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The ataxia-linked E1081Q mutation affects the sub-plasma membrane Ca 2+-microdomains by tuning PMCA3 activity. Cell Death Dis 2022; 13:855. [PMID: 36207321 PMCID: PMC9546857 DOI: 10.1038/s41419-022-05300-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2022] [Revised: 09/22/2022] [Accepted: 09/26/2022] [Indexed: 01/23/2023]
Abstract
Calcium concentration must be finely tuned in all eukaryotic cells to ensure the correct performance of its signalling function. Neuronal activity is exquisitely dependent on the control of Ca2+ homeostasis: its alterations ultimately play a pivotal role in the origin and progression of many neurodegenerative processes. A complex toolkit of Ca2+ pumps and exchangers maintains the fluctuation of cytosolic Ca2+ concentration within the appropriate threshold. Two ubiquitous (isoforms 1 and 4) and two neuronally enriched (isoforms 2 and 3) of the plasma membrane Ca2+ATPase (PMCA pump) selectively regulate cytosolic Ca2+ transients by shaping the sub-plasma membrane (PM) microdomains. In humans, genetic mutations in ATP2B1, ATP2B2 and ATP2B3 gene have been linked with hearing loss, cerebellar ataxia and global neurodevelopmental delay: all of them were found to impair pump activity. Here we report three additional mutations in ATP2B3 gene corresponding to E1081Q, R1133Q and R696H amino acids substitution, respectively. Among them, the novel missense mutation (E1081Q) immediately upstream the C-terminal calmodulin-binding domain (CaM-BD) of the PMCA3 protein was present in two patients originating from two distinct families. Our biochemical and molecular studies on PMCA3 E1081Q mutant have revealed a splicing variant-dependent effect of the mutation in shaping the sub-PM [Ca2+]. The E1081Q substitution in the full-length b variant abolished the capacity of the pump to reduce [Ca2+] in the sub-PM microdomain (in line with the previously described ataxia-related PMCA mutations negatively affecting Ca2+ pumping activity), while, surprisingly, its introduction in the truncated a variant selectively increased Ca2+ extrusion activity in the sub-PM Ca2+ microdomains. These results highlight the importance to set a precise threshold of [Ca2+] by fine-tuning the sub-PM microdomains and the different contribution of the PMCA splice variants in this regulation.
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2
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Lewis MA, Ingham NJ, Chen J, Pearson S, Di Domenico F, Rekhi S, Allen R, Drake M, Willaert A, Rook V, Pass J, Keane T, Adams DJ, Tucker AS, White JK, Steel KP. Identification and characterisation of spontaneous mutations causing deafness from a targeted knockout programme. BMC Biol 2022; 20:67. [PMID: 35296311 PMCID: PMC8928630 DOI: 10.1186/s12915-022-01257-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2021] [Accepted: 02/17/2022] [Indexed: 11/30/2022] Open
Abstract
Background Mice carrying targeted mutations are important for investigating gene function and the role of genes in disease, but off-target mutagenic effects associated with the processes of generating targeted alleles, for instance using Crispr, and culturing embryonic stem cells, offer opportunities for spontaneous mutations to arise. Identifying spontaneous mutations relies on the detection of phenotypes segregating independently of targeted alleles, and having a broad estimate of the level of mutations generated by intensive breeding programmes is difficult given that many phenotypes are easy to miss if not specifically looked for. Here we present data from a large, targeted knockout programme in which mice were analysed through a phenotyping pipeline. Such spontaneous mutations segregating within mutant lines may confound phenotypic analyses, highlighting the importance of record-keeping and maintaining correct pedigrees. Results Twenty-five lines out of 1311 displayed different deafness phenotypes that did not segregate with the targeted allele. We observed a variety of phenotypes by Auditory Brainstem Response (ABR) and behavioural assessment and isolated eight lines showing early-onset severe progressive hearing loss, later-onset progressive hearing loss, low frequency hearing loss, or complete deafness, with vestibular dysfunction. The causative mutations identified include deletions, insertions, and point mutations, some of which involve new genes not previously associated with deafness while others are new alleles of genes known to underlie hearing loss. Two of the latter show a phenotype much reduced in severity compared to other mutant alleles of the same gene. We investigated the ES cells from which these lines were derived and determined that only one of the 8 mutations could have arisen in the ES cell, and in that case, only after targeting. Instead, most of the non-segregating mutations appear to have occurred during breeding of mutant mice. In one case, the mutation arose within the wildtype colony used for expanding mutant lines. Conclusions Our data show that spontaneous mutations with observable effects on phenotype are a common side effect of intensive breeding programmes, including those underlying targeted mutation programmes. Such spontaneous mutations segregating within mutant lines may confound phenotypic analyses, highlighting the importance of record-keeping and maintaining correct pedigrees. Supplementary Information The online version contains supplementary material available at 10.1186/s12915-022-01257-8.
