D3 and measuring 1,25-(OH)2D3 production. DNA sequencing of the patient suspected of pseudovitamin D deficiency revealed compound heterozygosity in the CYP27B1 gene for a (c413G>T) mutation in exon 3 (R138L) and a (c1232G>A) mutation in exon 8 (C411Y). In silico analyses confirmed that mutations at these positions are probably damaging for the protein since the amino acids are situated in a highly conserved region. In vitro analyses showed a nearly absent 1α-hydroxylase activity in the patient compared to the healthy blood donors. Her healthy parents each of whom carried one of the mutations also had compromised conversion of 25-(OH)D3 into 1,25-(OH)2D3 in peripheral blood mononuclear cells, being only marginally higher than in the patient. We discovered novel compound heterozygous mutations in the CYP27B1 gene in a young girl presenting with pseudovitamin D-deficient rickets, leading to severely decreased 1,25-(OH)2D3 production. Furthermore, both heterozygous parents showed a diminished 1α-hydroxylase activity.
authors.affiliation: Department of Internal Medicine, Erasmus MC, Po. Box 2040, 3000 CA, Rotterdam, The Netherlands.
authors.forename: W Nadia H
authors.initials: WN
authors.lastname: Koek
authors.affiliation: Department of Internal Medicine, Erasmus MC, Po. Box 2040, 3000 CA, Rotterdam, The Netherlands. m.c.zillikens@erasmusmc.nl.
authors.forename: M Carola
authors.initials: MC
authors.lastname: Zillikens
authors.affiliation: Department of Internal Medicine, Erasmus MC, Po. Box 2040, 3000 CA, Rotterdam, The Netherlands.
authors.forename: Bram C J
authors.initials: BC
authors.lastname: van der Eerden
authors.affiliation: Department of Internal Medicine, Erasmus MC, Po. Box 2040, 3000 CA, Rotterdam, The Netherlands.
authors.forename: Johannes P T M
authors.initials: JP
authors.lastname: van Leeuwen
mesh_terms: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence / Q000235:genetics; D005091:Exons / Q000235:genetics; D005260:Female; D006579:Heterozygote; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D014808:Vitamin D Deficiency / Q000097:blood / Q000235:genetics*
chemical_list: D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase
keywords: 1α-hydroxylase; CYP27B1 pseudovitamin D deficiency; Peripheral blood mononuclear cells