1
|
Bosman W, Butler KM, Chang CA, Ganapathi M, Guzman E, Latta F, Chung WK, Claverie-Martin F, Davis JM, Hoenderop JGJ, de Baaij JHF. Pathogenic heterozygous TRPM7 variants and hypomagnesemia with developmental delay. Clin Kidney J 2024; 17:sfae211. [PMID: 39099563 PMCID: PMC11295107 DOI: 10.1093/ckj/sfae211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2024] [Indexed: 08/06/2024] Open
Abstract
Background Heterozygous variants in Transient receptor potential melastatin type 7 (TRPM7), encoding an essential and ubiquitously expressed cation channel, may cause hypomagnesemia, but current evidence is insufficient to draw definite conclusions and it is unclear whether any other phenotypes can occur. Methods Individuals with unexplained hypomagnesemia underwent whole-exome sequencing which identified TRPM7 variants. Pathogenicity of the identified variants was assessed by combining phenotypic, functional and in silico analyses. Results We report three new heterozygous missense variants in TRPM7 (p.Met1000Thr, p.Gly1046Arg, p.Leu1081Arg) in individuals with hypomagnesemia. Strikingly, autism spectrum disorder and developmental delay, mainly affecting speech and motor skills, was observed in all three individuals, while two out of three also presented with seizures. The three variants are predicted to be severely damaging by in silico prediction tools and structural modeling. Furthermore, these variants result in a clear loss-of-function of TRPM7-mediated magnesium uptake in vitro, while not affecting TRPM7 expression or insertion into the plasma membrane. Conclusions This study provides additional evidence for the association between heterozygous TRPM7 variants and hypomagnesemia and adds developmental delay to the phenotypic spectrum of TRPM7-related disorders. Considering that the TRPM7 gene is relatively tolerant to loss-of-function variants, future research should aim to unravel by what mechanisms specific heterozygous TRPM7 variants can cause disease.
Collapse
Affiliation(s)
- Willem Bosman
- Department of Medical BioSciences, Radboudumc, Nijmegen, The Netherlands
| | | | - Caitlin A Chang
- Department of Medical Genetics, BC Women and Children's Hospital, Vancouver, British Columbia, Canada
| | - Mythily Ganapathi
- Department of Pathology and Cell Biology, Columbia University Irving Medical Center, New York, NY, USA
| | - Edwin Guzman
- Department of Pediatrics, Columbia University Irving Medical Center, New York, NY, USA
| | - Femke Latta
- Department of Medical BioSciences, Radboudumc, Nijmegen, The Netherlands
| | - Wendy K Chung
- Department of Pediatrics, Boston Children's Hospital and Harvard Medical School, Boston, MA, USA
| | - Felix Claverie-Martin
- Unidad de Investigación, RenalTube Group, Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | | | | | | |
Collapse
|
2
|
Lin CM, Ding YX, Huang SM, Chen YC, Lee HJ, Sung CC, Lin SH. Identification and characterization of a novel CASR mutation causing familial hypocalciuric hypercalcemia. Front Endocrinol (Lausanne) 2024; 15:1291160. [PMID: 38487341 PMCID: PMC10937390 DOI: 10.3389/fendo.2024.1291160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/08/2023] [Accepted: 01/22/2024] [Indexed: 03/17/2024] Open
Abstract
Context Although a monoallelic mutation in the calcium-sensing receptor (CASR) gene causes familial hypocalciuric hypercalcemia (FHH), the functional characterization of the identified CASR mutation linked to the clinical response to calcimimetics therapy is still limited. Objective A 45-year-old male presenting with moderate hypercalcemia, hypocalciuria, and inappropriately high parathyroid hormone (PTH) had a good response to cinacalcet (total serum calcium (Ca2+) from 12.5 to 10.1 mg/dl). We identified the genetic mutation and characterized the functional and pathophysiological mechanisms, and then linked the mutation to calcimimetics treatment in vitro. Design Sanger sequencing of the CASR, GNA11, and AP2S1 genes was performed in his family. The simulation model was used to predict the function of the identified mutant. In vitro studies, including immunoblotting, immunofluorescence, a cycloheximide chase study, Calbryte™ 520 Ca2+ detection, and half-maximal effective concentration (EC50), were examined. Results This proband was found to carry a de novo heterozygous missense I554N in the cysteine-rich domain of CASR, which was pathogenic based on the different software prediction models and ACGME criteria. The simulation model showed that CASR I554N mutation decreased its binding energy with Ca2+. Human CASR I554N mutation attenuated the stability of CASR protein, reduced the expression of p-ERK 1/2, and blunted the intracellular Ca2+ response to gradient extracellular Ca2+ (eCa2+) concentration. The EC50 study also demonstrated the correctable effect of calcimimetics on the function of the CASR I554N mutation. Conclusion This novel CASR I554N mutation causing FHH attenuates CASR stability, its binding affinity with Ca2+, and the response to eCa2+ corrected by therapeutic calcimimetics.
Collapse
Affiliation(s)
- Chien-Ming Lin
- Department of Pediatrics, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Yi-Xuan Ding
- Department of Pediatrics, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Shih-Ming Huang
- Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan
| | - Ying-Chuan Chen
- Department of Physiology and Biophysics, National Defense Medical Center, Taipei, Taiwan
| | - Hwei-Jen Lee
- Department of Biochemistry, National Defense Medical Center, Taipei, Taiwan
| | - Chih-Chien Sung
- Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| | - Shih-Hua Lin
- Division of Nephrology, Department of Medicine, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan
| |
Collapse
|
3
|
Cuny T, Romanet P, Goldsworthy M, Guérin C, Wilkin M, Roche P, Sebag F, van Summeren LE, Stevenson M, Howles SA, Deharo JC, Thakker RV, Taïeb D. Cinacalcet Reverses Short QT Interval in Familial Hypocalciuric Hypercalcemia Type 1. J Clin Endocrinol Metab 2024; 109:549-556. [PMID: 37602721 PMCID: PMC7615553 DOI: 10.1210/clinem/dgad494] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 07/17/2023] [Accepted: 08/17/2023] [Indexed: 08/22/2023]
Abstract
CONTEXT Familial hypocalciuric hypercalcemia type 1 (FHH-1) defines an autosomal dominant disease, related to mutations in the CASR gene, with mild hypercalcemia in most cases. Cases of FHH-1 with a short QT interval have not been reported to date. OBJECTIVE Three family members presented with FHH-1 and short QT interval (<360 ms), a condition that could lead to cardiac arrhythmias, and the effects of cinacalcet, an allosteric modulator of the CaSR, in rectifying the abnormal sensitivity of the mutant CaSR and in correcting the short QT interval were determined. METHODS CASR mutational analysis was performed by next-generation sequencing and functional consequences of the identified CaSR variant (p.Ile555Thr), and effects of cinacalcet were assessed in HEK293 cells expressing wild-type and variant CaSRs. A cinacalcet test consisting of administration of 30 mg cinacalcet (8 Am) followed by hourly measurement of serum calcium, phosphate, and parathyroid hormone during 8 hours and an electrocardiogram was performed. RESULTS The CaSR variant (p.Ile555Thr) was confirmed in all 3 FHH-1 patients and was shown to be associated with a loss of function that was ameliorated by cinacalcet. Cinacalcet decreased parathyroid hormone by >50% within two hours, and decreases in serum calcium and increases in serum phosphate occurred within 8 hours, with rectification of the QT interval, which remained normal after 3 months of cinacalcet treatment. CONCLUSION Our results indicate that FHH-1 patients should be assessed for a short QT interval and a cinacalcet test used to select patients who are likely to benefit from this treatment.
Collapse
Affiliation(s)
- Thomas Cuny
- Aix Marseille Univ, APHM, Marseille Medical Genetics, Inserm U1251, Hôpital de la Conception, Service d'Endocrinologie, Marseille, France
| | - Pauline Romanet
- Aix Marseille Univ, APHM, Marseille Medical Genetics, Inserm U1251, Hôpital de la Conception, Laboratoire de Biochimie et Biologie moléculaire, Marseille, France
| | | | - Carole Guérin
- Aix Marseille Univ, APHM, Hôpital de la Conception, Service de Chirurgie endocrinienne, Marseille, France
| | - Marie Wilkin
- Aix Marseille Univ, APHM, Hôpital de la Timone, Service de Cardiologie, Marseille France
| | - Philippe Roche
- Integrative Structural & Chemical Biology (iSCB) & HiTS Platform, Cancer Research Centre of Marseille, CNRS UMR7258, Marseille, France
| | - Frédéric Sebag
- Aix Marseille Univ, APHM, Hôpital de la Conception, Service de Chirurgie endocrinienne, Marseille, France
| | - Lynn E van Summeren
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Mark Stevenson
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
| | - Sarah A Howles
- Nuffield Department of Surgical Sciences, University of Oxford, United Kingdom
| | - Jean-Claude Deharo
- Aix Marseille Univ, APHM, Hôpital de la Timone, Service de Cardiologie, Marseille France
| | - Rajesh V Thakker
- Academic Endocrine Unit, Radcliffe Department of Medicine, University of Oxford, Oxford, UK
- National Institute for Health Research Oxford Biomedical Research Centre, Oxford, UK
| | - David Taïeb
- Department of Nuclear Medicine, La Timone University Hospital, CERIMED, Aix-Marseille University, France
| |
Collapse
|
4
|
Lasbleiz A, Paladino NC, Romanet P, Castinetti F, Cuny T, Sebag F, Taïeb D. Familial hypocalciuric hypercalcemia: the challenge of diagnosis. Endocrine 2022; 75:646-649. [PMID: 34714514 DOI: 10.1007/s12020-021-02909-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2021] [Accepted: 10/13/2021] [Indexed: 10/20/2022]
Affiliation(s)
- Adele Lasbleiz
- Aix Marseille Univ, APHM, Department of Nuclear Medicine, La Timone University Hospital, Marseille, France
| | - Nunzia Cinzia Paladino
- Aix Marseille Univ, APHM, Department of Endocrine Surgery, Conception University Hospital, Marseille, France
| | - Pauline Romanet
- Aix Marseille Univ, APHM, Marseille Medical Genetics, Inserm U1251, Laboratory of Molecular Biology Conception University Hospital, Marseille, France
| | - Frédéric Castinetti
- Aix Marseille Univ, APHM, Department of Endocrinology, Conception University Hospital, Marseille, France
| | - Thomas Cuny
- Aix Marseille Univ, APHM, Department of Endocrinology, Conception University Hospital, Marseille, France
| | - Frédéric Sebag
- Aix Marseille Univ, APHM, Department of Endocrine Surgery, Conception University Hospital, Marseille, France
| | - David Taïeb
- Aix Marseille Univ, APHM, Department of Nuclear Medicine, La Timone University Hospital, Marseille, France.
| |
Collapse
|
5
|
Li SR, McCoy KL, Levitt HE, Kelley ML, Carty SE, Yip L. Is routine 24-hour urine calcium measurement useful during the evaluation of primary hyperparathyroidism? Surgery 2021; 171:17-22. [PMID: 34325903 DOI: 10.1016/j.surg.2021.04.055] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 04/17/2021] [Accepted: 04/30/2021] [Indexed: 11/24/2022]
Abstract
BACKGROUND Primary hyperparathyroidism and familial hypocalciuric hypercalcemia have similar biochemical profiles, and calcium-to-creatinine-clearance ratio helps distinguish the two. Additionally, 24-hour urine calcium >400 mg/day indicates surgery and guidelines recommend obtaining 24-hour urine calcium preoperatively. Our aim was to assess how 24-hour urine calcium altered care in the evaluation of suspected primary hyperparathyroidism. METHODS Consecutive patients assessed for primary hyperparathyroidism from 2018 to 2020 were reviewed. Primary hyperparathyroidism was diagnosed by 2016 American Association of Endocrine Surgeons Parathyroidectomy Guidelines criteria. 24-hour urine calcium-directed change in care was defined as familial hypocalciuric hypercalcemia diagnosis, surgical deferment for additional testing, or 24-hour urine calcium >400 mg/day as the sole surgical indication. RESULTS Of 613 patients, 565 (92%) completed 24-hour urine calcium and 477 (84%) had concurrent biochemical testing to calculate calcium-to-creatinine-clearance ratio. 24-hour urine calcium was <100 mg/day in 9% (49/565) and calcium-to-creatinine-clearance ratio was <0.01 in 17% (82/477). No patient had confirmed familial hypocalciuric hypercalcemia, although 1 had a CASR variant of undetermined significance. When calcium-to-creatinine-clearance ratio was <0.01, familial hypocalciuric hypercalcemia was excluded by 24-hour urine calcium >100 mg/day (56%), prior normal calcium (16%), renal insufficiency (11%), absence of familial hypercalcemia (3%), normal repeat 24-hour urine calcium (10%), or interfering diuretic (1%). 24-hour urine calcium-directed change in care occurred in 25 (4%), including 4 (1%) who had genetic testing. Four-gland hyperplasia was more common with calcium-to-creatinine-clearance ratio <0.01 (17% vs calcium-to-creatinine-clearance ratio ≥ 0.01, 4%, P < .001), but surgical failure rates were equivalent (P = .24). CONCLUSION 24-hour urine calcium compliance was high, and results affected management in 4%, including productive identification of hypercalciuria as the sole surgical indication in 2 patients. When calcium-to-creatinine-clearance ratio <0.01, clinical assessment was sufficient to exclude familial hypocalciuric hypercalcemia and only 1% required genetic testing. 24-hour urine calcium should be ordered judiciously during primary hyperparathyroidism assessment.