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Affiliation(s)
- Morag A Lewis
- Wolfson Centre for Age-Related Diseases, King's College London, London, SE1 1UL, England. .,Wellcome Sanger Institute, Hinxton, CB10 1SA, England.
| | - Neil J Ingham
- Wolfson Centre for Age-Related Diseases, King's College London, London, SE1 1UL, England.,Wellcome Sanger Institute, Hinxton, CB10 1SA, England
| | - Jing Chen
- Wolfson Centre for Age-Related Diseases, King's College London, London, SE1 1UL, England.,Wellcome Sanger Institute, Hinxton, CB10 1SA, England
| | | | - Francesca Di Domenico
- Wolfson Centre for Age-Related Diseases, King's College London, London, SE1 1UL, England
| | - Sohinder Rekhi
- Wolfson Centre for Age-Related Diseases, King's College London, London, SE1 1UL, England
| | - Rochelle Allen
- Wolfson Centre for Age-Related Diseases, King's College London, London, SE1 1UL, England
| | - Matthew Drake
- Wolfson Centre for Age-Related Diseases, King's College London, London, SE1 1UL, England
| | - Annelore Willaert
- Research Group of Experimental Oto-Rhino-Laryngology, Department of Neurosciences, KU Leuven - University of Leuven, Leuven, Belgium
| | - Victoria Rook
- Wolfson Centre for Age-Related Diseases, King's College London, London, SE1 1UL, England
| | - Johanna Pass
- Wolfson Centre for Age-Related Diseases, King's College London, London, SE1 1UL, England.,Wellcome Sanger Institute, Hinxton, CB10 1SA, England
| | - Thomas Keane
- Wellcome Sanger Institute, Hinxton, CB10 1SA, England
| | - David J Adams
- Wellcome Sanger Institute, Hinxton, CB10 1SA, England
| | - Abigail S Tucker
- Centre for Craniofacial and Regenerative Biology, King's College London, London, SE1 9RT, England
| | | | - Karen P Steel
- Wolfson Centre for Age-Related Diseases, King's College London, London, SE1 1UL, England.,Wellcome Sanger Institute, Hinxton, CB10 1SA, England
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3
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Bortolozzi M, Mammano F. PMCA2 pump mutations and hereditary deafness. Neurosci Lett 2019; 663:18-24. [PMID: 29452611 DOI: 10.1016/j.neulet.2017.09.059] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2017] [Revised: 09/25/2017] [Accepted: 09/28/2017] [Indexed: 01/21/2023]
Abstract
Hair cells of the inner ear detect sound stimuli, inertial or gravitational forces by deflection of their apical stereocilia. A small number of stereociliary cation-selective mechanotransduction (MET) channels admit K+ and Ca2+ ions into the cytoplasm promoting hair cell membrane depolarization and, consequently, neurotransmitter release at the cell basolateral pole. Ca2+ influx into the stereocilia compartment is counteracted by the unusual w/a splicing variant of plasma-membrane calcium-pump isoform 2 (PMCA2) which, unlike other PMCA2 variants, increases only marginally its activity in response to a rapid variation of the cytoplasmic free Ca2+ concentration ([Ca2+]c). Missense mutations of PMCA2w/a cause deafness and loss of balance in humans. Mouse models in which the pump is genetically ablated or mutated show hearing and balance impairment, which correlates with defects in homeostatic regulation of stereociliary [Ca2+]c, decreased sensitivity of mechanotransduction channels to hair bundle displacement and progressive degeneration of the organ of Corti. These results highlight a critical role played by the PMCA2w/a pump in the control of hair cell function and survival, and provide mechanistic insight into the etiology of deafness and vestibular disorders.
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Affiliation(s)
- Mario Bortolozzi
- University of Padua, Department of Physics and Astronomy "G. Galilei", Padua, Italy; Venetian Institute of Molecular Medicine (VIMM), Padua, Italy; CNR Institute of Protein Biochemistry, Naples, Italy.
