Huntington's Disease in Chile: Epidemiological and Genetic Aspects.

INTRODUCTION: Huntington's disease (HD) is a neurodegenerative, autosomal dominant disabling condition due to an expansion of the CAG trinucleotide in the HTT gene. Motor, psychiatric, and cognitive disorders characterize it. Chilean reports on HD in the era of molecular diagnosis were wanted. METHODS: This is a retrospective analysis of a prospective cohort of patients with HD seen at the Center for Movement Disorders (CETRAM) in Chile between 2013 and 2019. Sociodemographic, genotype, and neuropsychiatric features were investigated. RESULTS: One hundred three probands with HD were identified. The majority (63.1%) were born in the metropolitan region, followed by the VIII and V regions with 8.73% and 7.76%, respectively. When pedigrees were analyzed, ninety unrelated families encompassing 1,007 individuals were identified; among relatives, other 35 manifested HD, and 106 died of HD. Besides, five hundred seventy-nine individuals were at genetic risk. The minimum estimated prevalence of HD in Chile in 2019 was 0.72 × 100,000 inhabitants. The mean CAG repeats (CAGR) of 47.2 ± 10.74 for the expanded allele and 17.93 ± 2.05 for the normal allele. The mean age of onset was 41.39 ± 13.47 years. Juvenile cases represented 7.8% of this cohort, and 4.9% had a late onset. There was a negative correlation between the age of onset and the CAGR of the expanded allele (r =-0.84 p < 0.0001). Besides, 79.6% had a family history of HD. CONCLUSIONS: This is the first report characterizing genetics, motor, and neuropsychiatric features in patients with HD in Chile. The mean length of CAGR expansion of the abnormal allele was similar to previous reports in North America (i.e., Mexico and Canada) and higher than that reported in the neighboring country of Argentina. According to previous estimations, the minimal prevalence of HD in Chile may be lower than expected.

Valores de referencia de β-glucosidasa y quitotriosidasa en gotas de sangre seca de lactantes venezolanos / Reference Values for β-glucosidase and chitotriosidase using dried blood spots in Venezuelan infants

La enfermedad de Gaucher es un trastorno de herencia autosómica recesiva y la enfermedad de depósito lisosomal más frecuente causada por deficiencia de la actividad enzimática de la β-Glucosidasa. Objetivo: establecer valores de referencia de actividad enzimática lisosomal de β-glucosidasa y quitotriosidasa en lactantes en población Venezolana. Método: Se realizó un estudio prospectivo y transversal en 98 lactantes sanos con edades comprendidas entre 1 mes y 24 meses, de ambos sexos (48 femeninos y 50 masculinos). La actividad enzimática de β-glucosidasa y quitotriosidasa fue determinada en gotas de sangre seca (siglas en inglés, DBS) siguiendo el protocolo propuesto por Chamoles y col. El análisis estadístico de los datos se realizó con el programa estadístico SPSS Statistics 17.0 para Windows. Resultados: El rango de actividad enzimática para la β-Glucosidasa obtenido en esta investigación fue 2,3 - 12 nmol/ml/h, con una media de 6,7 ± 2,5 y para la Quitotriosidasa 0 - 44,2 nmol/ml/h con una media de 18,4 ± 10,4 nmol/ml/h, utilizando discos de papel de filtro de 3mm de diámetro con sangre seca (aproximadamente 3,6 μl de sangre). Conclusión: Los valores de referencia de actividad enzimática lisosomal en DBS para β-glucosidasa y quitotriosidasa son establecidos por vez primera en lactantes sanos venezolanos; no obstante, estos resultados difieren con los reportados en estudios internacionales, recomendándose la determinación de valores de referencias autóctonos en diferentes grupos etarios.

