Genetic variants in Colombian patients with inherited cardiac conditions.

BACKGROUND: Clinical and molecular diagnosis of inherited cardiac conditions is key to find at-risk subjects and avoid preventable deaths. This study aimed to identify genetic variants in a sample of Colombian patients diagnosed with inherited cardiac conditions. METHODS: Next-generation sequencing (Illumina platform) using a 231 gene panel was performed in blood samples of 25 unrelated patients with age disease onset between 9 and 55 years. RESULTS: Genetic testing yield was 52%. Two novel likely pathogenic/ pathogenic variants were found: a DSP nonsense variant in a patient with arrhythmogenic cardiomyopathy and a KCNE1 frameshift variant in two patients with long QT syndrome. Younger individuals (<18 years) had the highest genetic testing yield (66.6%) compared to 50% and 20% in young adults and patients over 40 years, respectively. All subjects affected with long QT syndrome with a severe event while exercising had a positive genetic test. They also had four times more loss of consciousness events and, resuscitated sudden cardiac arrest was more representative. CONCLUSION: This study is the first one undertaken in Colombia to evaluate inherited cardiac conditions. It highlights the need to perform mutational analysis to provide adequate genetic counseling and to be able to identify patients at risk of severe events.

Philadelphia-like acute lymphoblastic leukemia: Characterization in a pediatric cohort in a referral center in Colombia.

BACKGROUND: Philadelphia-like (Ph-like) acute lymphoblastic leukemia (ALL) is a subtype of pediatric leukemia with high risk factors and poor outcome. There are few reports of its prevalence in Latin America. AIM: This study evaluated the frequency and clinical and biological characteristics of Ph-like ALL in a pediatric cancer center in Colombia. METHODS: The Ph-like genetic profile was analyzed by a low-density array (LDA). Samples from patients with Ph-like ALL were analyzed by fluorescent in situ hybridization for cytokine receptor like factor 2 (CRLF2) and ABL proto-oncogene 1, non-receptor tyrosine kinase (ABL1) rearrangements. Copy number variations were assessed by multiplex ligation probe amplification. RESULTS: Data from 121 patients were analyzed. Fifteen patients (12.4%) had Ph-like ALL, and these patients had significantly higher leukocyte counts at diagnosis and higher levels of minimal residual disease on days 15 and 33 of induction than patients without the Ph-like subtype. There were no significant differences in sex, age, or response to prednisone at day 8 between the two groups. CRLF2 rearrangements were identified in eight patients, and ABL1 rearrangements were identified in two patients. Other genetic alterations alone or in combination were identified in 77% of patients, including deletions in cyclin dependent kinase inhibitor 2 A/B (46.2%), IKAROS family zinc finger 1 (38.3%), and paired box 5 (30.8%). CONCLUSIONS: Ph-like ALL had a 12.4% prevalence in our cohort of patients with pediatric ALL. The identification of this group of patients has importance for risk stratification and future targeted therapy.

Susceptibility to thiopurine toxicity by TPMT and NUDT15 variants in Colombian children with acute lymphoblastic leukemia / Asociación de variantes genéticas en TPMT y NUDT15 con los eventos de toxicidad durante la terapia de mantenimiento en niños colombianos con Leucemia Linfoide Aguda

Abstract Objective: This study aimed to correlate the genetic profile of the NUDT15 and TPMT genes with the side effects of the treatment of pediatric patients with acute lymphoid leukemia who were undergoing maintenance therapy at a tertiary care hospital in 2017. Methods: This was an analytical, longitudinal, observational study in which the genotypes of the genes of interest were determined by PCR allelic discrimination with TaqMan® probes in patients receiving chemotherapy during the maintenance phase in the Pediatric Hematology and Oncology Unit in 2017. Sociodemographic and clinical data corresponding to the first six months of their maintenance chemotherapy were collected, and the correlation between the genotypes obtained and the development of side effects during the maintenance phase of chemotherapy in these patients was evaluated. Results: Seventy pediatric patients were included in the study. Genetic analyses were carried out of these for NUDT15 and TPMT (rs1800462 and rs1800460) on 68 patients, while for the rs1142345 polymorphism, typing was achieved in 42 patients. 4/68 patients were heterozygous for NUDT15, and the same number of patients were heterozygous for rs1800462 and rs1142345, while for rs1800460, 6 heterozygous patients were identified. No statistically significant association was identified between the genetic variants and the outcomes of interest. Conclusion: Studies with a larger population size are needed and the evaluation of other genetic variants that may influence the development of side effects during maintenance chemotherapy.