| | - Fabio Mammano
- University of Padua, Department of Physics and Astronomy "G. Galilei", Padua, Italy; Venetian Institute of Molecular Medicine (VIMM), Padua, Italy; CNR Institute of Cell Biology and Neurobiology, Monterotondo Scalo, Rome, Italy
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4
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The Protective Role of Peroxisome Proliferator-Activated Receptor-Gamma in Seizure and Neuronal Excitotoxicity. Mol Neurobiol 2019; 56:5497-5506. [PMID: 30623373 DOI: 10.1007/s12035-018-1457-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 12/17/2018] [Indexed: 01/09/2023]
Abstract
The peroxisome proliferator-activated receptor (PPAR) family, type II nucleus receptors have been successfully tested for their neuroprotective potential in certain central nervous system diseases. The aim of the present study was to determine if modulation by PPAR-γ could attenuate pilocarpine-induced seizures and decrease neuronal excitability. Adult male C57BL/6 mice were divided into two groups: one group received pretreatment with pioglitazone and the other received dimethyl sulfoxide (DMSO) for a period of 2 weeks. Status epilepticus was then induced in both groups by lithium-pilocarpine, after which seizure susceptibility, severity, and mortality were evaluated. Hippocampal histopathology was carried out on all mice at 24 h post-status epilepticus as well as blood-brain barrier (BBB) damage analysis. With the aid of patch clamp technology, the hippocampal neuronal excitability from mice with PPAR-γ 50% expression (PpargC/C) and PPAR-γ 25% expression (PpargC/-), as well as the effect of pioglitazone on the sodium currents in hippocampal neurons, were evaluated. It was found that pioglitazone, a PPAR-γ agonist, could attenuate pilocarpine-induced seizure severity in mice. Pathological examination showed that pioglitazone significantly attenuated pilocarpine-induced status epilepticus-related hippocampal neuronal loss and BBB damage. Further characterization of neuronal excitability revealed higher excitability in the brain slices from mice with PpargC/- expression, compared with the PpargC/C group. It was also found that pioglitazone could decrease sodium currents in hippocampal neurons. In conclusion, PPAR-γ deficiency aggravated neuronal excitability and excitotoxicity. PPAR-γ attenuated pilocarpine-induced seizure severity, neuronal loss, BBB damage, and sodium currents in hippocampal neurons. Modulation of PPAR-γ could be a potential novel treatment for epileptic seizures.
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5
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Smits JJ, Oostrik J, Beynon AJ, Kant SG, de Koning Gans PAM, Rotteveel LJC, Klein Wassink-Ruiter JS, Free RH, Maas SM, van de Kamp J, Merkus P, Koole W, Feenstra I, Admiraal RJC, Lanting CP, Schraders M, Yntema HG, Pennings RJE, Kremer H. De novo and inherited loss-of-function variants of ATP2B2 are associated with rapidly progressive hearing impairment. Hum Genet 2018; 138:61-72. [PMID: 30535804 PMCID: PMC6514080 DOI: 10.1007/s00439-018-1965-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2018] [Accepted: 11/30/2018] [Indexed: 01/21/2023]
Abstract
ATP2B2 encodes the PMCA2 Ca2+ pump that plays an important role in maintaining ion homeostasis in hair cells among others by extrusion of Ca2+ from the stereocilia to the endolymph. Several mouse models have been described for this gene; mice heterozygous for loss-of-function defects display a rapidly progressive high-frequency hearing impairment. Up to now ATP2B2 has only been reported as a modifier, or in a digenic mechanism with CDH23 for hearing impairment in humans. Whole exome sequencing in hearing impaired index cases of Dutch and Polish origins revealed five novel heterozygous (predicted to be) loss-of-function variants of ATP2B2. Two variants, c.1963G>T (p.Glu655*) and c.955delG (p.Ala319fs), occurred de novo. Three variants c.397+1G>A (p.?), c.1998C>A (p.Cys666*), and c.2329C>T (p.Arg777*), were identified in families with an autosomal dominant inheritance pattern of hearing impairment. After normal newborn hearing screening, a rapidly progressive high-frequency hearing impairment was diagnosed at the age of about 3–6 years. Subjects had no balance complaints and vestibular testing did not yield abnormalities. There was no evidence for retrocochlear pathology or structural inner ear abnormalities. Although a digenic inheritance pattern of hearing impairment has been reported for heterozygous missense variants of ATP2B2 and CDH23, our findings indicate a monogenic cause of hearing impairment in cases with loss-of-function variants of ATP2B2.
