Distribution of the CAG Triplet Repeat in ATXN1, ATXN3, and CACNA1A Loci in Peruvian Population.

Spinocerebellar ataxia subtypes 1, 3, and 6 (SCA1, MJD/SCA3, and SCA6) are among the most prevalent autosomal dominant cerebellar ataxias worldwide, but their relative frequencies in Peru are low. Frequency of large normal (LN) alleles at spinocerebellar ataxia-causative genes has been proposed to be associated with disease prevalence. To investigate the allelic distribution of the CAG repeat in ATXN1, ATXN3, and CACNA1A genes in a Peruvian mestizo population and examine their association with the relative frequency of SCA1, MJD/SCA3, and SCA6 across populations. We genotyped 213 healthy mestizo individuals from Northern Lima, Peru, for ATXN1, ATXN3, and CACNA1A using polymerase chain reaction (PCR) and polyacrylamide gel electrophoresis (PAGE). We compared the frequency of LN alleles and relative disease frequency between populations. We also tested 40 samples for CAT repeat interruptions within the CAG tract of ATXN1. We found no association between disease frequency and population frequency of LN alleles at ATXN1 and ATXN3. All 40 ATXN1 samples tested for CAT interruptions were positive. Frequency of LN alleles at CACNA1A correlates with SCA6 frequency across several populations, but this effect was largely driven by data from a single population. Low frequency of SCA1 and MJD/SCA3 in Peru is not explained by frequency of LN alleles at ATXN1 and ATXN3, respectively. The observed correlation between CACNA1A LN alleles and SCA6 frequency requires further assessment.

Correction to: Genetic Analysis of Hereditary Ataxias in Peru Identifies SCA10 Families with Incomplete Penetrance.

The original version of this article unfortunately contained some mistakes in Table 2. The additional row (just above SCA2) with the following information "SCA1, 1(1), 1, 50, 74, 24, 46 and 0/1" should be inserted.

Genetic Analysis of Hereditary Ataxias in Peru Identifies SCA10 Families with Incomplete Penetrance.

Relative frequency of hereditary ataxias remains unknown in many regions of Latin America. We described the relative frequency in spinocerebellar ataxias (SCA) due to (CAG)n and to (ATTCT)n expansions, as well as Friedreich ataxia (FRDA), among cases series of ataxic individuals from Peru. Among ataxic index cases from 104 families (38 of them with and 66 without autosomal dominant pattern of inheritance), we identified 22 SCA10, 8 SCA2, 3 SCA6, 2 SCA3, 2 SCA7, 1 SCA1, and 9 FRDA cases (or families). SCA10 was by far the most frequent one. Findings in SCA10 and FRDA families were of note. Affected genitors were not detected in 7 out of 22 SCA10 nuclear families; then overall maximal penetrance of SCA10 was estimated as 85%; in multiplex families, penetrance was 94%. Two out of nine FRDA cases carried only one allele with a GAA expansion. SCA10 was the most frequent hereditary ataxia in Peru. Our data suggested that ATTCT expansions at ATXN10 might not be fully penetrant and/or instability between generations might frequently cross the limits between non-penetrant and penetrant lengths. A unique distribution of inherited ataxias in Peru requires specific screening panels, considering SCA10 as first line of local diagnosis guidelines.

MLPA followed by target-NGS to detect mutations in the dystrophin gene of Peruvian patients suspected of DMD/DMB.

BACKGROUND: We report the molecular analysis of the DMD gene in a group of Peruvian patients with Duchenne/Becker dystrophinopathy. This is the first study to thoroughly characterize mutations in this population. METHODS: We used the combination of multiplex ligation-dependent probe amplification (MLPA) and sequencing analysis of the DMD gene. We recruited Peruvian patients in 2 years from reference national hospitals. We performed DNA tests in 152 patients, checking first exon deletion/duplication by MLPA, and subsequently, if negative, samples were sequenced to detect point mutations. RESULTS: The average age for diagnosis was 9.8 years, suggesting a delay for timely diagnosis and care. We found causal DMD mutations in 125 patients: 72 (57.6%) exon deletions/duplications (41.6% deletions, 16.0% duplications), and 53 (42.4%) point mutations (27.2% nonsense, 9.6% small indels, and 5.6% splice site). CONCLUSION: Due to our genetic background, we expected a higher number of novel and recurrent causal mutations in our sample. Results showed 16% of novel mutations, similar to other well-studied populations.

