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Dokurel Çetin İ, Betül Gerik-Çelebi H, Demiral M, Çetin O. Hereditary hypomagnesemia with secondary hypocalcemia caused by a novel mutation in TRPM6 gene. J Pediatr Endocrinol Metab 2024; 37:184-188. [PMID: 38084506 DOI: 10.1515/jpem-2023-0378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2023] [Accepted: 11/27/2023] [Indexed: 02/09/2024]
Abstract
OBJECTIVES Hereditary hypomagnesemia with secondary hypocalcemia (HSH), which results from variations in the transient receptor potential melastatin 6 (TRPM6) genes, is a rare hereditary cause of extremely low serum magnesium levels. We describe an infant with triggered seizures due to hypomagnesemia and a novel mutation in TRPM6 gene was identified. CASE PRESENTATION A 10-month-old boy presented with multidrug resistant seizures, and axial hypotonia due to severe hypomagnesemia. Electroencephalography and neuroimaging of the patient was normal. He had a favorable outcome with magnesium supplement. In this study, the patient underwent clinical exome sequencing (CES) which detected a novel homozygous variant in the TRPM6 gene: NM_017662.5: c.5571-3C>G. After replacing his magnesium orally, he was free from seizures and had an encouraging outcome at the twelfth-month follow-up. CONCLUSIONS HSH often presents with developmental issues, treatment-resistant seizures, and increased neuromuscular excitability. Untreated hypomagnesemia can potentially be fatal and severely impair cognitive function. Clinical suspicion is essential for early diagnosis and treatment.
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Affiliation(s)
- İpek Dokurel Çetin
- Department of Pediatrics, Division of Pediatric Neurology, Balikesir University Medical Faculty, Balikesir, Türkiye
| | | | - Meliha Demiral
- Department of Pediatrics, Division of Pediatric Endocrinology, Ataturk City Hospital, Balikesir, Türkiye
| | - Orkun Çetin
- Department of Obstetrics and Gynecology, Division of Perinatology, Balikesir University Medical Faculty, Balıkesir, Türkiye
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Kamali F, Jamee M, Sayer JA, Sadeghi-Bojd S, Golchehre Z, Dehghanzad R, Keramatipour M, Mohkam M. Intestinal hypomagnesemia in an Iranian patient with a novel TRPM6 variant: a case report and review of the literature. CEN Case Rep 2023; 12:413-418. [PMID: 36967423 PMCID: PMC10620355 DOI: 10.1007/s13730-023-00785-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2022] [Accepted: 03/13/2023] [Indexed: 03/28/2023] Open
Abstract
TRPM6 is predominantly expressed in the kidney and colon and encodes a protein containing an ion channel domain and a protein kinase domain. It is crucial for magnesium homeostasis and plays important roles in epithelial magnesium transport and the active magnesium absorption. In this study, we present a 70-day-old Iranian female patient from consanguineous parents with hypomagnesemia and secondary hypocalcemia. She presented with seizures 19 days after birth and refractory watery non-bloody diarrhea. She consequently had failure to thrive. Other features included hypotonia, wide anterior fontanel, ventriculomegaly, and pseudotumor cerebri following administration of nalidixic acid. She had severe hypomagnesemia and hypocalcemia which were treated with magnesium and calcium supplementation. Despite initial unstable response to supplemental magnesium, she eventually improved and the diarrhea discontinued. The patient was discharged by magnesium and calcium therapy. At the last follow-up at age 2.5 years, the patient remained well without any recurrence or complication. Genetic testing by whole-exome sequencing revealed a novel homozygous frameshift insertion-deletion (indel) variant in exon 26 of the TRPM6 gene, c.3693-3699del GCAAGAG ins CTGCTGTTGACATCTGCT, p.L1231Ffs*36. Segregation analysis revealed the TRPM6 heterozygous variant in both parents. Patients with biallelic TRPM6 pathogenic variants typically exhibit hypomagnesemia with secondary hypocalcemia and present with neurologic manifestations including seizures. In some patients, this is also complicated by chronic diarrhea and failure to thrive. Long-term complications are rare and most of the patients show a good prognosis with supplemental magnesium therapy.
