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Chen X, Cai C, Lun S, Ye Q, Pan W, Chen Y, Wu Y, Feng T, Su F, Ma C, Luo J, Liu M, Ma G. The contribution of a novel PHEX gene mutation to X-linked hypophosphatemic rickets: a case report and an analysis of the gene mutation dosage effect in a rat model. Front Endocrinol (Lausanne) 2023; 14:1251718. [PMID: 38116308 PMCID: PMC10728720 DOI: 10.3389/fendo.2023.1251718] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/02/2023] [Accepted: 11/15/2023] [Indexed: 12/21/2023] Open
Abstract
A Chinese family was identified to have two patients with rickets, an adult female and a male child (proband), both exhibiting signs related to X-linked hypophosphatemic rickets (XLH). Gene sequencing analysis revealed a deletion of adenine at position 1985 (c.1985delA) in the PHEX-encoding gene. To investigate the relationship between this mutation and the pathogenicity of XLH, as well as analyze the effects of different dosages of PHEX gene mutations on clinical phenotypes, we developed a rat model carrying the PHEX deletion mutation. The CRISPR/Cas9 gene editing technology was employed to construct the rat model with the PHEX gene mutation (c.1985delA). Through reproductive procedures, five genotypes of rats were obtained: female wild type (X/X), female heterozygous (-/X), female homozygous wild type (-/-), male wild type (X/Y), and male hemizygous (-/Y). The rats with different genotypes underwent analysis of growth, serum biochemical parameters, and bone microstructure. The results demonstrated the successful generation of a stable rat model inheriting the PHEX gene mutation. Compared to the wild-type rats, the mutant rats displayed delayed growth, shorter femurs, and significantly reduced bone mass. Among the female rats, the homozygous individuals exhibited the smallest body size, decreased bone mass, shortest femur length, and severe deformities. Moreover, the mutant rats showed significantly lower blood phosphorus concentration, elevated levels of FGF23 and alkaline phosphatase, and increased expression of phosphorus regulators. In conclusion, the XLH rat model with the PHEX gene mutation dosage demonstrated its impact on growth and development, serum biochemical parameters, and femoral morphology.
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Affiliation(s)
- Xiaoming Chen
- Department of Endocrinology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
- Faculty of Chinese Medicine, Macau University of Science and Technology, Avenida Wai Long, Taipa, Macau, China
| | - Cijing Cai
- Department of Endocrinology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
- Maternal and Children’s Health Research Institute, Shunde Women and Children’s Hospital, Guangdong Medical University, Foshan, China
| | - Shaocong Lun
- Department of Endocrinology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Qiuli Ye
- Department of Traditional Chinese Medicine, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Weiyuan Pan
- Department of Endocrinology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Yushi Chen
- Department of Endocrinology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Yuexuan Wu
- Department of Endocrinology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Taoshan Feng
- Department of Endocrinology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Faming Su
- Department of Endocrinology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Choudi Ma
- Department of Endocrinology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Jiaxin Luo
- Department of Endocrinology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Meilian Liu
- Department of Pulmonary Oncology, Affiliated Hospital of Guangdong Medical University, Zhanjiang, China
| | - Guoda Ma
- Maternal and Children’s Health Research Institute, Shunde Women and Children’s Hospital, Guangdong Medical University, Foshan, China
- Key Laboratory of Research in Maternal and Child Medicine and Birth Defects, Guangdong Medical University, Foshan, China
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Robinson ME, AlQuorain H, Murshed M, Rauch F. Mineralized tissues in hypophosphatemic rickets. Pediatr Nephrol 2020; 35:1843-1854. [PMID: 31392510 DOI: 10.1007/s00467-019-04290-y] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 06/03/2019] [Accepted: 06/06/2019] [Indexed: 12/19/2022]
Abstract
Hypophosphatemic rickets is caused by renal phosphate wasting that is most commonly due to X-linked dominant mutations in PHEX. PHEX mutations cause hypophosphatemia indirectly, through the increased expression of fibroblast growth factor 23 (FGF23) by osteocytes. FGF23 decreases renal phosphate reabsorption and thereby increases phosphate excretion. The lack of phosphate leads to a mineralization defect at the level of growth plates (rickets), bone tissue (osteomalacia), and teeth, where the defect facilitates the formation of abscesses. The bone tissue immediately adjacent to osteocytes often remains unmineralized ("periosteocytic lesions"), highlighting the osteocyte defect in this disorder. Common clinical features of XLH include deformities of the lower extremities, short stature, enthesopathies, dental abscesses, as well as skull abnormalities such as craniosynostosis and Chiari I malformation. For the past four decades, XLH has been treated by oral phosphate supplementation and calcitriol, which improves rickets and osteomalacia and the dental manifestations, but often does not resolve all aspects of the mineralization defects. A newer treatment approach using inactivating FGF23 antibodies leads to more stable control of serum inorganic phosphorus levels and seems to heal rickets more reliably. However, the long-term benefits of FGF23 antibody treatment remain to be elucidated.
