Biology subjects

Mashiko, D.

Publications and source records attributed to Mashiko, D..

4 recordsLinked to original sources

bioRxiv2025

Early transcriptional divergence underlies cell fate bias in bovine embryos

Developmental plasticity, or the ability of early embryonic cells to contribute to multiple lineages, is traditionally considered equal among sister blastomeres during early cleavage. However, divergence may occur earlier than expected. We performed single-cell RNA sequencing of bovine embryos from the 2- to 8-cell stages to examine transcriptional asymmetry. While gene expression was uniform at the 2-cell stage, variability increased at the 4-cell stage and became pronounced by the 8-cell stage. At this stage, blastomeres showed heterogeneity in MAPK pathway genes (e.g., RAC1, MAPK14) and the trophectoderm marker CDX2. These differences were associated with blastomere size; larger blastomeres more frequently initiated cavity formation, a functional marker of trophectoderm fate. Our findings suggest that both molecular and physical asymmetries contribute to early lineage bias, and that developmental plasticity may be lost in an asynchronous, cell-specific manner before visible morphological events such as compaction.

developmental biology↗

bioRxiv2025

SLC35G3 is a UDP-N-acetylglucosamine transporter for sperm glycoprotein formation and underpins male fertility in mice

Despite the recognized importance of glycans in biological phenomena, their complex roles in spermatogenesis and sperm function remain unclear. SLC35G3, a 10-transmembrane protein specifically found in early round spermatids, belongs to the sugar-nucleotide transporter family, indicating its involvement in glycan formation. In this study, we found that Slc35g3 knockout male mice were sterile due to impaired sperm functions in uterotubal junction passage, zona pellucida binding, and oocyte fusion. Mouse SLC35G3 has UDP-GlcNAc transporter activity, and its ablation caused abnormal processing of the sperm plasma membrane and acrosome membrane proteins. Reported human SLC35G3 mutations (F267L and T179HfsTer27) diminished the UDP-GlcNAc transporter activity of SLC35G3, implying infertility risks in males carrying these mutations. Our findings unveil the vital roles of SLC35G3 in the glycan formation of sperm membrane proteins critical for sperm fertilizing ability.

developmental biology↗

bioRxiv2021

Deep learning-based algorithm for predicting the live birth potential of mouse embryos

In assisted reproductive technology (ART), embryos produced by in vitro fertilization (IVF) are graded according to their live birth potential, and high-grade embryos are preferentially transplanted. However, the rate of live birth following clinical ART remains low worldwide, suggesting that grading is inaccurate. One explanation is that grading is classically based on the characteristic shape of embryos at a limited number of developmental stages and does not consider the shape of embryos and intracellular structures, e.g., nuclei, at various stages important for normal embryogenesis. Therefore, here we developed a Normalized Multi-View Attention Network (NVAN) that directly predicts live birth potential from nuclear structural features in live-cell fluorescence images taken of mouse embryos across a wide range of stages. The classification accuracy of our method was 83.87%, which greatly exceeded that of existing machine-learning methods and that of visual inspection by embryo culture specialists. By visualizing the features that contributed most to the prediction of live birth potential, we found that the size and shape of the cell nucleus at the morula stage and at the time of cell division were important for live birth prediction. We anticipate that our method will help ART and developmental engineering as a new basic technology for IVF embryo selection.

developmental biology↗

bioRxiv2021

Chromosome counting in the mouse and human zygote using low-invasive super-resolution live-cell imaging

In preimplantation embryos, an abnormal chromosome number causes developmental failure and a reduction in the pregnancy rate. Conventional chromosome testing methods requiring biopsy reduce the risk of associated genetic diseases; nevertheless, the reduction in cell number also reduces the pregnancy rate. Therefore, we attempted to count the chromosomes in mouse (Slc:ICR) embryos using super-resolution live-cell imaging as a new method of chromosome counting that does not reduce the cell number or viability. We counted the forty chromosomes at the first mitosis by injecting embryos with histone H2B-mCherry mRNA under conditions by which pups could be obtained; however, the results were often an underestimation of chromosome number and varied by embryo and time point. Therefore, we developed a method to count the chromosomes via CRISPR/dCas-mediated live-cell fluorescence in situ hybridization targeting the sequence of the centromere region, enabling us to count the chromosomes more accurately in mouse embryos. The methodology presented here may provide useful information for assisted reproductive technologies, such as those used in livestock animals/humans, as a technique for assessing the chromosomal integrity of embryos prior to transfer. Impact StatementLow-toxic super-resolution observation enables chromosome counting in preimplantation embryos without cell collection.

developmental biology↗