Genome-scale pan-cancer interrogation of lncRNA dependencies using CasRx.

Although long noncoding RNAs (lncRNAs) dominate the transcriptome, their functions are largely unexplored. The extensive overlap of lncRNAs with coding and regulatory sequences restricts their systematic interrogation by DNA-directed perturbation. Here we developed genome-scale lncRNA transcriptome screening using Cas13d/CasRx. We show that RNA targeting overcomes limitations inherent to other screening methods, thereby considerably expanding the explorable space of the lncRNAome. By evolving the screening system toward pan-cancer applicability, it supports molecular and phenotypic data integration to contextualize screening hits or infer lncRNA function. We thereby addressed challenges posed by the enormous transcriptome size and tissue specificity through a size-reduced multiplexed gRNA library termed Albarossa, targeting 24,171 lncRNA genes. Its rational design incorporates target prioritization based on expression, evolutionary conservation and tissue specificity, thereby reconciling high discovery power and pan-cancer representation with scalable experimental throughput. Applied across entities, the screening platform identified numerous context-specific and common essential lncRNAs. Our work sets the stage for systematic exploration of lncRNA biology in health and disease.

In vivo interrogation of regulatory genomes reveals extensive quasi-insufficiency in cancer evolution.

In contrast to mono- or biallelic loss of tumor-suppressor function, effects of discrete gene dysregulations, as caused by non-coding (epi)genome alterations, are poorly understood. Here, by perturbing the regulatory genome in mice, we uncover pervasive roles of subtle gene expression variation in cancer evolution. Genome-wide screens characterizing 1,450 tumors revealed that such quasi-insufficiency is extensive across entities and displays diverse context dependencies, such as distinct cell-of-origin associations in T-ALL subtypes. We compile catalogs of non-coding regions linked to quasi-insufficiency, show their enrichment with human cancer risk variants, and provide functional insights by engineering regulatory alterations in mice. As such, kilo-/megabase deletions in a Bcl11b-linked non-coding region triggered aggressive malignancies, with allele-specific tumor spectra reflecting gradual gene dysregulations through modular and cell-type-specific enhancer activities. Our study constitutes a first survey toward a systems-level understanding of quasi-insufficiency in cancer and gives multifaceted insights into tumor evolution and the tissue-specific effects of non-coding mutations.

TERRA regulate the transcriptional landscape of pluripotent cells through TRF1-dependent recruitment of PRC2.

The mechanisms that regulate pluripotency are still largely unknown. Here, we show that Telomere Repeat Binding Factor 1 (TRF1), a component of the shelterin complex, regulates the genome-wide binding of polycomb and polycomb H3K27me3 repressive marks to pluripotency genes, thereby exerting vast epigenetic changes that contribute to the maintenance of mouse ES cells in a naïve state. We further show that TRF1 mediates these effects by regulating TERRA, the lncRNAs transcribed from telomeres. We find that TERRAs are enriched at polycomb and stem cell genes in pluripotent cells and that TRF1 abrogation results in increased TERRA levels and in higher TERRA binding to those genes, coincidental with the induction of cell-fate programs and the loss of the naïve state. These results are consistent with a model in which TRF1-dependent changes in TERRA levels modulate polycomb recruitment to pluripotency and differentiation genes. These unprecedented findings explain why TRF1 is essential for the induction and maintenance of pluripotency.

TERRA recruitment of polycomb to telomeres is essential for histone trymethylation marks at telomeric heterochromatin.

TERRAs are long non-coding RNAs generated from the telomeres. Lack of TERRA knockout models has hampered understanding TERRAs' functions. We recently identified chromosome 20q as one of the main origins of human TERRAs, allowing us to generate the first 20q-TERRA knockout models and to demonstrate that TERRAs are essential for telomere length maintenance and protection. Here, we use ALT 20q-TERRA knockout cells to address a direct role of TERRAs in telomeric heterochromatin formation. We find that 20q-TERRAs are essential for the establishment of H3K9me3, H4K20me3, and H3K27me3 heterochromatin marks at telomeres. At the mechanistic level, we find that TERRAs bind to PRC2, responsible for catalyzing H3K27 tri-methylation, and that its localization to telomeres is TERRA-dependent. We further demonstrate that PRC2-dependent H3K27me3 at telomeres is required for the establishment of H3K9me3, H4K20me3, and HP1 binding at telomeres. Together, these findings demonstrate an important role for TERRAs in telomeric heterochromatin assembly.

Auditoría médica concurrente de certificados de incapacidad temporal para el trabajo / Concurrent medical audit of temporary disability to work certificates (TDWC)

La auditoría médica, busca identificar las irregularidades y disfunciones médicas y administrativas con miras a proponer alternativas que permitan mejorar la calidad. Objetivo: Identificar y analizar las causas de la emisión de los Certificados de Incapacidad Temporal para el Trabajo (CITT). Material y métodos: El estudio se realizó en 17 centros asistenciales de EsSalud de Lima y Callao, en 1996. Se auditaron 41,918 CITT, excluyendo aquellos emitidos para descanso pre y post natal, y por los servicios médicos PAAD (Programa de Atención Ambulatoria y Domiciliaria). S establecieron 8 criterios para determinar la adecuada emisión de los mismos. Resultados: Del total de CITT auditados 52.93 por ciento presentaron observaciones. La mayor parte de las observaciones fueron de tipo administrativo, las relacionadas a la práctica médica fueron escasas. Las observaciones más frecuentes fueron: No estar en la historia clínica (45.46 por ciento de CITT observados), No estar la consulta registrada en la historia clínica (16.61 por ciento) y No coincidir la fecha registrada en la historia clínica con la fecha del CITT (10.82 por ciento). Conclusiones : Muchos de los errores encontrados que justificaron la observación técnica de los CITT estaban relacionados con problemas administrativos, producto generalmente del llenado inadecuado de los documentos historias clínicas y CITT). Se recomienda la implementación de un sistema autosostenible de auditoría concurrente, y diseños de programas de educación y capacitación en este tema.