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Affiliation(s)
- Marie-Eve Robinson
- Shriners Hospital for Children and McGill University, 1003 Boulevard Decarie, Montreal, Québec, H4A 0A9, Canada
| | - Haitham AlQuorain
- Shriners Hospital for Children and McGill University, 1003 Boulevard Decarie, Montreal, Québec, H4A 0A9, Canada
| | - Monzur Murshed
- Shriners Hospital for Children and McGill University, 1003 Boulevard Decarie, Montreal, Québec, H4A 0A9, Canada
| | - Frank Rauch
- Shriners Hospital for Children and McGill University, 1003 Boulevard Decarie, Montreal, Québec, H4A 0A9, Canada.
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Fuente R, Gil-Peña H, Claramunt-Taberner D, Hernández-Frías O, Fernández-Iglesias Á, Hermida-Prado F, Anes-González G, Rubio-Aliaga I, Lopez JM, Santos F. Marked alterations in the structure, dynamics and maturation of growth plate likely explain growth retardation and bone deformities of young Hyp mice. Bone 2018; 116:187-195. [PMID: 30096468 DOI: 10.1016/j.bone.2018.08.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 08/02/2018] [Accepted: 08/07/2018] [Indexed: 12/11/2022]
Abstract
Mechanisms underlying growth impairment and bone deformities in X-linked hypophosphatemia are not fully understood. We here describe marked alterations in the structure, dynamics and maturation of growth plate in growth-retarded young Hyp mice, in comparison with wild type mice. Hyp mice exhibited reduced proliferation and apoptosis rates of chondrocytes as well as severe disturbance in the process of chondrocyte hypertrophy disclosed by abnormal expression of proteins likely involved in cell enlargement, irregular chondro-osseous junction and disordered bone trabecular pattern and vascular invasion in the primary spongiosa. (Hyp mice had elevated circulating FGF23 levels and over activation of ERK in the growth plate.) All these findings provide a basis to explain growth impairment and metaphyseal deformities in XLH. Hyp mice were compared with wild type mice serum parameters, nutritional status and growth impairment by evaluation of growth cartilage and bone structures. Hyp mice presented hyphosphatemia with high FGF23 levels. Weight gain and longitudinal growth resulted reduced in them with numerous skeletal abnormalities at cortical bone. It was also observed aberrant trabecular organization at primary spongiosa and atypical growth plate organization with abnormal proliferation and hypertrophy of chondrocytes and diminished apoptosis and vascular invasion processes. The present results show for the first time the abnormalities present in the growth plate of young Hyp mice and suggest that both cartilage and bone alterations may be involved in the growth impairment and the long bone deformities of XLH.
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Affiliation(s)
- Rocío Fuente
- Division of Pediatrics, Department of Medicine, Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain; Harvard School of Dental Medicine, Developmental Biology, Harvard University, Boston, MA, USA
| | - Helena Gil-Peña
- Department of Pediatrics, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain.