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Affiliation(s)
- Jeroen J Smits
- Hearing and Genes, Department of Otorhinolaryngology, Head and Neck Surgery, Radboud University Medical Center, Nijmegen, The Netherlands
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Jaap Oostrik
- Hearing and Genes, Department of Otorhinolaryngology, Head and Neck Surgery, Radboud University Medical Center, Nijmegen, The Netherlands
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Andy J Beynon
- Hearing and Genes, Department of Otorhinolaryngology, Head and Neck Surgery, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Sarina G Kant
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | - Pia A M de Koning Gans
- Department of Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | | | | | - Rolien H Free
- Department of Otorhinolaryngology, Head and Neck Surgery, University Medical Center Groningen, Groningen, The Netherlands
| | - Saskia M Maas
- Department of Clinical Genetics, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Jiddeke van de Kamp
- Department of Clinical Genetics, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Paul Merkus
- Department of Otolaryngology, Head and Neck Surgery, Ear and Hearing, Amsterdam Public Health Research Institute, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Wouter Koole
- Hearing and Genes, Department of Human Genetics, Radboud University Medical Center, Internal postal code 855, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Ilse Feenstra
- Hearing and Genes, Department of Human Genetics, Radboud University Medical Center, Internal postal code 855, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Ronald J C Admiraal
- Hearing and Genes, Department of Otorhinolaryngology, Head and Neck Surgery, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Cornelis P Lanting
- Hearing and Genes, Department of Otorhinolaryngology, Head and Neck Surgery, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Margit Schraders
- Hearing and Genes, Department of Otorhinolaryngology, Head and Neck Surgery, Radboud University Medical Center, Nijmegen, The Netherlands
- Hearing and Genes, Department of Human Genetics, Radboud University Medical Center, Internal postal code 855, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Helger G Yntema
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
- Hearing and Genes, Department of Human Genetics, Radboud University Medical Center, Internal postal code 855, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Ronald J E Pennings
- Hearing and Genes, Department of Otorhinolaryngology, Head and Neck Surgery, Radboud University Medical Center, Nijmegen, The Netherlands
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Hannie Kremer
- Hearing and Genes, Department of Otorhinolaryngology, Head and Neck Surgery, Radboud University Medical Center, Nijmegen, The Netherlands.
- Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, The Netherlands.
- Hearing and Genes, Department of Human Genetics, Radboud University Medical Center, Internal postal code 855, P.O. Box 9101, 6500 HB, Nijmegen, The Netherlands.
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6
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Vicario M, Zanni G, Vallese F, Santorelli F, Grinzato A, Cieri D, Berto P, Frizzarin M, Lopreiato R, Zonta F, Ferro S, Sandre M, Marin O, Ruzzene M, Bertini E, Zanotti G, Brini M, Calì T, Carafoli E. A V1143F mutation in the neuronal-enriched isoform 2 of the PMCA pump is linked with ataxia. Neurobiol Dis 2018; 115:157-166. [PMID: 29655659 DOI: 10.1016/j.nbd.2018.04.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2018] [Revised: 03/21/2018] [Accepted: 04/09/2018] [Indexed: 12/13/2022] Open
Abstract
The fine regulation of intracellular calcium is fundamental for all eukaryotic cells. In neurons, Ca2+ oscillations govern the synaptic development, the release of neurotransmitters and the expression of several genes. Alterations of Ca2+ homeostasis were found to play a pivotal role in neurodegenerative progression. The maintenance of proper Ca2+ signaling in neurons demands the continuous activity of Ca2+ pumps and exchangers to guarantee physiological cytosolic concentration of the cation. The plasma membrane Ca2+ATPases (PMCA pumps) play a key role in the regulation of Ca2+ handling in selected sub-plasma membrane microdomains. Among the four basic PMCA pump isoforms existing in mammals, isoforms 2 and 3 are particularly enriched in the nervous system. In humans, genetic mutations in the PMCA2 gene in association with cadherin 23 mutations have been linked to hearing loss phenotypes, while those occurring in the PMCA3 gene were associated with X-linked congenital cerebellar ataxias. Here we describe a novel missense mutation (V1143F) in the calmodulin binding domain (CaM-BD) of the PMCA2 protein. The mutant pump was present in a patient showing congenital cerebellar ataxia but no overt signs of deafness, in line with the absence of mutations in the cadherin 23 gene. Biochemical and molecular dynamics studies on the mutated PMCA2 have revealed that the V1143F substitution alters the binding of calmodulin to the CaM-BD leading to impaired Ca2+ ejection.
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Affiliation(s)
- Mattia Vicario
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Ginevra Zanni
- Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Francesca Vallese
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | | | - Alessandro Grinzato
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Domenico Cieri
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Paola Berto
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Martina Frizzarin
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Raffaele Lopreiato
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Francesco Zonta
- Shanghai Institute of Advanced Immunochemical Studies, ShanghaiTech University, Shanghai, China; Department of Biomedical Sciences, Institute of Cell Biology and Neurobiology, Italian National Research Council, 00015 Monterotondo, Rome, Italy
| | - Stefania Ferro
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Michele Sandre
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Oriano Marin
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Maria Ruzzene
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Enrico Bertini
- Department of Neurosciences, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Giuseppe Zanotti
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy
| | - Marisa Brini
- Department of Biology, University of Padova, Italy.
| | - Tito Calì
- Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy; Padua Neuroscience Center (PNC), University of Padua, 35122 Padova, Italy.
