Project description:Notch signaling is essential for proper lens development, however the specific requirements of individual Notch receptors has not been previously investigated. Here we report the lens phenotypes of Notch2 conditionally mutant mice, which exhibited severe microphthalmia, reduced pupillary openings, disrupted fiber cell morphology, eventual loss of the anterior epithelium, fiber cell dysgenesis, and cataracts. Notch2 mutants also had a persistent lens stalk phenotype at E11.5, and aberrant DNA synthesis in the fiber cell compartment by E14.5. Gene expression analyses showed elevated levels of the cell cycle regulators Cdkn1a (p21Cip1), Ccnd2 (CyclinD2) and Trp63 (p63) that negatively regulates Wnt signaling. Although removal of Notch2 phenocopied the increased proportion of fiber cells of Rbpj and Jag1 conditional mutant lenses, Notch2 is not required for AEL proliferation, suggesting that a different receptor regulates this process. Instead, we found that the Notch2 normally blocks progenitor cell death. Overall, we conclude that Notch2-mediated signaling regulates lens morphogenesis, apoptosis, cell cycle withdrawal, and secondary fiber cell differentiation. We have compared gene expression of ocular lenses of mice that are lens specific conditional mutants of Notch2 gene to that of littermate controls that had no ablation of Notch2 gene in the lens. Two lenses of each of the three conditional mutants and controls were pooled together and total RNA was harvested from embryonic day 19.5 (E19.5) lenses. Gene expression changes caused by absence of Notch2 gene in the lens were analyzed.
Project description:Notch signaling is essential for proper lens development, however the specific requirements of individual Notch receptors has not been previously investigated. Here we report the lens phenotypes of Notch2 conditionally mutant mice, which exhibited severe microphthalmia, reduced pupillary openings, disrupted fiber cell morphology, eventual loss of the anterior epithelium, fiber cell dysgenesis, and cataracts. Notch2 mutants also had a persistent lens stalk phenotype at E11.5, and aberrant DNA synthesis in the fiber cell compartment by E14.5. Gene expression analyses showed elevated levels of the cell cycle regulators Cdkn1a (p21Cip1), Ccnd2 (CyclinD2) and Trp63 (p63) that negatively regulates Wnt signaling. Although removal of Notch2 phenocopied the increased proportion of fiber cells of Rbpj and Jag1 conditional mutant lenses, Notch2 is not required for AEL proliferation, suggesting that a different receptor regulates this process. Instead, we found that the Notch2 normally blocks progenitor cell death. Overall, we conclude that Notch2-mediated signaling regulates lens morphogenesis, apoptosis, cell cycle withdrawal, and secondary fiber cell differentiation.
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.