| | - Débora Claramunt-Taberner
- Division of Pediatrics, Department of Medicine, Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - Olaya Hernández-Frías
- Division of Pediatrics, Department of Medicine, Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - Ángela Fernández-Iglesias
- Division of Pediatrics, Department of Medicine, Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - Francisco Hermida-Prado
- Department of Otolaryngologist, Hospital Universitario Central de Asturias, Instituto Universitario de Oncología del Principado de Asturias, Oviedo, Spain
| | - Gonzalo Anes-González
- Department of Pediatrics, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain
| | - Isabel Rubio-Aliaga
- University of Zurich, Institute of Physiology, Kidney and Acid-base Physiology Group, Zurich, Switzerland
| | - Jose Manuel Lopez
- Division of Pediatrics, Department of Medicine, Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - Fernando Santos
- Division of Pediatrics, Department of Medicine, Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain; Department of Pediatrics, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain
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Fuente R, Gil-Peña H, Claramunt-Taberner D, Hernández O, Fernández-Iglesias A, Alonso-Durán L, Rodríguez-Rubio E, Santos F. X-linked hypophosphatemia and growth. Rev Endocr Metab Disord 2017; 18:107-115. [PMID: 28130634 DOI: 10.1007/s11154-017-9408-1] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
X-Linked hypophosphatemia (XLH) is the most common form of hereditary rickets caused by loss-of function mutations in the PHEX gene. XLH is characterized by hypophosphatemia secondary to renal phosphate wasting, inappropriately low concentrations of 1,25 dihydroxyvitamin D and high circulating levels of fibroblast growth factor 23 (FGF23). Short stature and rachitic osseous lesions are characteristic phenotypic findings of XLH although the severity of these manifestations is highly variable among patients. The degree of growth impairment is not dependent on the magnitude of hypophosphatemia or the extent of legs´ bowing and height is not normalized by chronic administration of phosphate supplements and 1α hydroxyvitamin D derivatives. Treatment with growth hormone accelerates longitudinal growth rate but there is still controversy regarding the potential risk of increasing bone deformities and body disproportion. Treatments aimed at blocking FGF23 action are promising, but information is lacking on the consequences of counteracting FGF23 during the growing period. This review summarizes current knowledge on phosphorus metabolism in XLH, presents updated information on XLH and growth, including the effects of FGF23 on epiphyseal growth plate of the Hyp mouse, an animal model of the disease, and discusses growth hormone and novel FGF23 related therapies.
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Affiliation(s)
- R Fuente
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - H Gil-Peña
- Department of Pediatrics, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain
| | - D Claramunt-Taberner
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - O Hernández
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - A Fernández-Iglesias
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - L Alonso-Durán
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - E Rodríguez-Rubio
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain
| | - F Santos
- Division of Pediatrics, Department of Medicine. Faculty of Medicine, University of Oviedo, Oviedo, Asturias, Spain.
- Department of Pediatrics, Hospital Universitario Central de Asturias (HUCA), Oviedo, Asturias, Spain.
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Razali NN, Hwu TT, Thilakavathy K. Phosphate homeostasis and genetic mutations of familial hypophosphatemic rickets. J Pediatr Endocrinol Metab 2015; 28:1009-17. [PMID: 25894638 DOI: 10.1515/jpem-2014-0366] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2014] [Accepted: 02/26/2015] [Indexed: 01/17/2023]
Abstract
Hypophosphatemic rickets (HR) is a syndrome of hypophosphatemia and rickets that resembles vitamin D deficiency, which is caused by malfunction of renal tubules in phosphate reabsorption. Phosphate is an essential mineral, which is important for bone and tooth structure. It is regulated by parathyroid hormone, 1,25-dihydroxyvitamin D and fibroblast-growth-factor 23 (FGF23). X-linked hypophosphatemia (XLH), autosomal dominant HR (ADHR), and autosomal recessive HR (ARHR) are examples of hereditary forms of HR, which are mainly caused by mutations in the phosphate regulating endopeptidase homolog, X-linked (PHEX), FGF23, and, dentin matrix protein-1 (DMP1) and ecto-nucleotide pyro phosphatase/phosphodiesterase 1 (ENPP1) genes, respectively. Mutations in these genes are believed to cause elevation of circulating FGF23 protein. Increase in FGF23 disrupts phosphate homeostasis, leading to HR. This review aims to summarize phosphate homeostasis and focuses on the genes and mutations related to XLH, ADHR, and ARHR. A compilation of XLH mutation hotspots based on the PHEX gene database and mutations found in the FGF23, DMP1, and ENPP1 genes are also made available in this review.
