Prognostic value of mutations in isocitrate dehydrogenase 1 (IDH1) and reverse telomerase transcriptase (TERT ) in Argentine patients` gliomas / Valor pronóstico de mutaciones en Isocitrato dehidrogenasa1 (IDH1) y Telomerasa transcriptasa reversa (TERT ) en gliomas de pacientes argentinos

Background and aim: Gliomas are the most common primary brain tumors, classified according to their histopathological and genetic features. Tumorigenesis depends on alterations in different genes. The aim of this study was the identification of mutations in IDH1 and TERT genes in gliomas of Argentine patients and to correlate them with clinical features and prognosis. Methods: DNA was isolated from 19 biopsies with different glioma grades matched with blood samples. IDH1 and TERT mutations were studied by PCR amplifica-tion and sequencing. Results: Six out of seven patients with low-grade glioma (grade II) harbor IDH1 mutations, mainly without tumor growth and overall survival of more than 12 months. Eleven out of twelve patients with high-grade gliomas (grade III/IV) showed wild type IDH1, mainly with tumor growth and shorter survival than low-grade gliomas. Mutated TERT promoter was present in 5 out of 11 high-grade gliomas, showing the prevalence of polymorphic C allele. In 1 out of 5 low-grade gliomas with a predominance of T allele. TERT and IDH1 mutations were mutually exclusive in most gliomas. Conclusions: Our results show that genetic tests provided a more accurate prognosis than histopathological analysis. The evolution of gliomas can be predicted primarily by the mutational status of IDH1 and secondarily by other markers, such as TERT mutational status

Antecedentes y objetivo: los gliomas son los tumores cerebrales primarios más comunes y se clasifican según sus características histopatológicas y genéticas. La tumorigénesis depende de alteraciones en diferentes genes. El objetivo de este estudio fue identificar mutaciones en los genes IDH1 y TERT en gliomas de pacientes argentinos y correlacionarlos con la evolución clínica. Métodos: se obtu-vieron 19 muestras pareadas de ADN de gliomas y de la sangre. Las mutaciones en IDH1 y TERT se analizaron por PCR y secuenciación. Resultados: la IDH1 mutada se encontró en 6 de los 7 gliomas de bajo grado (grado II), mayormente sin crecimiento tumoral y una sobrevida mayor de 12 meses. La IDH1 salvaje estaba presente en 11 de los 12 gliomas de alto grado (grado III y IV) mayormente con crecimiento tumoral y menor sobrevida que los tumores de bajo grado. Las mutaciones en el promotor del gen TERT se observaron en 5 de los 11 gliomas de alto grado, con la prevalencia de alelo polimórfico C, en cambio, en gliomas de bajo grado TERT mutado estaba presente en 1 de los 5 gliomas con predominio del alelo T. Las mutaciones en IDH1 y TERT fueron mutuamente excluyentes en la mayoría de los gliomas. Conclusiones: el análisis genético provee un pronóstico más certero que el análisis histopatológico. Nuestros resulta-dos muestran que la evolución de gliomas puede predecirse primariamente por el estado mutacional de IDH1 y secundariamente por mutaciones en otros marcadores tales como el TERT

RB1 gene mutations in Argentine retinoblastoma patients. Implications for genetic counseling.

Retinoblastoma (RB) is an inherited childhood ocular cancer caused by mutations in the tumor suppressor RB1 gene. Identification of RB1 mutations is essential to assess the risk of developing retinoblastoma in the patients´ relatives. Retinoblastoma is a potentially curable cancer and an early diagnosis is critical for survival and eye preservation. Unilateral retinoblastoma is mostly non-heritable and results from two somatic mutations whereas bilateral retinoblastoma is heritable and results from one germline and one somatic mutation, both have high penetrance, 90%. The purpose of this study was to identify causative RB1 mutations in RB patients with different clinical presentations. A comprehensive approach was used to study a cohort of 34 patients with unilateral, bilateral and trilateral retinoblastoma. Blood and tumor DNA was analyzed by sequencing and multiplex ligation-dependent probe amplification (MLPA) assay. Validation of an insertion mutation was performed by cloning the PCR product. Most of the patients in our cohort had unilateral RB, eight patients had bilateral RB and one patient had a trilateral tumor with ocular and suprasellar/sellar locations. Other tumors in addition to retinoblastoma were also found in the affected families. One patient had two syndromes, retinoblastoma and schwannomatosis, and another RB patient had a father with a retinoma. Five out of the 25 unilateral RB patients carried germinal mutations (20%), which were mostly missense mutations. The bilateral and trilateral patients carried splice-site, nonsense and frameshift mutations as well as a whole RB1 gene deletion. Missense mutations were associated with mild phenotype: unilateral retinoblastoma, retinoma or no tumor. In this study we identified causative RB1 mutations in most bilateral RB patients and in some unilateral RB patients, including five novel mutations. These data are crucial for genetic counseling and confirm the need to perform complete genetic screening for RB1 mutations in both constitutional and tumor tissues.

