Embryo culture in presence of oviductal fluid induces DNA methylation changes in bovine blastocysts

During the transit through the oviduct, the early embryo initiates an extensive DNA methylation reprogramming of its genome. Given that these epigenetic modifications are susceptible to environmental factors, components present in the oviductal milieu could affect the DNA methylation marks of the developing embryo. The aim of this study was to examine if culture of bovine embryos with oviductal fluid (OF) can induce DNA methylation changes at specific genomic regions in the resulting blastocysts. In vitro produced zygotes were cultured in medium with 3 mg/mL bovine serum albumin (BSA) or 1.25% OF added at the one- to 16-cell stage (OF1-16), one- to 8-cell stage (OF1-8) or 8- to 16-cell stage (OF8-16), and then were cultured until Day 8 in medium with 3 mg/mL BSA. Genomic regions in four developmentally important genes (MTERF2, ABCA7, OLFM1, GMDS) and within LINE-1 retrotransposons were selected for methylation analysis by bisulfite sequencing on Day 7-8 blastocysts. Blastocysts derived from OF1-16 group showed lower CpG methylation levels in MTERF2 and ABCA7 compared with the BSA group. However, CpG sites within MTERF2, ABCA7 and OLFM1 showed higher methylation levels in groups OF1-8 and OF8-16 than in OF1-16. For LINE-1 elements, higher CpG methylation levels were observed in blastocysts from the OF1-16 group than in the other experimental groups. In correlation with the methylation changes observed, mRNA expression level of MTERF2 was increased, while LINE-1 showed a decreased expression in blastocysts from OF1-16 group. Our results suggest that embryos show transient sensitivity to OF at early stages, which is reflected by specific methylation changes at the blastocyst stage.Fil: Barrera, Antonio Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Garcia, Elina Vanesa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tucumán. Instituto Superior de Investigaciones Biológicas. Universidad Nacional de Tucumán. Instituto Superior de Investigaciones Biológicas; ArgentinaFil: Hamdi, Meriem. Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria. Departamento de Reproducción Animal; EspañaFil: Sánchez Calabuig, María Jesús. Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria. Departamento de Reproducción Animal; EspañaFil: López Cardona, Ángela Patricia. Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria. Departamento de Reproducción Animal; EspañaFil: Fonseca Balvís, Noelia. Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria. Departamento de Reproducción Animal; EspañaFil: Rizos, Dimitrios. Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria. Departamento de Reproducción Animal; EspañaFil: Gutiérrez Adan, Alfonso. Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria. Departamento de Reproducción Animal; Españ

Zrsr2 and functional U12-dependent spliceosome are necessary for follicular development

SUMMARY ZRSR2 is a splicing factor involved in recognition of 30 -intron splice sites that is frequently mutated in myeloid malignancies and several tumors; however, the role of mutations of Zrsr2 in other tissues has not been analyzed. To explore the bio logical role of ZRSR2,we generated threeZrsr2 mutantmouse lines. AllZrsr2 mutant lines exhibited blood cell anomalies, and in two lines, oogenesis was blocked at the secondary follicle stage. RNA-seq of Zrsr2mu secondary follicles showed aberrations in gene expression and showed altered alternative splicing (AS) events involving enrichment of U12-type intron retention (IR), supporting the functional Zrsr2 action in minor spliceosomes. IR events were preferentially associated with centriole repli cation, protein phosphorylation, and DNA damage checkpoint. Notably, we found alterations in AS events of 50 meiotic genes. These results indicate that ZRSR2 mu tations alter splicing mainly in U12-type introns, which may affect peripheral blood cells, and impede oogenesis and female fertility

Impaired spermatogenesis, muscle, and erythrocyte function in U12 intron splicing-defective Zrsr1 mutant mice

The U2AF35-like ZRSR1 has been implicated in the recognition of 3' splice site during spliceosome assembly, but ZRSR1 knockout mice do not show abnormal phenotypes. To analyze ZRSR1 function and its precise role in RNA splicing, we generated ZRSR1 mutant mice containing truncating mutations within its RNA-recognition motif. Homozygous mutant mice exhibited severe defects in erythrocytes, muscle stretch, and spermatogenesis, along with germ cell sloughing and apoptosis, ultimately leading to azoospermia and male sterility. Testis RNA sequencing (RNA-seq) analyses revealed increased intron retention of both U2- and U12-type introns, including U12-type intron events in genes with key functions in spermatogenesis and spermatid development. Affected U2 introns were commonly found flanking U12 introns, suggesting functional cross-talk between the two spliceosomes. The splicing and tissue defects observed in mutant mice attributed to ZRSR1 loss of function suggest a physiological role for this factor in U12 intron splicing.This work was funded by grants AGL2012-39652, BFU2014-55058-P, and AGL2015-66145 from the Spanish Ministry of Economy and Competitiveness and Japan Grants-in-Aid for Scientific Research 26830124 from the Ministry of Education, Culture, Sports, Science and Technology. K.H. was supported by Young Scientists Development Program, Research Center for Advanced Science and Technology at the University of Tokyo (funded by FUJIFILM Corporation). Work in J.V.'s lab was also supported by the European Research Council (ERC AdG - GA670146 - MASCP)