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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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董 沙, 车 若, 郑 必, 张 爱, 王 春, 白 咪, 陈 颖. [Value of serum fibroblast growth factor 23 in diagnosis of hypophosphatemic rickets in children]. ZHONGGUO DANG DAI ER KE ZA ZHI = CHINESE JOURNAL OF CONTEMPORARY PEDIATRICS 2023; 25:705-710. [PMID: 37529952 PMCID: PMC10414175 DOI: 10.7499/j.issn.1008-8830.2303016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Accepted: 06/02/2023] [Indexed: 08/03/2023]
Abstract
OBJECTIVES To study the value of serum fibroblast growth factor 23 (FGF23) in the diagnosis of hypophosphatemic rickets in children. METHODS A total of 28 children who were diagnosed with hypophosphatemic rickets in Children's Hospital of Nanjing Medical University from January 2016 to June 2021 were included as the rickets group. Forty healthy children, matched for sex and age, who attended the Department of Child Healthcare of the hospital were included as the healthy control group. The serum level of FGF23 was compared between the two groups, and the correlations of the serum FGF23 level with clinical characteristics and laboratory test results were analyzed. The value of serum FGF23 in the diagnosis of hypophosphatemic rickets was assessed. RESULTS The rickets group had a significantly higher serum level of FGF23 than the healthy control group (P<0.05). In the rickets group, the serum FGF23 level was positively correlated with the serum alkaline phosphatase level (rs=0.38, P<0.05) and was negatively correlated with maximum renal tubular phosphorus uptake/glomerular filtration rate (rs=-0.64, P<0.05), while it was not correlated with age, height Z-score, sex, and parathyroid hormone (P>0.05). Serum FGF23 had a sensitivity of 0.821, a specificity of 0.925, an optimal cut-off value of 55.77 pg/mL, and an area under the curve of 0.874 in the diagnosis of hypophosphatemic rickets (P<0.05). CONCLUSIONS Serum FGF23 is of valuable in the diagnosis of hypophosphatemic rickets in children, which providing a theoretical basis for early diagnosis of this disease in clinical practice.
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Affiliation(s)
| | | | - 必霞 郑
- 南京医科大学附属儿童医院儿科学重点实验室,江苏南京210000
| | | | - 春莉 王
- 南京医科大学附属儿童医院儿科学重点实验室,江苏南京210000
| | - 咪 白
- 南京医科大学附属儿童医院儿科学重点实验室,江苏南京210000
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Buss DJ, Rechav K, Reznikov N, McKee MD. Mineral tessellation in mouse enthesis fibrocartilage, Achilles tendon, and Hyp calcifying enthesopathy: A shared 3D mineralization pattern. Bone 2023:116818. [PMID: 37295663 DOI: 10.1016/j.bone.2023.116818] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Revised: 05/17/2023] [Accepted: 06/01/2023] [Indexed: 06/12/2023]
Abstract
The hallmark of enthesis architecture is the 3D compositional and structural gradient encompassing four tissue zones - tendon/ligament, uncalcified fibrocartilage, calcified fibrocartilage and bone. This functional gradient accommodates the large stiffness differential between calcified bone and uncalcified tendon/ligament. Here we analyze in 3D the organization of the mouse Achilles enthesis and mineralizing Achilles tendon in comparison to lamellar bone. We use correlative, multiscale high-resolution volume imaging methods including μCT with submicrometer resolution and FIB-SEM tomography (both with deep learning-based image segmentation), and TEM and SEM imaging, to describe ultrastructural features of physiologic, age-related and aberrant mineral patterning. We applied these approaches to murine wildtype (WT) Achilles enthesis tissues to describe in normal calcifying fibrocartilage a crossfibrillar mineral tessellation pattern similar to that observed in lamellar bone, but with greater variance in mineral tesselle morphology and size. We also examined Achilles enthesis structure in Hyp mice, a murine model for the inherited osteomalacic disease X-linked hypophosphatemia (XLH) with calcifying enthesopathy. In Achilles enthesis fibrocartilage of Hyp mice, we show defective crossfibrillar mineral tessellation similar to that which occurs in Hyp lamellar bone. At the cellular level in fibrocartilage, unlike in bone where enlarged osteocyte mineral lacunae are found as peri-osteocytic lesions, mineral lacunar volumes for fibrochondrocytes did not differ between WT and Hyp mice. While both WT and Hyp aged mice demonstrate Achilles tendon midsubstance ectopic mineralization, a consistently defective mineralization pattern was observed in Hyp mice. Strong immunostaining for osteopontin was observed at all mineralization sites examined in both WT and Hyp mice. Taken together, this new 3D ultrastructural information describes details of common mineralization trajectories for enthesis, tendon and bone, which in Hyp/XLH are defective.