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7
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Bortolozzi M, Mammano F. PMCA2w/a Splice Variant: A Key Regulator of Hair Cell Mechano-transduction Machinery. REGULATION OF CA2+-ATPASES,V-ATPASES AND F-ATPASES 2016:27-45. [DOI: 10.1007/978-3-319-24780-9_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/02/2023]
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8
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Carpinelli MR, Manning MG, Kile BT, Burt RA. Two ENU-induced alleles of Atp2b2 cause deafness in mice. PLoS One 2013; 8:e67479. [PMID: 23826306 PMCID: PMC3691321 DOI: 10.1371/journal.pone.0067479] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2013] [Accepted: 05/14/2013] [Indexed: 12/12/2022] Open
Abstract
Over 120 loci are known to cause inherited hearing loss in humans. The deafness gene has been identified for only half of these loci. With the aim of identifying some of the remaining deafness genes, we performed an ethylnitrosourea mutagenesis screen for deaf mice. We isolated two mutants with semi-dominant hearing loss, Deaf11 and Deaf13. Both contained causative mutations in Atp2b2, which encodes the plasma membrane calcium ATPase 2. The Atp2b2Deaf11 mutation leads to a p. I1023S substitution in the tenth transmembrane domain. The Atp2b2Deaf13 mutation leads to a p. R561S substitution in the catalytic core. Mice homozygous for these mutations display profound hearing loss. Heterozygotes display mild to moderate, progressive hearing loss.
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Affiliation(s)
- Marina R Carpinelli
- Murdoch Childrens Research Institute, Royal Children's Hospital, Parkville, Victoria, Australia.
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9
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Ceriani F, Mammano F. Calcium signaling in the cochlea - Molecular mechanisms and physiopathological implications. Cell Commun Signal 2012; 10:20. [PMID: 22788415 PMCID: PMC3408374 DOI: 10.1186/1478-811x-10-20] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2012] [Accepted: 07/12/2012] [Indexed: 12/20/2022] Open
Abstract
Calcium ions (Ca2+) regulate numerous and diverse aspects of cochlear and vestibular physiology. This review focuses on the Ca2+ control of mechanotransduction and synaptic transmission in sensory hair cells, as well as on Ca2+ signalling in non-sensory cells of the developing cochlea.
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Affiliation(s)
- Federico Ceriani
- Dipartimento di Fisica e Astronomia "G, Galilei", Università di Padova, 35131, Padova, Italy.
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10
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Giacomello M, De Mario A, Primerano S, Brini M, Carafoli E. Hair cells, plasma membrane Ca2+ ATPase and deafness. Int J Biochem Cell Biol 2012; 44:679-83. [DOI: 10.1016/j.biocel.2012.02.006] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2011] [Revised: 01/24/2012] [Accepted: 02/03/2012] [Indexed: 11/29/2022]
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11
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Giacomello M, De Mario A, Lopreiato R, Primerano S, Campeol M, Brini M, Carafoli E. Mutations in PMCA2 and hereditary deafness: A molecular analysis of the pump defect. Cell Calcium 2011; 50:569-76. [DOI: 10.1016/j.ceca.2011.09.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 09/19/2011] [Indexed: 10/16/2022]
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12
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Xu L, Wang Z, Xiong X, Gu X, Gao X, Gao X. Identification of a novel point mutation of mouse Atp2b2 induced by N-ethyl-N-nitrosourea mutagenesis. Exp Anim 2011; 60:71-8. [PMID: 21325754 DOI: 10.1538/expanim.60.71] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
N-ethyl-N-nitrosourea (ENU)-induced mutagenesis is an important approach in the study of gene function and the establishment of human disease models. Here we report an ENU-induced mutation, Elfin, as a mouse model with hearing loss. Homozygous mutants were deaf and displayed severe ataxia, while heterozygous mice had a significant hearing loss. Histological analysis of the inner ear revealed that Elfin had progressive degeneration of the organ of Corti, spiral ganglion cells and an absence of otoconia in the vestibular system. The new mutation was mapped to chromosome 6 between microsatellite markers D6Mit39 and D6Mit254, where the Ca(2+)-ATPase type 2 (Atp2b2) gene resides. Sequence analysis revealed a unique T-to-A transition mutation at amino acid 655 resulting in Ile-to-Asn substitution. These results for the Elfin mutant confirm the role of ATP2B2 in balance, hearing and formation of otoconia and suggest it may serve as a new model of human hereditary hearing loss.
