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Diana A, Ghilardi A, Del Giacco L. Differentiation and functioning of the lateral line organ in zebrafish require Smpx activity. Sci Rep 2024; 14:7862. [PMID: 38570547 PMCID: PMC10991396 DOI: 10.1038/s41598-024-58138-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2023] [Accepted: 03/26/2024] [Indexed: 04/05/2024] Open
Abstract
The small muscle protein, X-linked (SMPX) gene encodes a cytoskeleton-associated protein, highly expressed in the inner ear hair cells (HCs), possibly regulating auditory function. In the last decade, several mutations in SMPX have been associated with X-chromosomal progressive non syndromic hearing loss in humans and, in line with this, Smpx-deficient animal models, namely zebrafish and mouse, showed significant impairment of inner ear HCs development, maintenance, and functioning. In this work, we uncovered smpx expression in the neuromast mechanosensory HCs of both Anterior and Posterior Lateral Line (ALL and PLL, respectively) of zebrafish larvae and focused our attention on the PLL. Smpx was subcellularly localized throughout the cytoplasm of the HCs, as well as in their primary cilium. Loss-of-function experiments, via both morpholino-mediated gene knockdown and CRISPR/Cas9 F0 gene knockout, revealed that the lack of Smpx led to fewer properly differentiated and functional neuromasts, as well as to a smaller PLL primordium (PLLp), the latter also Smpx-positive. In addition, the kinocilia of Smpx-deficient neuromast HCs appeared structurally and numerically altered. Such phenotypes were associated with a significant reduction in the mechanotransduction activity of the neuromast HCs, in line with their positivity for Smpx. In summary, this work highlights the importance of Smpx in lateral line development and, specifically, in proper HCs differentiation and/or maintenance, and in the mechanotransduction process carried out by the neuromast HCs. Because lateral line HCs are both functionally and structurally analogous to the cochlear HCs, the neuromasts might represent an invaluable-and easily accessible-tool to dissect the role of Smpx in HCs development/functioning and shed light on the underlying mechanisms involved in hearing loss.
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Affiliation(s)
- Alberto Diana
- Department of Biosciences, Università degli Studi di Milano, Via Celoria 26, 20133, Milan, Italy
| | - Anna Ghilardi
- Department of Biosciences, Università degli Studi di Milano, Via Celoria 26, 20133, Milan, Italy
| | - Luca Del Giacco
- Department of Biosciences, Università degli Studi di Milano, Via Celoria 26, 20133, Milan, Italy.
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Johari M, Sarparanta J, Vihola A, Jonson PH, Savarese M, Jokela M, Torella A, Piluso G, Said E, Vella N, Cauchi M, Magot A, Magri F, Mauri E, Kornblum C, Reimann J, Stojkovic T, Romero NB, Luque H, Huovinen S, Lahermo P, Donner K, Comi GP, Nigro V, Hackman P, Udd B. Missense mutations in small muscle protein X-linked (SMPX) cause distal myopathy with protein inclusions. Acta Neuropathol 2021; 142:375-393. [PMID: 33974137 PMCID: PMC8270885 DOI: 10.1007/s00401-021-02319-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2021] [Revised: 04/26/2021] [Accepted: 04/26/2021] [Indexed: 01/05/2023]
Abstract
Using
deep phenotyping and high-throughput sequencing, we have identified a novel type of distal myopathy caused by mutations in the Small muscle protein X-linked (SMPX) gene. Four different missense mutations were identified in ten patients from nine families in five different countries, suggesting that this disease could be prevalent in other populations as well. Haplotype analysis of patients with similar ancestry revealed two different founder mutations in Southern Europe and France, indicating that the prevalence in these populations may be higher. In our study all patients presented with highly similar clinical features: adult-onset, usually distal more than proximal limb muscle weakness, slowly progressing over decades with preserved walking. Lower limb muscle imaging showed a characteristic pattern of muscle involvement and fatty degeneration. Histopathological and electron microscopic analysis of patient muscle biopsies revealed myopathic findings with rimmed vacuoles and the presence of sarcoplasmic inclusions, some with amyloid-like characteristics. In silico predictions and subsequent cell culture studies showed that the missense mutations increase aggregation propensity of the SMPX protein. In cell culture studies, overexpressed SMPX localized to stress granules and slowed down their clearance.
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Affiliation(s)
- Mridul Johari
- Folkhälsan Research Center, Helsinki, Finland.
- Department of Medical Genetics, Medicum, University of Helsinki, Helsinki, Finland.