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Affiliation(s)
- Daniel J Buss
- Department of Anatomy and Cell Biology, School of Biomedical Sciences, Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada
| | - Katya Rechav
- Electron Microscopy Unit, Weizmann Institute of Science, Rehovot, Israel
| | - Natalie Reznikov
- Department of Anatomy and Cell Biology, School of Biomedical Sciences, Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada; Department of Bioengineering, Faculty of Engineering, McGill University, Montreal, Quebec, Canada; Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, Quebec, Canada
| | - Marc D McKee
- Department of Anatomy and Cell Biology, School of Biomedical Sciences, Faculty of Medicine and Health Sciences, McGill University, Montreal, Quebec, Canada; Faculty of Dental Medicine and Oral Health Sciences, McGill University, Montreal, Quebec, Canada.
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Chertok Shacham E, Maman N, Lazareva T, Masalha R, Mahagna L, Sela G, Ishay A. Normocalcemic primary hyperparathyroidism is an early stage of primary hyperparathyroidism according to fibroblast growth factor 23 level. Front Endocrinol (Lausanne) 2023; 14:1152464. [PMID: 37065752 PMCID: PMC10098304 DOI: 10.3389/fendo.2023.1152464] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Accepted: 03/13/2023] [Indexed: 04/01/2023] Open
Abstract
INTRODUCTION Normocalcemic primary hyperparathyroidism is a variant of primary hyperparathyroidism with consistently normal albumin-adjusted or free-ionized calcium levels. It may be an early stage of classic primary hyperparathyroidism or could represent primary kidney or bone disorder characterized by permanent elevation of PTH level. AIM OF THE STUDY The study aims to compare the FGF-23 levels in patients with PHPT, NPHPT, and normal calcium and PTH levels. METHODS Our study included patients who were referred to the endocrinology clinic with a presumptive diagnosis of primary hyperparathyroidism, an isolated increased level of PTH, or reduced bone densitometry. For each patient, we performed blood analysis of FGF-23, calcium, phosphate, vitamin D [25(OH)D3], estimated glomerular filtration rate (eGFR), bone turnover markers, and urine analysis for calcium/creatinine ratio. RESULTS Our study included 105 patients. Thirty patients with hypercalcemic hyperparathyroidism (HPHPT group), thirty patients with elevated PTH and normal calcium levels (NPHPT group), and 45 patients with normal calcium and PTH levels in the control group. FGF 23 level was 59.5± 23 pg/ml in the NPHPT group, 77 ± 33 pg/ml in the HPHPT group, and 49.7 ± 21.7 pg/ml in the control group (p=0.012). The phosphate level was lowest in the HPHPT group: 2.9 ± 0.6 vs 3.5 ± 0.44 in the NPHPT and 3.8 ± 0.5 in the control groups (p=0.001). No differences were found in eGFR, 25(OH)D3, C-terminal telopeptide type I collagen (CTX) and procollagen type 1 N-terminal propeptide (P1NP) levels, and bone densitometry scores between the three study groups. CONCLUSION Our findings suggest that NPHPT is an early stage of PHPT. Further studies are needed to determine the role of FGF-23 and its usefulness in NPHPT.