Gaucher´s Disease is an autosomal recessive disorder and the most common lysosomal storage disease caused by deficiency of β-glucosidase enzyme activity. Objetive: to establish reference values for lysosomal enzyme activity of β-glucosidase and chitotriosidase in Venezuelan infants. Methods:A prospective cross-sectional study was conducted in 98 healthy infants with ages ranging from 1 month to 24 months (48 females and 50 males). Enzymatic activity of β-glucosidase and chitotriosidase were determined in dried blood spots (DBS) following the protocol by Chamoles et al. Statistical analysis of data was performed with software SPSS 17.0 for Windows Statistics. Results: The range of enzymatic activity for β-glucosidase was 2.3 to 12 nmol/ml/h, with an average of 6.7 ± 2.5. Chitotriosidase activity was from 0 to 44.2 nmol/ml/h with an average of 18.4 ± 10.4 using 3mm diameter discs of filter paper with dried blood (approximately 3.6 μl of blood). Conclusions: The reference values of lysosomal enzyme activity in DBS for β-Glucosidase and quitotriosidase were established for the first time in healthy Venezuelan infants; however, these results differ from those reported in international studies, for which reason autochthonous reference values should be determined in different age groups.

Síndrome PAGOD y anomalías vasculares: ¿es un defecto de la angiogénesis embrionaria? Un nuevo caso y revisión / PAGOD syndrome and vascular anomalies: is a defect embryonic angiogenesis? A case report and review

El Síndrome PAGOD es un acrónimo de hipoplasia de pulmón y arterias pulmonares, agonadismo, onfalocele / defecto diafragmático y dextrocardia. Se describe una serie de 21 pacientes, en la cual, 90,5 % presentó un cariotipo 46,XY y solo dos casos 46,XX; el 66,6 % exhibió un fenotipo femenino y 28,6 % genitales ambiguos. La ocurrencia de dos paciente 46,XX excluye al cromosoma Y como portador del defecto genético y plantea la posibilidad de una herencia recesiva ligada al cromosoma X, sin descartar que los casos observados en hermanos puedan deberse a mutaciones en otros genes como STRA6, VEGFA, VEGFB, VEGFC, transcritos de empalmes alternativos de VEGFA, HIF1, HIF2, entre otros. Las malformaciones congénitas observadas en los pacientes fueron: genitales y gónadas 85,7 %, diafragma y pared 66,6 %, cardíaco 80,9 %, pulmonar 71,4 %, vascular 80,9 % y abdomen 42,8 %. La revisión de los pacientes ha demostrado un alto grado de variabilidad en la expresividad de malformaciones de órganos, aparatos o sistemas. Las malformaciones vasculares representan un componente importante y característico del síndrome PAGOD y cuya base morfogenética del síndrome pueda deberse a un defecto de la angiogénesis embrionaria temprana con repercusión en la organogénesis de aparatos y sistemas. Dentro de los genes relacionados con el remodelamiento vascular durante la embriogénesis, regeneración tisular y carcinogénesis está el Factor de Crecimiento del Endotelio Vascular D (VEGFD), localizado en Xp22.31, con expresión en pulmón, corazón, intestino delgado, pulmón fetal, útero, mamas, tejido neural y neuroblastoma, el cual representa un fuerte candidato para su análisis molecular como una de las posibles causa del síndrome.

PAGOD Syndrome is an acronym for lung and pulmonary arteries hypoplasia, agonadism, omphalocele / diaphragmatic defect and dextrocardia. A series of 21 patients is described, where 90.5% had a 46,XY karyotype and only two cases 46,XX; 66.6% exhibited a female phenotype and 28.6% ambiguous genitalia. The occurrence of two patients 46,XX excludes the Y chromosome as a carrier of the genetic defect and raises the possibility of a recessive X-linked inheritance, without ruling out that the observed cases in siblings may be due to mutations in other genes as Stra6, VEGFA, VEGFB, VEGFC, and alternative splicing of transcripts VEGFA, HIF1, HIF2, among others. Congenital malformations were observed in patients’ genitals and gonads 85.7%, 66.6% in diaphragm and abdominal wall , heart 80.9%, 71.4% lungs, blood vessels 80.9% and 42.8% in abdomen. The review of patients has demonstrated a high degree of variability in the expression of malformations of organs and organ systems. Vascular malformations represent an important and characteristic component of PAGOD syndrome and whose base morphogenetic syndrome may be due to a defect in early embryonic angiogenesis with impact on organogenesis and system development. Among genes related to vascular remodeling during embryogenesis, tissue regeneration and carcinogenesis, the Endothelial Growth Factor D Vascular (VEGFD), located in the Xp22.31 region, with expression in lung, heart, small intestine, uterus, breast, neuroblastoma and neural tissue, represents a strong candidate for molecular analysis as a cause of the syndrome.