Collapse
Affiliation(s)
- Shimena R Li
- Department of Surgery, University of Pittsburgh, PA
| | - Kelly L McCoy
- Department of Surgery, University of Pittsburgh, PA; Division of Endocrine Surgery, University of Pittsburgh, PA
| | - Helena E Levitt
- Department of Medicine, Division of Endocrinology and Metabolism, University of Pittsburgh, PA
| | | | - Sally E Carty
- Department of Surgery, University of Pittsburgh, PA; Division of Endocrine Surgery, University of Pittsburgh, PA
| | - Linwah Yip
- Department of Surgery, University of Pittsburgh, PA; Division of Endocrine Surgery, University of Pittsburgh, PA.
| |
Collapse
|
6
|
A Novel Variant in the Calcium-Sensing Receptor Associated with Familial Hypocalciuric Hypercalcemia and Low-to-Normal PTH. Case Rep Endocrinol 2020; 2020:8752610. [PMID: 33062349 PMCID: PMC7555459 DOI: 10.1155/2020/8752610] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Revised: 09/03/2020] [Accepted: 09/16/2020] [Indexed: 12/18/2022] Open
Abstract
Familial hypocalciuric hypercalcemia (FHH) is considered a relatively benign condition characterized by mild elevations in serum calcium and relatively low urinary calcium excretion. It results from an elevated set point in serum calcium arising from variants in the calcium-sensing receptor (CaSR) gene but also AP2S1 and GNA11 genes, which encode for adaptor-related protein complex 2 and G11 proteins, respectively. The manifestations of FHH can vary and sometimes overlap with primary hyperparathyroidism making the diagnosis challenging. Case Presentations. We report a mother and daughter with a novel heterozygous variant in the CaSR gene resulting in a serine to leucine substitution at position 147 (S147L) of the CaSR. Both patients had mild hypercalcemia, relatively low urinary calcium excretion, elevated calcitriol, and low-to-normal intact PTH. The proband (daughter) presented with symptoms associated with hypercalcemia and was incidentally found to have a bony lesion suspicious for osteitis fibrosa cystica, and she was also diagnosed with sarcoidosis. Subtotal parathyroidectomy revealed normal-weight parathyroid glands comprised of 50–80% parathyroid epithelial cells, which has been documented as within the spectrum of normal. Her mother had no symptoms, and no intervention was pursued. Conclusion. We report a novel variant in the CaSR associated with FHH in two patients with similar biochemical features yet differing clinical manifestations. While the relationship of the bony findings and parathyroid histology with this variant remains unclear, these cases enrich our knowledge of CaSR physiology and provide further examples of how varied the manifestations of FHH can be.
Collapse
|
7
|
Magno AL, Leatherbarrow KM, Brown SJ, Wilson SG, Walsh JP, Ward BK. Functional Analysis of Calcium-Sensing Receptor Variants Identified in Families Provisionally Diagnosed with Familial Hypocalciuric Hypercalcaemia. Calcif Tissue Int 2020; 107:230-239. [PMID: 32638038 DOI: 10.1007/s00223-020-00715-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2020] [Accepted: 06/18/2020] [Indexed: 12/11/2022]
Abstract
Identification of variants in the calcium-sensing receptor (CASR) gene is an important means of distinguishing between familial hypocalciuric hypercalcaemia (FHH) and primary hyperparathyroidism. However, identification and bioinformatics analysis of genetic variants alone is now considered insufficient as definitive proof; additional functional assessment is required to diagnose FHH with certainty. We identified two novel variants, D433Y and C739Y, and one previously reported variant G509R in the CASR of four kindreds provisionally diagnosed with FHH and aimed to functionally characterise these variants to confirm the diagnosis. Variant receptors were cloned as FLAG-tagged constructs into the mammalian expression vector, pcDNA3.1. Wild type and variant receptor constructs were expressed in HEK293 cells and their expression assessed by Western blot analysis and their functionality analysed using an IP-One assay which measures myo-inositol 1-phosphate accumulation following CaSR activation. Western blot analysis showed that the D433Y receptor had diminished mature glycosylated receptor compared with wild type CaSR whereas the G509R receptor had a complete lack of mature receptor. The C739Y receptor was consistently overexpressed. Functional assessment showed the D433Y receptor to be mildly inactivating at physiological calcium concentrations whereas the G509R receptor was inactive at all calcium concentrations. By contrast, the C739Y variant was activating compared to wild type receptor which is inconsistent with it causing FHH. We conclude that functional assessment of CaSR variants using the IP-One assay was useful in the investigation of suspected FHH probands, confirming the D433Y and G509R variants as likely pathogenic/pathogenic, but dismissing the C739Y variant as causing FHH.
Collapse
Affiliation(s)
- Aaron L Magno
- Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Block C, Level 1, Hospital Avenue, Nedlands, WA, Australia
| | - Kassandra M Leatherbarrow
- Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Block C, Level 1, Hospital Avenue, Nedlands, WA, Australia
| | - Suzanne J Brown
- Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Block C, Level 1, Hospital Avenue, Nedlands, WA, Australia
| | - Scott G Wilson
- Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Block C, Level 1, Hospital Avenue, Nedlands, WA, Australia
- School of Biomedical Sciences, University of Western Australia, Nedlands, WA, Australia
- Department of Twin Research and Genetic Epidemiology, King's College London, London, UK
| | - John P Walsh
- Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Block C, Level 1, Hospital Avenue, Nedlands, WA, Australia
- Medical School, University of Western Australia, Nedlands, WA, Australia
| | - Bryan K Ward
- Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Block C, Level 1, Hospital Avenue, Nedlands, WA, Australia.
- Harry Perkins Institute of Medical Research, Centre for Medical Research, QEII Medical Centre, University of Western Australia, Nedlands, WA, Australia.
| |
Collapse
|
8
|
Mahajan A, Buse J, Kline G. Parathyroid hormone-dependent familial hypercalcemia with low measured PTH levels and a presumptive novel pathogenic mutation in CaSR. Osteoporos Int 2020; 31:203-207. [PMID: 31641801 DOI: 10.1007/s00198-019-05170-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2019] [Accepted: 09/13/2019] [Indexed: 10/25/2022]
Abstract
Familial hypocalciuric hypercalcemia (FHH) is a benign autosomal dominant condition characterized by lifelong asymptomatic hypercalcemia. FHH is typically caused by a heterozygous inactivating mutation of the calcium-sensing receptor (CaSR) and characterized by moderate hypercalcemia, inappropriately normal or elevated serum parathyroid hormone (PTH), and relative hypocalciuria (FeCa < 2%) with histologically normal parathyroid glands. FHH should be distinguished from primary hyperparathyroidism so that unnecessary parathyroid surgery is avoided. We report a case that presented with asymptomatic, familial hypercalcemia but low PTH and normal (non-low) urinary calcium excretion found to be secondary to a novel pathogenic inactivating mutation of the CaSR gene. We present an asymptomatic 54-year-old Malaysian woman with incidentally discovered hypercalcemia, intermittent hypophosphatemia, and FeCa > 2%. PTH levels were repeatedly below the mean of the reference range (on two separate assays) and sometimes even below the lower reference limit. Two siblings, one niece, and her son had hypercalcemia without nephrolithiasis. Cinacalcet, used as a PTH-suppression test, normalized serum total and ionized calcium after 7 days of cinacalcet 30 mg BID, confirming her hypercalcemia was PTH-mediated. Given her family history, genetic testing was pursued and discovered a novel pathogenic mutation of the CaSR gene confirming the diagnosis of FHH type 1. Our case represents an atypical presentation of FHH1 with low PTH and FeCa > 2%. This contributes to the expanding clinical and biochemical spectrum of CaSR inactivating mutations and presents an innovative approach to evaluating biochemically uncertain familial hypercalcemia with cinacalcet before pursuing expensive genetic analysis.
Collapse
Affiliation(s)
- A Mahajan
- Division of Endocrinology, Department of Medicine, University of Calgary, 1820 Richmond Rd SW, Calgary, AB, T2T5C7, Canada.
| | - J Buse
- Department of Pathology and Laboratory Medicine, Cumming School of Medicine, University of Calgary, Calgary, Canada
- Clinical Biochemistry Section, Calgary Laboratory Services, 9-3535 Research Road NW, Calgary, AB, T2L 2K8, Canada
| | - G Kline
- Division of Endocrinology, Department of Medicine, University of Calgary, 1820 Richmond Rd SW, Calgary, AB, T2T5C7, Canada
| |
Collapse
|
9
|
Nissen PH, Rejnmark L. Expanding the spectrum of genetic variants in the calcium-sensing receptor (CASR) gene in hypercalcemic individuals. Clin Endocrinol (Oxf) 2019; 91:683-690. [PMID: 31433865 DOI: 10.1111/cen.14078] [Citation(s) in RCA: 2] [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] [Received: 03/29/2019] [Revised: 08/02/2019] [Accepted: 08/19/2019] [Indexed: 01/09/2023]
Abstract
OBJECTIVE Familial hypocalciuric hypercalcemia (FHH) is an autosomal dominantly inherited disorder with overlapping biochemistry profile with primary hyperparathyroidism (PHPT), making the correct diagnosis a challenge. The objective of the study was to evaluate the results of the clinical work-up of a large group of hypercalcemic individuals. DESIGN Cross-sectional study. PATIENTS Patients undergoing clinical work-up of hypercalcemia. MEASUREMENTS Molecular genetic analysis of the CASR gene and exon 2 of the AP2S1 gene. Plasma levels of ionized calcium and PTH as well as calcium creatinine clearance ratio (CCCR). RESULTS A rare CASR variant was identified in 38 of 624 index patients (6.1%). A total of 18 CASR variants identified in this study were novel. No variants were identified in exon 2 of the AP2S1 gene. The majority of the variants (N = 16) were classified as likely pathogenic. The level of plasma calcium, plasma PTH and the CCCR was not affected by the type of variant (ie nonsense vs missense) (all P-values >.05). The CCCR was found to be significantly lower for variants in the transmembrane domain compared with variants located in the extracellular domain (P < .05). Plasma levels of calcium and PTH were not associated with the location of the variant (P > .05). CONCLUSIONS We expanded the spectrum of CASR variants in hypercalcemia with 18 novel variants, and suggest that the location of the CASR variant may affect calcium excretion as determined by the CCCR.
