Kat6b Modulates Oct4 and Nanog Binding to Chromatin in Embryonic Stem Cells and Is Required for Efficient Neural Differentiation.

Chromatin remodeling is fundamental for the dynamical changes in transcriptional programs that occur during development and stem cell differentiation. The histone acetyltransferase Kat6b is relevant for neurogenesis in mouse embryos, and mutations of this gene cause intellectual disability in humans. However, the molecular mechanisms involved in Kat6b mutant phenotype and the role of this chromatin modifier in embryonic stem (ES) cells remain elusive. In this work, we show that Kat6b is expressed in ES cells and is repressed during differentiation. Moreover, we found that this gene is regulated by the pluripotency transcription factors Nanog and Oct4. To study the functional relevance of Kat6b in ES cells, we generated a Kat6b knockout ES cell line (K6b-/-) using CRISPR/Cas9. Fluorescence correlation spectroscopy analyses suggest a more compact chromatin organization in K6b-/- cells and impaired interactions of Oct4 and Nanog with chromatin. Remarkably, K6b-/- cells showed a reduced efficiency to differentiate to neural lineage. These results reveal a role of Kat6b as a modulator of chromatin plasticity, its impact on chromatin-transcription factors interactions and its influence on cell fate decisions during neural development.

Gerstmann-Sträussler-Scheinker syndrome with variable phenotype in a new kindred with PRNP-P102L mutation.

Gerstmann-Sträussler-Scheinker syndrome (GSS) is a dominantly inherited disorder belonging to the group of transmissible human spongiform encephalopathies or prion diseases. Several families affected by GSS with patients carrying mutations in the prion protein gene have been described worldwide. We report clinical, genealogical, neuropathology and molecular study results from two members of the first Argentine kindred affected by GSS. Both family members presented a frontotemporal-like syndrome, one with and the other without ataxia, with different lesions on neuropathology. A Pro to Leu point mutation at codon 102 (P102L) of the prion protein gene was detected in one of the subjects studied. The pathogenic basis of phenotypic variability observed in this family remains unclear, but resembles that observed in other P102L GSS patients from the same family.

Familial dementia with frontotemporal features associated with M146V presenilin-1 mutation.

Most of the mutations in the presenilin-1 gene (PS-1) are associated with familial Alzheimer's disease (AD). However, certain examples can be associated with frontotemporal dementia (FTD). We performed a clinical evaluation of individuals belonging to a family with the FTD phenotype, and additional molecular studies and neuropathological assessment of the proband. The PS-1 M146V mutation was found in the 50-year-old subject (the proband) with family history of early-onset FTD. Neuropathological examination showed abundant amyloid plaques, widespread neurofibrillary pathology, Pick bodies in the hippocampus and cortex, cortical globose tangles and ubiquitin-positive nuclear inclusions in white matter oligodendrocytes. We report a kindred with clinical features of FTD, whose proband bore the PS-1 M146V mutation and showed diffuse Alzheimer's type pathology and Pick bodies on post-mortem neuropathological examination. As with other mutations within the same codon, this substitution may predispose to both diseases by affecting APP and/or tau processing.

Creutzfeldt-Jakob disease surveillance in Argentina, 1997-2008.

