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Berti B, Longo G, Mari F, Doccini S, Piccolo I, Donati MA, Moro F, Guerrini R, Santorelli FM, Petruzzella V. Bi-allelic variants in MTMR5/SBF1 cause Charcot-Marie-Tooth type 4B3 featuring mitochondrial dysfunction. BMC Med Genomics 2021; 14:157. [PMID: 34118926 PMCID: PMC8199524 DOI: 10.1186/s12920-021-01001-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Accepted: 06/06/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Charcot-Marie-Tooth disease (CMT) type 4B3 (CMT4B3) is a rare form of genetic neuropathy associated with variants in the MTMR5/SBF1 gene. MTMR5/SBF1 is a pseudophosphatase predicted to regulate endo-lysosomal trafficking in tandem with other MTMRs. Although almost ubiquitously expressed, pathogenic variants primarily impact on the peripheral nervous system, corroborating the involvement of MTMR5/SBF1 and its molecular partners in Schwann cells-mediated myelinization. CASE PRESENTATION We report a case of severe CMT4B3 characterized by early-onset motor and axonal polyneuropathy in an Italian child in absence of any evidence of brain and spine MRI abnormalities or intellectual disability and with a biochemical profile suggestive of mitochondrial disease. Using an integrated approach combining both NGS gene panels and WES analysis, we identified two novel compound heterozygous missense variants in MTMR5/SBF1 gene, p.R763H (c.2291G > A) and p.G1064E (c.3194G > A). Studies in muscle identified partial defects of oxidative metabolism. CONCLUSION We describe the first case of an early onset severe polyneuropathy with motor and axonal involvement, due to recessive variants in the MTMR5/SBF1 gene, with no evidence of brain and spine MRI abnormalities, intellectual disability, no clinical and neurophysiological evidences of distal sensory impairment, and rapid neuromuscular deterioration. This report suggests that MTMR5/SBF1 should be considered in cases of infantile-onset CMT with secondary mitochondrial dysfunction.
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Affiliation(s)
- Beatrice Berti
- Pediatric Neurology and Centro Clinico Nemo, Fondazione Policlinico Universitario Agostino Gemelli - IRCCS, Rome, Italy
| | - Giovanna Longo
- Department of Medical Basic Sciences, Neurosciences and Sense Organs, University of Bari Aldo Moro, Piazza G. Cesare, 11, 70124, Bari, Italy
| | - Francesco Mari
- Child Neurology Unit, Meyer Children's Hospital, Florence, Italy
| | - Stefano Doccini
- IRCCS Fondazione Stella Maris, via dei Giacinti 2, Calambrone, 56128, Pisa, Italy
| | - Ilaria Piccolo
- Department of Medical Basic Sciences, Neurosciences and Sense Organs, University of Bari Aldo Moro, Piazza G. Cesare, 11, 70124, Bari, Italy
| | | | - Francesca Moro
- IRCCS Fondazione Stella Maris, via dei Giacinti 2, Calambrone, 56128, Pisa, Italy
| | - Renzo Guerrini
- Child Neurology Unit, Meyer Children's Hospital, Florence, Italy
| | - Filippo M Santorelli
- IRCCS Fondazione Stella Maris, via dei Giacinti 2, Calambrone, 56128, Pisa, Italy.
| | - Vittoria Petruzzella
- Department of Medical Basic Sciences, Neurosciences and Sense Organs, University of Bari Aldo Moro, Piazza G. Cesare, 11, 70124, Bari, Italy.
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Flusser H, Halperin D, Kadir R, Shorer Z, Shelef I, Birk OS. Novel SBF1 splice-site null mutation broadens the clinical spectrum of Charcot-Marie-Tooth type 4B3 disease. Clin Genet 2018; 94:473-479. [PMID: 30039846 DOI: 10.1111/cge.13419] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Accepted: 07/13/2018] [Indexed: 11/29/2022]
Abstract
Four siblings of consanguineous Bedouin kindred presented at infancy with an autosomal recessive syndrome of congenital microcephaly, facial dysmorphism, strabismus, developmental delay and ataxia with positive pyramidal signs. Toward the end of their first decade, they developed areflexia, multiple cranial neuropathies and severe polyneuropathy with progressive muscle weakness, affecting proximal and distal extremities. Physical assessment exhibited kyphoscoliosis, bilateral syndactyly and distal muscle wasting with drop-foot and pes cavus. Magnetic resonance imaging (MRI) showed profound cerebellar atrophy with highly unique findings at the pontine and mesencephalic levels, previously described as "fork and bracket" signs. Genome-wide linkage analysis identified a single ~1.5 Mbp disease-associated locus on chromosome 22q13.33. Whole exome sequencing identified a single novel homozygous deleterious splice-site mutation within this locus in SET binding factor 1 (SBF1). SBF1 missense mutations were shown to underlie Charcot-Marie-Tooth (CMT) type 4B3 disease, a rare autosomal recessive subtype of CMT4. The novel SBF1 null mutation highlights distinct severe phenotypic manifestations, broadening the clinical spectrum of SBF1-related neuropathies: cerebellar and pyramidal signs evident in the first months of life with peripheral polyneuropathy emerging only toward the end of the first decade, together with unique MRI findings.
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Affiliation(s)
- H Flusser
- Zussman Child Development Center, Division of Pediatrics, Soroka Medical Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - D Halperin
- The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - R Kadir
- The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - Z Shorer
- Pediatric Neurology Unit, Division of Pediatrics, Soroka Medical Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - I Shelef
- Department of Imaging, Soroka Medical Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
| | - O S Birk
- The Morris Kahn Laboratory of Human Genetics, National Institute for Biotechnology in the Negev, Ben-Gurion University of the Negev, Beer-Sheva, Israel.,Genetics Institute, Soroka University Medical Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel
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