Collapse
Affiliation(s)
- Peter H Nissen
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus, Denmark
| | - Lars Rejnmark
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
| |
Collapse
|
10
|
van der Wijst J, Belge H, Bindels RJM, Devuyst O. Learning Physiology From Inherited Kidney Disorders. Physiol Rev 2019; 99:1575-1653. [PMID: 31215303 DOI: 10.1152/physrev.00008.2018] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The identification of genes causing inherited kidney diseases yielded crucial insights in the molecular basis of disease and improved our understanding of physiological processes that operate in the kidney. Monogenic kidney disorders are caused by mutations in genes coding for a large variety of proteins including receptors, channels and transporters, enzymes, transcription factors, and structural components, operating in specialized cell types that perform highly regulated homeostatic functions. Common variants in some of these genes are also associated with complex traits, as evidenced by genome-wide association studies in the general population. In this review, we discuss how the molecular genetics of inherited disorders affecting different tubular segments of the nephron improved our understanding of various transport processes and of their involvement in homeostasis, while providing novel therapeutic targets. These include inherited disorders causing a dysfunction of the proximal tubule (renal Fanconi syndrome), with emphasis on epithelial differentiation and receptor-mediated endocytosis, or affecting the reabsorption of glucose, the handling of uric acid, and the reabsorption of sodium, calcium, and magnesium along the kidney tubule.
Collapse
Affiliation(s)
- Jenny van der Wijst
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - Hendrica Belge
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - René J M Bindels
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| | - Olivier Devuyst
- Department of Physiology, Radboud Institute for Molecular Life Sciences, Radboud University Medical Center , Nijmegen , The Netherlands ; Institute of Physiology, University of Zurich , Zurich , Switzerland ; and Division of Nephrology, Institute of Experimental and Clinical Research (IREC), Medical School, Université catholique de Louvain, Brussels, Belgium
| |
Collapse
|
11
|
A Novel Mutation of the Calcium-Sensing Receptor Gene Causing Familial Hypocalciuric Hypercalcemia Complicates Medical Followup after Roux-en-Y Gastric Bypass: A Case Report and a Summary of Mutations Found in the Same Hospital Laboratory. Case Rep Endocrinol 2019; 2019:9468252. [PMID: 30895164 PMCID: PMC6393866 DOI: 10.1155/2019/9468252] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Accepted: 02/05/2019] [Indexed: 12/22/2022] Open
Abstract
Heterozygous inactivating mutations in the calcium-sensing receptor (CaSR) gene are known to cause familial hypocalciuric hypercalcemia (FHH), usually a benign form of hypercalcemia without symptoms of a disrupted calcium homeostasis. FHH can be mistaken for the more common primary hyperparathyroidism (PHPT), for which surgical treatment may be needed. We describe a case of a 36-year-old woman with hypercalcemia and elevated PTH, initially suspected of having PHPT. Sequencing of the CaSR-gene revealed a mutation in nucleotide 437, changing the amino acid in position 146 from Glycine to Aspartate. The mutation was previously undescribed in the literature, but a very low calcium:creatinine clearance ratio supported the diagnosis FHH. A few years later, the patient's two daughters were tested and the association between mutation and hypercalcemia could be confirmed. The patient was gastric bypass-operated and therefore, due to malabsorption and increased risk of fracture, was in need of adequate calcium supplementation. The chronically elevated calcium levels challenged medical followup, as calcium sufficiency could not be monitored in a traditional manner. Eventually the patient developed elevated alkaline phosphatase, a further increased PTH and a decreased DXA T-score indicating calcium deficiency and bone resorption. As a supplement, all CaSR-mutations found at our hospital, 2005-2018.
Collapse
|
12
|
Moore EC, Berber E, Jin J, Krishnamurthy V, Shin J, Siperstein A. CALCIUM CREATININE CLEARANCE RATIO IS NOT HELPFUL IN DIFFERENTIATING PRIMARY HYPERPARATHYROIDISM FROM FAMILIAL HERPERCALCEMIC HYPOCALCIURIA: A STUDY OF 1000 PATIENTS. Endocr Pract 2018; 24:S1530-891X(20)35470-7. [PMID: 30289313 DOI: 10.4158/ep-2018-0350] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/28/2024]
Abstract
OBJECTIVE With increasing recognition of more subtle presentations of primary hyperparathyroidism (pHPT), laboratory values are frequently seen in a range that would be expected for patients who have familial hypercalcemic hypocalciuria (FHH). Calcium creatinine clearance ratio (CCCR) has been advocated as a diagnostic tool to differentiate between these two disorders. However, it is limited by an indeterminate range (0.01-0.02). The aim of this study is to assess the relevance of CCCR in a modern series of patients with surgically managed pHPT. METHODS We performed a retrospective cohort study of 1000 patients who underwent parathyroid surgery for pHPT over eleven years. CCCR was evaluated by degree of biochemical derangement, single versus multiple gland disease and interfering medications. RESULTS Patient demographics and resected histopathology were typical for a current series of patients with pHPT. In retrospect, none of the patients were suspected to have FHH post operatively. CCCR was less than 0.01 for 19.0%, between 0.01-0.02 for 43.7% and greater than 0.02 in 37.3%. Distribution of CCCR for patients free from interfering medications and different histological subtypes were the same. One third of the cohort had mild calcium elevations, more typical for FHH. Of these, almost two thirds had a CCCR in a range suspect for FHH (<0.02). CONCLUSION To our knowledge this is the largest series to evaluate the validity of CCCR for patients with surgically confirmed pPHT. The utility of CCCR in screening for FHH is limited, as 63% of modern patients with confirmed pHPT have low values.
Collapse
|
13
|
Gorvin CM, Babinsky VN, Malinauskas T, Nissen PH, Schou AJ, Hanyaloglu AC, Siebold C, Jones EY, Hannan FM, Thakker RV. A calcium-sensing receptor mutation causing hypocalcemia disrupts a transmembrane salt bridge to activate β-arrestin-biased signaling. Sci Signal 2018; 11:eaan3714. [PMID: 29463778 PMCID: PMC6166785 DOI: 10.1126/scisignal.aan3714] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The calcium-sensing receptor (CaSR) is a G protein-coupled receptor (GPCR) that signals through Gq/11 and Gi/o to stimulate cytosolic calcium (Ca2+i) and mitogen-activated protein kinase (MAPK) signaling to control extracellular calcium homeostasis. Studies of loss- and gain-of-function CASR mutations, which cause familial hypocalciuric hypercalcemia type 1 (FHH1) and autosomal dominant hypocalcemia type 1 (ADH1), respectively, have revealed that the CaSR signals in a biased manner. Thus, some mutations associated with FHH1 lead to signaling predominantly through the MAPK pathway, whereas mutations associated with ADH1 preferentially enhance Ca2+i responses. We report a previously unidentified ADH1-associated R680G CaSR mutation, which led to the identification of a CaSR structural motif that mediates biased signaling. Expressing CaSRR680G in HEK 293 cells showed that this mutation increased MAPK signaling without altering Ca2+i responses. Moreover, this gain of function in MAPK activity occurred independently of Gq/11 and Gi/o and was mediated instead by a noncanonical pathway involving β-arrestin proteins. Homology modeling and mutagenesis studies showed that the R680G CaSR mutation selectively enhanced β-arrestin signaling by disrupting a salt bridge formed between Arg680 and Glu767, which are located in CaSR transmembrane domain 3 and extracellular loop 2, respectively. Thus, our results demonstrate CaSR signaling through β-arrestin and the importance of the Arg680-Glu767 salt bridge in mediating signaling bias.
Collapse
Affiliation(s)
- Caroline M Gorvin
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LJ, UK
| | - Valerie N Babinsky
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LJ, UK
| | - Tomas Malinauskas
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Peter H Nissen
- Department of Clinical Biochemistry, Aarhus University Hospital, DK-8200 Aarhus N, Denmark
| | - Anders J Schou
- Hans Christian Andersen Children's Hospital, Odense University Hospital, 5000 Odense C, Denmark
| | - Aylin C Hanyaloglu
- Institute of Reproductive and Developmental Biology, Faculty of Medicine, Imperial College London W12 0NN, UK
| | - Christian Siebold
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - E Yvonne Jones
- Division of Structural Biology, Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Fadil M Hannan
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LJ, UK.
- Institute of Ageing and Chronic Disease, University of Liverpool, Liverpool L7 8TX, UK
| | - Rajesh V Thakker
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Radcliffe Department of Medicine, University of Oxford, Oxford OX3 7LJ, UK.
| |
Collapse
|
14
|
Hovden S, Rejnmark L, Ladefoged SA, Nissen PH. AP2S1 and GNA11 mutations - not a common cause of familial hypocalciuric hypercalcemia. Eur J Endocrinol 2017; 176:177-185. [PMID: 27913609 DOI: 10.1530/eje-16-0842] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 11/10/2016] [Accepted: 11/15/2016] [Indexed: 01/28/2023]
Abstract
OBJECTIVE Familial hypocalciuric hypercalcemia (FHH) type 1 is caused by mutations in the gene encoding the calcium-sensing receptor (CASR). Recently, mutations affecting codon 15 in the gene AP2S1 have been shown to cause FHH type 3 in up to 26% of CASR-negative FHH patients. Similarly, mutations in the gene GNA11 have been shown to cause FHH type 2. We hypothesized that mutations in AP2S1 and GNA11 are causative in Danish patients with suspected FHH and that these mutations are not found in patients with primary hyperparathyroidism (PHPT), which is the main differential diagnostic disorder. DESIGN Cross-sectional study. METHODS We identified patients with unexplained hyperparathyroid hypercalcemia and a control group of verified PHPT patients through review of 421 patients tested for CASR mutations in the period 2006-2014. DNA sequencing of all amino acid coding exons including intron-exon boundaries in AP2S1 and GNA11 was performed. RESULTS In 33 CASR-negative patients with suspected FHH, we found two (~6%) with a mutation in AP2S1 (p.Arg15Leu and p.Arg15His). Family screening confirmed the genotype-phenotype correlations. We did not identify any pathogenic mutations in GNA11. No pathogenic mutations were found in the PHPT control group. CONCLUSIONS We suggest that the best diagnostic approach to hyperparathyroid hypercalcemic patients suspected to have FHH is to screen the CASR and AP2S1 codon 15 for mutations. If the results are negative and there is still suspicion of an inherited condition (i.e. family history), then GNA11 should be examined.
Collapse
Affiliation(s)
| | - Lars Rejnmark
- Endocrinology and Internal MedicineAarhus University Hospital, Aarhus N, Denmark
| | | | | |
Collapse
|
15
|
Breum Jakobsen NF, Laugesen E, Rolighed L, Nissen PH, Poulsen PL, Pedersen EB, Mosekilde L, Rejnmark L. The cardiovascular system in familial hypocalciuric hypercalcemia: a cross-sectional study on physiological effects of inactivating variants in the calcium-sensing receptor gene. Eur J Endocrinol 2016; 175:299-309. [PMID: 27418061 DOI: 10.1530/eje-16-0369] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 07/14/2016] [Indexed: 01/10/2023]
Abstract
OBJECTIVE Loss-of-function variants in the gene encoding the calcium-sensing receptor (CASR) result in familial hypocalciuric hypercalcemia (FHH), causing hypercalcemia with high normal or elevated parathyroid hormone levels. The CASR may also influence electrolyte and water homeostasis. It is unknown whether FHH affects cardiovascular health. We, therefore investigated whether FHH is associated with changes in the regulation of the cardiovascular system by measuring 24-h blood pressure (BP), arterial stiffness and vasoactive hormones. DESIGN Cross-sectional study comparing 50 patients with FHH to age- and gender-matched controls. RESULTS Studied subjects (69% women) had a mean age of 56years. A similar number of patients and controls (33%) were on treatment with antihypertensive drugs. Overall, no differences were found between groups in 24-h ambulatory BP or pulse wave velocity. However, compared with controls, diastolic BP during nighttime was lower in FHH females (60±5 vs 66±9mmHg, P<0.01) and higher in FHH males (69±6 vs 64±5mmHg, P=0.02). FHH was associated with a significantly higher plasma osmolality (P<0.01), higher plasma levels of vasopressin (P<0.01) and a higher renal excretion of epithelial sodium channels (ENaCs) (P=0.03), whereas urine aquaporin-2 and plasma sodium, aldosterone and renin did not differ between groups. FHH patients had a lower urinary volume with an increased osmolality if analyses were restricted to those not on treatments with antihypertensive drugs. CONCLUSIONS FHH does not seem to be associated with an increased risk of CVD.
