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Habacher G, Malik R, Lait PJP, Coghill LM, Middleton RP, Warren WC, Lyons LA. Feline precision medicine using whole-exome sequencing identifies a novel frameshift mutation for vitamin D-dependent rickets type 2. J Feline Med Surg 2023; 25:1098612X231165630. [PMID: 37387221 PMCID: PMC10811982 DOI: 10.1177/1098612x231165630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/01/2023]
Abstract
OBJECTIVES A 14-week-old female domestic longhair kitten presented with shifting lameness and disproportionately smaller size compared with a co-housed littermate. METHODS Hematology and serum biochemical testing were conducted to investigate causes for delayed growth, and radiographs of the appendicular skeleton were obtained. RESULTS The afflicted kitten had marked hypocalcemia, mild hypophosphatemia and substantial elevations in alkaline phosphatase activity, as well as pathognomonic radiographic findings consistent with rickets. Skeletal changes and hypocalcemia prompted testing of concentrations of parathyroid hormone (PTH) and vitamin D metabolites. Endocrine testing demonstrated significant increases in serum concentrations of PTH and 1,25-dihydroxycholecalciferol (calcitriol), supporting a diagnosis of vitamin D-dependent rickets type 2. Provision of analgesia, supraphysiologic doses of calcitriol and calcium carbonate supplementation achieved normalization of the serum calcium concentration and restoration of normal growth, although some skeletal abnormalities persisted. Once skeletally mature, ongoing calcitriol supplementation was not required. Whole-exome sequencing (WES) was conducted to identify the underlying DNA variant. A cytosine deletion at cat chromosome position B4:76777621 in VDR (ENSFCAT00000029466:c.106delC) was identified and predicted to cause a stop codon in exon 2 (p.Arg36Glufs*18), disrupting >90% of the receptor. The variant was unique and homozygous in this patient and absent in the sibling and approximately 400 other cats for which whole-genome and whole-exome data were available. CONCLUSIONS AND RELEVANCE A unique, heritable form of rickets was diagnosed in a domestic longhair cat. WES identified a novel frameshift mutation affecting the gene coding for the vitamin D3 receptor, determining the likely causal genetic variant. Precision medicine techniques, including whole-exome and whole-genome sequencing, can be a standard of care in cats to identify disease etiologies, and to target therapeutics and personalize treatment.
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Affiliation(s)
| | - Richard Malik
- Centre for Veterinary Education, The University of Sydney, Sydney, NSW, Australia
| | | | - Lyndon M Coghill
- Department of Veterinary Pathobiology, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA
| | | | - Wesley C Warren
- Division of Animal Sciences, College of Agriculture, Department of Surgery, School of Medicine, Institute for Data Science and Informatics, University of Missouri, Columbia, MO, USA
| | - Leslie A Lyons
- Department of Veterinary Medicine and Surgery, College of Veterinary Medicine, University of Missouri, Columbia, MO, USA
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Kashyap J, Kumari N, Ponnusamy K, Tyagi RK. Hereditary Vitamin D-Resistant Rickets (HVDRR) associated SNP variants of vitamin D receptor exhibit malfunctioning at multiple levels. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2023; 1866:194891. [PMID: 36396100 DOI: 10.1016/j.bbagrm.2022.194891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2022] [Revised: 10/11/2022] [Accepted: 11/02/2022] [Indexed: 11/16/2022]
Abstract
Vitamin D receptor (VDR) is a member of the nuclear receptor superfamily. It is a primary regulator of calcium and phosphate homeostasis required for skeleton and bone mineralization. Vitamin D in active form 1α,25 dihydroxyvitamin-D3 mediates its cellular functions by binding to VDR. Active VDR forms heterodimers with partner RXR (retinoid X receptor) to execute its physiological actions. HVDRR (Hereditary Vitamin D-Resistant Rickets) is a rare genetic disorder that occurs because of generalized resistance to the 1α,25(OH)2D3. HVDRR is caused by the polymorphic variations in VDR gene leading to defective intestinal calcium absorption and mineralization of newly forming bones. Using point and deletion SNPs of VDR we have studied several HVDRR-associated SNP variants for their subcellular dynamics, transcriptional functions, 'genome bookmarking', heterodimeric interactions with RXR, and receptor stability. We previously reported that VDR is a 'mitotic bookmarking factor' that remains constitutively associated with the mitotic chromatin to inherit 'transcriptional memory', however the mechanistic details remained unclear. We document that 'genome bookmarking' property by VDR is critically impaired by naturally occurring HVDRR-associated point and deletion variants found in patients. Furthermore, these HVDRR-associated SNP variants of VDR were found to be compromised in transcriptional function, nuclear translocation, protein stability and intermolecular interactions with its heterodimeric partner RXR. Intriguingly, majority of these disease-allied functional defects failed to be rescued by RXR. Our findings suggest that the HVDRR-associated SNP variations influence the normal functioning of the receptor, and this derived understanding may help in the management of disease with precisely designed small molecule modulators.
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Affiliation(s)
- Jyoti Kashyap
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi 110067, India
| | - Neha Kumari
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi 110067, India
| | | | - Rakesh K Tyagi
- Special Centre for Molecular Medicine, Jawaharlal Nehru University, New Delhi 110067, India; Special Centre for Systems Medicine (Concurrent Faculty), Jawaharlal Nehru University, New Delhi 110067, India.