PAGOD syndrome and vascular anomalies: is a defect embryonic angiogenesis? A case report and review.

PAGOD Syndrome is an acronym for lung and pulmonary arteries hypoplasia, agonadism, omphalocele / diaphragmatic defect and dextrocardia. A series of 21 patients is described, where 90.5% had a 46,XY karyotype and only two cases 46,XX; 66.6% exhibited a female phenotype and 28.6% ambiguous genitalia. The occurrence of two patients 46,XX excludes the Y chromosome as a carrier of the genetic defect and raises the possibility of a recessive X-linked inheritance, without ruling out that the observed cases in siblings may be due to mutations in other genes as Stra6, VEGFA, VEGFB, VEGFC, and alternative splicing of transcripts VEGFA, HIF1, HIF2, among others. Congenital malformations were observed in patients' genitals and gonads 85.7%, 66.6% in diaphragm and abdominal wall , heart 80.9%, 71.4% lungs, blood vessels 80.9% and 42.8% in abdomen. The review of patients has demonstrated a high degree of variability in the expression of malformations of organs and organ systems. Vascular malformations represent an important and characteristic component of PAGOD syndrome and whose base morphogenetic syndrome may be due to a defect in early embryonic angiogenesis with impact on organogenesis and system development. Among genes related to vascular remodeling during embryogenesis, tissue regeneration and carcinogenesis, the Endothelial Growth Factor D Vascular (VEGFD), located in the Xp22.31 region, with expression in lung, heart, small intestine, uterus, breast, neuroblastoma and neural tissue, represents a strong candidate for molecular analysis as a cause of the syndrome.

Mutation c.1190-1delG/N in intron 8 and c.1708G>C/N in exon 12 not reported in the IDUA gene developed a clinical phenotype of Scheie syndrome / Mutación c.1190-1delG/N en el intrón 8 y c.1708G>C/N en el exón 12 no reportada en el gen de IDUA desarrolló un fenotipo clínico de síndrome de Scheie

Mucopolysaccharidoses are a group of lysosomal storage disorders caused by deficiency of enzymes catalyzing the degradation of glycosaminoglycans. Mucopoly-saccharidosis I can present a wide range of phenotypic characteristics with three major recognized clinical entities: Hurler and Scheie syndromes represent phenotypes at the severe and mild ends of the clinical spectrum, respectively, and the Hurler-Scheie syndrome is intermediate in phenotypic expression. These are caused by the deficiency or absence of α-L-iduronidase, essential to the metabolism of both dermatan and heparan sulfate, and it is encoded by the IDUA gene. We report the case of a 34-year-old male patient with enzymatic deficiency of α-L-iduronidase, accumulation of its substrate and a previously unreported mutation in the IDUA gene that developed a phenotype of Scheie syndrome.

Las mucopolisacaridosis son un grupo de trastornos de almacenamiento lisosomal causada por la deficiencia de enzimas que catalizan la degradación de glicosaminoglicanos. La mucopolisacaridosis tipo I puede presentar un amplio rango de características fenotípicas englobadas en tres entidades clínicas reconocidas: los síndromes de Hurler y Scheie representan los fenotipos graves y leves del espectro clínico, respectivamente y el síndrome de Hurler-Scheie intermedio en la expresión fenotípica. Estos son causados por la deficiencia o ausencia de la α-L-iduronidasa esencial para el metabolismo del dermatán y el heparán sulfato y es codificada por el gen IDUA. Se presenta el caso de paciente masculino de 34 años de edad con deficiencia enzimática de α-L-iduronidasa, acumulación de su sustrato y una mutación en el gen IDUA, no reportada previamente, que desarrolló un fenotipo del síndrome de Scheie.

Mutation c.1190-1delG/N in intron 8 and c.1708G>C/N in exon 12 not reported in the IDUA gene developed a clinical phenotype of Scheie syndrome.

Mucopolysaccharidoses are a group of lysosomal storage disorders caused by deficiency of enzymes catalyzing the degradation of glycosaminoglycans. Mucopoly-saccharidosis I can present a wide range of phenotypic characteristics with three major recognized clinical entities: Hurler and Scheie syndromes represent phenotypes at the severe and mild ends of the clinical spectrum, respectively, and the Hurler-Scheie syndrome is intermediate in phenotypic expression. These are caused by the deficiency or absence of alpha-L-iduronidase, essential to the metabolism of both dermatan and heparan sulfate, and it is encoded by the lDUA gene. We report the case of a 34-year-old male patient with enzymatic deficiency of alpha-L-iduronidase, accumulation of its substrate and a previously unreported mutation in the IDUA gene that developed a phenotype of Scheie syndrome.

