Meiotic prophase length modulates Tel1-dependent DNA double-strand break interference.

During meiosis, genetic recombination is initiated by the formation of many DNA double-strand breaks (DSBs) catalysed by the evolutionarily conserved topoisomerase-like enzyme, Spo11, in preferred genomic sites known as hotspots. DSB formation activates the Tel1/ATM DNA damage responsive (DDR) kinase, locally inhibiting Spo11 activity in adjacent hotspots via a process known as DSB interference. Intriguingly, in S. cerevisiae, over short genomic distances (<15 kb), Spo11 activity displays characteristics of concerted activity or clustering, wherein the frequency of DSB formation in adjacent hotspots is greater than expected by chance. We have proposed that clustering is caused by a limited number of sub-chromosomal domains becoming primed for DSB formation. Here, we provide evidence that DSB clustering is abolished when meiotic prophase timing is extended via deletion of the NDT80 transcription factor. We propose that extension of meiotic prophase enables most cells, and therefore most chromosomal domains within them, to reach an equilibrium state of similar Spo11-DSB potential, reducing the impact that priming has on estimates of coincident DSB formation. Consistent with this view, when Tel1 is absent but Ndt80 is present and thus cells are able to rapidly exit meiotic prophase, genome-wide maps of Spo11-DSB formation are skewed towards pericentromeric regions and regions that load pro-DSB factors early-revealing regions of preferential priming-but this effect is abolished when NDT80 is deleted. Our work highlights how the stochastic nature of Spo11-DSB formation in individual cells within the limited temporal window of meiotic prophase can cause localised DSB clustering-a phenomenon that is exacerbated in tel1Δ cells due to the dual roles that Tel1 has in DSB interference and meiotic prophase checkpoint control.

Viral RNA load in plasma is associated with critical illness and a dysregulated host response in COVID-19.

BACKGROUND: COVID-19 can course with respiratory and extrapulmonary disease. SARS-CoV-2 RNA is detected in respiratory samples but also in blood, stool and urine. Severe COVID-19 is characterized by a dysregulated host response to this virus. We studied whether viral RNAemia or viral RNA load in plasma is associated with severe COVID-19 and also to this dysregulated response. METHODS: A total of 250 patients with COVID-19 were recruited (50 outpatients, 100 hospitalized ward patients and 100 critically ill). Viral RNA detection and quantification in plasma was performed using droplet digital PCR, targeting the N1 and N2 regions of the SARS-CoV-2 nucleoprotein gene. The association between SARS-CoV-2 RNAemia and viral RNA load in plasma with severity was evaluated by multivariate logistic regression. Correlations between viral RNA load and biomarkers evidencing dysregulation of host response were evaluated by calculating the Spearman correlation coefficients. RESULTS: The frequency of viral RNAemia was higher in the critically ill patients (78%) compared to ward patients (27%) and outpatients (2%) (p < 0.001). Critical patients had higher viral RNA loads in plasma than non-critically ill patients, with non-survivors showing the highest values. When outpatients and ward patients were compared, viral RNAemia did not show significant associations in the multivariate analysis. In contrast, when ward patients were compared with ICU patients, both viral RNAemia and viral RNA load in plasma were associated with critical illness (OR [CI 95%], p): RNAemia (3.92 [1.183-12.968], 0.025), viral RNA load (N1) (1.962 [1.244-3.096], 0.004); viral RNA load (N2) (2.229 [1.382-3.595], 0.001). Viral RNA load in plasma correlated with higher levels of chemokines (CXCL10, CCL2), biomarkers indicative of a systemic inflammatory response (IL-6, CRP, ferritin), activation of NK cells (IL-15), endothelial dysfunction (VCAM-1, angiopoietin-2, ICAM-1), coagulation activation (D-Dimer and INR), tissue damage (LDH, GPT), neutrophil response (neutrophils counts, myeloperoxidase, GM-CSF) and immunodepression (PD-L1, IL-10, lymphopenia and monocytopenia). CONCLUSIONS: SARS-CoV-2 RNAemia and viral RNA load in plasma are associated with critical illness in COVID-19. Viral RNA load in plasma correlates with key signatures of dysregulated host responses, suggesting a major role of uncontrolled viral replication in the pathogenesis of this disease.

Evaluación de la calidad de las notas de envío / Evaluation of referral letters

Introducción. La sobrepoblación de los servicios médicos ha incrementado la necesidad de referir pacientes a otras unidades médicas; en esas situaciones la nota de envío representa frecuentemente la vía de comunicación entre las unidades médicas. Objetivo: evaluar con qué frecuencia las notas de envío incluyen la información requerida así como la asociación entre integridad de éstas y el tipo de formato estructurado para elaborarlas. Material y métodos. Se colectaron y evaluaron las notas de envío de pacientes referidos al Hospital Infantil de México Federico Gómez de acuerdo a las recomendaciones propuestas por la Secretaría de Salud. A cada nota se le evaluó un total de 12 apartados. Se correlacionó la información incluida de cada categoría con la presencia de un espacio especialmente reservado para esa categoría de información en el formato utilizado.Resultados. Se evaluaron 100 notas de envío de pacientes atendidos desde el 15 de noviembre de 1997 al 15 de julio de 1998. En la mayoría de las notas evaluadas no se incluían ni la información ni los apartados para cada uno los puntos relevantes. Ninguna nota incluía toda la información requerida. Sólo en 4 de los 12 puntos evaluados se pudo demostrar asociación entre la inclusión de un espacio en el formato con la inclusión de dicha información.Conclusión. Las notas de envío frecuentemente no incluyen información referente a cada uno de los reactivos que se consideran necesarios. El uso de un formato que incluya apartados para cada tipo de información pudiera mejorar la integridad de las notas de envío.

Frecuencia de hemorragia intracraneana en niños hemofílicos / Intracranial hemmorrhage frequency in patients hemophilic

La hemorragia intracraneana es la principal causa de muerte entre los pacientes hemofílicos. Por esta razón se revisaron 75 expedientes clínicos de pacientes menores de 16 años con el diagnóstico de hemofilia. Se encontraron seis niños con hemorragia intracraneana (HIC). El tiempo de inicio de la sintomatología fue de 12 h hasta cuatro días con una media de 39 h. Los signos y síntomas encontrados fueron: cefalea, vómito, crisis convulsiva, hematoma en el sitio del traumatismo, hemiperesia corporal izquierda, nistagmus, náusea. Se dio tratamiento substitutivo en todos los niños. Cuatro presentaron secuelas neurológicas. La frecuencia de HIC se estimó en 8 por ciento de los hemofílicos. Se concluye que para prevenir la muerte y minimizar las secuelas, una terapia de reemplazo adecuada, ésta debe ser instituida tan pronto como se sospecha el sangrado o inmediatamente después del traumatismo craneoencefálico