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Affiliation(s)
- Farnaz Kamali
- Pediatric Nephrology Research Center, Research Institute for Children's Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran
- Student Research Committee, Alborz University of Medical Sciences, Karaj, Iran
| | - Mahnaz Jamee
- Pediatric Nephrology Research Center, Research Institute for Children's Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - John A Sayer
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Central Parkway, Newcastle Upon Tyne, NE1 3BZ, UK
- Renal Services, The Newcastle Upon Tyne Hospitals NHS Foundation Trust, Newcastle Upon Tyne, NE7 7DN, UK
- NIHR Newcastle Biomedical Research Centre, Newcastle University, Newcastle Upon Tyne, NE45PL, Tyne and Wear, UK
| | - Simin Sadeghi-Bojd
- Genetics of Non-Communicable Disease Research Center, Zahedan University of Medical Sciences, Zahedan, Iran
| | - Zahra Golchehre
- Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Reyhaneh Dehghanzad
- Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran
| | - Mohammad Keramatipour
- Watson Genetic Laboratory, North Kargar Street, Tehran, Iran.
- Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran.
| | - Masoumeh Mohkam
- Pediatric Nephrology Research Center, Research Institute for Children's Health, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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Acar S, Schlingmann KP, Nalbantoğlu Ö, Köprülü Ö, Arslan G, Özkaya B, Özkan B. A novel synonymous homozygous variant [c.2538G>A (p.Thr846Thr)] in TRPM6 in a patient with hypomagnesemia with secondary hypocalcemia. J Pediatr Endocrinol Metab 2021; 34:1481-1486. [PMID: 34261199 DOI: 10.1515/jpem-2021-0165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Accepted: 06/20/2021] [Indexed: 11/15/2022]
Abstract
OBJECTIVES Hypomagnesemia 1, intestinal (HOMG1) is characterized by neurological symptoms that occur due to hypocalcemia and hypomagnesemia and caused by mutations in the TRPM6. Most of the identified variants in TRPM6 lead to premature termination: nonsense, frameshift, deletion, and splice site mutations. CASE PRESENTATION Herein, we report a 1.5 month-old case who presented with convulsion due to hypocalcemia and hypomagnesemia in the early infancy. Sequencing of TRPM6 revealed a novel homozygous synonymous variant [c.2538G > A (p.Thr846Thr)] in the last codon of exon 19, which is most likely to affect the splicing. We report a novel homozygous synonymous variant in the TRPM6 leading to HOMG1, expanding the mutational spectrum. CONCLUSIONS Synonymous mutations that were previously considered as harmless should be evaluated at the nucleotide level, keeping in mind that they may affect splicing and cause to the disease.
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Affiliation(s)
- Sezer Acar
- Division of Pediatric Endocrinology, Dr. Behçet Uz Children's Education and Research Hospital, Izmir, Turkey
| | | | - Özlem Nalbantoğlu
- Division of Pediatric Endocrinology, Dr. Behçet Uz Children's Education and Research Hospital, Izmir, Turkey
| | - Özge Köprülü
- Division of Pediatric Endocrinology, Dr. Behçet Uz Children's Education and Research Hospital, Izmir, Turkey
| | - Gülçin Arslan
- Division of Pediatric Endocrinology, Dr. Behçet Uz Children's Education and Research Hospital, Izmir, Turkey
| | - Beyhan Özkaya
- Division of Pediatric Endocrinology, Dr. Behçet Uz Children's Education and Research Hospital, Izmir, Turkey
| | - Behzat Özkan
- Division of Pediatric Endocrinology, Dr. Behçet Uz Children's Education and Research Hospital, Izmir, Turkey
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Bayramoğlu E, Keskin M, Aycan Z, Savaş-Erdeve Ş, Çetinkaya S. Long-term Clinical Follow-up of Patients with Familial Hypomagnesemia with Secondary Hypocalcemia. J Clin Res Pediatr Endocrinol 2021; 13:300-307. [PMID: 33565749 PMCID: PMC8388043 DOI: 10.4274/jcrpe.galenos.2021.2020.0192] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
OBJECTIVE Familial hypomagnesemia with secondary hypocalcemia (HSH) is an autosomal recessive disease caused by a mutation in the transient receptor potential melastatin 6 (TRPM6) gene and is characterized by selective magnesium malabsorption. Affected cases are usually diagnosed during infancy and usually present with seizures due to hypocalcemia and hypomagnesemia. Irreversible neurological deficits and arrhythmias can be observed without appropriate treatment. The aim was to evaluate the long-term follow-up of patients with genetically confirmed HSH. METHODS A total of six patients with HSH, two of whom were siblings, were included. Age at diagnosis, clinical, laboratory and follow-up data on admission were recorded. All 39 exons of the TRPM6 gene and flanking exon-intron junctions from genomic DNA were amplified and sequenced in all cases. RESULTS The median (range) follow-up duration was 12.1 (7.6-21.7) years. All cases were diagnosed in infancy. Four different mutations, three of which had not been previously reported, were detected in the TRPM6 gene. Treatment compliance was good and there were no severe complications in the long-term follow-up of cases. However, mental retardation, specific learning difficulty and attention deficit/hyperactive disorder were observed as comorbidities. CONCLUSION Of the four different TRPM6 mutations in this small cohort, three had not been previously reported. The long-term prognosis of HSH appears to be good, given early diagnosis and good treatment compliance. This long-term follow-up and prognostic data and the three novel mutations will contribute to the published evidence concerning this rare condition, HSH, and it is hoped will prevent negative outcomes.