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Ichikawa S, Gray AK, Bikorimana E, Econs MJ. Dosage effect of a Phex mutation in a murine model of X-linked hypophosphatemia. Calcif Tissue Int 2013; 93:155-62. [PMID: 23700148 PMCID: PMC3742319 DOI: 10.1007/s00223-013-9736-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 04/22/2013] [Indexed: 10/26/2022]
Abstract
X-linked hypophosphatemia (XLH) is caused by mutations in the PHEX gene, which increase circulating levels of the phosphaturic hormone, fibroblast growth factor 23 (FGF23). Because XLH is a dominant disease, one mutant allele is sufficient for manifestation of the disease. However, the dosage effect of a PHEX mutation in XLH is not completely understood. To examine the effect of Phex genotypes, we compared serum biochemistries and skeletal measures between all five possible genotypes of a new murine model of XLH (Phex (K496X) or Phex (Jrt) ). Compared to sex-matched littermate controls, all Phex mutant mice had hypophosphatemia, mild hypocalcemia, and increased parathyroid hormone and alkaline phosphatase levels. Furthermore, mutant mice had markedly elevated serum Fgf23 levels due to increased Fgf23 expression and reduced cleavage of Fgf23. Although females with a homozygous Phex mutation were slightly more hypocalcemic and hypophosphatemic than heterozygous females, the two groups had comparable intact Fgf23 levels. Similarly, there was no difference in intact Fgf23 or phosphorus concentrations between hemizygous males and heterozygous females. Compared to heterozygous females, homozygous counterparts were significantly smaller and had shorter femurs with reduced bone mineral density, suggesting the existence of dosage effect in the skeletal phenotype of XLH. However, overall phenotypic trends in regards to mineral ion homeostasis were mostly unaffected by the presence of one or two mutant Phex allele(s). The lack of a gene dosage effect on circulating Fgf23 (and thus phosphorus) levels suggests that a Phex mutation may create the lower set point for extracellular phosphate concentrations.
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Affiliation(s)
- Shoji Ichikawa
- Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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Abstract
Over the last decade the discovery of fibroblast growth factor 23 (FGF23) and the progressive and ongoing clarification of its role in phosphate and mineral metabolism have led to expansion of the diagnostic spectrum of primary hypophosphatemic syndromes. This article focuses on the impairment of growth in these syndromes. Growth retardation is a common, but not constant, feature and it presents with large variability. As a result of the very low prevalence of other forms of primary hypophosphatemic syndromes, the description of longitudinal growth and the pathogenesis of its impairment have been mostly studied in X-linked hypophosphatemia (XLH) patients and in Hyp mice, the animal model of this disease. In general, children with XLH have short stature with greater shortness of lower limbs than trunk. Treatment with phosphate supplements and 1α vitamin D derivatives heals active lesions of rickets, but does not normalize growth of XLH patients. Patients might benefit from recombinant human growth hormone (rhGH) therapy, which may accelerate the growth rate without increasing body disproportion or correcting hypophosphatemia. These clinical data as well as research findings obtained in Hyp mice suggest that the pathogenesis of defective growth in XLH and other hypophosphatemic syndromes is not entirely dependent on the mineralization disorder and point to other effects of hypophosphatemia itself or FGF23 on the metabolism of bone and growth plate.
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Affiliation(s)
- Fernando Santos
- Hospital Universitario Central de Asturias & University of Oviedo, Oviedo, Asturias, Spain.
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Growth in PHEX-associated X-linked hypophosphatemic rickets: the importance of early treatment. Pediatr Nephrol 2012; 27:581-8. [PMID: 22101457 DOI: 10.1007/s00467-011-2046-z] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Revised: 09/16/2011] [Accepted: 09/19/2011] [Indexed: 01/10/2023]
Abstract
Inactivating mutations in phosphate-regulating endopeptidase (PHEX) cause X-linked hypophosphatemic rickets (XLHR) characterized by phosphaturia, hypophosphatemia, bony deformities, and growth retardation. We assessed the efficacy of combined calcitriol and orally administered phosphate (Pi) therapy on longitudinal growth in relation to age at treatment onset in a retrospective, single-center review of children with XLHR and documented PHEX mutations. Growth was compared in those who started treatment before (G1; N = 10; six boys) and after (G2; N = 13; five boys) 1 year old. Median height standard deviation score (HSDS) at treatment onset was normal in G1: 0.1 [interquartile range (IR) -1.3 to 0.4) and significantly (p = 0.004) lower in G2 (IR -2.1 (-2.8 to -1.4). Treatment duration was similar [G1 8.5 (4.0-15.2) vs G2 11.9 (6.2-14.3) years; p = 0.56], as were prescribed phosphate and calcitriol doses. Recent HSDS was significantly (p = 0.009) better in G1 [-0.7 (-1.5 to 0.3)] vs G2 [-2.0 (-2.3 to -1.0)]. No effects of gender or genotype on growth could be identified. Children with PHEX-associated XLHR benefit from early treatment and can achieve normal growth. Minimal catchup growth was seen in those who started treatment later. Our findings emphasize the importance of early diagnosis to allow treatment before growth has been compromised.