Genetic counseling to a DMD asymptomatic carrier: First case report in the Peruvian public healthcare system / Asesoramiento genético a una portadora asintomática de DMD: Primer caso reportado en el Sistema de Salud Pública del Perú

SUMMARY Duchenne muscular dystrophy (DMD) is a rapidly progressive dystrophinopathy with X-linked inheritance. This report describes a woman with a family history of male relatives affected by DMD, as she sought out genetic counseling about her concerns related to family planning and risks of eventually having children with the disease. We proposed her to get involved in a pilot program for carrier-status diagnosis and genetic counseling. This case illustrates the importance of a genetic counseling program for diagnosis of asymptomatic carriers in neurogenetic diseases, particularly in regions with low-resource settings. We discussed successes and misunderstandings faced throughout the process, supporting policies for present and future challenges from this and similar kinds of diagnoses.

RESUMEN La distrofia muscular de Duchenne (DMD) es una distrofinopatía rápidamente progresiva con herencia ligada al cromosoma X. Este reporte describe el caso de una mujer con historia familiar de hermano y sobrinos con DMD, que acudió a consulta para orientación e información sobre riesgos inherentes a una eventual planificación familiar. Le propusimos participar en un programa piloto de asesoramiento genético para determinar su estado de portador o no de la variante causal de DMD en la familia. Esta primera experiencia ilustra la importancia de tener un programa de asesoramiento genético para el diagnóstico de portadores asintomáticos de enfermedades neurogenéticas en regiones con bajos recursos. Se incluyen reflexiones y comentarios sobre aspectos positivos y retos presentados durante el proceso, las políticas de apoyo presente y futuro para el afronte de los complejos problemas planteados por éste y similares diagnósticos.

Neurogenetics in Peru: clinical, scientific and ethical perspectives.

Neurogenetics, the science that studies the genetic basis of the development and function of the nervous system, is a discipline of recent development in Peru, an emerging Latin American country. Herein, we review the clinical, scientific and ethical aspects regarding the development of this discipline, starting with the first molecular diagnosis of neurogenetic diseases, to family and population-based genetic association studies. Neurogenetics in Peru aims to better explain the epidemiology of monogenic and complex neurodegenerative disorders that will help in implementing public health policies for these disorders. The characterization of Peru and its health system, legal issues regarding rare diseases and the historical milestones in neurogenetics are also discussed.

Clinical and Molecular Features of Late Onset Huntington Disease in a Peruvian Cohort.

BACKGROUND: Late onset cases of Huntington disease (HD), with onset ≥60 years, account for up to 20% of HD cases worldwide. Clinical features include mild motor dysfunction with slow progression and cognitive impairment, frequent absence of family history and low number of CAG repeats. The clinical and molecular features of late onset HD is still understudied in Latin America. OBJECTIVES: To describe the clinical and molecular characteristics of late onset HD in a Peruvian cohort. METHODS: An observational study was carried out by reviewing the HD registry at the Neurogenetics Research Center-INCN from 2000 to 2014. Genotyping of HTT gene …was confirmed using standard PCR and PAGE in accordance to protocols previously established. RESULTS: Thirty-one late onset HD cases from 27 pedigrees were identified (9.42% of total HD cases, n = 329), 51.61% were male. Mean age at onset was 64.1 ± 4.2 and CAG repeats mean was 42.5 ± 2.5. We did not find significant correlation between age at onset and CAG repeats. 33.3% of cases were traced back to Cañete valley. Twenty-two cases had a positive family history, 14 of them with paternal transmission. Choreic movements and cognitive impairment were the main existing manifestations reported in this cohort, with lower frequency of psychiatric disturbances. CONCLUSIONS: This report of late onset HD affected individuals shows a mild phenotype expression of the disease, associated with low range of CAG repeats and up to 30% of cases with absence of clear family history. Cañete valley remains the region with more cases.