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Affiliation(s)
- Elvan Bayramoğlu
- University of Health Sciences Turkey, Ankara Dr. Sami Ulus Obstetrics and Gynecology and Child Health and Diseases Training and Research Hospital, Clinic of Pediatric Endocrinology, Ankara, Turkey,* Address for Correspondence: University of Health Sciences Turkey, Ankara Dr. Sami Ulus Obstetrics and Gynecology and Child Health and Diseases Training and Research Hospital, Clinic of Pediatric Endocrinology, Ankara, Turkey Phone: +90 312 305 65 13 E-mail:
| | - Melikşah Keskin
- University of Health Sciences Turkey, Ankara Dr. Sami Ulus Obstetrics and Gynecology and Child Health and Diseases Training and Research Hospital, Clinic of Pediatric Endocrinology, Ankara, Turkey
| | - Zehra Aycan
- University of Health Sciences Turkey, Ankara Dr. Sami Ulus Obstetrics and Gynecology and Child Health and Diseases Training and Research Hospital, Clinic of Pediatric Endocrinology, Ankara, Turkey
| | - Şenay Savaş-Erdeve
- University of Health Sciences Turkey, Ankara Dr. Sami Ulus Obstetrics and Gynecology and Child Health and Diseases Training and Research Hospital, Clinic of Pediatric Endocrinology, Ankara, Turkey
| | - Semra Çetinkaya
- University of Health Sciences Turkey, Ankara Dr. Sami Ulus Obstetrics and Gynecology and Child Health and Diseases Training and Research Hospital, Clinic of Pediatric Endocrinology, Ankara, Turkey
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Papez J, Starha J, Slaba K, Hubacek JA, Pecl J, Aulicka S, Urik M, Ceylaner S, Vesela P, Slaby O, Jabandziev P. Novel mutations in TRPM6 gene associated with primary hypomagnesemia with secondary hypocalcemia. Case report. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub 2021; 165:454-457. [PMID: 34012148 DOI: 10.5507/bp.2021.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Accepted: 04/22/2021] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Primary hypomagnesemia with secondary hypocalcemia (HSH) is a rare genetic disorder. Dysfunctional transient receptor potential melastatin 6 causes impaired intestinal absorption of magnesium, leading to low serum levels accompanied by hypocalcemia. Typical signs at initial manifestation are generalized seizures, tetany, and/or muscle spasms. CASE REPORT We present a 5 w/o female manifesting tonic-clonic seizures. Laboratory tests detected severe hypomagnesemia and hypocalcemia. The molecular genetic analysis revealed two novel mutations within the TRPM6 gene c.3308dupC (p.Pro1104Thrfs*28) (p.P1104Tfs*28) and c.3958C>T (p.Gln1302*) (p.Q1302*) and the patient was successfully treated with Mg supplementation. CONCLUSION Ion disbalance should be taken into account in the differential diagnosis of infantile seizures. Accurate diagnosis of HSH together with appropriate treatment are crucial to prevent irreversible neurological outcomes.