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Affiliation(s)
- Lin Xu
- Department of Otolaryngology and Head & Neck Surgery, The Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing 210008, China
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13
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Abstract
Ca(2+) acts as a fundamental signal transduction element in inner ear, delivering information about sound, acceleration and gravity through a small number of mechanotransduction channels in the hair cell stereocilia and voltage activated Ca(2+) channels at the ribbon synapse, where it drives neurotransmission. The mechanotransduction process relies on the endocochlear potential, an electrical potential difference between endolymph and perilymph, the two fluids bathing respectively the apical and basolateral membrane of the cells in the organ of Corti. In mouse models, deafness and lack or reduction of the endocochlear potential correlate with ablation of connexin (Cx) 26 or 30. These Cxs form heteromeric channels assembled in a network of gap junction plaques connecting the supporting and epithelial cells of the organ of Corti presumably for K(+) recycle and transfer of key metabolites, for example, the Ca(2+) -mobilizing second messenger IP(3) . Ca(2+) signaling in these cells could play a crucial role in regulating Cx expression and function. Another district where Ca(2+) signaling alterations link to hearing loss is hair cell apex, where ablation or missense mutations of the PMCA2 Ca(2+) -pump of the stereocilia cause deafness and loss of balance. If less Ca(2+) is exported from the stereocilia, as in the PMCA2 mouse mutants, Ca(2+) concentration in endolymph is expected to fall causing an alteration of the mechanotransduction process. This may provide a clue as to why, in some cases, PMCA2 mutations potentiated the deafness phenotype induced by coexisting mutations of cadherin-23 (Usher syndrome type 1D), a single pass membrane Ca(2+) binding protein that is abundantly expressed in the stereocilia.
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Affiliation(s)
- Fabio Mammano
- Department of Physics "G. Galilei," University of Padova, Italy.
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14
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Bortolozzi M, Brini M, Parkinson N, Crispino G, Scimemi P, De Siati RD, Di Leva F, Parker A, Ortolano S, Arslan E, Brown SD, Carafoli E, Mammano F. The novel PMCA2 pump mutation Tommy impairs cytosolic calcium clearance in hair cells and links to deafness in mice. J Biol Chem 2010; 285:37693-703. [PMID: 20826782 PMCID: PMC2988374 DOI: 10.1074/jbc.m110.170092] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2010] [Revised: 09/03/2010] [Indexed: 11/17/2022] Open
Abstract
The mechanotransduction process in hair cells in the inner ear is associated with the influx of calcium from the endolymph. Calcium is exported back to the endolymph via the splice variant w/a of the PMCA2 of the stereocilia membrane. To further investigate the role of the pump, we have identified and characterized a novel ENU-induced mouse mutation, Tommy, in the PMCA2 gene. The mutation causes a non-conservative E629K change in the second intracellular loop of the pump that harbors the active site. Tommy mice show profound hearing impairment from P18, with significant differences in hearing thresholds between wild type and heterozygotes. Expression of mutant PMCA2 in CHO cells shows calcium extrusion impairment; specifically, the long term, non-stimulated calcium extrusion activity of the pump is inhibited. Calcium extrusion was investigated directly in neonatal organotypic cultures of the utricle sensory epithelium in Tommy mice. Confocal imaging combined with flash photolysis of caged calcium showed impairment of calcium export in both Tommy heterozygotes and homozygotes. Immunofluorescence studies of the organ of Corti in homozygous Tommy mice showed a progressive base to apex degeneration of hair cells after P40. Our results on the Tommy mutation along with previously observed interactions between cadherin-23 and PMCA2 mutations in mouse and humans underline the importance of maintaining the appropriate calcium concentrations in the endolymph to control the rigidity of cadherin and ensure the function of interstereocilia links, including tip links, of the stereocilia bundle.
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Affiliation(s)
- Mario Bortolozzi
- From the Department of Physics “G. Galilei,” University of Padua, Padua 35131, Italy
- the Venetian Institute of Molecular Medicine, Padua 35129, Italy
| | - Marisa Brini
- the Department of Biological Chemistry, University of Padua, Padua 35121, Italy
| | - Nick Parkinson
- the MRC Mammalian Genetics Unit, MRC Harwell, Oxfordshire OX11 0RD, United Kingdom, and
| | - Giulia Crispino
- the Venetian Institute of Molecular Medicine, Padua 35129, Italy
| | - Pietro Scimemi
- the Department of Medical and Surgical Specialities-Audiology and Phoniatric Service, University of Padua, Padua 35128, Italy
| | - Romolo Daniele De Siati
- the Department of Medical and Surgical Specialities-Audiology and Phoniatric Service, University of Padua, Padua 35128, Italy
| | - Francesca Di Leva
- the Department of Biological Chemistry, University of Padua, Padua 35121, Italy
| | - Andrew Parker
- the MRC Mammalian Genetics Unit, MRC Harwell, Oxfordshire OX11 0RD, United Kingdom, and
| | - Saida Ortolano
- the Venetian Institute of Molecular Medicine, Padua 35129, Italy
| | - Edoardo Arslan
- the Department of Medical and Surgical Specialities-Audiology and Phoniatric Service, University of Padua, Padua 35128, Italy
| | - Steve D. Brown
- the MRC Mammalian Genetics Unit, MRC Harwell, Oxfordshire OX11 0RD, United Kingdom, and
| | - Ernesto Carafoli
- the Venetian Institute of Molecular Medicine, Padua 35129, Italy
| | - Fabio Mammano
- From the Department of Physics “G. Galilei,” University of Padua, Padua 35131, Italy
- the Venetian Institute of Molecular Medicine, Padua 35129, Italy
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15