BACKGROUND: Epidemiological data on Creutzfeldt-Jakob disease (CJD) from Latin America are limited. We present a comprehensive epidemiological survey on CJD patients in Argentina based on systematic surveillance between 1997 and 2008. METHODS: A CJD Surveillance Referral Center (SRC) was established in Argentina in 1997; previously a Neuropathology Referral Center was used from 1983 to 1996. All suspected cases referred to the SRC were classified using established criteria on the basis of information derived from the following: clinical data form, EEG, MRI (both for central review), cerebrospinal fluid (CSF) for protein 14-3-3 Western blot (WB), autopsy or biopsy material for neuropathology, prion protein (PrP) immunohistochemistry and PrP WB, as well as blood for DNA studies (when brain tissue was not available). RESULTS: Of the 517 patients referred to the SRC between 1997 and 2008, 211 (40.8%) had CJD or other transmissible spongiform encephalopathies (TSEs) (definite or probable). Possible cases totaled 14.5%, while cases with no WHO criteria accounted for 16.4%. Non-CJD cases excluded by biopsy/autopsy or during follow-up corresponded to 28.2% of the 517 referrals. Main differential diagnoses included neurodegenerative diseases such as Alzheimer's disease, frontotemporal dementia, vascular, metabolic or viral encephalopathy, and Hashimoto's disease. Five percent of referred patients ultimately recovered. Eighty-three percent of TSE cases were sporadic CJD; 17% were genetic, mainly E200K (15.6%); the remaining 1.4% included an octarepeat insertion and two Gerstmann-Sträussler-Scheinker cases (P102L). Seventy-four of 100 definite cases had frozen tissue available for molecular subtyping (PrP(Sc)/codon 129). CSF protein 14-3-3 WB sensitivity was 72.3% and specificity was 92.1%. Clinical diagnostic criteria for probable CJD when compared to definite diagnosis by neuropathology showed 71.3% sensitivity, 86.2% specificity, 94.4% positive predictive value and 48% negative predictive value. Country incidence increased over time and reached 0.85 cases per million in 2008, with the highest rate detected in the city of Buenos Aires (1.8). Districts with 6% of the total population have never reported suspected cases. CONCLUSION: In spite of an increase in incidence observed over time, the difference between Buenos Aires city, where the incidence is comparable to that of smaller European countries with higher population density, and the incidence observed in the rest of the country suggests underreporting in nonmetropolitan areas, probably due to a lack of access to specialized medical facilities. CSF WB sensitivity results for protein 14-3-3 were probably linked to the fact that testing was not routinely repeated during the course of the disease, when earlier test results had been negative. The spectrum of molecular CJD subtypes observed did not differ from other countries in Europe. No iatrogenic or variant CJD cases were identified. The sensitivity and negative predictive value of clinical diagnostic criteria for probable CJD (which includes EEG and/or CSF protein 14-3-3 levels) may have been resulted from confirmed cases not meeting probable criteria before autopsy, due to a lack of ancillary tests such as EEG and/or CSF 14-3-3 WB, or because negative tests were not repeated during follow-up.

Accidental intrathecal administration of vincristine.

We describe a case of accidental intrathecal administration of vincristine in a 33-year-old man with clinical diagnosis of acute lymphocytic leukemia. The patient died 20 days after receiving the drug. Clinically, the patient developed acute ascending paralysis with motor and sensory dysfunctions, and respiratory failure. Neuropathological investigation revealed lesions in spinal cord, roots, and cerebellum characterized by rarefaction of the neuropil, axonal, and myelin degeneration, accompanied by macrophagic infiltration.

Seminested polymerase chain reaction (PCR) for detecting Helicobacter pylori DNA in carotid atheromas.

A polymerase chain reaction (PCR) method for the detection of the glmM gene, selected as Helicobacter pylori target sequence, was improved. While performing pathogenicity island cagA gene detection to discriminate pathogenic strains in atherosclerotic carotid samples, several cagA-positive but glmM-negative samples were found. Polymorphisms present in the region amplified in the nested PCR reaction could explain this result; primers were therefore designed to perform a seminested reaction; this modification optimized sensitivity while maintaining specificity. A real-time PCR for Helicobacter DNA detection was also setup. The combination of all 4 PCR reactions detected 83% of H. pylori DNA-positive samples in atherosclerotic carotid tissue, 64% of which were cagA gene positive.

Heme oxygenase-1 is expressed in carotid atherosclerotic plaques infected by Helicobacter pylori and is more prevalent in asymptomatic subjects.

BACKGROUND AND PURPOSE: It is not well established what are the features, if any, that distinguish symptomatic from asymptomatic carotid atherosclerotic plaques. Inducible heme oxygenase-1 (HO-1) is a component of cellular defense mechanisms against oxidative stress. We aimed to assess the presence of Helicobacter pylori (H pylori) and the expression of HO-1 in carotid atherosclerotic plaques of patients with and without prior neurologic symptoms attributable to the operated artery. METHODS: We examined 25 symptomatic and 23 asymptomatic carotid atherosclerotic plaques removed during endarterectomy and 7 normal carotid arteries obtained at autopsy. We investigated the presence of H pylori DNA in the vessel wall and performed immunohistochemical detection of HO-1. RESULTS: H pylori DNA was present in 28 plaques and HO-1 was expressed in 30 plaques. HO-1 was found in 27 H pylori-positive specimens but in only 3 H pylori-negative specimens (P<0.001). All 7 normal carotid arteries were negative for both H pylori and HO-1. Although 82% of asymptomatic specimens were positive for H pylori and 87% for HO-1, only 36% of symptomatic specimens were positive for both H pylori and HO-1 (P<0.01). CONCLUSIONS: This study suggests a strong association between H pylori infection and expression of HO-1 in carotid atherosclerotic plaques. There was a substantial prevalence of these features in specimens obtained from asymptomatic subjects.