| | - Jaakko Sarparanta
- Folkhälsan Research Center, Helsinki, Finland
- Department of Medical Genetics, Medicum, University of Helsinki, Helsinki, Finland
| | - Anna Vihola
- Folkhälsan Research Center, Helsinki, Finland
- Department of Medical Genetics, Medicum, University of Helsinki, Helsinki, Finland
- Neuromuscular Research Center, Fimlab Laboratories, Tampere University and University Hospital, Tampere, Finland
| | - Per Harald Jonson
- Folkhälsan Research Center, Helsinki, Finland
- Department of Medical Genetics, Medicum, University of Helsinki, Helsinki, Finland
| | - Marco Savarese
- Folkhälsan Research Center, Helsinki, Finland
- Department of Medical Genetics, Medicum, University of Helsinki, Helsinki, Finland
| | - Manu Jokela
- Neuromuscular Research Center, Department of Neurology, Tampere University and University Hospital, Tampere, Finland
- Division of Clinical Neurosciences, Department of Neurology, Turku University Hospital, Turku, Finland
| | - Annalaura Torella
- Dipartimento di Medicina di Precisione, Università degli Studi della Campania "Luigi Vanvitelli", Naples, Italy
| | - Giulio Piluso
- Dipartimento di Medicina di Precisione, Università degli Studi della Campania "Luigi Vanvitelli", Naples, Italy
| | - Edith Said
- Section of Medical Genetics, Mater Dei Hospital, Msida, Malta
- Department of Anatomy and Cell Biology, Faculty of Medicine and Surgery, University of Malta, Msida, Malta
| | - Norbert Vella
- Neuroscience Department, Mater Dei Hospital, Msida, Malta
| | - Marija Cauchi
- Neuroscience Department, Mater Dei Hospital, Msida, Malta
| | - Armelle Magot
- Neuromuscular Disease Center AOC, University Hospital Nantes, Nantes, France
| | - Francesca Magri
- IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy
| | - Eleonora Mauri
- IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Neurology Unit, Milan, Italy
| | | | - Jens Reimann
- Department of Neurology, University Hospital Bonn, Bonn, Germany
| | - Tanya Stojkovic
- AP-HP, Institute of Myology, Centre de Référence des Maladies Neuromusculaires, Hôpital Pitié-Salpêtrière, Paris, France
| | - Norma B Romero
- Neuromuscular Morphology Unit, Institute of Myology, Myology Research Centre INSERM, Sorbonne Université, Hôpital Pitié-Salpêtrière, Paris, France
| | - Helena Luque
- Folkhälsan Research Center, Helsinki, Finland
- Department of Medical Genetics, Medicum, University of Helsinki, Helsinki, Finland
| | - Sanna Huovinen
- Department of Pathology, Fimlab Laboratories, Tampere University Hospital, Tampere, Finland
| | - Päivi Lahermo
- Institute for Molecular Medicine Finland FIMM, Technology Centre, University of Helsinki, Helsinki, Finland
| | - Kati Donner
- Institute for Molecular Medicine Finland FIMM, Technology Centre, University of Helsinki, Helsinki, Finland
| | - Giacomo Pietro Comi
- IRCCS Fondazione Ca' Granda Ospedale Maggiore Policlinico, Neuromuscular and Rare Disease Unit, Milan, Italy
- Dino Ferrari Center, Department of Pathophysiology and Transplantation, University of Milan, Milan, Italy
| | - Vincenzo Nigro
- Dipartimento di Medicina di Precisione, Università degli Studi della Campania "Luigi Vanvitelli", Naples, Italy
- Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - Peter Hackman
- Folkhälsan Research Center, Helsinki, Finland
- Department of Medical Genetics, Medicum, University of Helsinki, Helsinki, Finland
| | - Bjarne Udd
- Folkhälsan Research Center, Helsinki, Finland
- Department of Medical Genetics, Medicum, University of Helsinki, Helsinki, Finland
- Neuromuscular Research Center, Department of Neurology, Tampere University and University Hospital, Tampere, Finland
- Department of Neurology, Vaasa Central Hospital, Vaasa, Finland
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Ghilardi A, Diana A, Bacchetta R, Santo N, Ascagni M, Prosperi L, Del Giacco L. Inner Ear and Muscle Developmental Defects in Smpx-Deficient Zebrafish Embryos. Int J Mol Sci 2021; 22:ijms22126497. [PMID: 34204426 PMCID: PMC8235540 DOI: 10.3390/ijms22126497] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Revised: 06/09/2021] [Accepted: 06/12/2021] [Indexed: 12/20/2022] Open
Abstract
The last decade has witnessed the identification of several families affected by hereditary non-syndromic hearing loss (NSHL) caused by mutations in the SMPX gene and the loss of function has been suggested as the underlying mechanism. In the attempt to confirm this hypothesis we generated an Smpx-deficient zebrafish model, pointing out its crucial role in proper inner ear development. Indeed, a marked decrease in the number of kinocilia together with structural alterations of the stereocilia and the kinocilium itself in the hair cells of the inner ear were observed. We also report the impairment of the mechanotransduction by the hair cells, making SMPX a potential key player in the construction of the machinery necessary for sound detection. This wealth of evidence provides the first possible explanation for hearing loss in SMPX-mutated patients. Additionally, we observed a clear muscular phenotype consisting of the defective organization and functioning of muscle fibers, strongly suggesting a potential role for the protein in the development of muscle fibers. This piece of evidence highlights the need for more in-depth analyses in search for possible correlations between SMPX mutations and muscular disorders in humans, thus potentially turning this non-syndromic hearing loss-associated gene into the genetic cause of dysfunctions characterized by more than one symptom, making SMPX a novel syndromic gene.
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Affiliation(s)
- Anna Ghilardi
- Department of Biosciences, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy; (A.G.); (A.D.); (L.P.)
| | - Alberto Diana
- Department of Biosciences, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy; (A.G.); (A.D.); (L.P.)
| | - Renato Bacchetta
- Department of Environmental Science and Policy, Università degli Studi di Milano, 20133 Milan, Italy;
| | - Nadia Santo
- Unitech NOLIMITS, Università degli Studi di Milano, 20133 Milan, Italy; (N.S.); (M.A.)
| | - Miriam Ascagni
- Unitech NOLIMITS, Università degli Studi di Milano, 20133 Milan, Italy; (N.S.); (M.A.)
| | - Laura Prosperi
- Department of Biosciences, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy; (A.G.); (A.D.); (L.P.)
| | - Luca Del Giacco
- Department of Biosciences, Università degli Studi di Milano, Via Celoria 26, 20133 Milan, Italy; (A.G.); (A.D.); (L.P.)
- Correspondence:
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