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Amos A, Razzaque MS. Zinc and its role in vitamin D function. Curr Res Physiol 2022; 5:203-207. [PMID: 35570853 PMCID: PMC9095729 DOI: 10.1016/j.crphys.2022.04.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Revised: 04/01/2022] [Accepted: 04/26/2022] [Indexed: 02/06/2023] Open
Abstract
Zinc is an essential mineral with an important relationship with vitamin D. Studies have found that reduced blood zinc levels could predict vitamin D deficiency in adolescent girls, while zinc supplementation increased vitamin D levels in postmenopausal women. In vitro studies using human peritoneal macrophages have found that zinc induced the release of calcitriol (1,25-dihydroxycholecalciferol). Zinc also acts as a cofactor for vitamin D functions, as the transcriptional activity of vitamin D-dependent genes relies on zinc to exert pleiotropic functions, including mineral ion regulation. Vitamin D could also induce zinc transporters to regulate zinc homeostasis. Together, zinc and vitamin D in adequate concentrations help maintain a healthy musculoskeletal system and beyond; however, deficiency in either of these nutrients can result in various disorders affecting almost all body systems. This brief article will focus on the role of zinc in vitamin D functions.
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Kinoshita Y, Ito N, Makita N, Nangaku M, Fukumoto S. Changes in bone metabolic parameters following oral calcium supplementation in an adult patient with vitamin D-dependent rickets type 2A. Endocr J 2017; 64:589-596. [PMID: 28367941 DOI: 10.1507/endocrj.ej16-0583] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Vitamin D-dependent rickets type 2A (VDDR2A) is a rare inherited disorder with decreased tissue responsiveness to 1,25-dihydroxyvitamin D [1,25(OH)2D], caused by loss of function mutations in the vitamin D receptor (VDR) gene. Approximately 50 types of mutations have been identified so far that change amino acids in either the N-terminal DNA binding domain (DBD) or the C-terminal ligand binding domain (LBD) of the VDR protein. The degree of responsiveness to 1,25(OH)2D varies between patients with VDDR2A, which may depend on their residual VDR function. In this report, we describe a female patient with VDDR2A caused by an early stop codon (R30X) in the VDR gene that resulted in a severely truncated VDR protein. She developed alopecia and bowed legs within a year after birth and was diagnosed with rickets at the age of 2. She had been treated with active vitamin D and oral calcium supplementation until 22 years of age, when she developed secondary hyperparathyroidism and high bone turnover. The genetic diagnosis of VDDR2A promoted the discontinuation of active vitamin D treatment in favor of monotherapy with oral calcium supplementation. We observed amelioration of the secondary hyperparathyroidism and normalization of bone metabolic parameters within 6 years.
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Affiliation(s)
- Yuka Kinoshita
- Division of Nephrology & Endocrinology, Department of Medicine, the University of Tokyo Hospital, Tokyo, Japan
| | - Nobuaki Ito
- Division of Nephrology & Endocrinology, Department of Medicine, the University of Tokyo Hospital, Tokyo, Japan
| | - Noriko Makita
- Division of Nephrology & Endocrinology, Department of Medicine, the University of Tokyo Hospital, Tokyo, Japan
| | - Masaomi Nangaku
- Division of Nephrology & Endocrinology, Department of Medicine, the University of Tokyo Hospital, Tokyo, Japan
| | - Seiji Fukumoto
- Fujii Memorial Institute of Medical Sciences, Tokushima University, Tokushima, Japan
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Luo W, Johnson CS, Trump DL. Vitamin D Signaling Modulators in Cancer Therapy. VITAMINS AND HORMONES 2016; 100:433-72. [PMID: 26827962 DOI: 10.1016/bs.vh.2015.11.004] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
The antiproliferative and pro-apoptotic effects of 1α,25-dihydroxycholecalciferol (1,25(OH)2D3, 1,25D3, calcitriol) have been demonstrated in various tumor model systems in vitro and in vivo. However, limited antitumor effects of 1,25D3 have been observed in clinical trials. This may be attributed to a variety of factors including overexpression of the primary 1,25D3 degrading enzyme, CYP24A1, in tumors, which would lead to rapid local inactivation of 1,25D3. An alternative strategy for improving the antitumor activity of 1,25D3 involves the combination with a selective CYP24A1 inhibitor. The validity of this approach is supported by numerous preclinical investigations, which demonstrate that CYP24A1 inhibitors suppress 1,25D3 catabolism in tumor cells and increase the effects of 1,25D3 on gene expression and cell growth. Studies are now required to determine whether selective CYP24A1 inhibitors+1,25D3 can be used safely and effectively in patients. CYP24A1 inhibitors plus 1,25D3 can cause dose-limiting toxicity of vitamin D (hypercalcemia) in some patients. Dexamethasone significantly reduces 1,25D3-mediated hypercalcemia and enhances the antitumor activity of 1,25D3, increases VDR-ligand binding, and increases VDR protein expression. Efforts to dissect the mechanisms responsible for CYP24A1 overexpression and combinational effect of 1,25D3/dexamethasone in tumors are underway. Understanding the cross talk between vitamin D receptor (VDR) and glucocorticoid receptor (GR) signaling axes is of crucial importance to the design of new therapies that include 1,25D3 and dexamethasone. Insights gained from these studies are expected to yield novel strategies to improve the efficacy of 1,25D3 treatment.