Meduloblastoma de cerebelo: correlación del fenotipo inmunocitoquímico, contenido de ácidos nucleicos y cinética celular tumoral con el comportamiento biológico / Cerebellum medulloblastoma: correlation of the immunocytochemical phenotype, content of nucleic acids and tumoral cellular kinetics with the biological behavior

El meduloblastoma de cerebelo [MB] comprende el 25 por ciento de los tumores del sistema nervioso central [SNC] en la edad pediátrica. Pese a los tratamientos multidisciplinarios, la tasa de sobrevida a los 5 años sigue siendo del 50 por ciento aproximadamente, variable según las series. En el presente trabajo se analizan 123 Meduloblastomas tratados en el Hospital de Niños de Buenos Aires "Dr. Ricardo Gutierrez" [Sevicio de Neurocirugía y Oncología] entre 1975 y 1988, intentando analizar los fenómenos de diferenciación celular y su vinculación con la histogénesis de la entidad así como definir factores clínico-patológico que determinen o influyan en la evolución. La sobrevida global de la serie fue del 79 por ciento a los 12 meses y 40 por ciento a los 5 años. La presencia de células inmunoreactivas para la Proteína Gliofibrilar Acida, el filamento intermedio glial, se detectó en el 20,3 por ciento de los casos, en elementos neoplásicos. Criterios morfológicos e inmunocitoquímicos de diferenciación neuroblásticos coincidieron en el 10,3 por ciento de los casos. En ambas circunstancias la marcación era focal, correspondiendo a una subpoblación menor del tumor. Los elementos histológicos convencionales [exceptuando la necrosis de células tumorales] e inmunocitoquímicos no demostraron capacidad pronóstica definida. El análisis del contenido de ácidos nucleicos por citometría estática, plantea diferencias clínicas interesantes, sin impacto pronóstico definido en el marco de la presente serie. Los datos de la cinética celular, el agregado de quimioterapia sistémica, el tamaño tumoral [evaluado con el estadío T de Chang] y el porcentaje de resección quirúrgica parecen constituir los factores predictivos más útiles para definir grupos de riesgo diferencial.

Meduloblastoma de cerebelo: correlación del fenotipo inmunocitoquímico, contenido de ácidos nucleicos y cinética celular tumoral con el comportamiento biológico / Cerebellum medulloblastoma: correlation of the immunocytochemical phenotype, content of nucleic acids and tumoral cellular kinetics with the biological behavior

El meduloblastoma de cerebelo [MB] comprende el 25 por ciento de los tumores del sistema nervioso central [SNC] en la edad pediátrica. Pese a los tratamientos multidisciplinarios, la tasa de sobrevida a los 5 años sigue siendo del 50 por ciento aproximadamente, variable según las series. En el presente trabajo se analizan 123 Meduloblastomas tratados en el Hospital de Niños de Buenos Aires "Dr. Ricardo Gutierrez" [Sevicio de Neurocirugía y Oncología] entre 1975 y 1988, intentando analizar los fenómenos de diferenciación celular y su vinculación con la histogénesis de la entidad así como definir factores clínico-patológico que determinen o influyan en la evolución. La sobrevida global de la serie fue del 79 por ciento a los 12 meses y 40 por ciento a los 5 años. La presencia de células inmunoreactivas para la Proteína Gliofibrilar Acida, el filamento intermedio glial, se detectó en el 20,3 por ciento de los casos, en elementos neoplásicos. Criterios morfológicos e inmunocitoquímicos de diferenciación neuroblásticos coincidieron en el 10,3 por ciento de los casos. En ambas circunstancias la marcación era focal, correspondiendo a una subpoblación menor del tumor. Los elementos histológicos convencionales [exceptuando la necrosis de células tumorales] e inmunocitoquímicos no demostraron capacidad pronóstica definida. El análisis del contenido de ácidos nucleicos por citometría estática, plantea diferencias clínicas interesantes, sin impacto pronóstico definido en el marco de la presente serie. Los datos de la cinética celular, el agregado de quimioterapia sistémica, el tamaño tumoral [evaluado con el estadío T de Chang] y el porcentaje de resección quirúrgica parecen constituir los factores predictivos más útiles para definir grupos de riesgo diferencial. (AU)