Resumen Objetivo: la finalidad de este estudio fue evaluar las asociaciones entre los perfiles de los genes NUDT15 y TPMT con los efectos adversos del tratamiento de mantenimiento en pacientes pediátricos con Leucemia Linfoblástica Aguda atendidos en un hospital de referencia durante el 2017. Métodos: Este fue un estudio observacional analítico, de corte longitudinal en el que los genotipos de los genes de interés fueron determinados mediante PCR de discriminación alélica con sondas TaqMan® en pacientes que estaban recibiendo quimioterapia de mantenimiento en la Unidad de Oncohematología Pediátrica durante el 2017. Los datos clínicos y sociodemográficos correspondientes a los primeros 6 meses de sus tratamientos de mantenimiento fueron colectados, y se evaluó la correlación entre los genotipos identificados y el desarrollo de efectos secundarios en estos pacientes. Resultados: setenta pacientes fueron incluidos en el estudio, de estos, los análisis genéticos para NUDT15 y TPMT (rs1800462 and rs1800460) fueron realizados en 68 pacientes, en tanto que para el polimorfismo rs1142345 se logró la tipificación en 42 pacientes. 4/68 pacientes fueron heterocigotos para NUDT15 y el mismo número de pacientes fueron heterocigotos para rs1800462 and rs1142345, mientras que para rs1800460, 6 pacientes heterocigotos fueron identificados. No se identificaron asociaciones estadísticamente significantes entre las variants genéticas y los resultados clínicos de interés. Conclusiones: Estos hallazgos resaltan la importancia de realizar estudios de este tipo con un mayor número de sujetos de estudio, así como plantean la necesidad de evaluar otras variantes genéticas que podrían tener algún impacto en el desarrollo de efectos secundarios durante la quimioterapia de mantenimiento.

Susceptibility to thiopurine toxicity by TPMT and NUDT15 variants in Colombian children with acute lymphoblastic leukemia.

Objective: This study aimed to correlate the genetic profile of the NUDT15 and TPMT genes with the side effects of the treatment of pediatric patients with acute lymphoid leukemia who were undergoing maintenance therapy at a tertiary care hospital in 2017. Methods: This was an analytical, longitudinal, observational study in which the genotypes of the genes of interest were determined by PCR allelic discrimination with TaqMan® probes in patients receiving chemotherapy during the maintenance phase in the Pediatric Hematology and Oncology Unit in 2017. Sociodemographic and clinical data corresponding to the first six months of their maintenance chemotherapy were collected, and the correlation between the genotypes obtained and the development of side effects during the maintenance phase of chemotherapy in these patients was evaluated. Results: Seventy pediatric patients were included in the study. Genetic analyses were carried out of these for NUDT15 and TPMT (rs1800462 and rs1800460) on 68 patients, while for the rs1142345 polymorphism, typing was achieved in 42 patients. 4/68 patients were heterozygous for NUDT15, and the same number of patients were heterozygous for rs1800462 and rs1142345, while for rs1800460, 6 heterozygous patients were identified. No statistically significant association was identified between the genetic variants and the outcomes of interest. Conclusion: Studies with a larger population size are needed and the evaluation of other genetic variants that may influence the development of side effects during maintenance chemotherapy.