[Kennedy disease in Peru: first cases with molecular diagnosis]. / Enfermedad de Kennedy en el Perú: primeros casos con diagnóstico molecular.

Kennedy's disease is an X-linked recessive disorder with onset in adulthood, characterized by progressive degeneration of spinal motor neurons due to a dynamic mutation in the androgen receptor gene. We report three families (five cases) characterized by progressive weakness involving both limbs and bulbar muscles, atrophy, tremor, cramps and endocrinologic disturbances; the neurophysiological studies demonstrated second motor neuron impairment. The molecular analysis identified abnormal CAG repeats expansion in the androgen receptor gene (AR) in all cases. Clinical features were consistent with other previous reports. These are the first Peruvian cases of Kennedy's disease with confirmed molecular diagnosis.

Ausencia de la mutación A53T del gen SNCA en una muestra de pacientes con Enfermedad de Parkinson en el Perú / A53T-SNCA absence in a Peruvian sample of Parkinson's disease patients

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.

Introduction. Parkinson's Disease (PD) is a common neurodegenerative disorder, the second most frequent after Alzheimer's Disease. The A53T mutation in the SNCA gene was the first one identified in association with PD. Most of familial PD cases with this mutation come from regions close to the original discovery site. Objectives: To evaluate the presence of the A53T-SNCA mutation in a Peruvian sample of Parkinson´s Disease cases familial, sporadic and healthy controls. Material and Methods: DNA samples from 34 cases with sporadic PD, 7 cases of familial PD, and 32 control individuals were analyzed by PCR-RFLP. Results: The A53T mutation was not found. This mutation would be confined to a few families of European or Caucasian origin linked to the cases originally described. Conclusions: The A53T mutation would not be the primary causal factor of PD in the evaluated cases

[Genetic polymorphism of apolipoprotein E in a Peruvian population]. / Polimorfismo genético de la Apolipoproteína E en una población peruana.

OBJECTIVES: To determine the allelic and genotypic frequencies of the APOE gene in a sample of a population group in Peru. MATERIALS AND METHODS: Cross-sectional analytic study in 189 apparently healthy volunteers, workers of the Instituto Nacional de Ciencias Neurológicas in Lima, Perú, divided into 5 groups by birth department and two generations ancestry. Genomic DNA was amplified using PCR-RFLP. The resulting fragments were detected by 12 % polyacrylamide gel electrophoresis. RESULTS: The ε3 allele is the most frequent in all the groups (93.9 %), with low ε4 (5 %) and ε2 (1.1 %) allele frequencies. The analysis of heterozygosity (H) for each group displays intermediate diversity between 10 and 20%. Population genetic diversity (Ht) and diversity within populations (Hs) are 14.43 % and 14.31% respectively, suggesting genetic proximity between the studied groups for the ApoE polymorphism. CONCLUSIONS: Allele frequencies of the ApoE gene found show that allele ε3 has one of the highest frequencies and ε4 allele one of the lowest compared to other population groups in the world, with possible implications in the risk of neurological, cardiovascular and other diseases in our country.

Lrrk2 p.Q1111H substitution and Parkinson's disease in Latin America.