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Affiliation(s)
- Elena Chertok Shacham
- Endocrinology Unit, Haemek Medical Center, Afula, Israel
- *Correspondence: Elena Chertok Shacham,
| | - Nimra Maman
- Statistical Department, Haemek Medical Center, Afula, Israel
| | - Tatyana Lazareva
- Internal Medicine Department A, Haemek Medical Center, Afula, Israel
| | - Refaat Masalha
- Laboratory Medicine Department, Haemek Medical Center, Afula, Israel
| | - Lila Mahagna
- Laboratory Medicine Department, Haemek Medical Center, Afula, Israel
| | - Gala Sela
- Endocrinology Unit, Haemek Medical Center, Afula, Israel
| | - Avraham Ishay
- Endocrinology Unit, Haemek Medical Center, Afula, Israel
- Faculty of Medicine, Technion – Israel Institute of Technology, Haifa, Israel
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Jin JY, Zhang LY, Guo S, Tang K, Zeng L, Xiang R, Liang JY. Genetic analysis combined with 3D-printing assistant surgery in diagnosis and treatment for an X-linked hypophosphatemia patient. J Clin Lab Anal 2022; 36:e24243. [PMID: 35106857 PMCID: PMC8906030 DOI: 10.1002/jcla.24243] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2021] [Revised: 12/13/2021] [Accepted: 12/14/2021] [Indexed: 11/05/2022] Open
Abstract
Background Hypophosphatemia is mainly characterized by hypophosphatemia and a low level of 1alpha,25‐Dihydroxyvitamin D2 (1,25‐(OH)2D2) and/or 1alpha,25‐Dihydroxyvitamin D3 (1,25‐(OH)2D3) in the blood. Previous studies have demonstrated that variants in PHEX and FGF23 are primarily responsible for this disease. Although patients with variants of these two genes share almost the same symptoms, they exhibit the different hereditary pattern, X‐link dominant and autosome dominant, respectively. Three‐dimensional (3D) printing is a method which can accurately reconstruct physical objects, and its applications in orthopedics can contribute to realizing a more accurate surgical performance and a better outcome. Methods An X‐linked hypophosphatemia (XLH) family was recruited, with four patients across three generations. We screened candidate genes and filtered a duplication variant in PHEX. Variant analysis and co‐segregation confirmation were then performed. Before the operation of our patient, a digital model of our patient's leg had been rebuilt upon the CT scan data, and a polylactic acid (PLA) model had been 3D‐printed. Results A novel duplication PHEX variant c.574dupG (p.A192GfsX20) was identified in a family with XLH. Its pathogenicity was confirmed by the co‐segregation assay and online bioinformatics database. The preoperative plan was made with the help of the PLA model. Then, arch osteotomy and transverse osteotomy were performed under the guidance of the previous simulation. The appearance of the surgical‐intervened leg was satisfactory. Conclusions This study identified a novel PHEX variant and showed that 3D printing tech is a very promising approach for corrective osteotomies.