Objetivo: la finalidad de este estudio fue evaluar las asociaciones entre los perfiles de los genes NUDT15 y TPMT con los efectos adversos del tratamiento de mantenimiento en pacientes pediátricos con Leucemia Linfoblástica Aguda atendidos en un hospital de referencia durante el 2017. Métodos: Este fue un estudio observacional analítico, de corte longitudinal en el que los genotipos de los genes de interés fueron determinados mediante PCR de discriminación alélica con sondas TaqMan® en pacientes que estaban recibiendo quimioterapia de mantenimiento en la Unidad de Oncohematología Pediátrica durante el 2017. Los datos clínicos y sociodemográficos correspondientes a los primeros 6 meses de sus tratamientos de mantenimiento fueron colectados, y se evaluó la correlación entre los genotipos identificados y el desarrollo de efectos secundarios en estos pacientes. Resultados: setenta pacientes fueron incluidos en el estudio, de estos, los análisis genéticos para NUDT15 y TPMT (rs1800462 and rs1800460) fueron realizados en 68 pacientes, en tanto que para el polimorfismo rs1142345 se logró la tipificación en 42 pacientes. 4/68 pacientes fueron heterocigotos para NUDT15 y el mismo número de pacientes fueron heterocigotos para rs1800462 and rs1142345, mientras que para rs1800460, 6 pacientes heterocigotos fueron identificados. No se identificaron asociaciones estadísticamente significantes entre las variants genéticas y los resultados clínicos de interés. Conclusiones: Estos hallazgos resaltan la importancia de realizar estudios de este tipo con un mayor número de sujetos de estudio, así como plantean la necesidad de evaluar otras variantes genéticas que podrían tener algún impacto en el desarrollo de efectos secundarios durante la quimioterapia de mantenimiento.

[Brain-lung-thyroid syndrome in a newborn with deletion 14q12-q21.1]. / Síndrome cerebro-pulmón-tiroides en un recién nacido con deleción 14q12-q21.1.

INTRODUCTION: In newborns with respiratory failure and interstitial lung disease, it should be approached as chILD (Childhood Interstitial Lung Disease) syndrome to rule out alterations in surfactant metabolism and brain-lung-thyroid syndrome caused by pathogenic variants in the NKX2-1 gene. OBJECTIVE: To pre sent a newborn with chILD syndrome and a large deletion in chromosome 14q12-q21.1. CLINICAL CASE: Newborn patient with respiratory distress since birth, chILD syndrome, and hypothyroidism, in which brain-lung-thyroid syndrome was suspected. He also presented seizures, minor and ma jor abnormalities on physical examination. Microarray analysis revealed a 14.7 Mb deletion in the chromosome 14q12-q21.1, which includes the NKX2-1 gene. CONCLUSION: The brain-lung-thyroid syndrome should be considered in newborns with respiratory distress syndrome and diffuse lung disease (chILD syndrome), especially if they present hypotonia, choreoathetosis, or hypothyroidism. Diagnosis confirmation requires genetic analysis, even more, when there are other abnormalities not explained by the suspected syndrome.

The impact of smoking on disease activity, disability, and radiographic damage in rheumatoid arthritis: is cigarette protective?

The ojective of this study is to assess the effect of tobacco smoking on disease activity, functional ability, and joint damage in a cohort of patients with early onset rheumatoid arthritis (EORA). 129 EORA patients attending the Rheumatology Unit of the School of Medicine of the "Universidad Nacional de Colombia" and the "Clínica de Artritis y Rehabilitación" in Bogota, Colombia, were enrolled in a prospective observational cohort study with 3-year follow-up. Clinical, biological, immunogenetics, and radiographic data were analyzed. Active disease was defined as DAS28 > 2.6. Smoking status was assessed by self-report as "never smokers" and "ever smokers". Patient groups with different smoking status were compared for RA measures. Status as "never smokers" and "ever smokers" was reported by 81.3 and 18.7%. Ever smokers had less risk of disability (HAQ-DI ≥ 0.5) at 36 month (Ever smokers vs. Never smokers OR for HAQ ≥ 0.5 0.25, 95% CI 0.06-0.97, p = 0.04). When former smokers were excluded in analysis, we found that current smoking was also associated with less disability and less risk of active disease. The percentage of erosive disease, radiographic progression, and SvdH score were similar in all smoking categories. In Colombian patients with EORA, smoking was associated with less disease activity and disability. Radiographic joint damage progressed at an equivalent rate in smokers and non-smokers. These data suggest a more benign, or at least not deleterious clinical course in smokers with RA.

The Role of 25-Hydroxyvitamin D as a Predictor of Clinical and Radiological Outcomes in Early Onset Rheumatoid Arthritis.