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Moriyama K, Hanai A, Mekada K, Yoshiki A, Ogiwara K, Kimura A, Takahashi T. Kbus/Idr, a mutant mouse strain with skeletal abnormalities and hypophosphatemia: identification as an allele of 'Hyp'. J Biomed Sci 2011; 18:60. [PMID: 21854633 PMCID: PMC3175157 DOI: 10.1186/1423-0127-18-60] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2011] [Accepted: 08/20/2011] [Indexed: 12/17/2022] Open
Abstract
Background The endopeptidase encoded by Phex (phosphate-regulating gene with homologies to endopeptidases linked to the X chromosome) is critical for regulation of bone matrix mineralization and phosphate homeostasis. PHEX has been identified from analyses of human X-linked hypophosphatemic rickets and Hyp mutant mouse models. We here demonstrated a newly established dwarfism-like Kbus/Idr mouse line to be a novel Hyp model. Methods Histopathological and X-ray examination with cross experiments were performed to characterize Kbus/Idr. RT-PCR-based and exon-directed PCR screening performed to identify the presence of genetic alteration. Biochemical assays were also performed to evaluate activity of alkaline phosphatase. Results Kbus/Idr, characterized by bone mineralization defects, was found to be inherited in an X chromosome-linked dominant manner. RT-PCR experiments showed that a novel mutation spanning exon 16 and 18 causing hypophosphatemic rickets. Alkaline phosphatase activity, as an osteoblast marker, demonstrated raised levels in the bone marrow of Kbus/Idr independent of the age. Conclusions Kbus mice should serve as a useful research tool exploring molecular mechanisms underlying aberrant Phex-associated pathophysiological phenomena.
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Affiliation(s)
- Kenji Moriyama
- Department of Medicine & Clinical Science, School of Pharmacy and Pharmaceutical Sciences, Mukogawa Women's University, Nishinomiya 663-8179, Japan.
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Beck-Nielsen SS, Brusgaard K, Rasmussen LM, Brixen K, Brock-Jacobsen B, Poulsen MR, Vestergaard P, Ralston SH, Albagha OME, Poulsen S, Haubek D, Gjørup H, Hintze H, Andersen MG, Heickendorff L, Hjelmborg J, Gram J. Phenotype presentation of hypophosphatemic rickets in adults. Calcif Tissue Int 2010; 87:108-19. [PMID: 20524110 DOI: 10.1007/s00223-010-9373-0] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Accepted: 04/25/2010] [Indexed: 02/02/2023]
Abstract
Hypophosphatemic rickets (HR) is a group of rare disorders caused by excessive renal phosphate wasting. The purpose of this cross-sectional study of 38 HR patients was to characterize the phenotype of adult HR patients. Moreover, skeletal and endodontic severity scores were defined to assess possible gender differences in disease severity in patients with genetically verified X-linked HR. Compared to normal reference data, i.e., z = 0, HR patients had significantly lower final height, with a mean difference in z-score of -1.9 (95% CI -2.4 to -1.4, P < 0.001). Compared to paired z-scores of final height, z-scores of leg length were significantly lower and those of sitting height were significantly higher (P < 0.001), resulting in disproportion as indicated by the significantly elevated sitting height ratio, mean difference in z-score of 2.6 (95% CI 2.1-3.1, P < 0.001). Z-scores of head circumference (median 1.4, range -0.4 to 5.5, P < 0.001) and z-scores of bone mineral density (BMD) of the lumbar spine (median 1.9, range -1.5 to 8.6, P < 0.001) were significantly elevated compared to normal reference data. The relative risk (RR) of fracture was reduced (RR = 0.34, 95% CI 0.20-0.57, P < 0.001). The skeletal severity score tended to be higher in males compared to females (P = 0.07), and no gender difference in endodontic severity was found. In conclusion, adult HR patients were characterized by short stature and were disproportioned. They had elevated BMD of the lumbar spine and a reduced risk of fractures. We found a tendency for males to be more severely affected than females.
