Jorge Oliveira1, Ana Gonçalves1, Márcia E Oliveira1, Isabel Fineza2, Rita C M Pavanello3, Mariz Vainzof3, Elsa Bronze-da-Rocha4, Rosário Santos1, Mário Sousa5. 1. Unidade de Genética Molecular, Centro de Genética Médica Dr. Jacinto de Magalhães, Centro Hospitalar do Porto, Porto, Portugal. 2. Unidade de Neuropediatria, Centro de Desenvolvimento da Criança Luís Borges, Hospital Pediátrico de Coimbra, Centro Hospitalar Universitário de Coimbra, Coimbra, Portugal. 3. Centro de Estudos do Genoma Humano e Células Tronco, Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, São Paulo, SP, Brasil. 4. Departamento de Ciências Biológicas, Laboratório de Bioquímica, Faculdade de Farmácia, Universidade do Porto, Porto, Portugal. 5. Departamento de Microscopia, Laboratório de Biologia Celular, Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Porto, Portugal.
Abstract
BACKGROUND: Congenital muscular dystrophy (CMD) type 1A (MDC1A) is caused by recessive mutations in laminin-α2 (LAMA2) gene. Laminin-211, a heterotrimeric glycoprotein that contains the α2 chain, is crucial for muscle stability establishing a bond between the sarcolemma and the extracellular matrix. More than 215 mutations are listed in the locus specific database (LSDB) for LAMA2 gene (May 2014). OBJECTIVE: A limited number of large deletions/duplications have been reported in LAMA2. Our main objective was the identification of additional large rearrangements in LAMA2 found in CMD patients and a systematic review of cases in the literature and LSDB. METHODS: In four of the fifty-two patients studied over the last 10 years, only one heterozygous mutation was identified, after sequencing and screening for a frequent LAMA2 deletion. Initial screening of large mutations was performed by multiplex ligation-dependent probe application (MLPA). Further characterization implied several techniques: long-range PCR, cDNA and Southern-blot analysis. RESULTS: Three novel large deletions in LAMA2 and the first pathogenic large duplication were successfully identified, allowing a definitive molecular diagnosis, carrier screening and prenatal diagnosis. A total of fifteen deletions and two duplications previously reported were also reviewed. Two possible mutational "hotspots" for deletions may exist, the first encompassing exons 3 and 4 and second in the 3' region (exons 56 to 65) of LAMA2. CONCLUSIONS: Our findings show that this type of mutation is fairly frequent (18.4% of mutated alleles) and is underestimated in the literature. It is important to include the screening of large deletions/duplications as part of the genetic diagnosis strategy.
BACKGROUND:Congenital muscular dystrophy (CMD) type 1A (MDC1A) is caused by recessive mutations in laminin-α2 (LAMA2) gene. Laminin-211, a heterotrimeric glycoprotein that contains the α2 chain, is crucial for muscle stability establishing a bond between the sarcolemma and the extracellular matrix. More than 215 mutations are listed in the locus specific database (LSDB) for LAMA2 gene (May 2014). OBJECTIVE: A limited number of large deletions/duplications have been reported in LAMA2. Our main objective was the identification of additional large rearrangements in LAMA2 found in CMDpatients and a systematic review of cases in the literature and LSDB. METHODS: In four of the fifty-two patients studied over the last 10 years, only one heterozygous mutation was identified, after sequencing and screening for a frequent LAMA2 deletion. Initial screening of large mutations was performed by multiplex ligation-dependent probe application (MLPA). Further characterization implied several techniques: long-range PCR, cDNA and Southern-blot analysis. RESULTS: Three novel large deletions in LAMA2 and the first pathogenic large duplication were successfully identified, allowing a definitive molecular diagnosis, carrier screening and prenatal diagnosis. A total of fifteen deletions and two duplications previously reported were also reviewed. Two possible mutational "hotspots" for deletions may exist, the first encompassing exons 3 and 4 and second in the 3' region (exons 56 to 65) of LAMA2. CONCLUSIONS: Our findings show that this type of mutation is fairly frequent (18.4% of mutated alleles) and is underestimated in the literature. It is important to include the screening of large deletions/duplications as part of the genetic diagnosis strategy.
Authors: Edmund S Cauley; Alan Pittman; Swati Mummidivarpu; Ehsan G Karimiani; Samantha Martinez; Isabella Moroni; Reza Boostani; Daniele Podini; Marina Mora; Yalda Jamshidi; Eric P Hoffman; M Chiara Manzini Journal: Mol Genet Genomic Med Date: 2020-09-16 Impact factor: 2.183