Mutations in the LRRK2 gene are the most common genetic cause of Parkinson's disease, with frequencies displaying a high degree of population-specificity. Although more than 100 coding substitutions have been identified, only seven have been proven to be highly penetrant pathogenic mutations. Studies however are lacking in non-white populations. Recently, Lrrk2 p.Q1111H (rs78365431) was identified in two affected Hispanic brothers and absent in 386 non-Hispanic white healthy controls. We therefore screened this variant in 1460 individuals (1150 PD patients and 310 healthy controls) from 4 Latin American countries (Peru, Chile, Uruguay and Argentina). In our case-control series from Peru and Chile we observed an increased frequency of Lrrk2 p.Q1111H in patients (7.9%) compared to controls (5.4%) although the difference did not reach significance (OR 1.38; p = 0.10). In addition, the frequency of Lrrk2 p.Q1111H varied greatly between populations and further screening in a set of pure Amerindian and pure Spanish controls suggested that this variant likely originated in an Amerindian population. Further studies in other Latin American populations are warranted to assess its role as a risk factor for Parkinson's disease. Screening in Parkinson's disease patients from under-represented populations will increase our understanding of the role of LRRK2 variants in disease risk worldwide.

LRRK2 mutations in patients with Parkinson's disease from Peru and Uruguay.

Variation in the leucine-rich repeat kinase 2 (LRRK2) gene represents the most common genetic determinant of Parkinson's disease (PD) identified to date. While the frequency and distribution of LRRK2 mutations have been well-studied in Europe and North America, few data are available from South America. To address this gap in knowledge, we screened two cohorts of patients with PD from Peru (n=240) and Uruguay (n=125) for the three most common LRRK2 mutations (R1441C, R1441G, G2019S). We identified at total of seven patients with mutations, one with R1441G, and six with G2019S. The carrier frequency was significantly greater in the Uruguayan cohort (4.8%) than in the Peruvian cohort (0.4%; p=0.007). This likely resulted from a greater admixture proportion in the Peruvian sample. Haplotype analyses suggested that G2019S was probably brought to Peru and Uruguay by European settlers. In contrast, the origin of R1441G in our cohort was not clear, as the patient with this mutation had a background haplotype that was clearly distinct from that reported in carriers from Europe and North America. Our data add to a growing body of evidence indicating that LRRK2 mutations are widely distributed across South America but might differ by region in prevalence.

Estrategia de genotipado del gen FMR1: Método de diagnóstico alternativo para el Síndrome X Frágil y otras enfermedades por expansión de trinucleotidos / Genotyping strategy for the FMR1 gene: An alternative diagnostic method for the Fragile X syndrome and other trinucleotide expansion diseases

Objetivos: Diseñar una estrategia alternativa por PCR para el genotipado de secuencias ricas en citosinas, basada en modificación nucleotídica. Material y métodos: Se modificó el gen FMR1 nativo de ocho individuos clínicamente no afectados por el Síndrome X frágil, cambiando las citosinas por uracilos, empleando bisulfito de sodio. El ADN modificado fue purificado y cuantificado por espectrofotometría. Las estructuras alternativas y potenciales islas CpG que adopta el microsatélite inestable fueron simuladas con los programas MFOLD y CpGplot. Se generaron cebadores específicos que hibriden tanto con el microsatélite modificado (Primer T) y con una secuencia modificada de las islas CpG (Primer M), utilizando el programa MethPrimer. Finalmente, ambas secuencias fueron amplificadas por PCR y los amplicones fueron separados por electroforesis en gel de poliacrilamida (PAGE por sus siglas en inglés) al 6% y visualizados con tinción de nitrato de plata. Resultados: La modificación del ADN fue evidenciada por espectrofotometría al uracilo. Las estructuras observadas en la simulación fueron las horquillas encontrándose dos potenciales islas CpG. La amplificación con los cebadores T, confirmó el diseño in silico desarrollado para abordar la estructura en horquillas. La amplificación con los cebadores M permitió detectar metilación de la primera isla CpG del gen FMR1.Conclusión: Se propone un diseño alternativo para amplificación de secuencias de microsatélite que contengan citosinas metiladas y no metiladas. Se requieren estudios posteriores con muestras de ADN que contengan microsatélites muy expandidos para validar su aplicación para diagnóstico molecular. (AU)