OBJECTIVE: The aims of this study were to compare the levels of 25-hydroxyvitamin D (25(OH)D) in patients with early-onset rheumatoid arthritis (EORA) versus a healthy control group and to assess the association of 25(OH)D deficiency and the BsmI polymorphism of the vitamin D receptor gene with clinical, radiological, and laboratory parameters. METHODS: Early-onset RA Colombian patients were enrolled in a 3-year follow-up study. Vitamin D deficiency was diagnosed for 25(OH)D levels of less than 20 ng/mL. Pearson and Spearman correlation coefficients were used to assess data. RESULTS: Seventy patients and 70 matched healthy subjects were included. 25-Hydroxyvitamin D was lower in the EORA group (27.13 [SD, 13.4] ng/mL vs. 33.74 [SD, 16.7] ng/mL; P = 0.01); 31.4% of EORA patients were vitamin D deficient. Remission was higher in subjects without 25(OH)D deficiency (22.7% vs. 47.9%; P = 0.04). Patients with 25(OH)D deficiency at baseline had higher Health Assessment Questionnaire and Physician Global Disease Activity Assessment scores, fatigue levels, erythrocyte sedimentation rate, and morning stiffness after 3 years. At disease onset, only a relationship between 25(OH)D deficiency with fatigue and morning stiffness was found. Neither radiographic progression nor Sharp van der-Heidje score was associated to hypovitaminosis D after 36-month follow-up. The bb genotype was less frequent in patients with vitamin D deficiency (0% vs. 16.6%; P = 0.04). Patients with BB-Bb genotype had lower 25(OH)D and a propensity to more severe disease. CONCLUSIONS: Our data provide further support for a role of vitamin D as a clinical biomarker for RA. Baseline 25(OH)D could have potential as a predictor of disease severity in EORA.

Analysis of the LRRK2 p.G2019S mutation in Colombian Parkinson's Disease Patients.

INTRODUCTION: Mutations in the leucine-rich repeat kinase 2 gene (LRRK2 or Dardarin) are considered to be a common cause of autosomal dominant and sporadic Parkinson´s disease, but the prevalence of these mutations varies among populations. OBJECTIVE: to analyzed the frequency of the LRRK2 p.G2019S mutation (c.6055 G>A transition) in a sample of Colombian patients. METHODS: In the present study we have analyzed the frequency of the LRRK2 p.G2019S mutation in 154 patients with familial or sporadic Parkinson Disease, including early and late onset patients, and 162 normal controls. RESULTS: Our results show occurrence of this mutation in two cases (2/154, 1.3%) with classical Parkinson´s signs, and one completely asymptomatic control (1/162, 0.6%). CONCLUSION: The p.G2019S mutation is not an important causal factor of Parkinson Disease in Colombia having similar frequencies to those reported in other Latin American populations.

INTRODUCCIÓN: Mutaciones en el LRRK2 (del inglés gen leucine-rich repeat kinase 2) o Dardarina se consideran una causa común de enfermedad de Parkinson autosómica dominante. Sin embargo, la prevalencia de estas mutaciones varia en diferentes poblaciones. OBJETIVO: analizar la frecuencia de la mutación p.G2019S (transición c.6055 G>A) del gen LRRK2en una muestra de pacientes colombianos. MÉTODOS: En el presente estudio analizamos la frecuencia de la mutación en 154 pacientes con enfermedad de Parkinson familiar o esporádica, y 162 controles normales. RESULTADOS: se determinó la presencia de la mutación en 2 casos de Parkinson (2/154, 1.3%) los cuales presentan los signos clásicos de la enfermedad y en un control completamente asintomático (1/162, 0.6%). CONCLUSIÓN: La mutación p.G2019S no es un factor causal importante de la Enfermedad de Parkinson en la población Colombiana, y muestra frecuencias similares a las reportadas en otras poblaciones latinoamericanas.

Analysis of the LRRK2 p.G2019S mutation in Colombian Parkinson's Disease Patients / Análisis de la mutación p.G2019S del gen LRRK2 en pacientes colombianos con enfermedad de Parkinson

Introduction: Mutations in the leucine-rich repeat kinase 2 gene (LRRK2 or Dardarin) are considered to be a common cause of autosomal dominant and sporadic Parkinson's disease, but the prevalence of these mutations varies among populations. Objective: To analyzed the frequency of the LRRK2 p.G2019S mutation (c.6055G>A transition) in a sample of Colombian patients. Methods: In the present study we have analyzed the frequency of the LRRK2 p.G2019S mutation in 154 patients with familial or sporadic Parkinson Disease, including early and late onset patients, and 162 normal controls. Results: Our results show occurrence of this mutation in two cases (2/154, 1.3%) with classical Parkinson's signs, and one completely asymptomatic control (1/162, 0.6%). Conclusion: The p.G2019S mutation is not an important causal factor of Parkinson Disease in Colombia having similar frequencies to those reported in other Latin American populations.