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Affiliation(s)
- Signe S Beck-Nielsen
- Department of Pediatrics, H. C. Andersen Children's Hospital, Odense University Hospital, Sdr. Boulevard 29, 5000 Odense, Denmark.
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Migeon BR. X inactivation, female mosaicism, and sex differences in renal diseases. J Am Soc Nephrol 2008; 19:2052-9. [PMID: 18448583 DOI: 10.1681/asn.2008020198] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
A good deal of sex differences in kidney disease is attributable to sex differences in the function of genes on the X chromosome. Males are uniquely vulnerable to mutations in their single copy of X-linked genes, whereas females are often mosaic, having a mixture of cells expressing different sets of X-linked genes. This cellular mosaicism created by X inactivation in females is most often advantageous, protecting carriers of X-linked mutations from the severe clinical manifestations seen in males. Even subtle differences in expression of many of the 1100 X-linked genes may contribute to sex differences in the clinical expression of renal diseases.
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Affiliation(s)
- Barbara R Migeon
- McKusick-Nathans Institute of Genetic Medicine, 459 Broadway Research Building, 733 N. Broadway, Baltimore, MD 21205, USA.
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Goji K, Ozaki K, Sadewa AH, Nishio H, Matsuo M. Somatic and germline mosaicism for a mutation of the PHEX gene can lead to genetic transmission of X-linked hypophosphatemic rickets that mimics an autosomal dominant trait. J Clin Endocrinol Metab 2006; 91:365-70. [PMID: 16303832 DOI: 10.1210/jc.2005-1776] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/12/2023]
Abstract
CONTEXT Familial hypophosphatemic rickets is usually transmitted as an X-linked dominant disorder (XLH), although autosomal dominant forms have also been observed. Genetic studies of these disorders have identified mutations in PHEX and FGF23 as the causes of X-linked dominant disorder and autosomal dominant forms, respectively. OBJECTIVE The objective of the study was to describe the molecular genetic findings in a family affected by hypophosphatemic rickets with presumed autosomal dominant inheritance. PATIENTS We studied a family in which the father and the elder of his two daughters, but not the second daughter, were affected by hypophosphatemic rickets. The pedigree interpretation of the family suggested that genetic transmission of the disorder occurred as an autosomal dominant trait. METHODS AND RESULTS Direct nucleotide sequencing of FGF23 and PHEX revealed that the elder daughter was heterozygous for an R567X mutation in PHEX, rather than FGF23, suggesting that the genetic transmission occurred as an X-linked dominant trait. Unexpectedly, the father was heterozygous for this mutation. Single-nucleotide primer extension and denaturing HPLC analysis of the father using DNA from single hair roots revealed that he was a somatic mosaic for the mutation. Haplotype analysis confirmed that the father transmitted the genotypes for 18 markers on the X chromosome equally to his two daughters. The fact that the father transmitted the mutation to only one of his two daughters indicated that he was a germline mosaic for the mutation. CONCLUSIONS Somatic and germline mosaicism for an X-linked dominant mutation in PHEX may mimic autosomal dominant inheritance.
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Affiliation(s)
- Katsumi Goji
- Department of Endocrinology and Metabolism, Kobe Children's Hospital, 1-1-1 Takakuradai, Suma-ku, Kobe 654-0081, Japan.