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Affiliation(s)
- Wei Luo
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York, USA
| | - Candace S Johnson
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York, USA
| | - Donald L Trump
- Department of Medicine, Roswell Park Cancer Institute, Buffalo, New York, USA; Inova Dwight and Martha Schar Cancer Institute, Falls Church, Virginia, USA.
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Mazen I, Ismail S, Amr K, El Gammal M, Abdel-Hamid M. Hereditary 1,25-dihydroxyvitamin D-resistant rickets with alopecia in four Egyptian families: report of three novel mutations in the vitamin D receptor gene. J Pediatr Endocrinol Metab 2014; 27:873-8. [PMID: 24859502 DOI: 10.1515/jpem-2013-0443] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 04/01/2014] [Indexed: 11/15/2022]
Abstract
OBJECTIVE To study the vitamin D receptor (VDR) gene in five Egyptian patients with severe rickets and the clinical features of hereditary vitamin D-resistant rickets, including hypocalcemia, hypophosphatemia, total alopecia, and elevated serum levels of 1,25-dihydroxyvitamin D. STUDY DESIGN We amplified and sequenced DNA samples from blood from the patients, their parents, and available family members. RESULTS DNA sequence analyses of the VDR gene showed three novel mutations (p.Y295X, p.R343C, and p.R391H) and a previously reported one (p.R30X) in four patients, whereas no mutation was found in one patient. Mutations cosegregated perfectly with affected individuals in all families, and did not exist in unaffected family members or 200 ethnically matched chromosomes. CONCLUSION Three novel deleterious mutations in the VDR ligand-binding domain were identified, which are expected to render the VDR nonfunctional. Successful treatment with frequent high doses of oral calcium and calcidol was evident in all patients; however, hair growth occurred only in one patient.
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Malloy PJ, Tasic V, Taha D, Tütüncüler F, Ying GS, Yin LK, Wang J, Feldman D. Vitamin D receptor mutations in patients with hereditary 1,25-dihydroxyvitamin D-resistant rickets. Mol Genet Metab 2014; 111:33-40. [PMID: 24246681 PMCID: PMC3933290 DOI: 10.1016/j.ymgme.2013.10.014] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/05/2013] [Revised: 10/22/2013] [Accepted: 10/23/2013] [Indexed: 02/06/2023]
Abstract
CONTEXT Hereditary vitamin D resistant rickets (HVDRR), also known as vitamin D-dependent rickets type II, is an autosomal recessive disorder characterized by the early onset of rickets with hypocalcemia, secondary hyperparathyroidism and hypophosphatemia and is caused by mutations in the vitamin D receptor (VDR) gene. The human gene encoding the VDR is located on chromosome 12 and comprises eight coding exons and seven introns. OBJECTIVES, PATIENTS, AND METHODS We analyzed the VDR gene of 5 previously unreported patients, two from Singapore and one each from Macedonia (former Yugoslav Republic), Saudi Arabia and Turkey. Each patient had clinical and radiographic features of rickets, hypocalcemia, and the 4 cases that had the measurement showed elevated serum concentrations of 1,25-dihydroxyvitamin D (1,25(OH)(2)D). Mutations were re-created in the WT VDR cDNA and examined for 1,25(OH)(2)D(3)-mediated transactivation in COS-7 monkey kidney cells. RESULTS Direct sequencing identified four novel mutations and two previously described mutations in the VDR gene. The novel mutations included a missense mutation in exon 3 causing the amino acid change C60W; a missense mutation in exon 4 causing the amino acid change D144N; a missense mutation in exon 7 causing the amino acid change N276Y; and a 2bp deletion in exon 3 5'-splice site (IVS3∆+4-5) leading to a premature stop. CONCLUSIONS These 4 unique mutations add to the previous 45 mutations identified in the VDR gene in patients with HVDRR.