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Affiliation(s)
- Jan Papez
- Department of Pediatrics, University Hospital Brno, Brno, Czech Republic.,Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Jiri Starha
- Department of Pediatrics, University Hospital Brno, Brno, Czech Republic.,Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Katerina Slaba
- Department of Pediatrics, University Hospital Brno, Brno, Czech Republic.,Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Jaroslav A Hubacek
- Experimental Medicine Centre, Institute for Clinical and Experimental Medicine, Prague, Czech Republic.,3
| | - Jakub Pecl
- Department of Pediatrics, University Hospital Brno, Brno, Czech Republic.,Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Stefania Aulicka
- Faculty of Medicine, Masaryk University, Brno, Czech Republic.,Department of Pediatric Neurology, University Hospital Brno, Brno, Czech Republic
| | - Milan Urik
- Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | | | - Petra Vesela
- Central European Institute of Technology, Brno, Czech Republic
| | - Ondrej Slaby
- Faculty of Medicine, Masaryk University, Brno, Czech Republic.,Central European Institute of Technology, Brno, Czech Republic.,Department of Biology, Faculty of Medicine, Masaryk University, Brno, Czech Republic
| | - Petr Jabandziev
- Department of Pediatrics, University Hospital Brno, Brno, Czech Republic.,Faculty of Medicine, Masaryk University, Brno, Czech Republic.,Central European Institute of Technology, Brno, Czech Republic
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Mild hypotonia and recurrent seizures in an 8-month-old boy: Answers. Pediatr Nephrol 2019; 34:1729-1731. [PMID: 30903374 DOI: 10.1007/s00467-019-04236-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2019] [Revised: 02/10/2019] [Accepted: 03/07/2019] [Indexed: 10/27/2022]
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Altıncık A, Schlingmann KP, Tosun MS. A Novel Homozygous Mutation in the Transient Receptor Potential Melastatin 6 Gene: A Case Report. J Clin Res Pediatr Endocrinol 2016; 8:101-4. [PMID: 26759217 PMCID: PMC4805040 DOI: 10.4274/jcrpe.2254] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/01/2022] Open
Abstract
Hereditary hypomagnesemia with secondary hypocalcemia (HSH) is a rare autosomal recessive disease caused by mutations in the transient receptor potential melastatin 6 (TRPM6) gene. Affected individuals present in early infancy with seizures caused by the severe hypocalcemia and hypomagnesemia. By presenting this case report, we also aimed to highlight the need for molecular genetic analysis in inbred or familial cases with hypomagnesemia. A Turkish inbred girl, now aged six years, had presented to another hospital at age two months with seizures diagnosed to be due to hypomagnesemia. She was on magnesium replacement therapy when she was admitted to our clinic with complaints of chronic diarrhea at age 3.6 years. During her follow-up in our clinic, she showed an age-appropriate physical and neurological development. In molecular genetic analysis, a novel homozygous frame-shift mutation (c.3447delT>p.F1149fs) was identified in the TRPM6 gene. This mutation leads to a truncation of the TRPM6 protein, thereby complete loss of function. We present the clinical follow-up findings of a pediatric HSH case due to a novel mutation in the TRPM6 gene and highlight the need for molecular genetic analysis in inbred or familial cases with hypomagnesemia.
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Affiliation(s)
- Ayça Altıncık
- Denizli State Hospital, Clinic of Pediatric Endocrinology, Denizli, Turkey, E-mail: ,
| | | | - Mahya Sultan Tosun
- Denizli State Hospital, Clinic of Pediatric Gastroenterology, Denizli, Turkey
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9
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Katayama K, Povalko N, Yatsuga S, Nishioka J, Kakuma T, Matsuishi T, Koga Y. New TRPM6 mutation and management of hypomagnesaemia with secondary hypocalcaemia. Brain Dev 2015; 37:292-8. [PMID: 24985022 DOI: 10.1016/j.braindev.2014.06.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Revised: 06/04/2014] [Accepted: 06/06/2014] [Indexed: 11/25/2022]
Abstract
BACKGROUND TRPM6 gene mutation has been reported to cause hypomagnesemia with secondary hypocalcemia (HSH). However, the genotype-phenotype correlation for TRPM6 gene mutations has not been clarified. OBJECTIVE To elucidate the factors underlying the severe neurological complications in HSH and evaluate the potential association between the location of TRPM6 gene mutations and clinical data of HSH. METHODS A Japanese patient diagnosed with HSH at 10 weeks of age exhibited neurological damage and failed to thrive. Magnesium supplements were therefore started at 12 weeks of age. Mutational analysis of the TRPM6 gene was performed using a direct sequencing method to determine the position and type of mutation. Using the data of 29 HSH patients reported in the literature, linear regression analysis was also performed to examine the association between TRPM6 gene mutation location and HSH onset age, initial serum magnesium and calcium concentrations, and dose of oral magnesium. RESULTS A novel stop-codon homozygous mutation [c.4190 G>A] W1397X was identified in exon 26 of the patient's TRPM6 gene. No statistical correlation was found between the location of mutations in the TRPM6 gene and the clinical data for 4 clinical indicators of HSH. CONCLUSIONS We identified the first Japanese HSH patient with a novel nonsense mutation in the TRPM6 gene. Regression analysis of mutation locations in the protein-coding region of TRPM6 and the reported clinical data for 4 clinical indicators of HSH in 30 HSH patients did not detect a genotype-phenotype correlation.
