RESUMO
White matter hyperintensities (WMHs) of the brain are important markers of aging and small-vessel disease. WMHs are rare in healthy children and, when observed, often occur with comorbid neuroinflammatory or vasculitic processes. Here, we describe a complex 4 kb deletion in 2q36.3 that segregates with early childhood communication disorders and WMH in 15 unrelated families predominantly from Southeast Asia. The premature brain aging phenotype with punctate and multifocal WMHs was observed in ~70% of young carrier parents who underwent brain MRI. The complex deletion removes the penultimate exon 3 of TM4SF20, a gene encoding a transmembrane protein of unknown function. Minigene analysis showed that the resultant net loss of an exon introduces a premature stop codon, which, in turn, leads to the generation of a stable protein that fails to target to the plasma membrane and accumulates in the cytoplasm. Finally, we report this deletion to be enriched in individuals of Vietnamese Kinh descent, with an allele frequency of about 1%, embedded in an ancestral haplotype. Our data point to a constellation of early language delay and WMH phenotypes, driven by a likely toxic mechanism of TM4SF20 truncation, and highlight the importance of understanding and managing population-specific low-frequency pathogenic alleles.
Assuntos
Senilidade Prematura/genética , Sequência de Bases , Predisposição Genética para Doença , Transtornos do Desenvolvimento da Linguagem/genética , Leucoencefalopatias/genética , Deleção de Sequência , Tetraspaninas/genética , Idade de Início , Senilidade Prematura/complicações , Senilidade Prematura/etnologia , Senilidade Prematura/patologia , Povo Asiático , Encéfalo/metabolismo , Encéfalo/patologia , Criança , Pré-Escolar , Cromossomos Humanos Par 2 , Éxons , Feminino , Humanos , Transtornos do Desenvolvimento da Linguagem/complicações , Transtornos do Desenvolvimento da Linguagem/etnologia , Transtornos do Desenvolvimento da Linguagem/patologia , Leucoencefalopatias/complicações , Leucoencefalopatias/etnologia , Leucoencefalopatias/patologia , Imageamento por Ressonância Magnética , Masculino , Dados de Sequência Molecular , Linhagem , Análise de Sequência de DNARESUMO
Clubfoot is a common birth defect that affects 135,000 newborns each year worldwide. It is characterized by equinus deformity of one or both feet and hypoplastic calf muscles. Despite numerous study approaches, the cause(s) remains poorly understood although a multifactorial etiology is generally accepted. We considered the HOXA and HOXD gene clusters and insulin-like growth factor binding protein 3 (IGFBP3) as candidate genes because of their important roles in limb and muscle morphogenesis. Twenty SNPs from the HOXA and HOXD gene clusters and 12 SNPs in IGFBP3 were genotyped in a sample composed of non-Hispanic white and Hispanic multiplex and simplex families (discovery samples) and a second sample of non-Hispanic white simplex trios (validation sample). Four SNPs (rs6668, rs2428431, rs3801776, and rs3779456) in the HOXA cluster demonstrated altered transmission in the discovery sample, but only rs3801776, located in the HOXA basal promoter region, showed altered transmission in both the discovery and validation samples (P = 0.004 and 0.028). Interestingly, HOXA9 is expressed in muscle during development. An SNP in IGFBP3, rs13223993, also showed altered transmission (P = 0.003) in the discovery sample. Gene-gene interactions were identified between variants in HOXA, HOXD, and IGFBP3 and with previously associated SNPs in mitochondrial-mediated apoptotic genes. The most significant interactions were found between CASP3 SNPS and variants in HOXA, HOXD, and IGFBP3. These results suggest a biologic model for clubfoot in which perturbation of HOX and apoptotic genes together affect muscle and limb development, which may cause the downstream failure of limb rotation into a plantar grade position.
Assuntos
Apoptose/genética , Pé Torto Equinovaro/genética , Proteínas de Homeodomínio/genética , Padrões de Herança/genética , Proteína 3 de Ligação a Fator de Crescimento Semelhante à Insulina/genética , Polimorfismo de Nucleotídeo Único/genética , Transdução de Sinais/genética , Sítios de Ligação , Frequência do Gene , Ligação Genética , Haplótipos/genética , Hispânico ou Latino/genética , Humanos , Mitocôndrias/genética , Modelos Genéticos , Mutação/genética , Fatores de Transcrição/metabolismoRESUMO
Idiopathic talipes equinovarus, also known as clubfoot, is a common birth defect occurring in one of 1000 live births. It is a complex disorder in which multiple genes and environmental factors may play an etiologic role. Several chromosomal deletion regions, including 2q31-33, are associated with talipes equinovarus and may harbor genes that contribute to the idiopathic talipes equinovarus phenotype. Previously, two STRs in the 2q31-33, GATA149B10 and D2S1371, showed linkage with association to idiopathic talipes equinovarus. Single nucleotide polymorphisms (SNPs) in three apoptotic genes (Casp8, Casp10, and CFLAR) near GATA149B10 were genotyped in idiopathic talipes equinovarus families. rs3731714 in Casp10 showed linkage with association, suggesting variation in the apoptotic gene pathway, which is important in limb morphogenesis, and may play a role in the development of idiopathic talipes equinovarus. We genotyped SNPs spanning seven apoptotic genes-Casp3, Casp8, Casp9, Casp10, Bid, Bcl-2 and Apaf1-in 210 simplex trios and 139 multiplex families and tested for link-age and association to idiopathic talipes equinovarus. One SNP in each of the genes provided suggestive evidence of association with idiopathic talipes equinovarus. Several haplotypes constructed from these SNPs displayed altered transmission. These data suggest genetic variation in apoptotic genes may play a role in development of idiopathic talipes equinovarus.