MLPA analysis of an Argentine cohort of patients with dystrophinopathy: Association of intron breakpoints hot spots with STR abundance in DMD gene.

Dystrophinopathies are X-linked recessive diseases caused by mutations in the DMD gene. Our objective was to identify mutations in this gene by Multiplex Ligation Probe Amplification (MLPA), to confirm the clinical diagnosis and determine the carrier status of at-risk relatives. Also, we aimed to characterize the Dystrophinopathies argentine population and the DMD gene. We analyzed a cohort of 121 individuals (70 affected boys, 11 symptomatic women, 37 at-risk women and 3 male villus samples). The MLPA technique identified 56 mutations (45 deletions, 9 duplications and 2 point mutations). These results allowed confirming the clinical diagnosis in 63% (51/81) of patients and symptomatic females. We established the carrier status of 54% (20/37) of females at-risk and 3 male villus samples. We could establish an association between the most frequent deletion intron breakpoints and the abundance of dinucleotide microsatellites loci, despite the underlying mutational molecular mechanism remains to be elucidated. The MLPA demonstrate, again, to be the appropriate first mutation screening methodology for molecular diagnosis of Dystrophinopathies. The reported results permitted to characterize the Dystrophinopathies argentine population and lead to better understanding of the genetic and molecular basis of rearrangements in the DMD gene, useful information for the gene therapies being developed.

Spectrum of RB1 mutations in argentine patients: 20-years experience in the molecular diagnosis of retinoblastoma.

BACKGROUND: Retinoblastoma is a hereditary cancer of childhood caused by mutations in the RB1 tumor suppressor gene. An early diagnosis is critical for survival and eye preservation, thus identification of RB1 mutations is important for unequivocal diagnosis of hereditary retinoblastoma and risk assessment in relatives. METHODS: We studied 144 families for 20 years, performing methodological changes to improve detection of mutation. Segregation analysis of polymorphisms, MLPA, FISH and cytogenetic assays were used for detection of "at risk haplotypes" and large deletions. Small mutations were identified by heteroduplex/DNA sequencing. RESULTS: At risk haplotypes were identified in 11 familial and 26 sporadic cases, being useful for detection of asymptomatic carriers, risk exclusion from relatives and uncovering RB1 recombinations. Ten large deletions (eight whole gene deletions) were identified in six bilateral/familial and four unilateral retinoblastoma cases. Small mutations were identified in 29 cases (four unilateral retinoblastoma patients), being the majority nonsense/frameshift mutations. Genotype-phenotype correlations confirm that the retinoblastoma presentation is related to the type of mutation, but some exceptions may occur and it is crucial to be considered for genetic counseling. Three families included second cousins with retinoblastoma carrying different haplotypes, which suggest independent mutation events. CONCLUSION: This study enabled us to obtain information about molecular and genetic features of patients with retinoblastoma in Argentina and correlate them to their phenotype.

El impacto de la genética molecular en la clínica médica / The impact of the molecular genetics in the medical clinic

El desarrollo de la biología molecular en los últimos veinte años, con la aplicación de la ingeniería genética permite actualmente diagnosticar las alteraciones moleculares de una serie de enfermedades hereditarias y demostrar la presencia de diferentes agentes infecciosos en los más variados fluidos orgánicos. La amplificación de fragmentos de ADN por la reacción en cadena de la polimerasa (PCR) hace posible diagnosticar con gran precisión y sensibilidad siendo su mayor utilidad la identificación de portadores sanos heterocigotas de enfermedades recesivas.

El impacto de la genética molecular en la clínica médica / The impact of the molecular genetics in the medical clinic

El desarrollo de la biología molecular en los últimos veinte años, con la aplicación de la ingeniería genética permite actualmente diagnosticar las alteraciones moleculares de una serie de enfermedades hereditarias y demostrar la presencia de diferentes agentes infecciosos en los más variados fluidos orgánicos. La amplificación de fragmentos de ADN por la reacción en cadena de la polimerasa (PCR) hace posible diagnosticar con gran precisión y sensibilidad siendo su mayor utilidad la identificación de portadores sanos heterocigotas de enfermedades recesivas. (AU)