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Affiliation(s)
- Koujyu Katayama
- Department of Pediatrics and Child Health, Kurume University Graduate School of Medicine, Kurume, Japan
| | - Nataliya Povalko
- Department of Pediatrics and Child Health, Kurume University Graduate School of Medicine, Kurume, Japan
| | - Shuichi Yatsuga
- Department of Pediatrics and Child Health, Kurume University Graduate School of Medicine, Kurume, Japan
| | - Junko Nishioka
- Department of Pediatrics and Child Health, Kurume University Graduate School of Medicine, Kurume, Japan
| | - Tatsuyuki Kakuma
- Department of Biostatistics, Kurume University Graduate School of Medicine, Kurume, Japan
| | - Toyojiro Matsuishi
- Department of Pediatrics and Child Health, Kurume University Graduate School of Medicine, Kurume, Japan
| | - Yasutoshi Koga
- Department of Pediatrics and Child Health, Kurume University Graduate School of Medicine, Kurume, Japan.
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Abstract
TRPM6 is a bifunctional protein comprising a TRP cation channel segment covalently linked to an α-type serine/threonine protein kinase. TRPM6 is expressed in the intestinal and renal epithelial cells. Loss-of-function mutations in the human TRPM6 gene give rise to hypomagnesemia with secondary hypocalcemia (HSH), suggesting that the TRPM6 channel kinase plays a central role in systemic Mg(2+) homeostasis. In contrast, Trpm6 null mice show a delay in prenatal development, neural tube defects, and prenatal death. Possible functions of TRPM6 in prenatal and adult organisms will be discussed in this chapter.
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Affiliation(s)
- Vladimir Chubanov
- Walther-Straub-Institute for Pharmacology and Toxicology, Ludwig-Maximilians University Munich, Goethestrasse 33, Munich, 80336, Germany,
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Ndiaye M, Toffa DH, Sow AD, Sène MS, Basse AM, Fall AL, Seck LB, Touré K, Diop AG, Sow HD, Ndiaye MM. [Familial congenital hypomagnesemia revealed by neonatal convulsions]. Arch Pediatr 2013; 20:1212-1218. [PMID: 24090669 DOI: 10.1016/j.arcped.2013.08.019] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2012] [Revised: 01/07/2013] [Accepted: 08/27/2013] [Indexed: 11/26/2022]
Abstract
Congenital hypomagnesemia is a rare disease, with an impact on cognitive and neurological development. We report on three familial cases of congenital hypomagnesemia, two boys and one girl who belong to the same consanguineous family. They all presented neonatal seizures and a psychomotor developmental delay. Cerebral computed tomography showed cerebral atrophy and calcifications in one case and magnetic resonance imaging found predominant cerebellar atrophy in the two other cases. All three patients also had hypocalcemia, hyperphosphoremia, and hypomagnesemia. The parathyroid hormone blood level was low in two cases and normal in the third. One 7-month old patient died. The others received a supplementation of calcium and magnesium, which normalized calcemia, phosphatemia but not magnesemia, which remained low despite high doses. They have both developed cognitive and behavioral impairments.
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Affiliation(s)
- M Ndiaye
- Service de neurologie, CHU Fann, BP 5035, Dakar, Sénégal; Hôpital d'enfants Albert-Royer, Sénégal.