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Affiliation(s)
- Jie-Yuan Jin
- Department of Orthopaedics, Xiangya Hospital of Central South University, Changsha, China.,School of Life Sciences, Central South University, Changsha, China.,Hunan Key Laboratory of Animal Models for Human Diseases, Central South University, Changsha, China
| | - Li-Yang Zhang
- Department of Neurosurgery, Xiangya Hospital, Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, China
| | - Shuai Guo
- School of Life Sciences, Central South University, Changsha, China
| | - Ke Tang
- School of Life Sciences, Central South University, Changsha, China.,Hunan Key Laboratory of Animal Models for Human Diseases, Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, China
| | - Lei Zeng
- Department of Orthopaedics, Xiangya Hospital of Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, China
| | - Rong Xiang
- Department of Orthopaedics, Xiangya Hospital of Central South University, Changsha, China.,School of Life Sciences, Central South University, Changsha, China.,Hunan Key Laboratory of Animal Models for Human Diseases, Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, China
| | - Jie-Yu Liang
- Department of Orthopaedics, Xiangya Hospital of Central South University, Changsha, China.,Hunan Key Laboratory of Medical Genetics, School of Life Sciences, Central South University, Changsha, China
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Laurent MR, De Schepper J, Trouet D, Godefroid N, Boros E, Heinrichs C, Bravenboer B, Velkeniers B, Lammens J, Harvengt P, Cavalier E, Kaux JF, Lombet J, De Waele K, Verroken C, van Hoeck K, Mortier GR, Levtchenko E, Vande Walle J. Consensus Recommendations for the Diagnosis and Management of X-Linked Hypophosphatemia in Belgium. Front Endocrinol (Lausanne) 2021; 12:641543. [PMID: 33815294 PMCID: PMC8018577 DOI: 10.3389/fendo.2021.641543] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Accepted: 02/19/2021] [Indexed: 12/11/2022] Open
Abstract
X-linked hypophosphatemia (XLH) is the most common genetic form of hypophosphatemic rickets and osteomalacia. In this disease, mutations in the PHEX gene lead to elevated levels of the hormone fibroblast growth factor 23 (FGF23), resulting in renal phosphate wasting and impaired skeletal and dental mineralization. Recently, international guidelines for the diagnosis and treatment of this condition have been published. However, more specific recommendations are needed to provide guidance at the national level, considering resource availability and health economic aspects. A national multidisciplinary group of Belgian experts convened to discuss translation of international best available evidence into locally feasible consensus recommendations. Patients with XLH may present to a wide array of primary, secondary and tertiary care physicians, among whom awareness of the disease should be raised. XLH has a very broad differential-diagnosis for which clinical features, biochemical and genetic testing in centers of expertise are recommended. Optimal care requires a multidisciplinary approach, guided by an expert in metabolic bone diseases and involving (according to the individual patient's needs) pediatric and adult medical specialties and paramedical caregivers, including but not limited to general practitioners, dentists, radiologists and orthopedic surgeons. In children with severe or refractory symptoms, FGF23 inhibition using burosumab may provide superior outcomes compared to conventional medical therapy with phosphate supplements and active vitamin D analogues. Burosumab has also demonstrated promising results in adults on certain clinical outcomes such as pseudofractures. In summary, this work outlines recommendations for clinicians and policymakers, with a vision for improving the diagnostic and therapeutic landscape for XLH patients in Belgium.
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Affiliation(s)
- Michaël R. Laurent
- Centre for Metabolic Bone Diseases, University Hospitals Leuven, Leuven, Belgium
- *Correspondence: Michaël R. Laurent,
| | - Jean De Schepper
- Division of Pediatric Endocrinology, KidZ Health Castle, University Hospital Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
- Department of Pediatric Endocrinology, University Hospital Ghent, Ghent, Belgium
| | - Dominique Trouet
- Department of Pediatric Nephrology, Antwerp University Hospital, Antwerp, Belgium
- Laboratory of Experimental Medicine and Pediatrics, University of Antwerp, Antwerp, Belgium