Collapse
Affiliation(s)
| | - Esben Laugesen
- Department of Endocrinology and Internal MedicineAarhus University Hospital, Aarhus, Denmark Danish Diabetes AcademyOdense University Hospital, Odense, Denmark Department of Clinical MedicineAarhus University, Aarhus, Denmark
| | | | - Peter H Nissen
- Clinical BiochemistryAarhus University Hospital, Aarhus, Denmark
| | - Per Løgstrup Poulsen
- Department of Endocrinology and Internal MedicineAarhus University Hospital, Aarhus, Denmark
| | - Erling Bjerregaard Pedersen
- Department of Clinical MedicineAarhus University, Aarhus, Denmark University Clinic in Nephrology and HypertensionHolstebro Hospital, Hospital Jutland West, Holstebro, Denmark
| | - Leif Mosekilde
- Department of Endocrinology and Internal MedicineAarhus University Hospital, Aarhus, Denmark
| | - Lars Rejnmark
- Department of Endocrinology and Internal MedicineAarhus University Hospital, Aarhus, Denmark Department of Clinical MedicineAarhus University, Aarhus, Denmark
| |
Collapse
|
16
|
Mayr B, Glaudo M, Schöfl C. Activating Calcium-Sensing Receptor Mutations: Prospects for Future Treatment with Calcilytics. Trends Endocrinol Metab 2016; 27:643-652. [PMID: 27339034 DOI: 10.1016/j.tem.2016.05.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 05/17/2016] [Accepted: 05/20/2016] [Indexed: 12/20/2022]
Abstract
Activating mutations of the G protein-coupled receptor, calcium-sensing receptor (CaSR), cause autosomal dominant hypocalcemia and Bartter syndrome type 5. These mutations lower the set-point for extracellular calcium sensing, thereby causing decreased parathyroid hormone secretion and disturbed renal calcium handling with hypercalciuria. Available therapies increase serum calcium levels but raise the risk of complications in affected patients. Symptom relief and the prevention of adverse outcome is currently very difficult to achieve. Calcilytics act as CaSR antagonists that attenuate its activity, thereby correcting the molecular defect of activating CaSR proteins in vitro and elevating serum calcium in mice and humans in vivo, and have emerged as the most promising therapeutics for the treatment of these rare and difficult to treat diseases.
Collapse
Affiliation(s)
- Bernhard Mayr
- Division of Endocrinology and Diabetes, Department of Medicine I, Universitätsklinikum Erlangen, Friedrich-Alexander University Erlangen-Nuremberg, Germany.
| | - Markus Glaudo
- Division of Endocrinology and Diabetes, Department of Medicine I, Universitätsklinikum Erlangen, Friedrich-Alexander University Erlangen-Nuremberg, Germany
| | - Christof Schöfl
- Division of Endocrinology and Diabetes, Department of Medicine I, Universitätsklinikum Erlangen, Friedrich-Alexander University Erlangen-Nuremberg, Germany
| |
Collapse
|
17
|
Papadopoulou A, Gole E, Melachroinou K, Meristoudis C, Siahanidou T, Papadimitriou A. Identification and Functional Characterization of a Calcium-Sensing Receptor Mutation in an Infant with Familial Hypocalciuric Hypercalcemia. J Clin Res Pediatr Endocrinol 2016; 8:341-6. [PMID: 27087013 PMCID: PMC5096500 DOI: 10.4274/jcrpe.2800] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Familial hypocalciuric hypercalcemia (FHH) is an autosomal dominant disorder, associated with inactivating mutations of the calcium-sensing receptor (CaSR). To evaluate the functional significance of a CaSR mutation, identified in a young infant who presented with hypercalcemia and hypocalciuria. The CaSR gene coding sequences were analyzed by polymerase chain reaction amplification and direct sequencing analysis. The mutation identified was introduced by site-directed mutagenesis into a wild-type (WT) CaSR plasmid, and human embryonic kidney 293 T cells were transfected with either the WT or mutant CaSR. The function of the mutated CaSR protein was analyzed by evaluating the free intracellular calcium [(Ca2+)i] response after challenge with extracellular calcium (Ca2+). We identified a heterozygous mutation c.772_773delGTinsA in exon 4 resulting in the substitution of amino acid valine (Val) with amino acid arginine (Arg) and the premature pause of the translation 46 amino acids later (Val258ArgfsTer47). Functional assay showed that cells transfected with the mutant CaSR had a significantly poorer response to extracellular Ca2+ stimulation compared with the WT. We have shown that the c.772_773delGTinsA mutation causes a significant alteration of CaSR function leading to features of FHH in an affected young infant since the first months of life.
Collapse
Affiliation(s)
- Anna Papadopoulou
- Athens University Medical School, University General Hospital "Attikon", Third Department of Pediatrics, Athens, Greece, Phone: +30 2105832228 E-mail:
| | - Evangelia Gole
- Athens University Medical School, University General Hospital “Attikon”, Third Department of Pediatrics, Athens, Greece
| | - Katerina Melachroinou
- Biomedical Research Foundation of the Academy of Athens, Division of Basic Neurosciences, Athens, Greece
| | - Christos Meristoudis
- University of Ioannina, Department of Biological Applications and Technology, Ioannina, Greece
| | - Tania Siahanidou
- Athens University Medical School, “Aghia Sophia” Children’s Hospital, First Department of Pediatrics, Athens, Greece
| | - Anastasios Papadimitriou
- Athens University Medical School, University General Hospital “Attikon”, Third Department of Pediatrics, Athens, Greece
| |
Collapse
|
18
|
Hovden S, Jespersen ML, Nissen PH, Poulsen PL, Rolighed L, Ladefoged SA, Rejnmark L. Multiple endocrine neoplasia phenocopy revealed as a co-occurring neuroendocrine tumor and familial hypocalciuric hypercalcemia type 3. Clin Case Rep 2016; 4:922-927. [PMID: 27761240 PMCID: PMC5054464 DOI: 10.1002/ccr3.657] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2016] [Accepted: 07/11/2016] [Indexed: 11/26/2022] Open
Abstract
Familial hypocalciuric hypercalcemia type 3 should be considered as differential diagnosis in patients with suspected primary hyperparathyroidism and/or suspected multiple neoplasia syndrome, as correct diagnosis will spare the patients for going through multiple futile parathyroidectomies and for the worry of being diagnosed with a cancer susceptibility syndrome.
Collapse
Affiliation(s)
- Silje Hovden
- Department of Clinical Biochemistry Aarhus University Hospital Aarhus Denmark
| | | | - Peter H Nissen
- Department of Clinical Biochemistry Aarhus University Hospital Aarhus Denmark
| | - Per Løgstrup Poulsen
- Department of Endocrinology and Internal Medicine Aarhus University Hospital Aarhus Denmark
| | - Lars Rolighed
- Department of Surgery Aarhus University Hospital Aarhus Denmark
| | - Søren A Ladefoged
- Department of Clinical Biochemistry Aarhus University Hospital Aarhus Denmark
| | - Lars Rejnmark
- Department of Endocrinology and Internal Medicine Aarhus University Hospital Aarhus Denmark
| |
Collapse
|
19
|
Calcium-Sensing Receptor. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 132:127-50. [DOI: 10.1016/bs.pmbts.2015.02.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
|
20
|
Kulkarni A, Mohite M, Vijaykumar R, Bansode P, Murade S, Tamhankar PM. Neonatal severe hyperparathyroidism due to compound heterozygous mutation of calcium sensing receptor (CaSR) gene presenting as encephalopathy. Indian J Pediatr 2014; 81:1228-9. [PMID: 24763815 DOI: 10.1007/s12098-014-1442-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Accepted: 03/27/2014] [Indexed: 11/30/2022]
Abstract
The authors report a 14-d-old neonate who presented with lethargy, polyuria and dehydration and was found to have severe hypercalcemia with hyperparathyroidism. This neonate was treated with saline hydration, diuresis and injection pamidronate. Genetic analysis revealed a compound heterozygous mutation of CaSR.
Collapse
Affiliation(s)
- Abhishek Kulkarni
- Department of Pediatrics & Adolescent Endocrinology, Jaslok Hospital & Research Centre, Mumbai, India
| | | | | | | | | | | |
Collapse
|
21
|
Thim SB, Birkebaek NH, Nissen PH, Høst C. Activating calcium-sensing receptor gene variants in children: a case study of infant hypocalcaemia and literature review. Acta Paediatr 2014; 103:1117-25. [PMID: 25039540 DOI: 10.1111/apa.12743] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2013] [Revised: 05/02/2014] [Accepted: 07/08/2014] [Indexed: 12/17/2022]
Abstract
UNLABELLED Autosomal dominant hypocalcaemia (ADH) is caused by activating variants in the calcium-sensing receptor (CASR) gene, but detailed information on the paediatric phenotype is limited. The current paper presents a case of severe ADH and systematically reviews the literature on ADH in children. CONCLUSION We found that the severity of clinical neurological symptoms was inversely related to serum calcium levels and a high prevalence of renal calcifications and/or basal ganglia calcifications in children with ADH.
Collapse
Affiliation(s)
- Signe B Thim
- Department of Paediatrics; Aarhus University Hospital; Aarhus Denmark
| | - Niels H Birkebaek
- Department of Paediatrics; Aarhus University Hospital; Aarhus Denmark
| | - Peter H Nissen
- Department of Clinical Biochemistry; Aarhus University Hospital; Aarhus Denmark
| | - Christian Høst
- Department of Paediatrics; Aarhus University Hospital; Aarhus Denmark
| |
Collapse
|
22
|
Stratta P, Merlotti G, Musetti C, Quaglia M, Pagani A, Izzo C, Radin E, Airoldi A, Baorda F, Palladino T, Leone MP, Guarnieri V. Calcium-sensing-related gene mutations in hypercalcaemic hypocalciuric patients as differential diagnosis from primary hyperparathyroidism: detection of two novel inactivating mutations in an Italian population. Nephrol Dial Transplant 2014; 29:1902-1909. [DOI: 10.1093/ndt/gfu065] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023] Open
|
23
|
Wolf P, Krššák M, Winhofer Y, Anderwald CH, Zwettler E, Just Kukurová I, Gessl A, Trattnig S, Luger A, Baumgartner-Parzer S, Krebs M. Cardiometabolic phenotyping of patients with familial hypocalcuric hypercalcemia. J Clin Endocrinol Metab 2014; 99:E1721-6. [PMID: 24947037 DOI: 10.1210/jc.2014-1541] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Heterozygous inactivating mutations of the calcium-sensing receptor (CaSR) gene cause alterations in calcium metabolism [familial hypocalciuric hypercalcemia (FHH)]. In addition, calcium-sensing receptor is expressed in the myocardium and endocrine cells including pancreatic islets, enteroendocrine cells, and adipose tissue. OBJECTIVE To discern whether FHH is associated with cardiometabolic alterations of clinical significance, endocrine responses to systemic calcium stimulation and oral glucose tolerance tests were performed. Ectopic lipid deposition and heart function were assessed using magnetic resonance spectroscopy/imaging. PARTICIPANTS Eight FHH patients and nine controls matched for anthropometric characteristics (age 45 ± 18 y; body mass index 29 ± 4 vs 29 ± 6 kg/m(2)) were studied to determine cardiac function, ectopic and visceral lipid content, and insulin sensitivity and secretion. RESULTS Insulin sensitivity (clamp-like index: 4.5 ± 0.6 vs 4.3 ± 0.4 mg/kg · min), basal (insulin secretion rate: 266 ± 33 vs 218 ± 25 pmol/min), and glucose-stimulated β-cell function (adaptation index: 180.2 ± 12.2 vs 176.2 ± 17.4) as well as calcium-stimulated insulin secretion were comparable between FHH and controls, respectively. Ectopic lipid content in liver [3.75% (1.4%; 34%) vs 4.18% (0.9%; 28%)], soleus muscle (1.07% ± 0.38% vs 1.02% ± 0.56 %), and myocardium (0.39% ± 0.3% vs 0.32% ± 0.1 %), visceral and sc adipose tissue distribution (0.51 ± 0.16 vs 0.47 ± 0.17) as well as heart function (ejection fraction: 71.5% ± 8% vs 72.8% ± 8 %; E to A ratio: 1.4% ± 0.6% vs 1.3% ± 0.7%) were not different between the groups. CONCLUSION Despite comprehensive cardiometabolic phenotyping, no alterations in myocardial function, lipid distribution, or glucose metabolism were observed in FHH. Thus, FHH might reflect a laboratory finding without any relevant cardiometabolic alterations.