| | - D H Toffa
- Service de neurologie, CHU Fann, BP 5035, Dakar, Sénégal
| | - A-D Sow
- Service de neurologie, CHU Fann, BP 5035, Dakar, Sénégal
| | - M-S Sène
- Service de neurologie, CHU Fann, BP 5035, Dakar, Sénégal
| | - A-M Basse
- Service de neurologie, CHU Fann, BP 5035, Dakar, Sénégal
| | - A-L Fall
- Hôpital d'enfants Albert-Royer, Sénégal
| | - L-B Seck
- Service de neurologie, CHU Fann, BP 5035, Dakar, Sénégal
| | - K Touré
- Service de neurologie, CHU Fann, BP 5035, Dakar, Sénégal
| | - A-G Diop
- Service de neurologie, CHU Fann, BP 5035, Dakar, Sénégal
| | - H-D Sow
- Hôpital d'enfants Albert-Royer, Sénégal
| | - M-M Ndiaye
- Service de neurologie, CHU Fann, BP 5035, Dakar, Sénégal
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12
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Lainez S, Schlingmann KP, van der Wijst J, Dworniczak B, van Zeeland F, Konrad M, Bindels RJ, Hoenderop JG. New TRPM6 missense mutations linked to hypomagnesemia with secondary hypocalcemia. Eur J Hum Genet 2013; 22:497-504. [PMID: 23942199 DOI: 10.1038/ejhg.2013.178] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2012] [Revised: 06/20/2013] [Accepted: 07/11/2013] [Indexed: 11/09/2022] Open
Abstract
Despite recent progress in our understanding of renal magnesium (Mg(2+)) handling, the molecular mechanisms accounting for transepithelial Mg(2+) transport are still poorly understood. Mutations in the TRPM6 gene, encoding the epithelial Mg(2+) channel TRPM6 (transient receptor potential melastatin 6), have been proven to be the molecular cause of hypomagnesemia with secondary hypocalcemia (HSH; OMIM 602014). HSH manifests in the newborn period being characterized by very low serum Mg(2+) levels (<0.4 mmol/l) accompanied by low serum calcium (Ca(2+)) concentrations. A proportion of previously described TRPM6 mutations lead to a truncated TRPM6 protein resulting in a complete loss-of-function of the ion channel. In addition, five-point mutations have been previously described. The aim of this study was to complement the current clinical picture by adding the molecular data from five new missense mutations found in five patients with HSH. To this end, patch-clamp analysis and cell surface measurements were performed to assess the effect of the various mutations on TRPM6 channel function. All mutant channels, expressed in HEK293 cells, showed loss-of-function, whereas no severe trafficking impairment to the plasma membrane surface was observed. We conclude that the new TRPM6 missense mutations lead to dysregulated intestinal/renal Mg(2+) (re)absorption as a consequence of loss of TRPM6 channel function.
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Affiliation(s)
- Sergio Lainez
- 1] Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands [2] Department of Pharmacology, University of Cambridge, Cambridge, UK
| | | | - Jenny van der Wijst
- MRC Protein Phosphorylation Unit, College of Life Sciences, University of Dundee, Dundee, Scotland, UK
| | - Bernd Dworniczak
- Department of Human Genetics, Westfaelische Wilhelms Universität, Münster, Germany
| | - Femke van Zeeland
- Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands
| | - Martin Konrad
- Department of General Pediatrics, University Hospital Münster, Münster, Germany
| | - René J Bindels
- Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands
| | - Joost G Hoenderop
- Department of Physiology, Radboud University Nijmegen Medical Centre, Nijmegen Centre for Molecular Life Sciences, Nijmegen, The Netherlands
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13
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Zhao Z, Pei Y, Huang X, Liu Y, Yang W, Sun J, Si N, Xing X, Li M, Wang O, Jiang Y, Zhang X, Xia W. Novel TRPM6 mutations in familial hypomagnesemia with secondary hypocalcemia. Am J Nephrol 2013; 37:541-8. [PMID: 23689795 DOI: 10.1159/000350886] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Accepted: 03/20/2013] [Indexed: 12/15/2022]
Abstract
BACKGROUND Familial hypomagnesemia with secondary hypocalcemia (HSH) is a rare autosomal recessive disease characterized by severe hypomagnesemia and hypocalcemia associated with neurological symptoms, including generalized seizures, tetany and muscle spasms, which are refractory to anticonvulsant treatment. The pathophysiological hallmarks of HSH are the impaired intestinal absorption of magnesium accompanied by renal magnesium wasting as a result of a reabsorption defect in the distal convoluted tubule. Mutations in TRPM6, the gene encoding the transient receptor potential cation channel subfamily member 6, have been found to be responsible for this disease. In the present study, we report a Chinese family with 2 sisters affected with severe HSH, and elucidate the characteristics of TRPM6 gene mutations in these 2 patients. METHODS We evaluated the clinical, laboratory, and radiographic findings. All 39 TRPM6 exons and flanking exon-intron junctions from genomic DNA were amplified and sequenced in 2 affected members suffering from HSH and their family. RESULTS We found two novel mutations in the family, one frameshift mutation (c.1196delC) and one non-sense mutation (c.4577G>A). These mutations were predicted to result in a complete loss of function of TRPM6. Both of the sisters were compound heterozygotes for these mutations. CONCLUSION Our results suggested that the compound heterozygous mutations in TRPM6 were responsible for HSH in the Chinese family.
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Affiliation(s)
- Zhen Zhao
- Department of Endocrinology, Key Laboratory of Endocrinology, The Ministry of Health, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing, China
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