| | - Nathalie Godefroid
- Pediatric Nephrology, Cliniques Universitaires St. Luc (UCL), Brussels, Belgium
| | - Emese Boros
- Paediatric Endocrinology Unit, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles, Brussels, Belgium
| | - Claudine Heinrichs
- Paediatric Endocrinology Unit, Hôpital Universitaire des Enfants Reine Fabiola, Université Libre de Bruxelles, Brussels, Belgium
| | - Bert Bravenboer
- Department of Endocrinology, University Hospital Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Brigitte Velkeniers
- Department of Endocrinology, University Hospital Brussels, Vrije Universiteit Brussel (VUB), Brussels, Belgium
| | - Johan Lammens
- Department of Orthopaedic Surgery and Department of Development and Regeneration, Prometheus LRD Division of Skeletal Tissue Engineering, KU Leuven - University Hospitals Leuven, Leuven, Belgium
| | - Pol Harvengt
- XLH Belgium, Belgian X-Linked Hypophosphatemic Rickets (XLH) Patient Association, Waterloo, Belgium
| | - Etienne Cavalier
- Department of Clinical Chemistry, University Hospital Center of Liège, University of Liège, Liège, Belgium
| | - Jean-François Kaux
- Physical Medicine, Rehabilitation and Sports Traumatology, University and University Hospital of Liège, Liège, Belgium
| | - Jacques Lombet
- Division of Nephrology, Department of Pediatrics, University Hospital Center of Liège, Liège, Belgium
| | - Kathleen De Waele
- Department of Pediatric Endocrinology, University Hospital Ghent, Ghent, Belgium
| | - Charlotte Verroken
- Unit for Osteoporosis and Metabolic Bone Diseases, Department of Endocrinology and Metabolism, Ghent University Hospital, Ghent, Belgium
| | - Koenraad van Hoeck
- Department of Pediatric Nephrology, Antwerp University Hospital, Antwerp, Belgium
- Laboratory of Experimental Medicine and Pediatrics, University of Antwerp, Antwerp, Belgium
| | - Geert R. Mortier
- Department of Medical Genetics, Antwerp University Hospital and University of Antwerp, Antwerp, Belgium
| | - Elena Levtchenko
- Department of Pediatrics/Pediatric Nephrology, University Hospitals Leuven, Leuven, Belgium
| | - Johan Vande Walle
- Department of Pediatric Nephrology, University Hospital Ghent, Ghent, Belgium
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Beck-Nielsen SS, Mughal Z, Haffner D, Nilsson O, Levtchenko E, Ariceta G, de Lucas Collantes C, Schnabel D, Jandhyala R, Mäkitie O. FGF23 and its role in X-linked hypophosphatemia-related morbidity. Orphanet J Rare Dis 2019; 14:58. [PMID: 30808384 PMCID: PMC6390548 DOI: 10.1186/s13023-019-1014-8] [Citation(s) in RCA: 145] [Impact Index Per Article: 29.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 01/30/2019] [Indexed: 12/29/2022] Open
Abstract
Background X-linked hypophosphatemia (XLH) is an inherited disease of phosphate metabolism in which inactivating mutations of the Phosphate Regulating Endopeptidase Homolog, X-Linked (PHEX) gene lead to local and systemic effects including impaired growth, rickets, osteomalacia, bone abnormalities, bone pain, spontaneous dental abscesses, hearing difficulties, enthesopathy, osteoarthritis, and muscular dysfunction. Patients with XLH present with elevated levels of fibroblast growth factor 23 (FGF23), which is thought to mediate many of the aforementioned manifestations of the disease. Elevated FGF23 has also been observed in many other diseases of hypophosphatemia, and a range of animal models have been developed to study these diseases, yet the role of FGF23 in the pathophysiology of XLH is incompletely understood. Methods The role of FGF23 in the pathophysiology of XLH is here reviewed by describing what is known about phenotypes associated with various PHEX mutations, animal models of XLH, and non-nutritional diseases of hypophosphatemia, and by presenting molecular pathways that have been proposed to contribute to manifestations of XLH. Results The pathophysiology of XLH is complex, involving a range of molecular pathways that variously contribute to different manifestations of the disease. Hypophosphatemia due to elevated FGF23 is the most obvious contributor, however localised fluctuations in tissue non-specific alkaline phosphatase (TNAP), pyrophosphate, calcitriol and direct effects of FGF23 have been observed to be associated with certain manifestations. Conclusions By describing what is known about these pathways, this review highlights key areas for future research that would contribute to the understanding and clinical treatment of non-nutritional diseases of hypophosphatemia, particularly XLH.