Collapse
Affiliation(s)
- Peter Wolf
- Department of Internal Medicine III, and High Field MR-Centre (M.Krs., I.J.K., S.T.), Division of Endocrinology and Metabolism (P.W., M.Krs., Y.W., C.-H.A., A.G., A.L., S.B.-P., M.Kre.), Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, 1090 Vienna, Austria; Metabolic Unit (C.-H.A.), Institute of Biomedical Engineering, National Research Council, I-35127 Padova, Italy; Mariahilf Community Pharmacy (C.-H.A.), A-9601 Arnoldstein, Austria; Medical Direction (C.-H.A.), Specialized Hospital Complex Agathenhof, A-9322 Micheldorf, Austria; and Ludwig Boltzman Institute of Osteology (E.Z.), Hanusch Hospital of the Vienna Regional Health Insurance Fund and Austrian Workers' Compensation Board Trauma Center, 1100 Vienna, Austria
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Jakobsen NFB, Rolighed L, Moser E, Nissen PH, Mosekilde L, Rejnmark L. Increased trabecular volumetric bone mass density in Familial Hypocalciuric Hypercalcemia (FHH) type 1: a cross-sectional study. Calcif Tissue Int 2014; 95:141-52. [PMID: 24894639 DOI: 10.1007/s00223-014-9877-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 05/18/2014] [Indexed: 01/22/2023]
Abstract
Familial Hypocalciuric Hypercalcaemia (FHH) Type 1 is caused by an inactivating mutation in the calcium-sensing receptor (CASR) gene resulting in elevated plasma calcium levels. We investigated whether FHH is associated with change in bone density and structure. We compared 50 FHH patients with age- and gender-matched population-based controls (mean age 56 years, 69 % females). We assessed areal BMD (aBMD) by DXA-scans and total, cortical, and trabecular volumetric BMD (vBMD) as well as bone geometry by quantitative computed tomography (QCT) and High-Resolution peripheral-QCT (HR-pQCT). Compared with controls, FHH females had a higher total and trabecular hip vBMD and a lower cortical vBMD and hip bone volume. Areal BMD and HRpQCT indices did not differ except an increased trabecular thickness and an increased vBMD at the transition zone between cancellous and cortical bone in of the tibia in FHH. Finite element analyses showed no differences in bone strength. Multiple regression analyses revealed correlations between vBMD and P-Ca(2+) levels but not with P-PTH. Overall, bone health does not seem to be impaired in patients with FHH. In FHH females, bone volume is decreased, with a lower trabecular volume but a higher vBMD, whereas cortical vBMD is decreased in the hip. This may be due to either an impaired endosteal resorption or corticalization of trabecular bone. The smaller total bone volume suggests an impaired periosteal accrual, but bone strength is not impaired. The findings of more pronounced changes in females may suggest an interaction between sex hormones and the activity of the CaSR on bone.
Collapse
Affiliation(s)
- Niels Frederik Breum Jakobsen
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Tage-Hansens Gade 2, 8000, Aarhus C, Denmark
| | | | | | | | | | | |
Collapse
|
25
|
Jakobsen NFB, Rolighed L, Nissen PH, Mosekilde L, Rejnmark L. Muscle function and quality of life are not impaired in familial hypocalciuric hypercalcemia: a cross-sectional study on physiological effects of inactivating variants in the calcium-sensing receptor gene (CASR). Eur J Endocrinol 2013; 169:349-57. [PMID: 23764372 DOI: 10.1530/eje-13-0224] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
BACKGROUND Familial hypocalciuric hypercalcemia (FHH) is often due to inactivating variants in the calcium-sensing receptor (CASR) gene causing chronically elevated plasma calcium levels with inappropriately normal or elevated parathyroid hormone levels. In patients with primary hyperparathyroidism, the state of hyperparathyroid hypercalcemia is associated with reduced muscle strength and impaired quality of life (QoL). OBJECTIVE To study whether FHH affects muscle function, postural stability, and QoL. DESIGN In a cross-sectional study, we investigated muscle strength (handgrip, elbow flexion/extension, and knee flexion/extension), balance function, physical activity, and QoL in 50 patients with FHH and in a similar number of age- and gender-matched population-based healthy controls. All but one of the FHH cases had genetically verified inactivating variants in the CASR gene. RESULTS Studied subjects (n=100, 68% females) had a mean age of 56.0 years. Muscle strength as assessed by measuring maximum force and maximum force production did not differ between the groups. Neither did groups differ in terms of QoL, physical activity, or postural stability, as assessed during normal standing with eyes open, normal standing with eyes closed, semi-tandem standing, or tandem standing. Adjustment for vitamin D status (plasma 25-hydroxyvitamin D levels) and BMI did not change results. CONCLUSION Despite a state of chronic hypercalcemia, muscle strength, balance function, and QoL are not impaired in patients with FHH. Our findings are reassuring for patients with FHH as they should not be considered as having a severe disease.
Collapse
Affiliation(s)
- Niels Frederik Breum Jakobsen
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Tage-Hansens Gade 2, 8000 Aarhus C, Denmark.
| | | | | | | | | |
Collapse
|
26
|
Ward DT, Mughal MZ, Ranieri M, Dvorak-Ewell MM, Valenti G, Riccardi D. Molecular and clinical analysis of a neonatal severe hyperparathyroidism case caused by a stop mutation in the calcium-sensing receptor extracellular domain representing in effect a human 'knockout'. Eur J Endocrinol 2013; 169:K1-7. [PMID: 23612447 DOI: 10.1530/eje-13-0094] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
OBJECTIVE Loss-of-function calcium-sensing receptor (CAR) mutations cause elevated parathyroid hormone (PTH) secretion and hypercalcaemia. Although full Car deletion is possible in mice, most human CAR mutations result from a single amino acid substitution that maintains partial function. However, here, we report a case of neonatal severe hyperparathyroidism (NSHPT) in which the truncated CaR lacks any transmembrane domain (CaR(R392X)), in effect a full CAR 'knockout'. CASE REPORT The infant (daughter of distant cousins) presented with hypercalcaemia (5.5-6 mmol/l corrected calcium (2.15-2.65)) and elevated PTH concentrations (650-950 pmol/l (12-81)) together with skeletal demineralisation. NSHPT was confirmed by CAR gene sequencing (homozygous c.1174C-to-T mutation) requiring total parathyroidectomy during which only two glands were located and removed, resulting in normalisation of her serum PTH/calcium levels. DESIGN AND METHODS The R392X stop codon was inserted into human CAR and the resulting mutant (CaR(R392X)) expressed transiently in HEK-293 cells. RESULTS CaR(R392X) expressed as a 54 kDa dimeric glycoprotein that was undetectable in conditioned medium or in the patient's urine. The membrane localisation observed for wild-type CaR in parathyroid gland and transfected HEK-293 cells was absent from the proband's parathyroid gland and from CaR(R392X)-transfected cells. Expression of the mutant was localised to endoplasmic reticulum consistent with its lack of functional activity. CONCLUSIONS Intriguingly, the patient remained normocalcaemic throughout childhood (2.5 mM corrected calcium, 11 pg/ml PTH (10-71), age 8 years) but exhibited mild asymptomatic hypocalcaemia at age 10 years, now treated with 1-hydroxycholecalciferol and Ca2+ supplementation. Despite representing a virtual CAR knockout, the patient displays no obvious pathologies beyond her calcium homeostatic dysfunction.
Collapse
Affiliation(s)
- D T Ward
- Faculty of Life Sciences, The University of Manchester, Michael Smith Building, Oxford Road, Manchester M13 9PT, UK.
| | | | | | | | | | | |
Collapse
|
27
|
Hannan FM, Thakker RV. Calcium-sensing receptor (CaSR) mutations and disorders of calcium, electrolyte and water metabolism. Best Pract Res Clin Endocrinol Metab 2013; 27:359-71. [PMID: 23856265 DOI: 10.1016/j.beem.2013.04.007] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The extracellular calcium-sensing receptor (CaSR) is a family C G-protein-coupled receptor (GPCR) that is expressed at multiple sites, including the parathyroids and kidneys. The human CASR gene, located on chromosome 3q21.1, encodes a 1078 amino acid protein. More than 230 different disease-causing mutations of the CaSR have been reported. Loss-of-function mutations lead to three hypercalcemic disorders, which are familial hypocalciuric hypercalcemia (FHH), neonatal severe hyperparathyroidism and primary hyperparathyroidism. Gain-of-function mutations, on the other hand, result in the hypocalcemic disorders of autosomal dominant hypocalcemia and Bartter syndrome type V. Moreover, autoantibodies directed against the extracellular domain of the CaSR have been found to be associated with FHH in some patients, and also in some patients with hypoparathyroidism that may be part of autoimmune polyglandular syndrome type 1. Studies of disease-causing CASR mutations have provided insights into structure-function relationships and highlighted intra-molecular domains that are critical for ligand binding, intracellular signaling, and receptor trafficking.
Collapse
Affiliation(s)
- Fadil M Hannan
- Academic Endocrine Unit, Oxford Centre for Diabetes, Endocrinology and Metabolism, Nuffield Department of Clinical Medicine, University of Oxford, Churchill Hospital, Oxford OX3 7LJ, UK.
| | | |
Collapse
|
28
|
Lia-Baldini AS, Magdelaine C, Nizou A, Airault C, Salles JP, Moulin P, Delemer B, Aitouares M, Funalot B, Sturtz F, Lienhardt-Roussie A. Two novel mutations of the calcium-sensing receptor gene affecting the same amino acid position lead to opposite phenotypes and reveal the importance of p.N802 on receptor activity. Eur J Endocrinol 2013; 168:K27-34. [PMID: 23169696 DOI: 10.1530/eje-12-0714] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
OBJECTIVE Gain-of-function mutations of the calcium-sensing receptor (CASR) gene have been identified in patients with sporadic or familial autosomal dominant hypocalcemia (ADH). Inactivating mutations of the CASR gene cause familial hypocalciuric hypercalcemia (FHH). Here, we report two novel CASR mutations affecting the same amino acid (p.N802); one causes ADH and the other atypical FHH. PATIENTS AND METHODS The first patient, an 11-year-old girl suffering from hypocalcemia, developed nephrocalcinosis when she was only 5 years old. The second patient is a 30-year-old woman who presented with mild hypercalcemia. PCR amplification of CASR coding exons and direct sequencing of PCR products were used to identify mutations. Site-directed mutagenesis was used to generate mutated CASR cDNAs in an expression plasmid. Using the MAPK assay system and transient transfection of Cos-7 cells with wild-type (WT) and mutated CASR, we studied the responses of these mutated receptors to extracellular Ca(2+) and to the negative allosteric CASR modulator, NPS2143. RESULTS Two heterozygous missense mutations (p.N802I and p.N802S) affecting a residue in the sixth transmembrane domain of CASR were identified. In functional tests, the response of the p.N802S mutant to calcium was typical of an inactivating mutation. However, the p.N802I mutant had 70% of the maximally stimulated WT receptor activity even in the absence of extracellular calcium. This constitutive activity was only partially inhibited by the inhibitor, NPS2143. CONCLUSIONS The asparagine at amino acid position 802 appears to be essential for the activity of the CASR protein and is implicated in the mechanism of CASR signaling.
Collapse
Affiliation(s)
- Anne-Sophie Lia-Baldini
- EA 6309 - Maintenance Myélinique et Neuropathies Périphériques, Faculté de Médecine - Biochimie, Université de Limoges, 6ème étage, 2 rue du Dr Marcland, 87025 Limoges, France.