Introducción: Las mutaciones en el LRRK2 (del inglés gen leucinerich repeat kinase 2) o Dardarina se consideran una causa común de enfermedad de Parkinson autosómica dominante. Sin embargo, la prevalencia de estas mutaciones varia en diferentes poblaciones. Objetivo: Snalizar la frecuencia de la mutación p.G2019S (transición c.6055 G>A) del gen LRRK2en una muestra de pacientes colombianos. Métodos: En el presente estudio analizamos la frecuencia de la mutación en 154 pacientes con enfermedad de Parkinson familiar o esporádica, y 162 controles normales. Resultados: Se determinó la presencia de la mutación en 2 casos de Parkinson (2/154, 1.3%) los cuales presentan los signos clásicos de la enfermedad y en un control completamente asintomático (1/162, 0.6%). Conclusión: La mutación p.G2019S no es un factor causal importante de la Enfermedad de Parkinson en la población Colombiana, y muestra frecuencias similares a las reportadas en otras poblaciones latinoamericanas.

Identification of three new mutations in the RB1 gene in patients with sporadic retinoblastoma in Colombia.

INTRODUCTION: Retinoblastoma is a childhood cancer of the retina originated by altered or null retinoblastoma protein (pRb) expression. Genetic alterations in both RB1 alleles in the retinal cells are required for the development of retinoblastoma. In the sporadic form, non-hereditary RB1 gene mutations take place in a single retinoblast cell, and are therefore only present in tumor DNA (somatic mutations). Sporadic retinoblastoma is primarily unilateral, lacks family history and has no risk of transmission to descendants. Genetic tests for detection of RB1 mutation has improved the identification of carriers and facilitated accurate genetic counseling. OBJECTIVE: To identify mutations in the RB1 gene in Colombian patients with sporadic retinoblastoma by PCR-SSCP followed by sequence. MATERIALS AND METHODS: Four patients with sporadic retinoblastoma were analyzed by PCR-SSCP, followed by DNA sequencing to identify variations in the RB1 gene. RESULTS: We identified five variations in RB1 gene: three new mutations (one germline and two somatic mutations), one new polymorphism and one already reported somatic mutation. Four mutations were found in three patients with unilateral retinoblastoma and one mutation was found in a patient with bilateral retinoblastoma. One of these was a germline mutation in a sporadic unilateral retinoblastoma that was not present in the parents or three siblings analyzed. CONCLUSIONS: Our results emphasize the importance of identifying mutations for genetic counseling and clinical management of sporadic retinoblastoma patients. Description of a new RB1 gene variant is interesting since there have been a small number of polymorphisms reported for this gene.

Identification of three new mutations in the RB1 gene in patients with sporadic retinoblastoma in Colombia / Identificación de tres nuevas mutaciones en el gen RB1 en pacientes con retinoblastoma esporádico en Colombia

Introduction. Retinoblastoma is a childhood cancer of the retina originated by altered or null retinoblastoma protein (pRb) expression. Genetic alterations in both RB1 alleles in the retinal cells are required for the development of retinoblastoma. In the sporadic form, non-hereditary RB1 gene mutations take place in a single retinoblast cell, and are therefore only present in tumor DNA (somatic mutations). Sporadic retinoblastoma is primarily unilateral, lacks family history and has no risk of transmission to descendants. Genetic tests for detection of RB1 mutation has improved the identification of carriers and facilitated accurate genetic counseling. Objective. To identify mutations in the RB1 gene in Colombian patients with sporadic retinoblastoma by PCR-SSCP followed by sequence. Materials and methods. Four patients with sporadic retinoblastoma were analyzed by PCR-SSCP, followed by DNA sequencing to identify variations in the RB1 gene. Results. We identified five variations in RB1 gene: three new mutations (one germline and two somatic mutations), one new polymorphism and one already reported somatic mutation. Four mutations were found in three patients with unilateral retinoblastoma and one mutation was found in a patient with bilateral retinoblastoma. One of these was a germline mutation in a sporadic unilateral retinoblastoma that was not present in the parents or three siblings analyzed. Conclusions. Our results emphasize the importance of identifying mutations for genetic counseling and clinical management of sporadic retinoblastoma patients. Description of a new RB1 gene variant is interesting since there have been a small number of polymorphisms reported for this gene.

