Biology subjects

Ortega, M. S.

Publications and source records attributed to Ortega, M. S..

3 recordsLinked to original sources

bioRxiv2026

Aggregation of misfolded proteins in the sperm head impairs preimplantation embryo development

Paternal contributions to embryogenesis extend beyond DNA, yet the molecular cargo carried by sperm and its impact on development remain poorly defined. Aggresomes (AGG), cytoplasmic inclusions formed by misfolded proteins, are present in mammalian gametes, but their functional consequences are unclear. Here, we show that excessive AGG content in bovine sperm head compromises preimplantation embryo development. Using image-based flow cytometry, sperm from 32 sires were classified into low-, moderate-, and high-AGG groups. AGG levels were unrelated to sire age and did not affect in vitro capacitation or acrosome remodeling. However, embryos derived from high-AGG sires exhibited reduced blastocyst formation, delayed cleavage timing, and a higher incidence of developmental arrest at the 4-6 cell stage. Embryos from high-AGG sires also accumulated more AGG during development, showed elevated reactive oxygen species (ROS) levels, and displayed altered mitophagy dynamics. Supplementation with an ER stress inhibitor temporarily improved cleavage but did not enhance overall blastocyst formation, indicating a limited and stage-specific effect. In vivo, embryos from high-AGG sires showed lower transferable quality compared with those from low-AGG sires. These findings establish sperm head AGG content as a novel paternal determinant of embryo quality. By linking sperm-borne misfolded protein aggregates to disrupted developmental pathways in the resulting embryo, our study reveals a previously unrecognized mechanism of paternal influence on fertility and suggests new opportunities for molecular screening for male fertility. Significance StatementSperm contribute more to the embryo than DNA alone, yet the consequences of sperm-borne molecular cargo for early development remain largely unknown. We show that aggregates of misfolded proteins in the sperm head, a marker of disrupted protein quality control, impair preimplantation embryo development in cattle. Sires with elevated sperm aggregate content produce embryos that cleave later, arrest more frequently, and reach the blastocyst stage at lower rates, both in vitro and in vivo. These embryos carry greater aggregate loads, show heightened oxidative stress, and display dysregulated mitochondrial clearance. Our findings establish paternal proteostasis as a determinant of embryo quality and identify a class of sperm defects invisible to conventional semen analysis, opening new avenues for molecular fertility screening.

cell biology↗

bioRxiv2025

Short- and long-term effects of uterine disease on oocyte developmental capacity in postpartum dairy cows

The hypothesis was that early postpartum uterine disease would reduce the developmental capacity of oocytes thus contributing to the reduced fertility of dairy cows with uterine disease. Dairy cows were diagnosed healthy or with metritis at 7 to 10 d postpartum. The reproductive tract was collected at approximately 1 mo (Exp. 1) or approximately 80 or 165 d (Exp. 2) postpartum for the collection of cumulus-oocyte complexes (COC). The COC were matured, co- incubated with sperm for fertilization, and cultured to the blastocyst stage (8 d) in vitro. For Exp.1, the disease diagnosis (healthy or metritis) did not affect the number of collected COC or the subsequent embryo development to the blastocyst stage. The presence of purulent material in the uterine lumen (endometritis) at time of oocyte collection, however, was associated with a reduced cleavage rate evaluated 3 d following fertilization. For Exp. 2, there was no effect of disease diagnosis (healthy or metritis) on the number of COC or their subsequent development. Reduced cleavage rates were observed in COC retrieved from cows slaughtered at 80 d postpartum, but not at 165 d postpartum, and this reduction was associated with a vaginal microbiome indicative of uterine disease at 4 to 5 wk postpartum. Regression analyses that included plasma haptoglobin or energy metabolite concentrations or uterine bacterial genera abundance did not explain a large percentage of the variation in oocyte development in vitro. We conclude that there is an effect of uterine disease at one month postpartum on the oocyte and its capacity for development (Exp. 1) and this effect may be present at 80 d postpartum (Exp. 2). In later postpartum cows (165 d postpartum; Exp. 2) there was no effect of uterine disease on in vitro oocyte development. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=141 SRC="FIGDIR/small/636469v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@7ab5d7org.highwire.dtl.DTLVardef@3845e3org.highwire.dtl.DTLVardef@743f52org.highwire.dtl.DTLVardef@1e95c38_HPS_FORMAT_FIGEXP M_FIG C_FIG HIGHLIGHTSO_LIOocytes collected at 1 month postpartum from dairy cows with endometritis (purulent uterine lumen) had a lower cleavage rate following in vitro fertilization when compared with oocytes collected from healthy cows (Exp. 1). C_LIO_LIOocytes collected at approximately 80 d postpartum from dairy cows with evidence of uterine disease at 4 to 5 wk postpartum had a lower cleavage rate following in vitro fertilization but this disease-associated difference was not observed when oocytes were collected from cows later postpartum (approximately 165 d postpartum; Exp. 2). C_LIO_LIRegardless of the study (Exp. 1 or 2), uterine disease primarily affected the percentage of oocytes that cleaved after fertilization. C_LIO_LIStatistical associations between circulating metabolites or relative abundance of uterine bacteria were either not significant or explained only a small percentage of the variation in the in vitro embryo development in either experiment. C_LI

physiology↗

bioRxiv2023

Extensive rewiring of the gene regulatory interactions between in vitro-produced conceptuses and endometrium during attachment

Pregnancy loss is a significant problem when embryos produced in vitro are transferred to a synchronized uterus. Currently, mechanisms that underlie losses of in vitro-produced embryos during implantation are largely unknown. We investigated this problem using cattle as a model of conceptus attachment by analyzing transcriptome data of paired extraembryonic membrane and endometrial samples collected on gestation days 18 and 25, which spans the attachment window in cattle. We identified that the transfer of an in vitro-produced embryo caused a significant alteration in transcript abundance of hundreds of genes in extraembryonic and endometrial tissues on gestation days 18 and 25, when compared to pregnancies initiated by artificial insemination. Many of the genes with altered transcript abundance are associated with biological processes that are relevant to the establishment of pregnancy. An integrative analysis of transcriptome data from the conceptus and endometrium identified hundreds of putative ligand-receptor pairs. There was a limited variation of ligand-receptor pairs in pregnancies initiated by in vitro-produced embryos on gestation day 18, and no alteration was observed on gestation day 25. In parallel, we identified that in vitro production of embryos caused an extensive alteration in the co-expression of genes expressed in the extraembryonic membranes and the corresponding endometrium on both gestation days. Both the transcriptional dysregulation that exists in the conceptus or endometrium independently, and the rewiring of gene transcription between the conceptus and endometrium are a potential component of the mechanisms that contribute to pregnancy losses caused by in vitro production of embryos. SIGNIFICANCE STATEMENTThe successful establishment of pregnancies following the transfer of an in vitro produced embryo is essential for cattle production and assisted human reproduction. Most of the pregnancies initiated by the transfer of an in vitro produced embryo fail, in part because of dysfunctional interaction between the embryo and endometrium during pregnancy establishment. Our study identified that conceptuses produced in vitro and their corresponding endometrium have massive dysregulation in gene activity during the peri-implantation window, which affects crucial biological functions necessary for pregnancy. These gene expression alterations are a major contributor to the high rates of pregnancy loss following the transfer of an in vitro produced embryo. Our findings have implications for improving assisted reproduction in both agriculture and biomedicine.

developmental biology↗