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
29
|
Rasmussen TB, Hansen J, Nissen PH, Palmfeldt J, Dalager S, Jensen UB, Kim WY, Heickendorff L, Mølgaard H, Jensen HK, Sørensen KE, Baandrup UT, Bross P, Mogensen J. Protein expression studies of desmoplakin mutations in cardiomyopathy patients reveal different molecular disease mechanisms. Clin Genet 2012; 84:20-30. [PMID: 23137101 DOI: 10.1111/cge.12056] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2012] [Revised: 11/06/2012] [Accepted: 06/11/2012] [Indexed: 11/29/2022]
Abstract
Mutations in the gene for desmoplakin (DSP) may cause arrhythmogenic right ventricular cardiomyopathy (ARVC) and Carvajal syndrome (CS). Desmoplakin is part of all desmosomes, which are abundantly expressed in both myocardial and epidermal tissue and serve as intercellular mechanical junctions. This study aimed to investigate protein expression in myocardial and epidermal tissue of ARVC and CS patients carrying DSP mutations in order to elucidate potential molecular disease mechanisms. Genetic investigations identified three ARVC patients carrying different heterozygous DSP mutations in addition to a homozygous DSP mutation in a CS patient. The protein expression of DSP in mutation carriers was evaluated in biopsies from myocardial and epidermal tissue by immunohistochemistry. Keratinocyte cultures were established from skin biopsies of mutation carriers and characterized by reverse transcriptase polymerase chain reaction, western blotting, and protein mass spectrometry. The results showed that the mutation carriers had abnormal DSP expression in both myocardial and epidermal tissue. The investigations revealed that the disease mechanisms varied accordingly to the specific types of DSP mutation identified and included haploinsufficiency, dominant-negative effects, or a combination hereof. Furthermore, the results suggest that the keratinocytes cultured from patients are a valuable and easily accessible resource to elucidate the effects of desmosomal gene mutations in humans.
Collapse
Affiliation(s)
- T B Rasmussen
- Department of Cardiology; Research Unit for Molecular Medicine, Odense University Hospital, Sdr. Boulevard 29, Odense C, Denmark
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
30
|
Hiperparatiroidismo: ¿primario o secundario? ACTA ACUST UNITED AC 2012; 8:287-91. [DOI: 10.1016/j.reuma.2011.06.001] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 06/07/2011] [Accepted: 06/17/2011] [Indexed: 11/21/2022]
|
31
|
Breitwieser GE. Minireview: the intimate link between calcium sensing receptor trafficking and signaling: implications for disorders of calcium homeostasis. Mol Endocrinol 2012; 26:1482-95. [PMID: 22745192 DOI: 10.1210/me.2011-1370] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The calcium-sensing receptor (CaSR) regulates organismal Ca(2+) homeostasis. Dysregulation of CaSR expression or mutations in the CASR gene cause disorders of Ca(2+) homeostasis and contribute to the progression or severity of cancers and cardiovascular disease. This brief review highlights recent findings that define the CaSR life cycle, which controls the cellular abundance of CaSR and CaSR signaling. A novel mechanism, termed agonist-driven insertional signaling (ADIS), contributes to the unique hallmarks of CaSR signaling, including the high degree of cooperativity and the lack of functional desensitization. Agonist-mediated activation of plasma membrane-localized CaSR increases the rate of insertion of CaSR at the plasma membrane without altering the constitutive endocytosis rate, thereby acutely increasing the maximum signaling response. Prolonged CaSR signaling requires a large intracellular ADIS-mobilizable pool of CaSR, which is maintained by signaling-mediated increases in biosynthesis. This model provides a rational framework for characterizing the defects caused by CaSR mutations and the altered functional expression of wild-type CaSR in disease states. Mechanistic dissection of ADIS of CaSR should lead to optimized pharmacological approaches to normalize CaSR signaling in disorders of Ca(2+) homeostasis.
Collapse
Affiliation(s)
- Gerda E Breitwieser
- Weis Center for Research, Geisinger Clinic, Danville, Pennsylvania 17822-2604, USA.
| |
Collapse
|
32
|
Tonyushkina KN, O'Connor S, Dunbar NS. A novel CaSR mutation presenting as a severe case of neonatal familial hypocalciuric hypercalcemia. INTERNATIONAL JOURNAL OF PEDIATRIC ENDOCRINOLOGY 2012; 2012:13. [PMID: 22620673 PMCID: PMC3465174 DOI: 10.1186/1687-9856-2012-13] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 05/23/2012] [Indexed: 12/30/2022]
Abstract
BACKGROUND Familial Hypocalciuric Hypercalcemia (FHH) is a generally benign disorder caused by heterozygous inactivating mutations in the Calcium-Sensing Receptor (CaSR) gene resulting in altered calcium metabolism. OBJECTIVE We report a case of unusually severe neonatal FHH due to a novel CaSR gene mutation that presented with perinatal fractures and moderate hypercalcemia. CASE OVERVIEW: A female infant was admitted at 2 weeks of age for suspected non-accidental trauma (NAT). Laboratory testing revealed hypercalcemia (3.08 mmol/L), elevated iPTH (20.4 pmol/L) and low urinary calcium clearance (0.0004). Radiographs demonstrated multiple healing metaphyseal and rib fractures and bilateral femoral bowing. The femoral deformity and stage of healing were consistent with prenatal injuries rather than non-accidental trauma (NAT). Treatment was initiated with cholecalciferol, 400 IU/day, and by 6 weeks of age, iPTH levels had decreased into the high-normal range. Follow up radiographs demonstrated marked improvement of bone lesions by 3 months. A CaSR gene mutation study showed heterozygosity for a T>C nucleotide substitution at c.1664 in exon 6, resulting in amino acid change I555T in the extracellular domain consistent with a missense mutation. Her mother does not carry the mutation and the father is unknown. At 18 months of age, the child continues to have relative hyperparathyroidism and moderate hypercalcemia but is otherwise normal. CONCLUSION This neonate with intrauterine fractures and demineralization, moderate hypercalcemia and hyperparathyroidism was found to have a novel inactivating missense mutation of the CaSR not detected in her mother. Resolution of bone lesions and reduction of hyperparathyroidism was likely attributable to the natural evolution of the disorder in infancy as well as the mitigating effect of cholecalciferol treatment.
Collapse
Affiliation(s)
- Ksenia N Tonyushkina
- Baystate Children's Hospital, Tufts University School of Medicine, 759 Chestnut St, Dept of Pediatrics, Springfield, MA 01199, USA.
| | | | | |
Collapse
|
33
|
Falchetti A, Gozzini A, Terranegra A, Soldati L, Vezzoli G, Leoncini G, Giusti F, Franceschelli F, Masi L, Tanini A, Cavalli L, Brandi ML. A novel germline inactivating mutation in the CASR gene in an Italian kindred affected by familial hypocalciuric hypercalcemia. Eur J Endocrinol 2012; 166:933-40. [PMID: 22315359 DOI: 10.1530/eje-11-0953] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
OBJECTIVE Familial hypocalciuric hypercalcemia (FHH) syndrome is a rare benign condition, inherited as an autosomal dominant trait, in which inactivating mutations of the calcium-sensing receptor (CASR) gene affects the body's ability to regulate calcium homeostasis. Its outcome is featured by increased levels of serum calcium, moderate hypophosphatemia, and inadequately normal or elevated circulating parathyroid hormone levels. Affected patients are mostly asymptomatic and do not benefit from surgical resection of their mildly enlarged parathyroids. DESIGN We evaluated for hypercalcemia an Italian family that was identified via a young adult male proband referred to our center for parathyroidectomy. METHODS The patients and the family members were evaluated both biochemically and genetically as suspected FHH subjects. An in vitro functional study was performed by site-directed mutagenesis, and CASR activity was monitored by measuring intracellular calcium ([Ca(2)(+)](i)). RESULTS The patient had a novel germline heterozygous CASR mutation (c.361_364GATT; p.D121del/fsX122). The mutation caused a premature stop codon at codon 122, exiting a truncated protein. The biochemical phenotype of all family members carrying the heterozygous deletion was concordant with classic FHH syndrome. CONCLUSIONS Our findings confirm the role of CASR gene mutational analysis to offer a valuable addition for the recognition of FHH in hypercalcemic patients not yet characterized for a positive familial history of hypercalcemia, the only condition that identifies CASR gene mutations in hypercalcemia.
Collapse
Affiliation(s)
- Alberto Falchetti
- Unit of Metabolic Bone Diseases, Department of Internal Medicine, University of Florence, Viale Morgagni 85, 50135 Florence, Italy
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
34
|
The role of the calcium-sensing receptor in human disease. Clin Biochem 2012; 45:943-53. [PMID: 22503956 DOI: 10.1016/j.clinbiochem.2012.03.034] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2012] [Revised: 03/22/2012] [Accepted: 03/27/2012] [Indexed: 01/18/2023]
Abstract
Following the discovery of the calcium-sensing receptor (CaSR) in 1993, its pivotal role in disorders of calcium homeostasis such as Familial Hypocalciuric Hypercalcemia (FHH) was quickly demonstrated. Since then, it has become clear that the CaSR has immense functional versatility largely through its ability to activate many different signaling pathways in a ligand- and tissue-specific manner. This allows the receptor to play diverse and crucial roles in human physiology and pathophysiology, both in calcium homeostasis and in tissues and biological processes unrelated to calcium balance. This review covers current knowledge of the role of the CaSR in disorders of calcium homeostasis (FHH, neonatal severe hyperparathyroidism, autosomal dominant hypocalcemia, primary and secondary hyperparathyroidism, hypercalcemia of malignancy) as well as unrelated diseases such as breast and colorectal cancer (where the receptor appears to play a tumor suppressor role), Alzheimer's disease, pancreatitis, diabetes mellitus, hypertension and bone and gastrointestinal disorders. In addition, it examines the use or potential use of CaSR agonists or antagonists (calcimimetics and calcilytics) and other drugs mediated through the CaSR, in the management of disorders as diverse as hyperparathyroidism, osteoporosis and gastrointestinal disease.
Collapse
|
35
|
Hannan FM, Nesbit MA, Zhang C, Cranston T, Curley AJ, Harding B, Fratter C, Rust N, Christie PT, Turner JJO, Lemos MC, Bowl MR, Bouillon R, Brain C, Bridges N, Burren C, Connell JM, Jung H, Marks E, McCredie D, Mughal Z, Rodda C, Tollefsen S, Brown EM, Yang JJ, Thakker RV. Identification of 70 calcium-sensing receptor mutations in hyper- and hypo-calcaemic patients: evidence for clustering of extracellular domain mutations at calcium-binding sites. Hum Mol Genet 2012; 21:2768-78. [DOI: 10.1093/hmg/dds105] [Citation(s) in RCA: 130] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
|
36
|
Nissen PH, Christensen SE, Ladefoged SA, Brixen K, Heickendorff L, Mosekilde L. Identification of rare and frequent variants of the CASR gene by high-resolution melting. Clin Chim Acta 2012; 413:605-11. [DOI: 10.1016/j.cca.2011.12.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2011] [Revised: 12/02/2011] [Accepted: 12/05/2011] [Indexed: 10/14/2022]
|
37
|
Familial hypocalciuric hypercalcemia: new mutation in the CASR gene converting valine 697 to methionine. Eur J Pediatr 2012; 171:147-50. [PMID: 21643651 DOI: 10.1007/s00431-011-1504-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2011] [Accepted: 05/24/2011] [Indexed: 10/18/2022]
Abstract
Familial hypocalciuric hypercalcemia is an uncommon cause of hypercalcemia that arises from mutations in the calcium-sensing receptor gene. Inactivation of this receptor leads to a decreased receptor sensitivity to calcium, determining that higher concentrations of calcium are needed to inhibit the release of parathormone in the parathyroid glands. Patients usually are asymptomatic. Diagnosis is usually made casually after a routine blood analysis. The syndrome is characterized by mild or moderate hypercalcemia, hypocalciuria, and normal or slightly increased levels of parathormone. The degree of hypercalcemia depends on the type of mutation. The accurate diagnosis is important since it is a benign disorder that does not require medical or surgical treatment. We report a 9-year-old female with persistent hypercalcemia in several routine blood analyses, who was diagnosed with familial hypocalciuric hypercalcemia after genetic studies were performed. A new mutation determining a nucleotide change c.2089G>A in the calcium-sensing receptor gene (exon 7) was detected. This mutation was also found in the patient's mother and brother.