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Rowe PSN. The wrickkened pathways of FGF23, MEPE and PHEX. CRITICAL REVIEWS IN ORAL BIOLOGY AND MEDICINE : AN OFFICIAL PUBLICATION OF THE AMERICAN ASSOCIATION OF ORAL BIOLOGISTS 2004; 15:264-81. [PMID: 15470265 PMCID: PMC3361894 DOI: 10.1177/154411130401500503] [Citation(s) in RCA: 129] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The last 350 years since the publication of the first medical monograph on rickets (old English term wrickken) (Glisson et al., 1651) have seen spectacular advances in our understanding of mineral-homeostasis. Seminal and exciting discoveries have revealed the roles of PTH, vitamin D, and calcitonin in regulating calcium and phosphate, and maintaining healthy teeth and skeleton. However, it is clear that the PTH/Vitamin D axis does not account for the entire picture, and a new bone-renal metabolic milieu has emerged, implicating a novel set of matrix proteins, hormones, and Zn-metallopeptidases. The primary defects in X-linked hypophosphatemic rickets (HYP) and autosomal-dominant hypophosphatemic rickets (ADHR) are now identified as inactivating mutations in a Zn-metalloendopeptidase (PHEX) and activating mutations in fibroblast-growth-factor-23 (FGF23), respectively. In oncogenic hypophosphatemic osteomalacia (OHO), several tumor-expressed proteins (MEPE, FGF23, and FRP-4) have emerged as candidate mediators of the bone-renal pathophysiology. This has stimulated the proposal of a global model that takes into account the remarkable similarities between the inherited diseases (HYP and ADHR) and the tumor-acquired disease OHO. In HYP, loss of PHEX function is proposed to result in an increase in uncleaved full-length FGF23 and/or inappropriate processing of MEPE. In ADHR, a mutation in FGF23 results in resistance to proteolysis by PHEX or other proteases and an increase in half-life of full-length phosphaturic FGF23. In OHO, over-expression of FGF23 and/or MEPE is proposed to result in abnormal renal-phosphate handling and mineralization. Although this model is attractive, many questions remain unanswered, suggesting a more complex picture. The following review will present a global hypothesis that attempts to explain the experimental and clinical observations in HYP, ADHR, and OHO, plus diverse mouse models that include the MEPE null mutant, HYP-PHEX transgenic mouse, and MEPE-PHEX double-null-mutant.
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Affiliation(s)
- Peter S N Rowe
- Department of Periodontics, The University of Texas Health Science Center at San Antonio, Mail Code 7894, 7703 Floyd Curl Drive, Room 3.579U, San Antonio, TX 78229-3900, USA.
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Brewer AJ, Canaff L, Hendy GN, Tenenhouse HS. Differential regulation of PHEX expression in bone and parathyroid gland by chronic renal insufficiency and 1,25-dihydroxyvitamin D3. Am J Physiol Renal Physiol 2004; 286:F739-48. [PMID: 14693675 DOI: 10.1152/ajprenal.00321.2003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Mutations in the PHEX gene are responsible for X-linked hypophosphatemia, a renal phosphate-wasting disorder associated with defective skeletal mineralization. PHEX is predominantly expressed in bones and teeth and in the parathyroid gland of patients with chronic renal failure and tertiary hyperparathyroidism. The purpose of the present study was to examine the effects of renal insufficiency and 1,25-dihydroxyvitamin D3[1,25(OH)2D3] on the regulation of PHEX expression in rat tibia and parathyroid gland. In rats fed a high-phosphate (Pi) diet, ⅚ nephrectomy elicited a significant increase in the serum parathyroid hormone (PTH) concentration that was associated with a significant increase in the abundance of PHEX mRNA and protein in the tibia and a significant increase in PHEX mRNA in the parathyroid gland. In contrast, 1,25(OH)2D3administration to intact rats fed a control diet elicited a significant decrease in the serum PTH concentration that was accompanied by a significant decrease in PHEX mRNA and protein abundance in the tibia and a significant decrease in PHEX mRNA in the parathyroid gland. In addition, the increases in serum PTH levels and PHEX mRNA in the tibia and parathyroid gland in ⅚ nephrectomized rats fed a high-Pidiet were blunted by 1,25(OH)2D3. Serum PTH concentration was positively and significantly correlated with tibial PHEX mRNA and protein abundance. In summary, we demonstrate that PHEX expression in the tibia and parathyroid gland is increased by chronic renal insufficiency and decreased by 1,25(OH)2D3administration and suggest that PTH status may play an important role in mediating these changes in PHEX expression.
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Affiliation(s)
- Angela J Brewer
- Montreal Children's Hospital Research Institute, 4060 St. Catherine St. West, Rm. 222, Montreal, Quebec, Canada H3Z 2Z3.
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