[C677T polymorphism of the methylentetrahydrofolate reductase gene as risk factor in women with recurrent abortion]. / Polimorfismo C677T del gen de la Metiltetrahidrofolato Reductasa como factor de riesgo en mujeres con aborto recurrente.

The pathogenesis of recurrent spontaneous abortion is multifactorial, presumably involving the interaction of several genetic and environmental factors. The methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism has been implicated as risk factor for recurrent spontaneous abortion (RA). The main objective of this research was to investigate the association between the C677T polymorphism of the MTHFR gene as a genetic risk factor for idiopathic RA. Molecular analysis was performed in 80 DNA samples from 30 patients with RA and among 50 healthy control subjects. Using the Polymerase Chain Reaction (PCR), a 198 bp (bases pairs) fragment, was digested with the restriction enzyme Hinf1, which can recognize the C > T substitution responsible for the polymorphism. 677T MTHFR allele frequencies for group with RA and the control group were 35% and 33%, respectively and 677C MTHFR allele frequencies were 65% and 67%, respectively. There was no significant difference in allele frequency between these two groups. The data presented in this study fail to support the relationship between MTHFR C677T polymorphism and risk in women with RA.

[Immunogenetic aspects of autism. Review]. / Aspectos inmunogenéticos del autismo. Revisión.

Autism is a generalized or pervasive developmental disorder that affects about five in ten thousand children worldwide (5/10.000). In Maracaibo the incidence is 1.1/1000, with a ratio of male/female, 4:1. The autistic disorder is defined entirely based on the impairment in three areas: 1) Impairment of social interaction, 2) Impairment in communication and 3) Stereotyped and repetitive behavior. Autism is a disorder with a large genetic component and a oligogenic inheritance model has been proposed. Quantitative and qualitative disturbances of certain components of the immune system in patients with autism have been used as endophenotype, one of the strategies used to identify candidate genes for susceptibility to autism. On the other hand the hypersensitivity to specific groups of foods such as casein and gluten has become clear, which has led to the postulation of immunogenetics theories in autism, which mainly involve genes of the histocompatibility major complex. Although it has not been confirmed that immunogenetics factors could be involved in the etiopathogenesis of autism, several studies have shown the influence of the complex Human Leucocyte Antigen (HLA) HLA DR4, DR13, DR11, A2 and others genes in the clinical status, risk and therapeutic response of some psychiatric disorders. The lack of literature demands a greater number of studies related to different ethnic groups and the participation of HLA, as well as the importance of this complex in the pathogenesis of psychiatric illness.

Petty-Laxova-Wiedemann progeroid syndrome: further phenotypical delineation and confirmation of a rare syndrome of premature aging.

A 10-year-old boy with manifestations of Petty-Laxova-Wiedemann progeroid syndrome (PLWPS), a rare neonatal progeroid condition, is described and compared with those previously reported. Clinical manifestation include: severe pre- and postnatal growth retardation, "progeroid" face, large open fontanelle in infancy, umbilical hernia at birth, pseudomacrocephaly, wide calvaria, sparse scalp hair, markedly diminished subcutaneous fat, scoliosis, partial cutaneous syndactyly, aplastic and hypoplastic distal phalanges with aplasia and hypoplasia of nails, undescended testes, and normal cognitive and motor development. This appears to be one of only a handful of cases of PLWPS reported in an older child or adult.