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Affiliation(s)
- Peter J Malloy
- Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Velibor Tasic
- Department of Pediatric Nephrology, Clinic for Children's Diseases, University Children's Hospital, Medical School of Skopje, Skopje, Macedonia
| | - Doris Taha
- Department of Endocrinology, Children's Hospital of Michigan, Detroit, MI 48201, USA
| | - Filiz Tütüncüler
- Pediatric Endocrinology, Trakya University, Faculty of Medicine, Edirne, Turkey
| | - Goh Siok Ying
- Department of Pediatrics, University Children's Medical Institute, National University Hospital, Singapore
| | - Loke Kah Yin
- Department of Pediatrics, University Children's Medical Institute, National University Hospital, Singapore
| | - Jining Wang
- Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - David Feldman
- Department of Medicine, Stanford University School of Medicine, Stanford, CA 94305, USA
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Luo W, Hershberger PA, Trump DL, Johnson CS. 24-Hydroxylase in cancer: impact on vitamin D-based anticancer therapeutics. J Steroid Biochem Mol Biol 2013; 136:252-7. [PMID: 23059474 PMCID: PMC3686893 DOI: 10.1016/j.jsbmb.2012.09.031] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/06/2012] [Accepted: 09/30/2012] [Indexed: 12/15/2022]
Abstract
The active vitamin D hormone 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) plays a major role in regulating calcium homeostasis and bone mineralization. 1,25(OH)2D3 also modulates cellular proliferation and differentiation in a variety of cell types. 24-Hydroxylase, encoded by the CYP24A1 gene, is the key enzyme which converts 1,25(OH)2D3 to less active calcitroic acid. Nearly all cell types express 24-hydroxylase, the highest activity being observed in the kidney. There is increasing evidence linking the incidence and prognosis of certain cancers to low serum 25(OH)D3 levels and high expression of vitamin D 24-hydroxylase, supporting the idea that elevated CYP24A1 expression may stimulate degradation of vitamin D metabolites including 25(OH)D3 and 1,25(OH)2D3. The over expression of CYP24A1 in cancer cells may be a factor affecting 1,25(OH)2D3 bioavailability and anti-proliferative activity pre-clinically and clinically. The combination of 1,25(OH)2D3 with CYP24A1 inhibitors enhances 1,25(OH)2D3 mediated signaling and anti-proliferative effects and may be useful in overcoming effects of aberrant CYP24A1 expression. This article is part of a Special Issue entitled 'Vitamin D Workshop'.
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Affiliation(s)
- Wei Luo
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263
| | - Pamela A. Hershberger
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263
| | - Donald L. Trump
- Department of Medicine, Roswell Park Cancer Institute, Buffalo, NY 14263
| | - Candace S. Johnson
- Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, NY 14263
- Corresponding author: Candace S. Johnson, PhD, Roswell Park Cancer Institute, Elm & Carlton Streets, Buffalo, NY 14263. Tel: 716-845-8300; fax: 716-845-1258.
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Supornsilchai V, Hiranras Y, Wacharasindhu S, Mahayosnond A, Suphapeetiporn K, Shotelersuk V. Two siblings with a novel nonsense mutation, p.R50X, in the vitamin D receptor gene. Endocrine 2011; 40:62-6. [PMID: 21424181 DOI: 10.1007/s12020-011-9450-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/23/2011] [Accepted: 03/02/2011] [Indexed: 10/18/2022]
Abstract
Hereditary vitamin D-resistant rickets (HVDRR), an autosomal recessive disorder caused by inactivating mutations in the vitamin D receptor (VDR) gene. We identified two affected children from the same family, one at the age of 10 years and 9 months and the other at 9 months old. Mutation analysis by PCR-sequencing the entire coding region of the VDR gene revealed a homozygous C to T transition in exon 2 of the VDR gene (c.148C>T) resulting in a stop codon at amino acid position 50 (p.R50X) in the proband and his younger sister. The p.R50X has never been previously described. Both asymptomatic parents were heterozygous for the mutation. In addition to most of the clinical features of HVDRR including total alopecia, symptoms of hypocalcemia at a later onset and normophosphatemia, rarely found in HVDRR were present in the proband. This study also emphasizes an important role of genetic testing for early diagnosis and genetic counseling.
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Affiliation(s)
- Vichit Supornsilchai
- Division of Endocrinology, Department of Pediatrics, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand
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Bao BY, Ting HJ, Hsu JW, Yasmin-Karim S, Messing E, Lee YF. Down-regulation of NF-kappaB signals is involved in loss of 1alpha,25-dihydroxyvitamin D3 responsiveness. J Steroid Biochem Mol Biol 2010; 120:11-21. [PMID: 20206692 DOI: 10.1016/j.jsbmb.2010.02.030] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2009] [Revised: 02/11/2010] [Accepted: 02/14/2010] [Indexed: 01/02/2023]
Abstract
Vitamin D anti-tumor effect is often found reduced in the late stages of cancer. To uncover vitamin D resistance mechanism, we established a vitamin D-resistant human prostate cancer LNCaP cell line, LNCaP-R, by chronic exposure of cells to 1alpha,25-dihydroxyvitamin D(3) (1,25-VD). The vitamin D receptor (VDR)-mediated transcriptional activity was reduced in LNCaP-R, whereas VDR expression level and DNA-binding capacity were similar compared to parental cells (LNCaP-P). The expressions of the key factors involved in VDR transactivity, including CYP24A1 and VDR-associated proteins are all increased in LNCaP-R cells, and yet treatment with ketoconazole, P450 enzymes inhibitor, as well as trichostatin A (TSA), a histone deacetylase inhibitor, did not sensitize LNCaP-R cells response to vitamin D, suggesting that neither a local 1,25-VD availability, nor VDR-associated proteins are responsible for the vitamin D resistance. Interestingly, nuclear factor-kappaB (NF-kappaB) signaling, which is critical for 1,25-VD/VDR activity was found reduced in LNCaP-R cells, thereby treatment with NF-kappaB activator, 12-O-tetradecanoylphorbol-13-acetate (TPA), can sensitize LNCaP-R vitamin D response. Together, we conclude that NF-kappaB signaling is critical for vitamin D sensitivity, and dysregulation of this pathway would result in vitamin D resistance and disease progression.
