Project description:To characterize the genetic basis of hybrid male sterility in detail, we used a systems genetics approach, integrating mapping of gene expression traits with sterility phenotypes and QTL. We measured genome-wide testis expression in 305 male F2s from a cross between wild-derived inbred strains of M. musculus musculus and M. m. domesticus. We identified several thousand cis- and trans-acting QTL contributing to expression variation (eQTL). Many trans eQTL cluster into eleven ‘hotspots,’ seven of which co-localize with QTL for sterility phenotypes identified in the cross. The number and clustering of trans eQTL - but not cis eQTL - were substantially lower when mapping was restricted to a ‘fertile’ subset of mice, providing evidence that trans eQTL hotspots are related to sterility. Functional annotation of transcripts with eQTL provides insights into the biological processes disrupted by sterility loci and guides prioritization of candidate genes. Using a conditional mapping approach, we identified eQTL dependent on interactions between loci, revealing a complex system of epistasis. Our results illuminate established patterns, including the role of the X chromosome in hybrid sterility.
Project description:Activated Notch signaling is highly prevalent in T-cell acute lymphoblastic leukemia (T-ALL). But in clinical trials, pan-Notch inhibitors caused excessive toxicity. To find alternative ways to target Notch signals, we investigated Cell division cycle 73 (Cdc73), which is a component of the RNA polymerase-associated transcriptional machinery and has been previously described as a Notch cofactor. Emerging evidence also suggests that transcriptional machinery might be an attractive vulnerability in T-ALL. In this setting, we show that CDC73 co-binds a subset of Notch-occupied regulatory elements in an ETS1-dependent context. In mouse models, Cdc73 is important for Notch-induced T-cell development and maintenance of Notch-induced T-ALL. Mechanistically, Cdc73, Ets1, and Notch activate genes that promote DNA repair and oxidative phosphorylation. Cdc73 induces these pathways through canonical functions in mRNA synthesis rather than non-canonical functions in enhancer activation. Our study suggests that Cdc73 acts through context-dependent mechanisms to promote a gene expression program that mitigates the genotoxic and metabolic stress of supraphysiological Notch signaling. We also provide mechanistic support for testing inhibitors of DNA repair, oxidative phosphorylation, and transcriptional machinery as anti-leukemic therapy while highlighting strategies that disable pathways that intersect with Notch at chromatin to target Notch signals without directly targeting the Notch complex.