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Affiliation(s)
| | - Zulf Mughal
- Royal Manchester Children's Hospital, Manchester, UK
| | | | - Ola Nilsson
- Karolinska Institutet, Stockholm, Sweden and Örebro University, Örebro, Sweden
| | | | - Gema Ariceta
- Hospital Universitario Materno-Infantil Vall d'Hebron, Universitat Autonoma de Barcelona, Barcelona, Spain
| | | | - Dirk Schnabel
- University Children's Hospital of Berlin, Berlin, Germany
| | | | - Outi Mäkitie
- Children's Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
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8
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Econs MJ. Genetic diseases resulting from disordered FGF23/klotho biology. Bone 2017; 100:56-61. [PMID: 27746322 DOI: 10.1016/j.bone.2016.10.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2016] [Revised: 10/07/2016] [Accepted: 10/12/2016] [Indexed: 01/29/2023]
Affiliation(s)
- Michael J Econs
- Indiana University School of Medicine, 1120 W. Michigan Street, Gatch Clinical Building 459, Indianapolis, Indiana 46202-5111, United States.
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Ichikawa S, Gerard-O'Riley RL, Acton D, McQueen AK, Strobel IE, Witcher PC, Feng JQ, Econs MJ. A Mutation in the Dmp1 Gene Alters Phosphate Responsiveness in Mice. Endocrinology 2017; 158:470-476. [PMID: 28005411 PMCID: PMC5460778 DOI: 10.1210/en.2016-1642] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2016] [Accepted: 12/21/2016] [Indexed: 01/23/2023]
Abstract
Mutations in the dentin matrix protein 1 (DMP1) gene cause autosomal recessive hypophosphatemic rickets (ARHR). Hypophosphatemia in ARHR results from increased circulating levels of the phosphaturic hormone, fibroblast growth factor 23 (FGF23). Similarly, elevated FGF23, caused by mutations in the PHEX gene, is responsible for the hypophosphatemia in X-linked hypophosphatemic rickets (XLH). Previously, we demonstrated that a Phex mutation in mice creates a lower set point for extracellular phosphate, where an increment in phosphorus further stimulates Fgf23 production to maintain low serum phosphorus levels. To test the presence of the similar set point defect in ARHR, we generated 4- and 12-week-old Dmp1/Galnt3 double knockout mice and controls, including Dmp1 knockout mice (a murine model of ARHR), Galnt3 knockout mice (a murine model of familial tumoral calcinosis), and phenotypically normal double heterozygous mice. Galnt3 knockout mice had increased proteolytic cleavage of Fgf23, leading to low circulating intact Fgf23 levels with consequent hyperphosphatemia. In contrast, Dmp1 knockout mice had little Fgf23 cleavage and increased femoral Fgf23 expression, resulting in hypophosphatemia and low femoral bone mineral density (BMD). However, introduction of the Galnt3 null allele to Dmp1 knockout mice resulted in a significant increase in serum phosphorus and normalization of BMD. This increased serum phosphorus was accompanied by markedly elevated Fgf23 expression and circulating Fgf23 levels, an attempt to reduce serum phosphorus in the face of improving phosphorus levels. These data indicate that a Dmp1 mutation creates a lower set point for extracellular phosphate and maintains it through the regulation of Fgf23 cleavage and expression.
