A Girl with a Novel Splice Site Mutation in  VDR  Supports the Role of a Ligand-Independent VDR Function on Hair Cycling

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Abstract

Mutations in vitamin D receptor ( VDR) cause hereditary vitamin D resistant rickets (HVDRR). We reported a Thai girl with HVDRR, presenting with an early onset of rickets and partial alopecia. She was a product of a consanguineous couple. Mutation analysis showed that she was homozygous for a novel splice site mutation of the VDR gene, 462 + 1 G → C, resulting in incorporation of the whole 254 bp of the intron 4 into its mRNA. The mutated protein is expected to contain no ligand-binding domain. The fact that she did not develop total alopecia despite of no VDR ligand-binding domain supports that VDR function on hair cycling is ligand independent.

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Most cited references 13

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Ligand-independent actions of the vitamin D receptor maintain hair follicle homeostasis.

D R Dowd, Marie Demay, N Macdonald … (2005)

Alopecia is a feature of vitamin D receptor (VDR) mutations in humans and in VDR null mice. This alopecia results from an inability to initiate the anagen phase of the hair cycle after follicle morphogenesis is complete. Thus, once the initial hair is shed it does not regrow. VDR expression in the epidermal component of the hair follicle, the keratinocyte, is critical for maintenance of the hair cycle. To determine which functional domains of the VDR are required for hair cycling, mutant VDR transgenes were targeted to the keratinocytes of VDR null mice. Keratinocyte-specific expression of a VDR transgene with a mutation in the hormone-binding domain that abolishes ligand binding restores normal hair cycling in VDR null mice, whereas a VDR transgene with a mutation in the activation function 2 domain that impairs nuclear receptor coactivator recruitment results in a partial rescue. Mutations in the nuclear receptor corepressor Hairless are also associated with alopecia in humans and mice. Hairless binds the VDR, resulting in transcriptional repression. Neither VDR mutation affects Hairless interactions or its ability to repress transcription. These studies demonstrate that the effects of the VDR on the hair follicle are ligand independent and point to novel molecular and cellular actions of this nuclear receptor.

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Metabolic and cellular analysis of alopecia in vitamin D receptor knockout mice.

Y. Sakai, J Kishimoto, M B Demay (2001)

Targeted ablation of the vitamin D receptor (VDR) results in hypocalcemia, hypophosphatemia, hyperparathyroidism, rickets, osteomalacia, and alopecia--the last a consequence of defective anagen initiation. To investigate whether the markedly elevated levels of 1,25-dihydroxyvitamin D led to the alopecia, we raised VDR-null mice in a ultraviolet light-free environment and fed them chow lacking vitamin D for five generations. Despite undetectable circulating levels of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D, alopecia persisted in the VDR-null mice, demonstrating that the alopecia was not secondary to toxic levels of 1,25-dihydroxyvitamin D interacting with an alternative receptor. Furthermore, alopecia was not seen in control littermates, suggesting that absence of ligand and absence of receptor cause different phenotypes. To identify the cell population responsible for the alopecia, we performed hair-reconstitution assays in nude mice and observed normal hair follicle morphogenesis, regardless of the VDR status of the keratinocytes and dermal papilla cells. However, follicles reconstituted with VDR-null keratinocytes demonstrated a defective response to anagen initiation. Hence, alopecia in the VDR-null mice is due to a defect in epithelial-mesenchymal communication that is required for normal hair cycling. Our results also identify the keratinocyte as the cell of origin of the defect and suggest that this form of alopecia is due to absence of ligand-independent receptor function.

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The molecular basis of hereditary 1,25-dihydroxyvitamin D3 resistant rickets in seven related families.

P Malloy, Christian Pike, D Tiosano … (1990)

Hereditary 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] resistant rickets (HVDRR) is an autosomal recessive disease caused by target organ resistance to the action of 1,25(OH)2D3, the active form of the hormone. The defect in target cells is heterogenous and commonly appears to be a mutation in the gene encoding the vitamin D receptor (VDR). We have studied cultured skin fibroblasts and Epstein-Barr virus transformed lymphoblasts of seven family branches of an extended kindred having eight children affected with HVDRR. We have previously shown that cells from three affected children in this group contain an "ochre" nonsense mutation coding for a premature stop codon in exon 7 within the steroid-binding domain of the VDR gene. In the current studies, we found that cells from affected children failed to bind [3H]1,25(OH)2D3 and had undetectable levels of VDR as determined by immunoblots using an anti-VDR monoclonal antibody. Measurement of VDR mRNA by hybridization to a human VDR cDNA probe showed undetectable or decreased abundance of steady-state VDR mRNA. Parents, expected to be obligate heterozygotes, showed approximately half the normal levels of [3H]1,25(OH)2D3 binding, VDR protein, and mRNA. The mutation at nucleotide 970 (counting from the mRNA CAP site) results in the conversion of GTAC to GTAA, which eliminates an Rsa I restriction enzyme site and facilitates identification of the mutation. We found that polymerase chain reaction (PCR) amplification of exons 7 and 8 from family members and subsequent Rsa I digestion allows detection of the specific genotype of the individuals. When Rsa I digests of PCR-amplified DNA are subjected to polyacrylamide gel electrophoresis, children with HVDRR exhibit a homozygous banding pattern with loss of an Rsa I site. Parents exhibit a heterozygotic DNA pattern with detection of both normal and mutant alleles. In summary, our data show that the genetic abnormality is a point mutation within the steroid-binding domain of the VDR in all seven related families with HVDRR. Analysis of restriction fragment length polymorphism at the 970 locus of PCR-amplified DNA fragments can be used to diagnose this mutation in both affected children and parents carrying the disease.

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Author and article information

Journal

Journal ID (publisher-id): HRE

Journal ID (nlm-ta): Horm Res Paediatr

Journal ID (doi): 10.1159/issn.1663-2818

Title: Hormone Research in Paediatrics

Publisher: S. Karger AG

ISSN (Print): 1663-2818

ISSN (Electronic): 1663-2826

Publication date Subscription-year: 2006

Publication date (Print): November 2006

Publication date (Electronic): 30 November 2006

Volume: 66

Issue: 6

Pages: 273-276

Affiliations

Departments of ^aPediatrics and ^bMedicine, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand

Article

Publisher ID: 95546 Other ID: Horm Res 2006;66:273–276

DOI: 10.1159/000095546

PubMed ID: 16946620

SO-VID: de6958f3-8712-45ba-8580-adafff6a1a03

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Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

History

Date received : 11 May 2006

Date accepted : 20 June 2006

Page count

Figures: 2, References: 14, Pages: 4

A Girl with a Novel Splice Site Mutation in VDR Supports the Role of a Ligand-Independent VDR Function on Hair Cycling

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Abstract

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Karger: Endocrinology

Most cited references 13

Ligand-independent actions of the vitamin D receptor maintain hair follicle homeostasis.

Metabolic and cellular analysis of alopecia in vitamin D receptor knockout mice.

The molecular basis of hereditary 1,25-dihydroxyvitamin D3 resistant rickets in seven related families.

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