Objectives: To design an alternative strategy for genotyping cytosine-rich sequences using PCR and nucleotide modification. Methods: The FMR1 gene wild type was modified in the DNA obtained from eight individuals clinically unaffected for Fragile X Syndrome; cytosines were replaced by uracils using sodium bisulfite. Modified DNA was purified and quantified by spectrophotometry. Alternative structures and potential CpG islands of the unstable microsatellite were simulated using MFOLD and CpGplot tools. Specific primers were generated to hybridize with both the modified microsatellite (Primer G) and a modified sequence of CpG islands (Primer M) using the MethPrimer software. Finally, both sequences were amplified by PCR and the amplicons were separated by electrophoresis in silver-stained PAGE 6% gels. Results: The DNA modification was evidenced by spectrophotometry to uracil. We found two potential CpG islands. The amplification with T primers confirmed the "in silico" design developed to engage hairpin structures. The amplification with M primers detected methylation of the first CpG island in the FMR1 gene. Conclusion: We propose an alternative design for amplifying microsatellite sequences that contain methylated and unmethylated cytosine bases. Further studies are required with DNA samples containing expanded microsatellites to validate its molecular diagnostic application. (AU)

Asociación entre el polimorfismo genético de la apolipoproteína E (ApoE) y la enfermedad de Parkinson / Association between apolipoprotein E (ApoE) genetic polymorphism and Parkinson’s disease

Introducción: En nuestro país, con el incremento en la esperanza de vida, existe una tendencia creciente de enfermedades neurodegenerativas, por lo que se hace necesario realizar estudios sobre factores de riesgo genético en personas afectadas con la enfermedad de Parkinson (EP), entre ellos el gen de la apolipoproteína E (ApoE), ya que esta asociación es desconocida en nuestra población. Objetivo: Determinar la asociación del polimorfismo en el gen ApoE con la EP. Diseño: Estudio asociativo, observacional tipo casos y controles. Lugar: Instituto Nacional de Ciencias Neurológicas, Lima, Perú. Participantes: Personas de ambos sexos, 163 pacientes con la EP y 176 controles. Intervenciones: Extracción de ADN genómico según metodología estándar. Análisis del gen APOE mediante técnica PCR-RFLP. Principales medidas de resultados: Frecuencias genotípicas y alélicas del gen ApoE en los casos y controles, medidas de asociación y de riesgo. Resultados: No se encontró diferencias significativas entre el grupo control y los pacientes según genotipo de ApoE. La frecuencia del alelo ε4 fue similar en pacientes y en controles. El odds ratio para el alelo ε4 de la ApoE fue 1,0852 (IC 95%: 0,5812 a 2,0266). La edad de inicio de la EP no tuvo relaciσn con los genotipos ApoE. Conclusiones: El alelo ε4 de la ApoE no podrνa ser considerado un factor de riesgo para la EP, y los genotipos de la ApoE no se asociaron con la edad de inicio en esta muestra evaluada.

Introduction: Due to the increase in life expectancy in our country, it is necessary to study risk factors for Parkinson’s disease (PD), including apolipoprotein E (ApoE) gene, as this association is not known in our country. Objectives: To determine association of ApoE gene polymorphism and PD. Design: Associative, observational case-control analytic study. Setting: Instituto Nacional de Ciencias Neurologicas, Lima, Peru. Participants: Male and females with and without Parkinson's disease. Interventions: Genomic DNA was extracted from 163 patients and 176 controls. PCR_RFLP technique was used for ApoE gene genotyping. Main outcome measures: ApoE gene genotype and allele frequencies in cases and controls, association and risk. Results: No significant ApoE genotype differences between the control group and patients were found. Allele ε4 frequency was similar in patients and controls: 6.5 and 6.0. Odds ratio for ApoE ε4 allele associated with PD was 1.2163 (IC 95%, 0.6574-2.2507). Conclusions: ApoE ε4 allele could not be considered a risk factor for PD in the population studied.