Aspectos inmunogenéticos del autismo: revisión / Immunogenetic aspects of autism: review

El autismo es un trastorno profundo o generalizado del desarrollo que afecta aproximadamente a cinco de cada diez mil niños a nivel mundial (5/10.000). En Maracaibo la incidencia es de 1,1/1000, con una relación por sexo masculino/femenino de 4:1. El trastorno autista es definido completamente con base en el deterioro de tres áreas: 1) Deterioro en la interacción social, 2) Deterioro en la comunicación y 3) Comportamiento estereotipado y repetitivo. El autismo es un trastorno con un gran componente genético y dentro de los modelos de herencia propuestos se encuentra la herencia oligogénica. Una de las estrategias utilizadas para la identificación de genes candidatos de susceptibilidad al autismo consiste en la utilización de endofenotipos, dentro de los cuales se encuentran la alteración cuantitativa y cualitativa de determinados componentes del sistema inmunitario, de igual forma se ha evidenciado una hipersensibilidad a grupos específicos de alimentos como la caseína y el gluten, todo lo cual ha llevado a la postulación de teorías inmunogenéticas en el autismo donde se implican principalmente los genes del complejo principal de histocompatibilidad. Aunque no se ha confirmado que los factores inmunogenéticos intervienen en la etiopatogénesis de los trastornos del comportamiento, como el autismo, diversos estudios han demostrado la influencia del complejo Antígeno Leucocitario Humano (siglas en inglés HLA) HLA DR4, DR13, DR11 y A2, entre otros genes, en el estatus clínico, riesgo y respuesta terapéutica de algunos desórdenes psiquiátricos. La escasa literatura existente demanda un mayor número de estudios relacionados con diferentes grupos étnicos y la participación del HLA; así como la importancia de este complejo en la patogénesis de enfermedades psiquiátricas

Autism is a generalized or pervasive developmental disorder that affects about five in ten thousand children worldwide (5/10.000). In Maracaibo the incidence is 1.1/1000, with a ratio of male/female, 4:1. The autistic disorder is defined entirely based on the impairment in three areas: 1) Impairment of social interaction, 2) Impairment in communication and 3) Stereotyped and repetitive behavior. Autism is a disorder with a large genetic component and a oligogenic inheritance model has been proposed. Quantitative and qualitative disturbances of certain components of the immune system in patients with autism have been used as endophenotype, one of the strategies used to identify candidate genes for susceptibility to autism. On the other hand the hypersensitivity to specific groups of foods such as casein and gluten has become clear, which has led to the postulation of immunogenetics theories in autism, which mainly involve genes of the histocompatibility major complex. Although it has not been confirmed that immunogenetics factors could be involved in the etiopathogenesis of autism, several studies have shown the influence of the complex Human Leucocyte Antigen (HLA) HLA DR4, DR13, DR11, A2 and others genes in the clinical status, risk and therapeutic response of some psychiatric disorders. The lack of literature demands a greater number of studies related to different ethnic groups and the participation of HLA, as well as the importance of this complex in the pathogenesis of psychiatric illness

Polimorfismo C677T del gen de la metiltetrahidrofolato reductasa como factor de riesgo en mujeres con aborto recurrente / C677T polymorphism of the methylentetrahydrofolate reductase gene as risk factor in women with recurrent abortion

La patogénesis de los abortos espontáneos recurrentes es multifactorial; probablemente se debe a la interacción de varios factores ambientales y genéticos. El polimorfismo C677T del gen de la metiltetrahidrofolato reductasa (MTHFR), ha sido implicado como factor de riesgo para aborto espontáneo recurrente (AR). El objetivo de este trabajo fue investigar la asociación del polimorfismo C677T de la MTHFR como factor de riesgo en AR idiopático. Se analizaron 80 muestras de ADN, correspondientes a 30 mujeres con AR y a 50 mujeres controles. A través de la reacción en cadena de la polimerasa (PCR) se amplificó un fragmento de 198 pares de base (pb), el cual se sometió a digestión con la enzima de restricción HinfI, que reconoce el sitio de restricción creado por la transición C>T en la posición 677. La frecuencia alélica de la MTHFR en el grupo de estudio y control fue 35% y 33% respectivamente; para el alelo T y 65% y 67% respectivamente, para el alelo C. No se encontró diferencia significativa entre el alelo T ni el C al ser comparados en ambos grupos. No se demostró un factor predisponente entre el polimorfismo C677T de la MTHFR y el AR en la muestra estudiada.