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Affiliation(s)
| | | | | | | | | | | | - Jian Q. Feng
- Department of Biomedical Sciences, Texas A&M College of Dentistry, Dallas, Texas 75246
| | - Michael J. Econs
- Departments of Medicine and
- Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana 46202; and
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Weng C, Chen J, Sun L, Zhou ZW, Feng X, Sun JH, Lu LP, Yu P, Qi M. A de novo mosaic mutation of PHEX in a boy with hypophosphatemic rickets. J Hum Genet 2015; 61:223-7. [PMID: 26559751 DOI: 10.1038/jhg.2015.133] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2015] [Revised: 09/13/2015] [Accepted: 10/09/2015] [Indexed: 01/11/2023]
Abstract
X-linked dominant hypophosphatemic rickets (XLHR), is characterized mainly by renal phosphate wasting with hypophosphatemia, short stature and abnormal bone mineralization. PHEX, located at Xp22.1-p22.2, is the gene causing XLHR. We aim to characterize the pathogenesis of a Chinese boy who is apparently 'heterozygous' in PHEX gene. Direct sequencing showed two peaks: one was a wild-type 'G' and the other was one base substitution to 'A', though the patient was a male. TA clone assay clearly showed each sequences and the ratios. The mutation effect was predicted via bioinformatics and validated by exon-trapping assay. Real-time PCR was applied to determine the copy number of PHEX. TA clone assay showed the frequency of normal (G) to mutant allele (A) as 19:13. Normal karyotype and real-time PCR results indicate the normal copy number of PHEX. This splice site mutation leads to 4 bp of exon 18 skipping out causing frame shift p.Gly590Glufs*28 that ends up with a loss of active site and Zn(2+)-binding site of PHEX, which probably interfere with renal phosphate reabsorption and bone mineralization. In conclusion, mutation at conserved splice acceptor site resulted in aberrant splicing, ending up with a damaged protein product. This novel mutation is de novo in mosaic pattern that may be induced during early postzygotic period. Taking mosaic somatic mutation of PHEX into consideration is strongly suggested in genetic counseling and etiology research for XLHR.
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Affiliation(s)
- Chen Weng
- Department of Cell Biology and Medical Genetics, School of Medicine Zhejiang University, Hangzhou, China
| | - Jiao Chen
- Department of Cell Biology and Medical Genetics, School of Medicine Zhejiang University, Hangzhou, China
| | - Li Sun
- Department of Nephrology and Rheumatology, Children's Hospital of Fudan University, Shanghai, China
| | - Zhong-Wei Zhou
- Department of Cell Biology and Medical Genetics, School of Medicine Zhejiang University, Hangzhou, China
| | - Xue Feng
- Department of Cell Biology and Medical Genetics, School of Medicine Zhejiang University, Hangzhou, China
| | - Jun-Hui Sun
- Department of Cell Biology and Medical Genetics, School of Medicine Zhejiang University, Hangzhou, China
| | - Ling-Ping Lu
- Department of Cell Biology and Medical Genetics, School of Medicine Zhejiang University, Hangzhou, China
| | - Ping Yu
- Department of Cell Biology and Medical Genetics, School of Medicine Zhejiang University, Hangzhou, China
| | - Ming Qi
- Department of Cell Biology and Medical Genetics, School of Medicine Zhejiang University, Hangzhou, China.,Center for Genetic and Genomic Medicine, Zhejiang University Medical School First Affiliated Hospital, Hangzhou, China.,Department of Pathology and Laboratory Medicine, University of Rochester, Rochester, NY, USA
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Econs MJ. Conventional Therapy in Adults With XLH Improves Dental Manifestations, But Not Enthesopathy. J Clin Endocrinol Metab 2015; 100:3622-4. [PMID: 26439151 PMCID: PMC4596048 DOI: 10.1210/jc.2015-3229] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Michael J Econs
- Indiana University School of Medicine, Indianapolis, Indiana 46202-5111
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12
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Abstract
Phosphate is essential for growth and maintenance of the skeleton and for generating high-energy phosphate compounds. Evolutionary adaptation to high dietary phosphorous in humans and other terrestrial vertebrates involves regulated mechanisms assuring the efficient renal elimination of excess phosphate. These mechanisms prominently include PTH, FGF23, and Vitamin D, which directly and indirectly regulate phosphate transport. Disordered phosphate homeostasis is associated with pathologies ranging from kidney stones to kidney failure. Chronic kidney disease results in hyperphosphatemia, an elevated calcium×phosphate product with considerable morbidity and mortality, mostly associated with adverse cardiovascular events. This chapter highlights recent findings and insights regarding the hormonal regulation of renal phosphate transport along with imbalances of phosphate balance due to acquired or inherited diseases states.