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Genetic variations in peroxisome proliferator-activated receptor gamma expression affect blood pressure. Proc Natl Acad Sci U S A 2009; 106:19084-9. [PMID: 19884495 DOI: 10.1073/pnas.0909657106] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Metabolic syndrome, a clustering of conditions including obesity, insulin resistance, and hypertension, is a risk factor for cardiovascular morbidity and mortality. Because peroxisome proliferator-activated receptor gamma (PPARgamma) regulates adipocyte differentiation and lipid metabolism and is the molecular target of a class of insulin sensitizers, genetic variants that alter Pparg gene expression are potential contributors to the metabolic syndrome. To test this possibility, we generated mice having 182% of the normal steady-state level of PPARgamma mRNA by replacing the 3'-UTR of the natural Pparg gene with that of the beta-globin gene, thereby stabilizing the Pparg transcripts. This increase in PPARgamma mRNA level had no apparent consequences in various physiological parameters, except that the mice repeatedly showed a trend toward lower blood pressures (by about 3 mm Hg) than their WT littermates. In contrast, the opposite trend, toward increased blood pressure, was observed in mice with genetically reduced levels of PPARgamma mRNA as a consequence of insertion of an allele with an mRNA-destabilizing sequence into the endogenous 3'-UTR of the Pparg gene. By combining 12 sets of blood pressure measurements in more than 350 mutant mice having PPARgamma expression levels varying from 28% to 182% and more than 280 WT littermates, we show that a 2-fold genetic increase (or decrease) in PPARgamma expression levels decreases (or increases) blood pressure by about 2.8 mm Hg. Thus, our experiments demonstrate that quantitative variants causing decreased Pparg expression are a potential causative risk factor for essential hypertension.
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16
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Tsai YS, Tsai PJ, Jiang MJ, Chou TY, Pendse A, Kim HS, Maeda N. Decreased PPAR gamma expression compromises perigonadal-specific fat deposition and insulin sensitivity. Mol Endocrinol 2009; 23:1787-98. [PMID: 19749155 DOI: 10.1210/me.2009-0073] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Mutations and polymorphisms in PPARG have been linked to adiposity and partial lipodystrophy in humans. However, how disturbances in PPARG lead to depot-specific effects on adipose tissue, as shown by the characteristic aberrant fat distribution in patients, remains unclear. By manipulating the 3'-untranslated region of the Pparg gene, we have generated mice with peroxisome proliferator-activated receptor gamma (PPAR gamma) gene expression ranging from 25% to 100% normal. Basal levels of PPAR gamma transcripts between 50% and approximately 100% had no significant effect on body weight, fat mass, and insulin sensitivity. In contrast, mice with 25% normal PPAR gamma expression exhibited reduced body weight and total fat mass, insulin resistance, and dyslipidemia. Interestingly, fat mass was selectively reduced in perigonadal depot without significant changes in inguinal and other depots. Expression of adipogenic factor CCAAT enhancer binding protein-alpha and some other metabolic genes containing peroxisome proliferator response element were reduced in a perigonadal depot-specific fashion. This was further associated with depot-specific reduction in the expression of adipokines, increased expression of TNFalpha, and increased ectopic lipid deposition in muscles. Together, these results underscore the differential sensitivity of the individual fat depots on PPAR gamma availability as an underlying mechanism of partial lipodystrophy.
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Affiliation(s)
- Yau-Sheng Tsai
- Institute of Clinical Medicine, National Cheng Kung University, Tainan 701, Taiwan, Republic of China.
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17
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Spiden SL, Bortolozzi M, Di Leva F, de Angelis MH, Fuchs H, Lim D, Ortolano S, Ingham NJ, Brini M, Carafoli E, Mammano F, Steel KP. The novel mouse mutation Oblivion inactivates the PMCA2 pump and causes progressive hearing loss. PLoS Genet 2008; 4:e1000238. [PMID: 18974863 PMCID: PMC2568954 DOI: 10.1371/journal.pgen.1000238] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2008] [Accepted: 09/25/2008] [Indexed: 11/19/2022] Open
Abstract
Progressive hearing loss is common in the human population, but we have few clues to the molecular basis. Mouse mutants with progressive hearing loss offer valuable insights, and ENU (N-ethyl-N-nitrosourea) mutagenesis is a useful way of generating models. We have characterised a new ENU-induced mouse mutant, Oblivion (allele symbol Obl), showing semi-dominant inheritance of hearing impairment. Obl/+ mutants showed increasing hearing impairment from post-natal day (P)20 to P90, and loss of auditory function was followed by a corresponding base to apex progression of hair cell degeneration. Obl/Obl mutants were small, showed severe vestibular dysfunction by 2 weeks of age, and were completely deaf from birth; sensory hair cells were completely degenerate in the basal turn of the cochlea, although hair cells appeared normal in the apex. We mapped the mutation to Chromosome 6. Mutation analysis of Atp2b2 showed a missense mutation (2630C-->T) in exon 15, causing a serine to phenylalanine substitution (S877F) in transmembrane domain 6 of the PMCA2 pump, the resident Ca(2+) pump of hair cell stereocilia. Transmembrane domain mutations in these pumps generally are believed to be incompatible with normal targeting of the protein to the plasma membrane. However, analyses of hair cells in cultured utricular maculae of Obl/Obl mice and of the mutant Obl pump in model cells showed that the protein was correctly targeted to the plasma membrane. Biochemical and biophysical characterisation showed that the pump had lost a significant portion of its non-stimulated Ca(2+) exporting ability. These findings can explain the progressive loss of auditory function, and indicate the limits in our ability to predict mechanism from sequence alone.