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Affiliation(s)
- Bo-Ying Bao
- Department of Urology and Pathology & Laboratory Medicine, Rochester, NY 14642, USA
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Compound heterozygous mutations in the vitamin D receptor in a patient with hereditary 1,25-dihydroxyvitamin D-resistant rickets with alopecia. J Bone Miner Res 2009; 24:643-51. [PMID: 19049339 PMCID: PMC2659515 DOI: 10.1359/jbmr.081216] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Hereditary vitamin D-resistant rickets (HVDRR) is a rare recessive genetic disorder caused by mutations in the vitamin D receptor (VDR). In this study, we examined the VDR in a young girl with clinical features of HVDRR including rickets, hypophosphatemia, and elevated serum 1,25(OH)(2)D. The girl also had total alopecia. Two mutations were found in the VDR gene: a nonsense mutation (R30X) in the DNA-binding domain and a unique 3-bp in-frame deletion in exon 6 that deleted the codon for lysine at amino acid 246 (DeltaK246). The child and her mother were both heterozygous for the 3-bp deletion, whereas the child and her father were both heterozygous for the R30X mutation. Fibroblasts from the patient were unresponsive to 1,25(OH)(2)D(3) as shown by their failure to induce CYP24A1 gene expression, a marker of 1,25(OH)(2)D(3) responsiveness. [(3)H]1,25(OH)(2)D(3) binding and immunoblot analysis showed that the patient's cells expressed the VDRDeltaK246 mutant protein; however, the amount of VDRDeltaK246 mutant protein was significantly reduced compared with wildtype controls. In transactivation assays, the recreated VDRDeltaK246 mutant was unresponsive to 1,25(OH)(2)D(3). The DeltaK246 mutation abolished heterodimerization of the mutant VDR with RXRalpha and binding to the coactivators DRIP205 and SRC-1. However, the DeltaK246 mutation did not affect the interaction of the mutant VDR with the corepressor Hairless (HR). In summary, we describe a patient with compound heterozygous mutations in the VDR that results in HVDRR with alopecia. The R30X mutation truncates the VDR, whereas the DeltaK246 mutation prevents heterodimerization with RXR and disrupts coactivator interactions.
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Ramasamy I. Inherited disorders of calcium homeostasis. Clin Chim Acta 2008; 394:22-41. [PMID: 18474231 DOI: 10.1016/j.cca.2008.04.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Revised: 03/30/2008] [Accepted: 04/14/2008] [Indexed: 12/19/2022]
Abstract
In mammals a complicated homeostatic mechanism has evolved to maintain near consistency of extracellular calcium ion levels. The homeostatic mechanism involves several hormones, which comprise among others, parathyroid hormone and vitamin D. The recent resurge in vitamin D deficiency, as a global health issue, has increased interest in the hormone. In addition to vitamin D deficiency, other causes of rickets are calcium deficiency and inherited disorders of vitamin D and phosphorus metabolism. Vitamin D-resistant syndromes are caused by hereditary defects in metabolic activation of the hormone or by mutations in the vitamin D receptor, which binds the hormone with high affinity and regulates the expression of genes through zinc finger mediated DNA binding and protein-protein interaction. Current interest is to correlate the type/position of mutations that result in disorders of vitamin D metabolism or in vitamin D receptor function with the variable phenotypic features and clinical presentation. The calcium sensing receptor plays a key role in calcium homeostasis. Loss of function mutations in the calcium sensing receptor can cause familial benign hypocalciuric hypercalcemia in heterozygotes and neonatal severe hyperparathyroidism when homozygous mutations occur in the calcium sensing receptor. Gain of function mutation can cause the opposite effect causing autosomal dominant hypocalcemia. Mouse models using targeted gene disruption strategies have been valuable tools to study the effect of mutations on the calcium sensing receptor or in the vitamin D activation pathway. Dysfunctional calcium sensing receptors with function altering mutations may be responsive to treatment with allosteric modulators of the calcium sensing receptor. Vitamin D analogs which induce unusual structural conformations on the vitamin D receptor may have a variety of therapeutic indications. This review summarises recent advances in knowledge of the molecular pathology of inherited disorders of calcium homeostasis.
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Affiliation(s)
- Indra Ramasamy
- Department of Chemical Pathology, Dumfries and Galloway District Hospital, Bankend Road, Dumfries, UK.
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Ting HJ, Bao BY, Reeder JE, Messing EM, Lee YF. Increased Expression of Corepressors in Aggressive Androgen-Independent Prostate Cancer Cells Results in Loss of 1α,25-Dihydroxyvitamin D3 Responsiveness. Mol Cancer Res 2007; 5:967-80. [PMID: 17855664 DOI: 10.1158/1541-7786.mcr-06-0318] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Vitamin D has antiproliferative activity in prostate cancer; however, resistance to vitamin D-mediated growth inhibition occurs. To investigate the mechanisms of vitamin D resistance, we screened two prostate cancer sublines of CWR22rv1, CWR22R-1, and CWR22R-2, with differential sensitivity to vitamin D. CWR22R-2 showed less response to the antiproliferative effect of vitamin D than CWR22R-1. The vitamin D receptor (VDR)-mediated transcriptional activity was also decreased in CWR22R-2. We further showed that the DNA-binding ability of VDR was decreased and the amount of NCoR in VDR response element was increased in CWR22R-2. Analysis of VDR-associated protein profiles found higher expression of the corepressors, NCoR1 and SMRT, in CWR22R-2 cells. Treatment with the histone deacetylase inhibitor, trichostatin A, increased vitamin D/VDR transcriptional activity and promoted the antiproliferative effect of vitamin D in CWR22R-2 cells. Targeted down-regulation of NCoR1 and SMRT by small interference RNA was able to restore CWR22R-2 response to vitamin D. Together, we showed that increased NCoR1 and SMRT expression in CWR22R-2 cells resulted in reduced VDR-mediated transcriptional activity and attenuated antiproliferative response to vitamin D. Our data suggest that the integrity of the vitamin D/VDR-mediated signaling pathway is crucial in predicting vitamin D responsiveness and thus provide a rational design to improve vitamin D-based treatment efficacy based on molecular profiles of patients.