Introducción. El retinoblastoma es un cáncer pediátrico de la retina originado por la expresión alterada o ausente de la proteína del retinoblastoma (pRb). Se requiere la alteración genética de ambos alelos RB1 en las células de la retina para el desarrollo del retinoblastoma. En la forma esporádica, las mutaciones no hereditarias del gen RB1 ocurren en un solo retinoblasto y están presentes sólo en el ADN del tumor (mutaciones somáticas). El retinoblastoma esporádico es generalmente unilateral, no tiene historia familiar y no tiene riesgo de transmisión a la descendencia. Las pruebas genéticas para la detección de mutaciones en RB1 han mejorado la identificación de portadores y han facilitado la precisión de la asesoría genética. Objetivo. Detectar mutaciones en el gen RB1 en pacientes colombianos con retinoblastoma esporádico mediante PCR-SSCP seguido de secuenciación. Materiales y métodos. Se analizaron cuatro pacientes con retinoblastoma esporádico para la detección de variaciones en el gen RB1 mediante PCR-SSCP, seguida de secuenciación. Resultados. Se identificaron cinco variaciones del gen RB1 : tres mutaciones nuevas (una de línea germinal y dos somáticas), un polimorfismo nuevo y una mutación somática ya reportada. Las cuatro mutaciones se encontraron en tres pacientes con retinoblastoma unilateral y uno con bilateral. La mutación germinal se detectó en un paciente con compromiso unilateral y no se encontró en los padres ni en los tres hermanos analizados. Conclusión. Estos resultados enfatizan la importancia, para asesoría genética y manejo clínico, de identificar mutaciones del gen RB1 en pacientes con retinoblastoma esporádico. La descripción de una nueva variante en RB1 es interesante, dado el muy bajo número de polimorfismos reportados para este gen.

Comparative study of elderly-onset rheumatoid arthritis and young-onset rheumatoid arthritis in a Colombian population: clinical, laboratory and HLA-DRB1 findings.

OBJECTIVES: Elderly-onset rheumatoid arthritis (EORA) is considered to have different features in relation to young-onset rheumatoid arthritis (YORA). However, results from different evaluated populations worldwide have been inconsistent and in Colombia there are no known descriptions of the differences between these pathologies. The aim of this paper is to compare the clinical, laboratory and immunogenetic features in a Colombian population suffering with EORA and YORA. METHODS: EORA (≥65, n=104) and YORA (<65, n=96) patients were compared regarding clinical, laboratory and HLA-DRB1 alleles features. A control group without rheumatoid arthritis over 65 (n=179) was used to compare the HLA-DRB1 alleles. All patients met the ACR/1987 criteria for rheumatoid arthritis and the clinimetric index was calculated. RESULTS: The gender ratio (female/male) was 1.8:1 in EORA. In both groups, the main onset pattern of disease was an insidious polyarticular onset (p=0.35). EORA was characterised by more distal-proximal joint involvement in comparison to YORA (p=0.0007). In EORA, the rheumatoid factor and anti-cyclic citrullinated peptide (anti-CCP) antibodies frequency was close to 50%, lower than in YORA (63%). In both groups, the DAS28 and HAQ-DI score was higher than 6 and 1, respectively. The HLA-DRB1*0403 and *1402 frequency was significantly higher in EORA than in YORA. Also, the shared epitope (p=0.0392), HLA-DRB1*01 (p=0.0068) and *0101 (p=0.0151) were associated with an anti-CCP positivity and the HLA-DRB1*0403 is protective for the anti-CCP presence in EORA (p=0.0201). CONCLUSIONS: EORA is characterised by a different clinical presentation and HLA-DRB1 alleles with respect to YORA. HLA-DRB1*0403 and *1402 are significantly more frequent in EORA compared to YORA.