The pathogenesis of recurrent spontaneous abortion is multifactorial, presumably involving the interaction of several genetic and environmental factors. The methylenetetrahydrofolate reductase (MTHFR) gene C677T polymorphism has been implicated as risk factor for recurrent spontaneous abortion (RA). The main objective of this research was to investigate the association between the C677T polymorphism of the MTHFR gene as a genetic risk factor for idiopathic RA. Molecular analysis was performed in 80 DNA samples from 30 patients with RA and among 50 healthy control subjects. Using the Polymerase Chain Reaction (PCR), a 198 bp (bases pairs) fragment, was digested with the restriction enzyme HinfI, which can recognize the C > T substitution responsible for the polymorphism. 677T MTHFR allele frequencies for group with RA and the control group were 35% and 33%, respectively and 677C MTHFR allele frequencies were 65% and 67%, respectively. There was no significant difference in allele frequency between these two groups. The data presented in this study fail to support the relationship between MTHFR C677T polymorphism and risk in women with RA.

[Indirect prenatal molecular diagnostic of haemophilia A and B]. / Diagnóstico prenatal molecular indirecto de Hemofilia A y B.

Haemophilia A (HA) and B (HB) are the most common inherited bleeding diseases. HA and HB are X-linked recessive disorders caused by mutation in the factor VIII gene which maps to Xq28 and factor IX located at Xq27, respectively; resulting in absence or deficiency of these proteins. Several mutations have been reported as responsible for the disturbance of these genes; therefore, the use of direct molecular techniques to analyze the carrier status of women and their affected fetuses in not easy to perform. Thus, gene linked polymorphisms analysis is the most convenient molecular test since it is independent from the nature of the mutation, allowing the identification of the mutant X chromosome by following its segregation along the pedigree. The main objective of this research was to perform the molecular diagnosis of HA or HB carrier status in pregnant women and male fetuses affected or not, who were referred to the Medical Genetic Unit of the University of Zulia (UGM-LUZ), Maracaibo, Venezuela. Molecular analysis for HA and HB was performed in 32 DNA samples from 8 pregnant women, 8 fetuses, 8 affected and 8 healthy males. Using the Polymerase Chain Reaction (PCR), a 142 bp (bases pairs) fragment, which corresponds to intron 18 of the Factor VIII gene, was amplified. This fragment has a restriction polymorphism for the enzyme Bcl I. Additionally, a Duplex PCR was performed for the STRs (short tandem repeat) of introns 13 and 22 of the same gene. On the other hand, Hinf I, Xmn I y Taq I polymorphism in the factor IX gene were also amplified, so, we were able to build the haplotypes for each one of the key members in the families affected. The latter, allowed us to identify, in five of the eight cases, the mutant X chromosome responsible of HA and HB, thus, prenatal diagnosis was possible with the following results: three healthy males fetuses, two affected males fetuses with HA and three females fetuses.

Autismo, cromosoma 15 y la hipótesis de disfunsión GABAérgica: revisión / Autism, chromosome 15 and the GABAergic dysfunction hypothesis: review

El autismo es un trastorno generalizado del desarrollo caracterizado por deterioro en las áreas de interacción social, comunicación, y comportamiento estereotipado y repetitivo. Estudios de familias y gemelos han demostrado una predisposición genética al autismo. A pesar de los avances recientes en la identificación de genes candidatos de susceptibilidad, la base neurológica subyacente es aún desconocida. Existe evidencia genética, bioquímica y anatomopatológica que apoyan la hipótesis de que en el autismo debe existir una disfunción en la vía GABAérgica, parcialmente responsable de la etiología de este trastorno. En este sentido, una de las regiones del genoma más estudiadas es el intervalo 15q11-q13, donde se encuentran los genes que codifican para las subunidades ß3, a5 y g3 del receptor GABAa. Esta revisión se propone mostrar la evidencia existente en la actualidad que involucra a esta región con la susceptibilidad al autismo y su posible relación con la hipótesis de disfunción GABAérgica.

[Molecular analysis of the GABRB3 gene in autistic patients: an exploratory study]. / Análisis molecular del gen GABRB3 en pacientes con autismo: estudio exploratorio.

