ABSTRACT
The aim of this study was to improve knowledge of the mutational spectrum causing tuberous sclerosis complex (TSC) in a sample of Mexican patients, given the limited information available regarding this disease in Mexico and Latin America. Four different molecular techniques were implemented to identify from single nucleotide variants to large rearrangements in the TSC1 and TSC2 genes of 66 unrelated Mexican-descent patients that clinically fulfilled the criteria for a definitive TSC diagnosis. The mutation detection rate was 94%, TSC2 pathogenic variants (PV) prevailed over TSC1 PV (77% vs. 23%) and a recurrent mutation site (hotspot) was observed in TSC1 exon 15. Interestingly, 40% of the identified mutations had not been previously reported. The wide range of novels PV made it difficult to establish any genotype-phenotype correlation, but most of the PV conditioned neurological involvement (intellectual disability and epilepsy). Our 3D protein modeling of two variants classified as likely pathogenic demonstrated that they could alter the structure and function of the hamartin (TSC1) or tuberin (TSC2) proteins. Molecular analyses of parents and first-degree affected family members of the index cases enabled us to distinguish familial (18%) from sporadic (82%) cases and to identify one case of apparent gonadal mosaicism.
Subject(s)
Genetic Predisposition to Disease , Tuberous Sclerosis Complex 1 Protein/genetics , Tuberous Sclerosis Complex 2 Protein/genetics , Tuberous Sclerosis/genetics , Adolescent , Child , Child, Preschool , DNA Mutational Analysis , Epilepsy/genetics , Epilepsy/pathology , Female , Genetic Association Studies , Genotype , Humans , Infant , Intellectual Disability/genetics , Intellectual Disability/pathology , Male , Mexico/epidemiology , Mutation/genetics , Phenotype , Tuberous Sclerosis/epidemiology , Tuberous Sclerosis/pathology , Young AdultABSTRACT
About 80% of patients with tuberous sclerosis complex (TSC) present renal involvement, usually as angiomyolipomas followed by cystic disease. An early diagnosis of polycystic kidney disease (PKD) in such patients is frequently related to the TSC2/PKD1 contiguous gene syndrome (PKDTS). Molecular confirmation of PKDTS is important for a prompt diagnosis, which can be complicated by the phenotypic heterogeneity of PKD and the absence of a clear phenotype-genotype correlation. Herein, we report three PKDTS pediatric patients. The case 3 did not present a classic PKDTS phenotype, having only one observable cyst on renal ultrasound at age 4 and multiple small cysts on magnetic resonance imaging at age 15. In this patient, chromosomal microarray analysis showed a gross deletion of 230.8 kb that involved TSC2, PKD1 and 13 other protein-coding genes, plus a heterozygous duplication of a previously undescribed copy number variant of 242.9kb that involved six protein-coding genes, including SSTR5, in the 16p13.3 region. Given the observations that the case 3 presented the mildest renal phenotype, harbored three copies of SSTR5, and the reported inhibition of cystogenesis (specially in liver) observed with somatostatin analogs in some patients with autosomal dominant PKD, it can be hypothesized that other genetic factors as the gene dosage of SSTR5 may influence the PKD phenotype and the progression of the disease; however, future work is needed to examine this possibility
Un 80% de los pacientes con complejo de esclerosis tuberosa (CET) presentan afectación renal, generalmente angiomiolipomas, seguidos de enfermedad quística. Un diagnóstico temprano de la enfermedad renal poliquística (ERP) en estos pacientes se relaciona con frecuencia con el síndrome de genes contiguos TSC2/PKD1 (PKDTS). La confirmación molecular de PKDTS es importante para establecer un diagnóstico oportuno, que puede complicarse por la heterogeneidad fenotípica de PKD y la ausencia de una clara correlación entre fenotipo y genotipo. En este artículo presentamos los casos de 3 pacientes pediátricos con PKDTS. El caso 3 no presentó un fenotipo PKDTS clásico, con solo un quiste observable en la ecografía renal a los 4 años y numerosos quistes pequeños en la resonancia magnética a los 15 años. En este paciente, el análisis de microarreglos para análisis cromosómico global mostró una eliminación total de 230,8 kb que involucró a TSC2, PKD1 y otros 13 genes codificantes de proteínas, más una duplicación heterocigota para una variante de número de copias no descrita previamente de 242,9 kb que involucró a 6 genes codificantes de proteínas, entre ellos SSTR5, en la región 16p13.3. Dado que el caso 3 mostraba el fenotipo renal menos severo, contaba con tres copias del gen SSTR5 y a que se ha observado una inhibición en la cistogénesis (especialmente en el hígado) con los análogos de somatostatina en algunos pacientes con ERP autosómica dominante, podemos hipotetizar que existen otros factores genéticos como la dosis génica de SSTR5 que pudieran influir en el fenotipo y la progresión de la ERP; sin embargo, se necesitan estudios adicionales para investigar esta posibilidad
Subject(s)
Humans , Male , Female , Infant , Child, Preschool , Child , Adolescent , Genetic Variation , Polycystic Kidney Diseases/genetics , TRPP Cation Channels/genetics , Tuberous Sclerosis/genetics , Exons/genetics , Gene Deletion , Phenotype , Polycystic Kidney Diseases , Polycystic Kidney Diseases/diagnostic imaging , Syndrome , Tuberous Sclerosis/diagnostic imagingABSTRACT
About 80% of patients with tuberous sclerosis complex (TSC) present renal involvement, usually as angiomyolipomas followed by cystic disease. An early diagnosis of polycystic kidney disease (PKD) in such patients is frequently related to the TSC2/PKD1 contiguous gene syndrome (PKDTS). Molecular confirmation of PKDTS is important for a prompt diagnosis, which can be complicated by the phenotypic heterogeneity of PKD and the absence of a clear phenotype-genotype correlation. Herein, we report three PKDTS pediatric patients. The case 3 did not present a classic PKDTS phenotype, having only one observable cyst on renal ultrasound at age 4 and multiple small cysts on magnetic resonance imaging at age 15. In this patient, chromosomal microarray analysis showed a gross deletion of 230.8kb that involved TSC2, PKD1 and 13 other protein-coding genes, plus a heterozygous duplication of a previously undescribed copy number variant of 242.9kb that involved six protein-coding genes, including SSTR5, in the 16p13.3 region. Given the observations that the case 3 presented the mildest renal phenotype, harbored three copies of SSTR5, and the reported inhibition of cystogenesis (specially in liver) observed with somatostatin analogs in some patients with autosomal dominant PKD, it can be hypothesized that other genetic factors as the gene dosage of SSTR5 may influence the PKD phenotype and the progression of the disease; however, future work is needed to examine this possibility.
