RESUMO
Next-generation sequencing was used to investigate 9 rare Chinese pedigrees with rare autosomal recessive neurologic Mendelian disorders. Five probands with ataxia-telangectasia and 1 proband with chorea-acanthocytosis were analyzed by targeted gene sequencing. Whole-exome sequencing was used to investigate 3 affected individuals with Joubert syndrome, nemaline myopathy, or spastic ataxia Charlevoix-Saguenay type. A list of known and novel candidate variants was identified for each causative gene. All variants were genetically verified by Sanger sequencing or quantitative polymerase chain reaction with the strategy of disease segregation in related pedigrees and healthy controls. The advantages of using next-generation sequencing to diagnose rare autosomal recessive neurologic Mendelian disorders characterized by genetic and phenotypic heterogeneity are demonstrated. A genetic diagnostic strategy combining the use of targeted gene sequencing and whole-exome sequencing with the aid of next-generation sequencing platforms has shown great promise for improving the diagnosis of neurologic Mendelian disorders.
Assuntos
Sequência de Bases/genética , Exoma/genética , Genes Recessivos/genética , Técnicas de Diagnóstico Molecular/métodos , Doenças do Sistema Nervoso/diagnóstico , Doenças do Sistema Nervoso/genética , Análise de Sequência de DNA/métodos , Anormalidades Múltiplas , Adulto , Povo Asiático/genética , Ataxia , Encéfalo/patologia , Doenças Cerebelares , Cerebelo/anormalidades , Criança , Pré-Escolar , Anormalidades do Olho , Feminino , Humanos , Lactente , Recém-Nascido , Deficiência Intelectual , Doenças Renais Císticas , Imageamento por Ressonância Magnética , Masculino , Espasticidade Muscular , Miopatias da Nemalina , Doenças do Sistema Nervoso/patologia , Neuroacantocitose , Atrofia Óptica , Retina/anormalidades , Ataxias Espinocerebelares , Telangiectasia , Adulto JovemRESUMO
Genetic heterogeneity is common in many Mendelian disorders such as hereditary spastic paraplegia (HSP), which makes the genetic diagnosis more complicated. The goal of this study was to investigate a Chinese family with recessive hereditary spastic paraplegia, of which causative mutations could not be identified using the conventional PCR-based direct sequencing. Next-generation sequencing of all the transcripts of whole genome exome, after on-array hybrid capture, was performed on two affected male subjects (the proband and his brother). A missense mutation (c.1661G>A, p.R554H) was identified in ABCD1. Subsequently, PCR-based direct sequencing of other family members revealed that the mutation was co-segregating with the disease, indicating that ABCD1 mutation was the pathogenic event for this family. Very long-chain fatty acids (VLCFA) assay in the two affected cases confirmed X-ALD. Our study suggests exome sequencing can be used not only to find a novel causative gene, but also to quickly identify mutations of known genes when the clinical elements are etiologically misleading.
Assuntos
Transportadores de Cassetes de Ligação de ATP/genética , Adrenoleucodistrofia/diagnóstico , Exoma/genética , Paraplegia Espástica Hereditária/diagnóstico , Membro 1 da Subfamília D de Transportadores de Cassetes de Ligação de ATP , Adrenoleucodistrofia/genética , Adulto , Diagnóstico Diferencial , Feminino , Heterogeneidade Genética , Humanos , Masculino , Mutação de Sentido Incorreto , Linhagem , Análise de Sequência de DNA , Paraplegia Espástica Hereditária/genéticaRESUMO
Paroxysmal kinesigenic dyskinesias is a paroxysmal movement disorder characterized by recurrent, brief attacks of abnormal involuntary movements induced by sudden voluntary movements. Although several loci, including the pericentromeric region of chromosome 16, have been linked to paroxysmal kinesigenic dyskinesias, the causative gene has not yet been identified. Here, we identified proline-rich transmembrane protein 2 (PRRT2) as a causative gene of paroxysmal kinesigenic dyskinesias by using a combination of exome sequencing and linkage analysis. Genetic linkage mapping with 11 markers that encompassed the pericentromeric of chromosome 16 was performed in 27 members of two families with autosomal dominant paroxysmal kinesigenic dyskinesias. Then, the whole-exome sequencing was performed in three patients from these two families. By combining the defined linkage region (16p12.1-q12.1) and the results of exome sequencing, we identified an insertion mutation c.649_650InsC (p.P217fsX7) in one family and a nonsense mutation c.487C>T (p.Q163X) in another family. To confirm our findings, we sequenced the exons and flanking introns of PRRT2 in another three families with paroxysmal kinesigenic dyskinesias. The c.649_650InsC (p.P217fsX7) mutation was identified in two of these families, whereas a missense mutation, c.796C>T (R266W), was identified in another family with paroxysmal kinesigenic dyskinesias. All of these mutations completely co-segregated with the phenotype in each family. None of these mutations was identified in 500 normal unaffected individuals of matched geographical ancestry. Thus, we have identified PRRT2 as the first causative gene of paroxysmal kinesigenic dyskinesias, warranting further investigations to understand the pathogenesis of this disorder.