Autism is a complex neurodevelopmental disorder characterized by impairment of social interaction, language, communication, and stereotyped, repetitive behavior. Genetic predisposition to Autism has been demonstrated in families and twin studies. There is evidence (linkage and genetic association, biochemical, neuropathological, functional and cytogenetic) that the gamma-amino-butyric acid receptor beta 3 subunit gene (GABRB3) at 15q11-q13 is a susceptibility candidate gene for Autism. The aim of this exploratory study was to identify new variants of this gene. We performed the molecular analysis (SSCP/Sequencing) of 10 exons and its intronic flanking regions of GABRB3, using a candidate gene screening approach in 18 idiopathic autistic patients. We did not find non-synonymous mutations at the encoding regions, but we identified four SNP (Single Nucleotide Polymorphism). The first one, represented a silent mutation p.P25P in exon la and was found in 33.33% of the patients. The second one: IVS3 + 13C > T (5b far from the intron 5' consensus sequence), was found in 44.44% of the patients, while it was also identified in 16.67% of the controls. Simultaneously, 33.33% of the patients had both variants, and although, 16.67% of the controls also had the same combination of variants, 66.66% of the patients with those alleles had a familiar history of Autism. The third and fourth SNP: IVS5 + 40T > G and IVS-70A > G were identified in two different patients. None of the last three SNPs have been reported at the SNP database (dbSNP). The proximity of SNP: IVS3 + 13C > T with the consensus and interaction sequence with U1 nucleoriboprotein, could disturb the normal splicing of mRNA. This is in agreement with the evidence of lower levels of GABA-A receptors in autistic brains; so, it could be a common variant, that by itself could not cause a phenotypic effect, but joined to other variants with the same gene, in different related genes or with epigenetic changes, could explain the autistic phenotype and its heterogeneity.

Análisis molecular del gen GABRB3 en pacientes con autismo: estudio exploratorio / Molecular analysis of the GABRB3 gene in autistic patients: an exploratory study

El autismoes un trantorno del desarrollo caracterizado por deterioro de la interacción social, la comunicación, y comportamiento estereotipado. Los estudios de familias y gemelos han demostrado predisposición genética al autismo. Existe evidencia (ligamento y asociación genética, bioquímica, anatomopatológica, funcional y citogenética) de que el gen de la subunidad B3 del receptor de GABA-A (GABRB3), en 15q11-q13, es un candidato de susceptibilidad al autismo. Con el objetivo de identificar nuevas variantes en este gen, se estudiaron 18 pacientes con autismo idiopático, utilizando un tamizaje de gen candidato. Se réalizo el análisis molecular (SSCP/secuencuaci¢n) de los 10 exones con sus correspondientes regiones intrónicas flanqueantes, pero se identificaron mutaciones no sinónimas en las regiones codificantes, pero se identificaron 4 polimorfismos de nucleótido simple (SNP). El primer SNP representó una mutación silente p. P25P en el exon 1a, encontrada en 33,33 por ciento de los pacientes. El Segundo SNP: IVS3 + 13C > T (a 5 b de la secuencia consenso 5' del intrón) fue encontrado en 44,44 por ciento de los pacientes, mientras fué indentificado en 16,67 por ciento de los controles. El 33,33 por ciento de los pacientes presentaron simultáneamente ambas variantes, y aunque el 16,67 por ciento de los controles también poseían la misma combinación, el 66,66 por ciento de los pacientes con esos alelos tenían antecedentes familiares de autismo. El tercer y cuarto SNP: IVS5 + 40T > G e IVS7-7OA > G fueron identificados en dos pacientes diferentes. Ninguno de los 3 últimos SNPs ha sido reportado en la base de datos de SNP (dbSNO). La cercanía del SNP: IVS3 + 13C > T con la secuencia consenso y de interación con la nucleorribonucleoproteína U1, pudiera alterar la maduración normal del pre-ARNm, en concordancia con la evidencia de niveles bajos del receptor GABA-A en cerebros de pacientes con autismo, pudiendo entonces tratarse, de una variante común, que por sí sola.

[Autism, chromosome 15 and the GAbaergic dysfunction hypothesis]. / Autismo, cromosoma 15 y la hipótesis de disfunción GABAérgica. Revisión.

Autism is a complex neurodevelopmental disorder characterized by impairment of social interaction, language, communication, and stereotyped, repetitive behavior. Genetic predisposition to autism has been demonstrated from families and twin studies. Despite recent advances in identifying some susceptibility candidate genes, its underlying neurological mechanism is uncertain. There are genetic, biochemical and neuropathological findings that support the hypothesis that autism could be caused by GABAergic dysfunction and it is partially responsible for the etiology of this disorder. One of the most studied genome regions is the 15q11-q13, where the genes that encode for beta3, alpha5 and gamma3 subunits of the GABAA receptor are located. This review demonstrates evidence that involves this region in autism susceptibility and its likely relation with the hypothesis of GABAergic dysfunction.