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Affiliation(s)
- Huei-Ju Ting
- Department of Urology, University of Rochester Medical Center, 601 Elmwood Avenue, Box 626, Rochester, NY 14642, USA
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Malloy PJ, Wang J, Peng L, Nayak S, Sisk JM, Thompson CC, Feldman D. A unique insertion/duplication in the VDR gene that truncates the VDR causing hereditary 1,25-dihydroxyvitamin D-resistant rickets without alopecia. Arch Biochem Biophys 2006; 460:285-92. [PMID: 17078924 PMCID: PMC1892178 DOI: 10.1016/j.abb.2006.09.027] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2006] [Revised: 09/27/2006] [Accepted: 09/29/2006] [Indexed: 11/26/2022]
Abstract
Hereditary vitamin D resistant rickets (HVDRR) is caused by mutations in the vitamin D receptor (VDR). Here we describe a patient with HVDRR who also exhibited some hypotrichosis of the scalp but otherwise had normal hair and skin. A 102 bp insertion/duplication was found in the VDR gene that introduced a premature stop (Y401X). The patient's fibroblasts expressed the truncated VDR, but were resistant to 1,25(OH)2D3. The truncated VDR weakly bound [3H]-1,25(OH)2D3 but was able to heterodimerize with RXR, bind to DNA and interact with the corepressor hairless (HR). However, the truncated VDR failed to bind coactivators and was transactivation defective. Since the patient did not have alopecia or papular lesions of the skin generally found in patients with premature stop mutations this suggests that this distally truncated VDR can still regulate the hair cycle and epidermal differentiation possibly through its interactions with RXR and HR to suppress gene transactivation.
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Affiliation(s)
- Peter J Malloy
- Division of Endocrinology, Gerontology and Metabolism, Department of Medicine, Stanford University School of Medicine, Stanford University Medical Center, Stanford, CA 94305, USA.
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15
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Uitto J, Pulkkinen L, Ringpfeil F. Progress in molecular genetics of heritable skin diseases: the paradigms of epidermolysis bullosa and pseudoxanthoma elasticum. J Investig Dermatol Symp Proc 2002; 7:6-16. [PMID: 12518787 DOI: 10.1046/j.1523-1747.2002.19637.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The 42nd Annual Symposium on the Biology of the Skin, entitled "The Genetics of Skin Disease", was held in Snowmass Village, Colorado, in July 1993. That meeting presented the opportunity to discuss how modern approaches to molecular genetics and molecular biology could be applied to understanding the mechanisms of skin diseases. The published proceedings of this meeting stated that "It is an opportune time to examine the genetics of skin disease" (Norris et al, 1994). Indeed, this meeting just caught the wave of early pioneering studies that have helped us to understand the molecular basis of a large number of genodermatoses. This overview presented in the 50th Annual Symposium on the biology of the skin, highlights the progress made in the molecular genetics of heritable skin diseases over the past decade.
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Affiliation(s)
- Jouni Uitto
- Department of Dermatology and Cutaneous Biology, Jefferson Medical College, Philadelphia, Pennsylvania 19107, USA.
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16
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Malloy PJ, Zhu W, Bouillon R, Feldman D. A novel nonsense mutation in the ligand binding domain of the vitamin D receptor causes hereditary 1,25-dihydroxyvitamin D-resistant rickets. Mol Genet Metab 2002; 77:314-8. [PMID: 12468277 DOI: 10.1016/s1096-7192(02)00173-7] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Hereditary 1,25-dihydroxyvitamin D resistant rickets (HVDRR) is a genetic disorder most often caused by mutations in the vitamin D receptor (VDR). In this report, we present our findings on a young girl who exhibited the typical clinical features of HVDRR with early onset rickets, hypocalcemia, secondary hyperparathyroidism, and elevated serum concentrations of alkaline phosphatase and 1,25-dihydroxyvitamin D [1,25(OH)(2)D(3)]. The patient also had total body alopecia. Fibroblasts from the patient were cultured for analysis of the VDR structure and function. In [3H]1,25(OH)(2)D(3) binding assays, no significant specific binding to the VDR was observed in cytosols from the patient's fibroblasts. The patient's fibroblast were also totally resistant to high doses of 1,25(OH)(2)D(3) as demonstrated by their failure to induce expression of the 24-hydroxylase gene, a marker of 1,25(OH)(2)D(3) activity. DNA sequence analysis of the VDR gene uncovered a unique C to T mutation in exon 8. The mutation changed the codon for glutamine to a premature stop codon at amino acid 317 (Q317X). Restriction enzyme analysis showed that the patient was homozygous for the mutation. Both parents were heterozygous for the mutant allele. In conclusion, we have identified a novel mutation in the VDR, Q317X, as the molecular defect in a patient with HVDRR. The Q317X mutation deletes 110 amino acids of the ligand-binding domain of the VDR and results in the loss of [3H]1,25(OH)(2)D(3) binding and target gene transactivation.