Enfermedad de Kennedy en el Perú: Primeros casos con diagnóstico molecular / Kennedy disease in Peru: First cases with molecular diagnosis

La enfermedad de Kennedy es un trastorno neurodegenerativo de herencia recesiva ligada al cromosoma X, de inicio en la adultez, caracterizado por degeneración progresiva de las neuronas motoras espinales, debido a una mutación dinámica del gen del receptor de andrógeno. Se presentan tres familias (cinco casos) con temblor, calambres, debilidad muscular generalizada lentamente progresiva con atrofia, afectación de músculos bulbares y alteraciones endocrinas. El estudio neurofisiológico demostró compromiso de segunda motoneurona. El análisis molecular mostró una expansión anormal de tripletes citosina-adenina-guanina en el gen de receptor de andrógeno en todos los casos. Todos los pacientes cursaron con una presentación clínica típica de la enfermedad siendo los primeros casos de enfermedad de Kennedy con diagnóstico molecular realizado en el Perú.

Kennedy’s disease is an X-linked recessive disorder with onset in adulthood, characterized by progressive degeneration of spinal motor neurons due to a dynamic mutation in the androgen receptor gene. We report three families (five cases) characterized by progressive weakness involving both limbs and bulbar muscles, atrophy, tremor, cramps and endocrinologic disturbances; the neurophysiological studies demonstrated second motor neuron impairment. The molecular analysis identified abnormal CAG repeats expansion in the androgen receptor gene (AR) in all cases. Clinical features were consistent with other previous reports. These are the first Peruvian cases of Kennedy´s disease with confirmed molecular diagnosis.

Polimorfismo genético de la Apolipoproteína E en una población peruana / Genetic polymorphism of Apolipoprotein E in a peruvian population

Objetivos. Determinar las frecuencias genotípicas y alélicas del gen APOE en una muestra poblacional peruana. Materiales y métodos. Estudio transversal analítico en 189 trabajadores voluntarios, aparentemente sanos, del Instituto Nacional de Ciencias Neurológicas en Lima, Perú, divididos en cinco grupos según departamento de origen y ascendencia en dos generaciones. El ADN genómico fue amplificado mediante PCR-RFLP. Se realizó la detección de los fragmentos resultantes por electroforesis en gel de poliacrilamida al 12 por ciento. Resultados. El alelo ε3 es el más frecuente en todos los grupos (93,9 por ciento), con bajas frecuencias de los alelos ε4 (5 por ciento) y ε2 (1,1 por ciento). El anαlisis de heterocigosidad (H) en cada grupo muestra una diversidad intermedia entre 10 y 20 por ciento. Las diversidades genιticas poblacional (Ht) e intrapoblacional (Hs), son 14,4 y 14,3 por ciento respectivamente, sugiriendo proximidad genética entre los grupos estudiados para el polimorfismo ApoE. Conclusiones. Las frecuencias alélicas del gen ApoE encontradas muestra que el alelo ε3 tiene una de las frecuencias más altas y, el alelo ε4, una de las más bajas respecto a otros grupos poblacionales del mundo, con posibles implicancias en el riesgo para enfermedades neurológicas, cardiovasculares y otras en nuestro país.

Objectives. To determine the allelic and genotypic frequencies of the APOE gene in a sample of a population group in Peru. Materials and methods. Cross-sectional analytic study in 189 apparently healthy volunteers, workers of the Instituto Nacional de Ciencias Neurológicas in Lima, Perú, divided into 5 groups by birth department and two generations ancestry. Genomic DNA was amplified using PCR-RFLP. The resulting fragments were detected by 12 percent polyacrylamide gel electrophoresis. Results. The ε3 allele is the most frequent in all the groups (93.9 percent), with low ε4 (5 percent) and ε2 (1.1 percent) allele frequencies. The analysis of heterozygosity (H) for each group displays intermediate diversity between 10 and 20 percent. Population genetic diversity (Ht) and diversity within populations (Hs) are 14.43 percent and 14.31 percent respectively, suggesting genetic proximity between the studied groups for the ApoE polymorphism. Conclusions. Allele frequencies of the ApoE gene found show that allele ε3 has one of the highest frequencies and ε4 allele one of the lowest compared to other population groups in the world, with possible implications in the risk of neurological, cardiovascular and other diseases in our country.