Detección de portadoras de distrofia muscular Duchenne/Becker a través del análisis de loci STRs ligados al gen de la distrofina en familias venezolanas / Carrier Detection of muscular dystrophy Duchenne/Becker by analysis de STRs loci linked to the gene of the distrofina in venezuelan families

La Distrofia Muscular tipo Duchenne/Becker (DMD/DMB) es una enfermedad letal recesiva ligada al cromosoma X; el riesgo de recurrencia en una mujer portadora de DMD/DMB es de 50 por ciento de hijos sanos y 50 por ciento de hijos enfermos, 50 por ciento de hijas no portadoras y 50 por ciento de hijas portadoras, en cada gestación. El diagnóstico de DMD/DMB en una familia establece la necesidad de detectar a las mujeres portadoras con la finalidad de poder establecer el asesoramiento genético y el diagnóstico prenatal. El análisis de los polimorfismos de repeticiones cortas en tandem (STRs) localizados en los extremos 5, 3ïe intrones 44, 45, 49 y 50 del gen de la Distrofina se han utilizado para determinar los haplotipos en personas normales y en riesgo, a través de establecer el ligamiento genético entre el gen mutado y el haplotipo segregado. Se analizaron 105 individuos provenientes de 15 familias venezolanas con DMD/DMB, con uno o más afectados y 7 varones no emparentados. De los 105 individuos, 37 eran varones (26 afectados y 11 sanos) y 68 mujeres. Se amplificaron las secuencias STRs (STR44, STR45, STR49, STR 50 y STR3ïDYS) del gen de la distrofina por reacción en cadena de la polimerasa y se analizaron loa alelos polimórficos en los individuos estudiados. En 5/15 (33 por ciento) familias demostró la deleción de uno o varios exones. De las 68 mujeres, 27 (39,7 por ciento) resultaron portadoras, 27 (39,7 por ciento) no portadoras y en 14 (20,58 por ciento) no se pudo establecer un diagnóstico definitivo. En conclusión esta investigación pudo establecer el diagnóstico en 79,4 por ciento de las mujeres. Además en una familia se demostró que la mutación original ocurrió con el cromosoma X del abuelo materno, en otra se hizo el diagnóstico directo de portadora por hemicigosidad para el alelo mutado y en otra fue posible el diagnóstico prenatal. No se pudo excluir el mosaicismo germinal en 3 casos

[Carrier detection of Duchenne/Becker muscular dystrophy by analysis of STRs loci linked to the gene of dystrophin in Venezuelan families]. / Detección de portadoras de distrofia muscular Duchenne/Becker a través del análisis de loci STRs ligados al gen de la distrofina en familias venezolanas.

The Duchenne/Becker Muscular Dystrophy (DMD/BMD) is an X linked recessive lethal disease. The female carrier will transmit the disease gene to half of her sons and half of her daughters; half of the daughters will be carriers, while half will be normal. Half of the sons will be normal and, on average, half will have the disease. It is of particular relevance to be able to detect carrier status among female relatives of the patients for genetic counseling and prenatal diagnosis. The method of Short Tandem Repeat (STR) sequence polymorphism analysis can determine haplotype at normal status or at risk status and, to establish genetic linkage between the mutated gene and the segregated haplotype. We have analyzed 105 members from 15 unrelated Venezuelan families with one or more siblings affected with DMD/DMB and 7 unrelated males. Of the 105, 37 were male (26 affected and 11 normal) and 68 were female. STR sequences (STR44, STR45, STR49, STR50, STR3'DYS) of the gene of the Dystrophin were amplified by polymerase chain reaction (PCR) to analyze allelic polymorphism in the families. Five of the 15 families (33%) had a deletion of one or several of the exons. Of the 68 females, 27 (39.7%) were carriers, 27 (39.7%) were non-carriers and in 14 cases (20.58%) it was not possible to reach a definitive diagnosis. The definitive diagnosis could be established in 79% of the females. This analysis also shows that the mutation occurred on the grandpaternal X chromosome in one family. Hemizygocity was detected and carrier status ascertained in the mother of other patient and in one family we were able to do prenatal diagnosis. The germinal mosaicism could not be excluded in 3 patients.