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Affiliation(s)
- Peter J Malloy
- Division of Endocrinology, Gerontology, and Metabolism, Department of Medicine, Stanford University School of Medicine, Stanford University Medical Center, Room S005, Stanford, CA 94305-5103, USA
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17
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Nguyen TM, Adiceam P, Kottler ML, Guillozo H, Rizk-Rabin M, Brouillard F, Lagier P, Palix C, Garnier JM, Garabedian M. Tryptophan missense mutation in the ligand-binding domain of the vitamin D receptor causes severe resistance to 1,25-dihydroxyvitamin D. J Bone Miner Res 2002; 17:1728-37. [PMID: 12211444 DOI: 10.1359/jbmr.2002.17.9.1728] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
In this study, two related young children, brother and sister, exhibited severe vitamin D-resistant rickets without alopecia. Sequence analysis of the total vitamin D receptor (VDR) cDNA from skin fibroblasts revealed a substitution of the unique tryptophan of the VDR by arginine at amino acid 286 (W286R). Cultured skin fibroblasts of the two patients expressed normal-size VDR protein (immunocytochemistry and Western blotting) and normal length VDR mRNA (Northern blotting). But, these fibroblasts, as well as COS-7 cells transfected with the W286R mutant, failed to bind 3H 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]. The tryptophan substitution did not affect VDR trafficking toward the nucleus but abolished the 24-hydroxylase gene response to 1,25(OH)2D3, even at 10(-6) M concentrations. In conclusion, this case report of a new family with hereditary vitamin D-resistant rickets (HVDRR) emphasizes the crucial role of the VDR tryptophan for ligand binding and for transactivation of 1,25(OH)2D3 target genes. It clearly shows the clinical significance of this VDR amino acid for calcium homeostasis and bone mineralization. This observation suggests further that the presence of a stable VDR-bound ligand may not be obligatory for normal hair follicle development.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Binding Sites/genetics
- COS Cells
- Calcitriol/pharmacology
- Cells, Cultured
- Child, Preschool
- Cytochrome P-450 Enzyme System/genetics
- DNA, Complementary/genetics
- Female
- Hair Follicle/growth & development
- Humans
- Hypophosphatemia, Familial/genetics
- Infant
- Ligands
- Male
- Mutation, Missense
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Calcitriol/drug effects
- Receptors, Calcitriol/genetics
- Receptors, Calcitriol/metabolism
- Recombinant Proteins/genetics
- Recombinant Proteins/metabolism
- Steroid Hydroxylases/genetics
- Transfection
- Tryptophan/genetics
- Vitamin D3 24-Hydroxylase
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Affiliation(s)
- T M Nguyen
- CNRS-UPR 1524, Hĵpital St. Vincent de Paul, Paris, France
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18
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Abstract
Most common forms of hair loss (alopecia) are caused by aberrant hair follicle cycling and changes in hair follicle morphology. However, current treatments for alopecia do not specifically target these processes. We are now beginning to identify the molecules and molecular pathways that control normal hair follicle formation, cycling and growth. In parallel, new techniques are being developed for delivering molecules to hair follicles. Here, we outline the characteristics of common hair loss diseases, and discuss ways in which recent advances in hair follicle biology could be translated into effective therapies for these conditions.
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Affiliation(s)
- G Cotsarelis
- Department of Dermatology and Cell and Developmental Biology, University of Pennsylvania School of Medicine, M8 Stellar-Chance Laboratories, 422 Curie Blvd, Philadelphia, PA 19104, USA.
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19
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Malloy PJ, Zhu W, Zhao XY, Pehling GB, Feldman D. A novel inborn error in the ligand-binding domain of the vitamin D receptor causes hereditary vitamin D-resistant rickets. Mol Genet Metab 2001; 73:138-48. [PMID: 11386849 DOI: 10.1006/mgme.2001.3181] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Mutations in the vitamin D receptor (VDR) cause hereditary vitamin D-resistant rickets (HVDRR), an autosomal recessive disease resulting in target organ resistance to 1,25-dihydroxyvitamin D(3) [1,25(OH)(2)D(3)]. In this report, we describe the clinical case and molecular basis of HVDRR in an Asian boy exhibiting the typical clinical features of the disease including alopecia. Using cultured dermal fibroblasts from the patient, 1,25(OH)(2)D(3) resistance was demonstrated by a shift in the dose response required for 25-hydroxyvitamin D-24-hydroxylase (24-hydroxylase) mRNA induction. Western blot showed that the cells express a normal size VDR but contained reduced levels of receptor compared to normal cells. At 24 degrees C, the affinity of the patient's VDR for [(3)H]1,25(OH)(2)D(3) was 50-fold lower than the VDR in normal fibroblasts. Sequence analysis identified a unique T to G missense mutation in exon 6 that changed phenylalanine to cysteine at amino acid 251 (F251C). The recreated F251C mutant VDR showed reduced transactivation activity using a 24-hydroxylase promoter-luciferase reporter. Maximal transactivation activity exhibited by the WT VDR was not achieved by the mutant VDR even when the cells were treated with up to 10(-6) M 1,25(OH)(2)D(3). However, the transactivation activity was partially rescued by addition of RXRalpha. In the yeast two-hybrid system and GST-pull-down assays, high concentrations of 1,25(OH)(2)D(3) were needed to promote F251C mutant VDR binding to RXRalpha, indicating defective heterodimerization. In conclusion, a novel mutation was identified in the VDR LBD that reduces VDR abundance and its affinity for 1,25(OH)(2)D(3) and interferes with RXRalpha heterodimerization resulting in the syndrome of HVDRR.