Parental origin, nondisjunction, and recombination of the extra chromosome 21 in Down syndrome: a study in a sample of the Colombian population.

INTRODUCTION: Free trisomy 21 is responsible for 95% of Down syndrome cases. Advanced maternal age and susceptible recombination patterns are recognized risk factors associated to Down syndrome. Maternal origin of trisomy occurs in approximately 90% of cases; paternal and mitotic origin share the remaining 10%. However, the recombination events that serve as a risk factors for trisomy 21 have not been carefully characterized. OBJECTIVE: To analyze and validate observations in a sample of Colombian trysonomy 21 cases. MATERIALS AND METHODS: Twenty-two Colombian families were selected, each with one affected Down syndrome (free trisomy 21) child. Microsatellite polymorphisms were used as DNA markers to determine the parental/stage origin of non-disjunction and recombination events. Non-parametric tests were used to compare our results with those reported. Multiple correspondence analysis was used to outline different groups and their associations. RESULTS: Distribution of trisomy 21 was 90.9% maternal, 4.5% paternal and 4.5% from mitotic origin, similar to distributions reported previously. However, we found differences in the frequency of maternal meiotic stage errors between the present study (46.1% meiosis I and 53.9% meiosis II) compared to those reported previously (70% meiosis I and 30% meiosis II). Multiple correspondence analyses showed association of either local recombination events or absence of recombination with specific non-disjunction stages. CONCLUSIONS: Recombination patterns found in this study support the hypothesis that susceptible chiasmate configurations are associated to maternal meiosis I and meiosis II errors. Non-disjunction frequencies between maternal meiotic stages need to be clarified in our population.

Origen parental, estado de no disyunción y recombinación meiótica del cromosoma 21 extra en el síndrome de Down: estudio en una muestra de población colombiana / Parental origin, nondisjunction, and recombination of the extra chromosome 21 in Down syndrome: a study in a sample of the Colombian population

Introduction. Free trisomy 21 is responsible for 95 por ciento of Down syndrome cases. Advanced maternal age and susceptible recombination patterns are recognized risk factors associated to Down syndrome. Maternal origin of trisomy occurs in approximately 90 por ciento of cases; paternal and mitotic origin share the remaining 10 por ciento. However, the recombination events that serve as a risk factors for trisomy 21 have not been carefully characterized. Objective. To analyze and validate observations in a sample of Colombian trysonomy 21 cases. Materials and methods. Twenty-two Colombian families were selected, each with one affected Down syndrome (free trisomy 21) child. Microsatellite polymorphisms were used as DNA markers to determine the parental/stage origin of non-disjunction and recombination events. Nonparametric tests were used to compare our results with those reported. Multiple correspondence analysis was used to outline different groups and their associations. Results. Distribution of trisomy 21 was 90.9 por ciento maternal, 4.5 por ciento paternal and 4.5 por ciento from mitotic origin, similar to distributions reported previously. However, we found differences in the frequency of maternal meiotic stage errors between the present study (46.1 por ciento meiosis I and 53.9 por ciento meiosis II) compared to those reported previously (70 por ciento meiosis I and 30 por ciento meiosis II). Multiple correspondence analyses showed association of either local recombination events or absence of recombination with specific non-disjunction stages. Conclusions. Recombination patterns found in this study support the hypothesis that susceptible chiasmate configurations are associated to maternal meiosis I and meiosis II errors. Nondisjunction frequencies between maternal meiotic stages need to be clarified in our population.