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MESH Headings
- Aequorin/metabolism
- Amino Acid Substitution
- Animals
- Calcium/metabolism
- Cell Membrane/metabolism
- Cells, Cultured
- Chromosome Mapping
- DNA Mutational Analysis
- Deafness/genetics
- Deafness/pathology
- Deafness/physiopathology
- Ear, Inner/pathology
- Ear, Inner/ultrastructure
- Evoked Potentials, Auditory, Brain Stem
- Hair Cells, Auditory/metabolism
- Hair Cells, Auditory/pathology
- Mice
- Microscopy, Electron, Scanning
- Mutagenesis
- Mutation, Missense
- Plasma Membrane Calcium-Transporting ATPases/genetics
- Plasma Membrane Calcium-Transporting ATPases/metabolism
- Saccule and Utricle/metabolism
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Affiliation(s)
- Sarah L. Spiden
- Wellcome Trust Sanger Institute, Genome Campus, Hinxton, Cambridge, United Kingdom
- MRC Institute of Hearing Research, University Park, Nottingham, United Kingdom
| | | | - Francesca Di Leva
- Department of Biochemistry and Department of Experimental Veterinary Sciences, University of Padua, Padua, Italy
| | | | - Helmut Fuchs
- Helmholtz Zentrum München, Institute of Experimental Genetics, Neuherberg, Germany
| | - Dmitry Lim
- Venetian Institute of Molecular Medicine (VIMM), Padua, Italy
| | - Saida Ortolano
- Venetian Institute of Molecular Medicine (VIMM), Padua, Italy
| | - Neil J. Ingham
- Wellcome Trust Sanger Institute, Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Marisa Brini
- Department of Biochemistry and Department of Experimental Veterinary Sciences, University of Padua, Padua, Italy
| | | | - Fabio Mammano
- Venetian Institute of Molecular Medicine (VIMM), Padua, Italy
- Department of Physics, University of Padua, Padua, Italy
| | - Karen P. Steel
- Wellcome Trust Sanger Institute, Genome Campus, Hinxton, Cambridge, United Kingdom
- MRC Institute of Hearing Research, University Park, Nottingham, United Kingdom
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18
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Sun XY, Chen ZY, Hayashi Y, Kanou Y, Takagishi Y, Oda SI, Murata Y. Insertion of an intracisternal A particle retrotransposon element in plasma membrane calcium ATPase 2 gene attenuates its expression and produces an ataxic phenotype in joggle mutant mice. Gene 2008; 411:94-102. [DOI: 10.1016/j.gene.2008.01.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Revised: 01/15/2008] [Accepted: 01/17/2008] [Indexed: 12/01/2022]
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19
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Abstract
The plasma membrane calcium ATPase (PMCA) uses energy to pump calcium (Ca2+) ions out of the cytosol into the extracellular milieu, usually against a strong chemical gradient. This energy expenditure is necessary to maintain a relatively low intracellular net Ca2+ load. Mammals have four genes (ATP2B1-ATP2B4), encoding the proteins PMCA1 through PMCA4. Transcripts from each of these genes are alternatively spliced to generate several variant proteins that are in turn post-translationally modified in a variety of ways. Expressed ubiquitously and with some level of functional redundancy in most vital tissues, only one of the four genes--Atp2b2--has been causally linked through naturally occuring mutations to disease in mammals: specifically to deafness and ataxia in spontaneous mouse mutants. In humans, a missense amino acid substitution in PMCA2 modifies the severity of hearing loss. Targeted null mutations of the Atp2b1 and Atp2b4 genes in mouse are embryonic lethal and cause a sperm motility defect, respectively. These phenotypes point to complex human diseases like hearing loss, cardiac function and infertility. Changes in PMCA expression are associated with other diseases including cataract formation, carciniogenesis, diabetes, and cardiac hypertension and hypertrophy. Severity of these diseases may be affected by subtle changes in expression of the PMCA isoforms expressed in those tissues.
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