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MESH Headings
- Animals
- Base Sequence
- Binding Sites/genetics
- Binding, Competitive
- COS Cells
- Cells, Cultured
- Child, Preschool
- Cytochrome P-450 Enzyme System/genetics
- DNA Mutational Analysis
- Fibroblasts/cytology
- Fibroblasts/drug effects
- Fibroblasts/metabolism
- Humans
- Hypophosphatemia, Familial/genetics
- Hypophosphatemia, Familial/pathology
- Ligands
- Male
- Molecular Sequence Data
- Mutation
- Mutation, Missense
- Plasmids/genetics
- RNA, Messenger/drug effects
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Calcitriol/genetics
- Receptors, Calcitriol/metabolism
- Receptors, Retinoic Acid/genetics
- Receptors, Retinoic Acid/metabolism
- Retinoid X Receptors
- Saccharomyces cerevisiae/genetics
- Sequence Alignment
- Sequence Homology, Amino Acid
- Steroid Hydroxylases/genetics
- Steroid Hydroxylases/metabolism
- Steroid Hydroxylases/pharmacology
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transcriptional Activation
- Tritium
- Two-Hybrid System Techniques
- Vitamin D3 24-Hydroxylase
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Affiliation(s)
- P J Malloy
- Department of Medicine, Stanford University School of Medicine, Stanford, California 94305-5103, USA
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20
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Affiliation(s)
- R W Chesney
- University of Tennessee, Memphis, Memphis, Tennessee, USA.
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21
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Malloy PJ, Pike JW, Feldman D. The vitamin D receptor and the syndrome of hereditary 1,25-dihydroxyvitamin D-resistant rickets. Endocr Rev 1999; 20:156-88. [PMID: 10204116 DOI: 10.1210/edrv.20.2.0359] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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22
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Affiliation(s)
- P J Malloy
- Department of Medicine, Stanford University School of Medicine, California 94305-5103, USA
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23
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Mehrara BJ, Rowe NM, Steinbrech DS, Dudziak ME, Saadeh PB, McCarthy JG, Gittes GK, Longaker MT. Rat mandibular distraction osteogenesis: II. Molecular analysis of transforming growth factor beta-1 and osteocalcin gene expression. Plast Reconstr Surg 1999; 103:536-47. [PMID: 9950542 DOI: 10.1097/00006534-199902000-00026] [Citation(s) in RCA: 110] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Distraction osteogenesis is a powerful technique capable of generating viable osseous tissue by the gradual separation of osteotomized bone edges. Although the histologic and ultrastructural changes associated with this process have been extensively delineated, the molecular events governing these changes remain essentially unknown. We have devised a rat model of mandibular distraction osteogenesis that facilitates molecular analysis of this process. Such information has significant clinical implications because it may enable targeted therapeutic manipulations designed to accelerate osseous regeneration. In this study, we have evaluated the expression of transforming growth factor beta-1, a major regulator of osteogenesis during endochondral bone formation and development, and osteocalcin, an abundant noncollagenous extracellular matrix protein implicated in the regulation of mineralization and bone turnover. The right hemimandible of 36 adult male rats was osteotomized, and a customized distraction device was applied. Animals were allowed to recover and, after a 3-day latency period, were distracted at a rate of 0.25 mm twice daily for 6 days followed by a 2- or 4-week consolidation period. Distraction regenerate was harvested after the latency period, days 2, 4, or 6 of distraction, and after 2 or 4 weeks of consolidation and processed for Northern analysis (n = 4 at each time point) and immunohistochemical localization of TGF-beta1 (n = 2 at each time point). Six sham-operated animals (i.e., skin incision without osteotomy) were also killed (immediately postoperatively), and the mandibles were harvested and prepared in a similar fashion. Equal loading and transfer of RNA for Northern analysis was ensured by stripping and probing membranes with a probe against GAPDH (a housekeeping gene). Our results demonstrate that the spatial and temporal patterns of TGF-beta1 mRNA expression and protein production coincide with osteoblast migration, differentiation, and extracellular matrix synthesis. In addition, we demonstrate that TGF-beta1 production may be an important regulator of vasculogenesis during mandibular distraction osteogenesis. Finally, we have shown that osteocalcin gene expression coincides temporally with mineralization during rat mandibular distraction osteogenesis.
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Affiliation(s)
- B J Mehrara
- Institute of Reconstructive Plastic Surgery, and Department of Surgery, New York University Medical Center, NY 10016, USA
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