Collapse
|
38
|
Zhuang X, Northup JK, Ray K. Large putative PEST-like sequence motif at the carboxyl tail of human calcium receptor directs lysosomal degradation and regulates cell surface receptor level. J Biol Chem 2011; 287:4165-76. [PMID: 22158862 DOI: 10.1074/jbc.m111.271528] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A deletion between amino acid residues Ser(895) and Val(1075) in the carboxyl terminus of the human calcium receptor (hCaR), which causes autosomal dominant hypocalcemia, showed enhanced signaling activity and increased cell surface expression in HEK293 cells (Lienhardt, A., Garabédian, M. G., Bai, M., Sinding, C., Zhang, Z., Lagarde, J. P., Boulesteix, J., Rigaud, M., Brown, E. M., and Kottler, M. L. (2000) J. Clin. Endocrinol. Metab. 85, 1695-1702). To identify the underlying mechanism(s) for these increases, we investigated the effects of carboxyl tail truncation and deletion in hCaR mutants using a combination of biochemical and cell imaging approaches to define motifs that participate in regulating cell surface numbers of this G protein-coupled receptor. Our data indicate a rapid constitutive receptor internalization of the cell surface hCaR, accumulating in early (Rab7 positive) and late endosomal (LAMP1 positive) sorting compartments, before targeting to lysosomes for degradation. Recycling of hCaR back to the cell surface was also evident. Truncation and deletion mapping defined a 51-amino acid sequence between residues 920 and 970 that is required for targeting to lysosomes and degradation but not for internalization or recycling of the receptor. No singular sequence motif was identified, instead the required sequence elements seem to distribute throughout this entire interval. This interval includes a high proportion of acidic and hydroxylated amino acid residues, suggesting a similarity to PEST-like degradation motif (PESTfind score of +10) and several glutamine repeats. The results define a novel large PEST-like sequence that participates in the sorting of internalized hCaR routed to the lysosomal/degradation pathway that regulates cell surface receptor numbers.
Collapse
Affiliation(s)
- Xiaolei Zhuang
- Laboratory of Cellular Biology, NIDCD, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | |
Collapse
|
39
|
Christensen SE, Nissen PH, Vestergaard P, Mosekilde L. Familial hypocalciuric hypercalcaemia: a review. Curr Opin Endocrinol Diabetes Obes 2011; 18:359-70. [PMID: 21986511 DOI: 10.1097/med.0b013e32834c3c7c] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
PURPOSE OF REVIEW Hypercalcaemia is a potentially life-threatening condition. Familial hypocalciuric hypercalcaemia (FHH) is a rare, lifelong, benign condition. It is important to separate this condition from other hypercalcaemic states such as hypercalcaemia of malignancy and primary hyperparathyroidism (PHPT). RECENT FINDINGS FHH is caused by inactivating mutations in the calcium sensing receptor (CASR) gene leading to a general calcium-hyposensitivity, compensatory hypercalcaemia and hypocalciuria. The inheritance of FHH is autosomal dominant. Similar to PHPT, FHH is characterized by hypercalcaemia, unsuppressed or elevated plasma parathyroid hormone, and typically normal renal function. The phenotype is normal, and hypercalcaemic symptoms are generally absent. The hallmark is a relatively low urine calcium excretion in contrast to PHPT, in which urine calcium excretion is increased. The vitamin D status as measured by plasma 25-hydroxyvitamin D has been reported to be normal with normal seasonal variations, whereas plasma 1,25-dihydroxyvitamin D has been found slightly increased compared to normal. Bone mineral density Z-scores are normal in spite of a slightly increased bone turnover. Differential diagnoses include mainly PHPT, but in some cases also hypercalcaemia of malignancy and use of thiazide diuretics. SUMMARY In general, FHH does not require treatment. We recommend a two-step diagnostic procedure. First, the calcium/creatinine clearance ratio is measured from a 24-h urine. Second, all patients with calcium/creatinine clearance ratio of 0.020 or less are tested for mutations in the CASR gene. The diagnostic sensitivity of this setup is 98%.
Collapse
Affiliation(s)
- Signe E Christensen
- Department of Medicine and Endocrinology, Aarhus University Hospital, Aarhus C, Denmark.
| | | | | | | |
Collapse
|
40
|
Isaksen T, Nielsen CS, Christensen SE, Nissen PH, Heickendorff L, Mosekilde L. Forearm bone mineral density in familial hypocalciuric hypercalcemia and primary hyperparathyroidism: a comparative study. Calcif Tissue Int 2011; 89:285-94. [PMID: 21785908 DOI: 10.1007/s00223-011-9517-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 05/25/2011] [Indexed: 10/18/2022]
Abstract
Studies have shown that cancellous bone is relatively preserved in primary hyperparathyroidism (PHPT), whereas bone loss is seen in cortical bone. Familial hypocalciuric hypercalcemia (FHH) patients seem to preserve bone mineral in spite of hypercalcemia and often elevated plasma parathyroid hormone (PTH). The objective of this study was to compare total and regional forearm bone mineral density (BMD) in patients with PHPT and FHH and to examine if differences can be used to separate the two disorders. We included 63 FHH, and 121 PHPT patients in a cross-sectional study. We performed dual-energy X-ray absorptiometry scans of the forearm, hip and lumbar spine and measured a number of biochemical variables. PTH patients had significantly lower Z-scores in all parts of the forearm compared to FHH. This was also the case after adjustment for body mass index. When stratifying for age, gender and PTH, T-scores were still significantly lower in PHPT patients than in FHH patients at the total, the mid and the ultradistal forearm, but not at the proximal 1/3 forearm. In a multiple regression analysis BMD Z-score was lower in PHPT compared to FHH at the total forearm, the mid forearm and the ultradistal forearm but not the proximal forearm when adjusting for biochemical variables including PTH, 1,25(OH)(2)D and Ca(2+). These observations support that inactivating mutations in the CASR gene in bone cells in FHH may protect against forearm bone loss. Differences between the two groups in total or regional forearm BMD were inferior to the calcium/creatinine clearance ratio as a diagnostic tool to separate FHH from PHPT.
Collapse
Affiliation(s)
- Troels Isaksen
- Department of Internal Medicine and Endocrinology MEA, Aarhus University Hospital, THG, Denmark.
| | | | | | | | | | | |
Collapse
|
41
|
Interdomain movements in metabotropic glutamate receptor activation. Proc Natl Acad Sci U S A 2011; 108:15480-5. [PMID: 21896740 DOI: 10.1073/pnas.1107775108] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Many cell surface receptors are multimeric proteins, composed of several structural domains, some involved in ligand recognition, whereas others are responsible for signal transduction. In most cases, the mechanism of how ligand interaction in the extracellular domains leads to the activation of effector domains remains largely unknown. Here we examined how the extracellular ligand binding to the venus flytrap (VFT) domains of the dimeric metabotropic glutamate receptors activate the seven transmembrane (7TM) domains responsible for G protein activation. These two domains are interconnected by a cysteine-rich domain (CRD). We show that any of the four disulfide bridges of the CRD are required for the allosteric coupling between the VFT and the 7TM domains. More importantly, we show that a specific association of the two CRDs corresponds to the active state of the receptor. Indeed, a specific crosslinking of the CRDs with intersubunit disulfide bridges leads to fully constitutively active receptors, no longer activated by agonists nor by allosteric modulators. These data demonstrate that intersubunit movement at the level of the CRDs represents a key step in metabotropic glutamate receptor activation.
Collapse
|
42
|
Al-Salameh A, Cetani F, Pardi E, Vulpoi C, Pierre P, de Calan L, Guyetant S, Jeunemaitre X, Lecomte P. A novel mutation in the calcium-sensing receptor in a French family with familial hypocalciuric hypercalcaemia. Eur J Endocrinol 2011; 165:359-63. [PMID: 21566075 DOI: 10.1530/eje-11-0141] [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] [Indexed: 01/12/2023]
Abstract
OBJECTIVE The calcium-sensing receptor (CASR) has an important role in calcium homoeostasis by controlling PTH secretion and renal calcium handling. Inactivating mutations in the CASR gene (HGNC ID: 1514) cause familial hypocalciuric hypercalcaemia (FHH). We present a case of FHH patient to describe a novel mutation in the CASR. SUBJECTS AND METHODS A 34-year-old patient was referred because of recurrent hypercalcaemia after resection of two hyperplastic parathyroids. Extensive evaluation found elevated PTH and low calcium/creatinine clearance ratio. One of her three children had high serum calcium concentrations. Genetic studies were performed by PCR amplification of CASR coding exons and direct sequencing of PCR products. Transient transfection of the wild-type (WT) CASR and the mutant CASR into COS-7 was performed to assess functional impact of the mutation and the capacity of either protein to mediate increases in cellular levels of inositol phosphates (IPs). RESULTS CASR sequencing found a previously undescribed heterozygous base substitution, determining a change of threonine to isoleucine at codon 550 (p.T550I) in the sixth exon. In contrast to those transfected with WT CASR, which showed a five- to eightfold increase in total IPs at high levels of calcium, COS-7 cells transfected with the (p.T550I) mutant showed no increase confirming to the inactivating nature of the mutation. COS-7 cells co-transfected with the WT and the (p.T550I) mutant showed an intermediate response suggesting a possible dominant negative effect. CONCLUSION This case report presents a not-yet-described mutation in the cysteine-rich region of the CASR extracellular domain, a mutation with a possible dominant negative effect.
Collapse
Affiliation(s)
- Abdallah Al-Salameh
- Department of Endocrinology, CHRU Bretonneau, University Hospital of Tours, 2 Bis Boulevard Tonnellé, 37044 Tours Cedex 9, France
| | | | | | | | | | | | | | | | | |
Collapse
|
43
|
Livadariu E, Auriemma RS, Rydlewski C, Vandeva S, Hamoir E, Burlacu MC, Maweja S, Thonnard AS, Betea D, Vassart G, Daly AF, Beckers A. Mutations of calcium-sensing receptor gene: two novel mutations and overview of impact on calcium homeostasis. Eur J Endocrinol 2011; 165:353-8. [PMID: 21566074 DOI: 10.1530/eje-11-0121] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
OBJECTIVE Genetic disorders of calcium metabolism arise in a familial or sporadic setting. The calcium-sensing receptor (CASR) plays a key role in maintaining calcium homeostasis and study of the CASR gene can be clinically useful in determining etiology and appropriate therapeutic approaches. We report two cases of novel CASR gene mutations that illustrate the varying clinical presentations and discuss these in terms of the current understanding of CASR function. PATIENTS AND METHODS A 16-year-old patient had mild hypercalcemia associated with low-normal urinary calcium excretion and normal-to-high parathyroid hormone (PTH) levels. Because of negative family history, familial hypocalciuric hypercalcemia was originally excluded. The second patient was a 54-year-old man with symptomatic hypocalcemia, hyperphosphatemia, low PTH, and mild hypercalciuria. Familial investigation revealed the same phenotype in the patient's sister. The coding region of the CASR gene was sequenced in both probands and their available first-degree relatives. RESULTS The first patient had a novel heterozygous inactivating CASR mutation in exon 4, which predicted a p.A423K change; genetic analysis was negative in the parents. The second patient had a novel heterozygous activating CASR mutation in exon 6, which predicted a p.E556K change; the affected sister of the proband was also positive. CONCLUSIONS We reported two novel heterozygous mutations of the CASR gene, an inactivating mutation in exon 4 and the first activating mutation reported to date in exon 6. These cases illustrate the importance of genetic testing of CASR gene to aid correct diagnosis and to assist in clinical management.
