Implementación de una metodología basada en las técnicas PCR y TP-PCR para la genotipificación del microsatélite CAG del gen ATXN2 asociado con ataxia espinocerebelosa tipo 2 en el Centro de Investigación Básica en Neurogenética

Publicación a texto completo no autorizada por el autorImplementa una metodología basada en PCR y TP-PCR para la genotipificación de este microsatélite en el Centro de Investigación Básica en Neurogenética (CIBN) del Instituto Nacional de Ciencias Neurológicas (INCN). Para determinar las condiciones óptimas para la genotipificación se emplean 9 muestras de genotipo conocido (alelos normales y expandidos). Posteriormente, 114 muestras de casos con diagnóstico presuntivo de ataxia hereditaria atendidos en el CIBN del INCN son analizadas por PCR convencional, de las cuales 91 muestras pasan a un segundo análisis por TP-PCR. Se confirma el diagnóstico en 10 muestras (8.77% de 114), que reportan una edad de inicio de la enfermedad en promedio de 27.5 ± 13.1 años y un 80% procede de la sierra central peruana. Finalmente, se logra la implementación del protocolo de genotipificación basado en PCR y TP-PCR para la genotipificación del microsatélite del gen ATXN2.Tesi

Ausencia de la mutación A53T del gen SNCA en una muestra de pacientes con Enfermedad de Parkinson en el Perú

Introducción. La enfermedad de Parkinson (EP) es un trastorno neurodegenerativo común, el segundo más frecuente después de la enfermedad de Alzheimer. La mutación A53T en el gen SNCA, fue la primera identificada en asociación con EP. La mayoría de casos de EP en familias con esta mutación provienen de regiones cercanas al lugar del descubrimiento original. Objetivos: Evaluar la presencia de la mutación A53T en el gen SNCA en una muestra peruana de casos con EP de incidencia familiar, esporádicos y controles sanos. Material y Métodos: Se analizaron, mediante la técnica de PCR-RFLP, las muestras de ADN de 34 casos con EP esporádico, 7 casos de EP familiar y 32 individuos control. Resultados: No se encontró la mutación A53T en la muestra analizada, por lo que se infiere que ella estaría confinada a pocas familias de origen caucásico (europeo) asociadas a aquéllas con los casos originalmente descritos. Conclusiones: La mutación A53T no sería un factor causal o primario de EP en los casos evaluados

Identification of Main Genetic Causes Responsible for Non-Syndromic Hearing Loss in a Peruvian Population

Hearing loss (HL) is a common sensory disorder affecting over 5% of the global population. The etiology underlying HL includes congenital and acquired causes; genetic factors are the main cause in over 50% of congenital cases. Pathogenic variants in the gene are a major cause of congenital non-syndromic hearing loss (NSHL), while their distribution is highly heterogeneous in different populations. To the best of our knowledge, there is no data regarding the genetic etiologies of HL in Peru. In this study, we screened 133 Peruvian families with NSHL living in Lima. We sequenced both exons of the gene for all probands. Seven probands with familial NSHL that remained negative for variants underwent whole genome sequencing (WGS). We identified biallelic pathogenic variants in in 43 probands; seven were heterozygous for only one allele. The c.427C>T variant was the most common pathogenic variant followed by the c.35delG variant. WGS revealed three novel variants in in two probands, one of them was predicted to affect splicing and the others produce a premature stop codon. The Peruvian population showed a complex profile for genetic variants in the gene, this particular profile might be a consequence of the admixture history in Peru

Identification of Main Genetic Causes Responsible for Non-Syndromic Hearing Loss in a Peruvian Population

Hearing loss (HL) is a common sensory disorder affecting over 5% of the global population. The etiology underlying HL includes congenital and acquired causes; genetic factors are the main cause in over 50% of congenital cases. Pathogenic variants in the GJB2 gene are a major cause of congenital non-syndromic hearing loss (NSHL), while their distribution is highly heterogeneous in different populations. To the best of our knowledge, there is no data regarding the genetic etiologies of HL in Peru. In this study, we screened 133 Peruvian families with NSHL living in Lima. We sequenced both exons of the GJB2 gene for all probands. Seven probands with familial NSHL that remained negative for GJB2 variants underwent whole genome sequencing (WGS). We identified biallelic pathogenic variants in GJB2 in 43 probands; seven were heterozygous for only one allele. The c.427C>T variant was the most common pathogenic variant followed by the c.35delG variant. WGS revealed three novel variants in MYO15A in two probands, one of them was predicted to affect splicing and the others produce a premature stop codon. The Peruvian population showed a complex profile for genetic variants in the GJB2 gene, this particular profile might be a consequence of the admixture history in Peru

Genome sequencing identifies coding and non-coding variants for non-syndromic hearing loss

Hearing loss (HL) is a common heterogeneous trait that involves variants in more than 200 genes. In this study, we utilized exome (ES) and genome sequencing (GS) to effectively identify the genetic cause of presumably non-syndromic HL in 322 families from South and West Asia and Latin America. Biallelic GJB2 variants were identified in 58 probands at the time of enrollment these probands were excluded. In addition, upon review of phenotypic findings, 38/322 probands were excluded based on syndromic findings at the time of ascertainment and no further evaluation was performed on those samples. We performed ES as a primary diagnostic tool on one or two affected individuals from 212/226 families. Via ES we detected a total of 78 variants in 30 genes and showed their co-segregation with HL in 71 affected families. Most of the variants were frameshift or missense and affected individuals were either homozygous or compound heterozygous in their respective families. We employed GS as a primary test on a subset of 14 families and a secondary tool on 22 families which were unsolved by ES. Although the cumulative detection rate of causal variants by ES and GS is 40% (89/226), GS alone has led to a molecular diagnosis in 7 of 14 families as the primary tool and 5 of 22 families as the secondary test. GS successfully identified variants present in deep intronic or complex regions not detectable by ES