Introducción. La trisomía 21 libre es responsable del 95% de los casos de síndrome de Down. La edad materna y la recombinación son los principales factores de riesgo asociados con la concepción de estos individuos. El origen materno de la trisomía ocurre en el 90% de los casos, mientras que los casos de origen paterno y mitótico comparten un 10%. Por otra parte, la recombinación como factor de riesgo para la trisomía 21 no ha sido comprobada completamente. Objetivo. Analizar y validar estas observaciones en una muestra colombiana de casos con trisomía 21 libre. Materiales y métodos. Se estudiaron 22 afectados con síndrome de Down (trisomía libre) y sus respectivos padres. Se usaron marcadores microsatélites de ADN para determinar el origen en los progenitores, el estado de no disyunción y los eventos de recombinación. Por medio de pruebas no paramétricas se compararon los resultados con los reportados en la literatura. Se realizó análisis de correspondencias múltiples para reconocer los diferentes grupos y sus asociaciones. Resultados. La distribución de la trisomía 21 fue 90,9% materna, 4,5% paterna y 4,5% mitótica, similar a las reportadas previamente. Sin embargo, existen diferencias en la frecuencia de errores del estado meiótico para origen materno (46,1% meiosis I y 53,9% meiosis II) comparada con la de los reportados previamente (70% meiosis I y 30% meiosis II). El análisis de correspondencias múltiples mostró asociación entre eventos de recombinación local y ausencia de recombinación con estados de no disyunción específicos. Conclusiones. Las configuraciones quiasmáticas susceptibles están asociadas de manera específica a errores en la meiosis I y la meiosis II materna. Es necesario clasificar la frecuencia de no disyunción en estados meióticos maternos en nuestra población.

Análisis de longitud telométrica en carcinogénesis gástrica / Telomere lenght analysis in gastric carcinogenesis

Antecedentes: El modelo de carcinogénesis gástrica de múltiples pasos implica alteraciones genéticas y epigenéticas pobremente definidas. Una de estas alteraciones conocida como disfunción telomérica ha sido propuesta como uno de los principales mecanismos generadores de la inestabilidad genética encontrada desde las etapas más tempranas en varios cánceres epiteliales, incluido el adenocarcinoma gástrico. Métodos: En el presente estudio, analizamos la longitud telomérica media (LTM) en tejidos gástricos tumorales y no tumorales, así como en condiciones precancerosas tales como gastritis atrófica, metaplasia y displasia, a partir de tejido fresco empleando las metodologías de Southern blot y Dot blot, con base en protocolos previamente descritos. Resultados: Se encontró una buena correlación entre los valores obtenidos para la LTM usando estas dos metodologías (r2: 0,84). No encontramos diferencias estadísticamente significativas en la LTM entre las muestras tumorales y no tumorales (9,38±3,2 Kb y 8,86±0,32 Kb, respectivamente, P: 0,53), tampoco encontramos una correlación significativa entre la LTM y variables tales como la edad, sexo, localización ó diagnostico histopatológico. Conclusiones: Aunque no se encontraron diferencias en la LTM en esta muestra de cáncer gástrico originaria de la población colombiana, es posible que la implementación en una muestra de mayor tamaño de otras metodologías moleculares más sensibles, tales como el Q-FISH y la PCR en tiempo real, permitan identificar diferencias en la longitud telomérica más pequeñas o específicas de cromosomas en cáncer gástrico (AU)

Introduction: Gastric cancer is the second most common cancer worldwide and the leading cause of cancer deaths in Colombia. Despite identification of some environmental and genetic risk factors, little is known about molecular mechanisms of gastric carcinogenesis. Recently, telomere instability has been suggested as a key factor in epithelial cancers including gastric cancer. Materials and Methods: In the current study mean telomere length (MTL) in tumoral and non tumoral tissues, as well as precancerous conditions such as atrophic gastritis, metaplasia and dysplasia were analyzed. Samples were obtained from endoscopy and gastric resection surgery procedures in different health institutions in Bogotá, Colombia. Genomic DNA was isolated from 57 tissue samples corresponding to 23 tumors, 1 dysplasia, 4 metaplasias, 6 atrophic gastritis, and 23 non tumoral tissues. The MTL was measured using Southern blot and Dot blot methodologies, as previously described. Results: A good correlation between values obtained using these both techniques (r2: 0.84) was found. No statistically significant differences in MTL between tumoral and non tumoral samples ( 9.38±3.2 Kb and 8.86±0.32 Kb, respectively, P: 0.53)were found. Also no any significant correlation among MTL and variables such as age, sex, localization or histopathological diagnoses was appreciated. Conclusions: Although differences in TLM in the studied gastric cancer samples from Colombian population were not found, it is possible that in larger patient series and using more sensitive complementary molecular analytical techniques such as Q-FISH and qPCR, smaller or chromosome specific telomere differences could be identified (AU)