Collapse
Affiliation(s)
- Elena Livadariu
- Department of Endocrinology, Centre Hospitalier Universitaire de Liège, University of Liège, 4000 Liège, Belgium
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Fernández López I, Fernández Peña I, Cózar León MV, Viloria Peñas MM, Martínez De Pinillos Gordillo G, Fernández-Ladreda MT, Duran García S. [Usefulness of genetic tests in familial hypocalciuric hypercalcemia with atypical clinical presentation]. ACTA ACUST UNITED AC 2011; 58:325-30. [PMID: 21697018 DOI: 10.1016/j.endonu.2011.04.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 04/07/2011] [Accepted: 04/17/2011] [Indexed: 11/18/2022]
Abstract
OBJECTIVES Biochemical tests related to calcium and phosphorus metabolism have traditionally been considered as a reliable tool to differentiate familial hypocalciuric hypercalcemia (FHH) from primary hyperparathyroidism (PHPT). However, diagnosis may sometimes be difficult even for experienced clinicians. Our objective was to assess the accuracy of diagnostic tests in FHH and the circumstances in which genetic studies are required. PATIENTS AND METHODS A descriptive study was conducted of two families with hypercalcemia and suspected atypical FHH. Urinary calcium excretion was measured in 24-hour urine using different tests (calcium excretion (CE), urinary calcium/creatinine clearance ratio (UCCR)), and serum PTH and 25-hydroxyvitamin D levels were tested. Index cases underwent genetic study. RESULTS One patient from the first family showed overt, persistent hypercalciuria with values more consistent with PHPT than with FHH if we consider, as proposed by guidelines, a UCCR lower than 0.01 as diagnostic of FHH and a value higher than 0.02 as diagnostic of PHPT. The index case of the second family underwent surgery for a parathyroid adenoma. Both cases had a mutation c. 164C>T (Pro55Leu) in exon 2 in heterozygosis. CONCLUSIONS According to current clinical guidelines, definitive diagnosis of FHH requires genetic confirmation, which allowed in our case for detection of two families with FHH and atypical clinical presentations. We think that rational use of genetic tests may avoid unnecessary surgery and excess monitoring costs.
Collapse
Affiliation(s)
- Ignacio Fernández López
- Unidad de Gestión Clínica, Endocrinología y Nutrición, Hospital Universitario Virgen de Valme, Sevilla, España.
| | | | | | | | | | | | | |
Collapse
|
45
|
Courbebaisse M, Souberbielle JC. Équilibre phosphocalcique : régulation et explorations. Nephrol Ther 2011; 7:118-38. [DOI: 10.1016/j.nephro.2010.12.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
|
46
|
Stepanchick A, McKenna J, McGovern O, Huang Y, Breitwieser GE. Calcium sensing receptor mutations implicated in pancreatitis and idiopathic epilepsy syndrome disrupt an arginine-rich retention motif. Cell Physiol Biochem 2010; 26:363-74. [PMID: 20798521 DOI: 10.1159/000320560] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/12/2010] [Indexed: 01/09/2023] Open
Abstract
Calcium sensing receptor (CaSR) mutations implicated in familial hypocalciuric hypercalcemia, pancreatitis and idiopathic epilepsy syndrome map to an extended arginine-rich region in the proximal carboxyl terminus. Arginine-rich motifs mediate endoplasmic reticulum retention and/or retrieval of multisubunit proteins so we asked whether these mutations, R886P, R896H or R898Q, altered CaSR targeting to the plasma membrane. Targeting was enhanced by all three mutations, and Ca(2+)-stimulated ERK1/2 phosphorylation was increased for R896H and R898Q. To define the role of the extended arginine-rich region in CaSR trafficking, we independently determined the contributions of R890/R891 and/or R896/K897/R898 motifs by mutation to alanine. Disruption of the motif(s) significantly increased surface expression and function relative to wt CaSR. The arginine-rich region is flanked by phosphorylation sites at S892 (protein kinase C) and S899 (protein kinase A). The phosphorylation state of S899 regulated recognition of the arginine-rich region; S899D showed increased surface localization. CaSR assembles in the endoplasmic reticulum as a covalent disulfide-linked dimer and we determined whether retention requires the presence of arginine-rich regions in both subunits. A single arginine-rich region within the dimer was sufficient to confer intracellular retention comparable to wt CaSR. We have identified an extended arginine-rich region in the proximal carboxyl terminus of CaSR (residues R890 - R898) which fosters intracellular retention of CaSR and is regulated by phosphorylation. Mutation(s) identified in chronic pancreatitis and idiopathic epilepsy syndrome therefore increase plasma membrane targeting of CaSR, likely contributing to the altered Ca(2+) signaling characteristic of these diseases.
Collapse
Affiliation(s)
- Ann Stepanchick
- Weis Center for Research, Geisinger Clinic, Danville, PA 17822, USA
| | | | | | | | | |
Collapse
|
47
|
Nissen PH, Christensen SE, Wallace A, Heickendorff L, Brixen K, Mosekilde L. Multiplex ligation-dependent probe amplification (MLPA) screening for exon copy number variation in the calcium sensing receptor gene: no large rearrangements identified in patients with calcium metabolic disorders. Clin Endocrinol (Oxf) 2010; 72:758-62. [PMID: 19912241 DOI: 10.1111/j.1365-2265.2009.03750.x] [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] [Indexed: 11/30/2022]
Abstract
BACKGROUND Mutation screening of the CASR by DNA sequencing is commonly used in the diagnosis of disorders of calcium metabolism, such as familial hypocalciuric hypercalcaemia (FHH). Exon copy number variation is not detected by currently used molecular genetic screening methods, and might be a genetic cause of inherited forms of hyper- or hypocalcaemia caused by the CASR. OBJECTIVE We wanted to further evaluate possible genetic causes for disorders of calcium metabolism, by investigating the prevalence of exon copy number variations, such as large deletions or duplications of the CASR. PATIENTS AND METHODS The study included 257 patient samples referred to our laboratory for molecular genetic analysis of the CASR gene. A total of 245 were patients suspected to have FHH, while the remaining 12 samples represent patients with a phenotype of idiopathic hypocalcaemia/hypoparathyroidism. All samples were previously found negative for CASR mutations. Multiplex ligation-dependent probe amplification was used to screen the patients for exon copy number variations. RESULTS All exons were amplified with mean normalised ratios between 0.98 and 1.06. We did not identify any exon copy number variation in the CASR. Bioinformatic analyses revealed that the CASR gene contains 52% repeated elements, of which approximately 6% consist of Alu elements. CONCLUSIONS The present study indicates that including CASR MLPA analysis as a routine part of the diagnostic setup is not necessary, but could still be of interest in cases with a clear family history and no evidence of missense mutations in the CASR gene.
Collapse
Affiliation(s)
- Peter H Nissen
- Department of Clinical Biochemistry, Aarhus University Hospital, Aarhus Sygehus, Denmark.
| | | | | | | | | | | |
Collapse
|
48
|
Guarnieri V, Canaff L, Yun FHJ, Scillitani A, Battista C, Muscarella LA, Wong BYL, Notarangelo A, D'Agruma L, Sacco M, Cole DEC, Hendy GN. Calcium-sensing receptor (CASR) mutations in hypercalcemic states: studies from a single endocrine clinic over three years. J Clin Endocrinol Metab 2010; 95:1819-29. [PMID: 20164288 DOI: 10.1210/jc.2008-2430] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
CONTEXT Inactivating mutations of the calcium-sensing receptor (CASR) are implicated in different hypercalcemic syndromes, including familial hypocalciuric hypercalcemia (FHH), primary hyperparathyroidism (PHPT), and familial isolated hyperparathyroidism (FIHP). However, molecular diagnostics applied to large nonselected hypercalcemic cohorts from a single center have not been reported. OBJECTIVE Our objective was to describe the prevalence, type, and potential pathogenicity of CASR mutations in a series of cases with FHH (n = 17), PHPT (n = 165), and FIHP (n = 3) and controls (n = 198) presenting at a single endocrine clinic. SUBJECTS All were prospectively evaluated at the "Casa Sollievo della Sofferenza" Hospital in southern Italy over a 3-yr period. METHODS CASR screening was conducted by denaturing HPLC. The variant CASRs were functionally characterized by transient transfection studies in kidney cells in vitro. RESULTS A single novel missense variant was identified in one PHPT case. However, in FHH probands, mutations were found in eight of 17 (47%). With a hypercalcemic family member, mutation detection rate in FHH rose to seven of eight (87%), whereas only one of nine sporadic cases was positive, and none of the three FIHP cases had detectable CASR mutations. Five missense variant CASRs, identified in control subjects, performed as wild type in functional assays, whereas the missense mutant CASRs identified in the FHH patients, and in the one PHPT case, exhibited significant impairment. A novel intronic mutation (IVS4-19a-->c) found in one FHH family, created an abnormally spliced product in an in vitro minigene assay. CONCLUSION CASR testing, with functional analysis, provides critical confirmatory evidence in the differential diagnosis of hypercalcemic states.
Collapse
Affiliation(s)
- Vito Guarnieri
- Departments of Laboratory Medicine and Pathobiology, University of Toronto, Ontario, Canada M5G 1L5
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
49
|
Christensen SE, Nissen PH, Vestergaard P, Heickendorff L, Rejnmark L, Brixen K, Mosekilde L. Skeletal consequences of familial hypocalciuric hypercalcaemia vs. primary hyperparathyroidism. Clin Endocrinol (Oxf) 2009; 71:798-807. [PMID: 19250271 DOI: 10.1111/j.1365-2265.2009.03557.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES Bone metabolism is only superficially described in familiar hypocalciuric hypercalcaemia (FHH). We describe and compare biochemical and osteodensitometric variables in FHH and primary hyperparathyroidism (PHPT) and assess whether they can improve the diagnostic discrimination between the groups. DESIGN Cross-sectional. PATIENTS Sixty-six FHH patients with known calcium-sensing receptor (CASR) gene mutations and 147 PHPT patients. MEASUREMENTS We determined calcium, creatinine, phosphate, magnesium, parathyroid hormone (PTH), 25OHD, 1,25(OH)(2) D and alkaline phosphatase (AP) in plasma, NTx/creatinine ratio in urine and calculated the calcium/creatinine clearance ratio (CCCR). We performed dual energy X-ray absorptiometry at the lumbar spine, hip, forearm and whole body. RESULTS When compared with normal controls, the FHH patients had increased levels of PTH and AP with normal U-NTx and regional Z-scores. Increased phenotypic expression of CASR mutations in terms of hypercalcaemia was associated with higher lumbar spine bone mineral density, but not with bone markers. FHH were younger and leaner than the PHPT patients. They had comparable plasma Ca(2+) and 25OHD, but lower levels of PTH, 1,25(OH)(2) D, AP and U-NTx. They had higher Z-scores in the hip and in the forearm. We achieved the best discrimination between groups by multiplying CCCR with AP, 1,25(OH)(2) D and PTH, but the difference between the area under the curves by receiver operating characteristic analysis remained insignificant. CONCLUSION Familiar hypocalciuric hypercalcaemia is associated with increased PTH and AP compared to normal controls, but not with bone loss irrespective of the severity of the CASR mutations. A multiplicative model including CCCR, AP, 1,25(OH)(2) D and PTH insignificantly improved the power of the CCCR to differentiate between FHH and PHPT. However, we still recommend CASR gene analysis in patients with a CCCR <0.020.
Collapse
|
50
|
Falchetti A, Marini F, Giusti F, Cavalli L, Cavalli T, Brandi ML. DNA-based test: when and why to apply it to primary hyperparathyroidism clinical phenotypes. J Intern Med 2009; 266:69-83. [PMID: 19522827 DOI: 10.1111/j.1365-2796.2009.02105.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Several cancer-related genes have been discovered and molecular test for the cancer genetic risk assessment has been widely increasing. Disorders such as Multiple Endocrine Neoplasia syndromes have received benefits from the identification of the responsible genes whose mutations account for the genetic susceptibility to develop endocrine tumours. Primary hyperparathyroidism (PHPT)is a clinical phenotype frequently associated to Multiple Endocrine Neoplasia syndromes, but it can also represent the unique endocrinopathy recurring as a familial cluster. In recent years, care options have been made available to patients and families with hereditary PHPT, and the process of systematically assessing the genetic risk has been becoming increasingly important. This review aims to help health providers not frequently dealing with genetic testing use and it will introduce some general concepts concerning genetic diagnosis issues. As an example the role and the practical usefulness of DNA-based diagnosis in patients affected by different forms of congenital PHPT is described, with a close look on why, when and how genetic testing should be performed in these subjects and their relatives. Some practical recommendations and suggestions concerning on how to deal when a suspect or known case of familial PHPT has to be faced conclude this manuscript.
Collapse
Affiliation(s)
- A Falchetti
- The Regional Centre for Hereditary Endocrine Tumors, Unit of Metabolic Bone Diseases, University Hospital of Careggi, Italy
| | | | | | | | | | | |
Collapse
|