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13
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Mumm S, Huskey M, Cajic A, Wollberg V, Zhang F, Madson KL, Wenkert D, McAlister WH, Gottesman GS, Whyte MP. PHEX 3'-UTR c.*231A>G near the polyadenylation signal is a relatively common, mild, American mutation that masquerades as sporadic or X-linked recessive hypophosphatemic rickets. J Bone Miner Res 2015; 30:137-43. [PMID: 25042154 DOI: 10.1002/jbmr.2307] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Revised: 06/11/2014] [Accepted: 07/01/2014] [Indexed: 01/11/2023]
Abstract
Heritable forms of hypophosphatemic rickets (HR) include X-linked dominant (XLH), autosomal recessive, and autosomal dominant HR (from deactivating mutations in PHEX, DMP1 or ENPP1, and activating mutations in FGF23, respectively). Over 30 years, we have cared for 284 children with HR. For those 72 deemed sporadic XLH, we preliminarily reported mutation analysis for 30 subjects. Eleven had PHEX mutations. However, the remaining 19 lacked readily identifiable defects in PHEX, DMP1, or FGF23. In 2008, a novel single-base change near the polyadenylation (pA) signal in the 3'-UTR of PHEX was identified in XLH by other investigators. This c.*231A > G mutation is 3-bp upstream of the putative pA signal (AATAAA) in PHEX. Accordingly, we investigated whether this 3'-UTR defect accounted for HR in any of these 19 sporadic XLH patients. PCR amplification and sequencing of their 3'-UTR region showed the c.*231A > G mutation in four unrelated boys. Then, among an additional 22 of our 72 "sporadic" XLH patients, one boy and one girl were found to have the 3'-UTR defect, totaling six patients. Among these 52 sporadic XLH patients with PHEX analysis, 36 were girls and 16 were boys; ie, a ∼2:1 gender ratio consistent with XLH. However, finding five boys and only one girl with this 3'-UTR mutation presented an unexplained gender bias (p = 0.02). Haplotyping for the five boys, all reportedly unrelated, showed a common core haplotype suggesting a founder. Five of their six mothers had been studied clinically and biochemically (three radiologically). Remarkably, the seemingly unaffected mothers of four of these boys carried the 3'-UTR mutation. These healthy women had normal height, straight limbs, lacked the radiographic presentation of XLH, and showed normal or slight decreases in fasting serum Pi levels and/or TmP/GFR. Hence, PHEX c.*231A > G can masquerade as sporadic or X-linked recessive HR.
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Affiliation(s)
- Steven Mumm
- Division of Bone and Mineral Diseases, Washington University School of Medicine at Barnes-Jewish Hospital, St. Louis, MO, USA; Center for Metabolic Bone Disease and Molecular Research, Shriners Hospital for Children, St. Louis, MO, USA
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14
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Abstract
Rapid and somewhat surprising advances have recently been made toward understanding the molecular mechanisms causing heritable disorders of hypophosphatemia. The results of clinical, genetic, and translational studies have interwoven novel concepts underlying the endocrine control of phosphate metabolism, with far-reaching implications for treatment of both rare Mendelian diseases as well as common disorders of blood phosphate excess such as chronic kidney disease (CKD). In particular, diseases caused by changes in the expression and proteolytic control of the phosphaturic hormone fibroblast growth factor-23 (FGF23) have come to the forefront in terms of directing new models explaining mineral metabolism. These hypophosphatemic disorders as well as others resulting from independent defects in phosphate transport or metabolism will be reviewed herein, and implications for emerging therapeutic strategies based upon these new findings will be discussed.
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Affiliation(s)
- Kenneth E. White
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN 46202
- Correspondence to: Kenneth E. White, Ph.D., Department of Medical & Molecular Genetics, Indiana University School of Medicine, 975 West Walnut St., IB130, Indianapolis, IN 46202, Office phone: (317) 278-1775, Fax: (317) 274-2293,
| | - Julia M. Hum
- Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, IN 46202
| | - Michael J. Econs
- Division of Endocrinology and Metabolism, Department of Medicine, Indiana University School of Medicine, Indianapolis, IN 46202
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