Biology subjects

Van Soom, A.

Publications and source records attributed to Van Soom, A..

4 recordsLinked to original sources

bioRxiv2024

Mechanistic origin and preimplantation development of uniparental and polyploid blastomeres

Whole-genome (WG) abnormalities, such as uniparental diploidy and triploidy, cause fetal death. Occasionally, they coexist with biparental diploid cells in live births. Understanding the origin and early development of WG abnormal blastomeres is crucial for explaining the formation of androgenotes, gynogenotes, triploidy, chimerism, and mixoploidy. By haplotyping 118 blastomeres from first cleavages, we identified various mechanisms of heterogoneic divisions that lead to WG abnormal blastomeres or their coexistence with normal blastomeres in both multipolar and bipolar cleaving zygotes. After culturing the totipotent blastomeres to three preimplantation stages and performing transcriptome profiling on over 600 cells, we discovered that stress responses contribute to developmental impairment in WG abnormal cells, resulting in either cell arrest or blastocyst formation. Some first-cleavage-derived WG abnormal blastomeres can survive early development and progress to blastocysts. Their potential dominance in preimplantation embryos represents an overlooked cause of abnormal development. Haplotype based screening could further increase pregnancy rates.

genetics↗

bioRxiv2022

Alternative culture systems for bovine oocyte in vitro maturation: liquid marbles and differentially shaped 96-well plates

In vivo matured oocytes exhibit higher developmental competence than those matured in vitro, but mimicking the in vivo environment by in vitro conditions has been challenging. Till now, conventional two-dimensional (2D) systems have been used for in vitro maturation of bovine cumulus-oocytes-complexes (COCs). However, using such systems may cause cell flattening and does not allow cumulus expansion in all dimensions, which is less physiological. Therefore, implementing a low-cost and highly effective in vivo-like microenvironment methodology may help to optimize oocyte in vitro maturation. Here, we used two different systems to culture COCs and evaluate their potential influence on embryo development and quality. In the first system, we used treated fumed silica particles to create a 3D microenvironment (liquid marbles; LM) to mature COCs. In the second system, we cultured COCs in 96-well plates with different dimensions (flat, ultra-low attachment round-bottom, and V-shaped 96-well plates). In both systems, the nuclear maturation rate remained similar to the control in 2D, showing that most oocytes reached metaphase II. However, the subsequent blastocyst rate remained lower in the liquid marble system compared to 96-well plates and control 2D systems. Interestingly, a lower total cell number was found in the resulting embryos from both systems (LM and 96-well plates) compared to the control. In conclusion, oocytes matured in liquid marbles or 96-well plates showed no remarkable change in terms of meiotic resumption, embryo development, and quality in both systems. None of the surface geometries influenced embryo development. These findings provide important inferences in many aspects of oocyte and embryo development. Further investigation is needed to determine other aspects like toxicity testing and ultrastructural changes in oocytes.

developmental biology↗

bioRxiv2021

Parental genomes segregate into different blastomeres during multipolar zygotic divisions leading to mixoploid and chimeric blastocysts

The zygotic division enables two haploid genomes to segregate into two biparental diploid blastomeres. This fundamental tenet was challenged by the observation that blastomeres with different genome ploidy or parental genotypes can coexist within individual embryos. We hypothesized that whole parental genomes can segregate into distinct blastomere lineages during the first division through "heterogoneic division". Here, we map the genomic landscape of 82 blastomeres from 25 embryos that underwent multipolar zygotic division. The coexistence of androgenetic and diploid or polyploid blastomeres with or without anuclear blastomeres, and androgenetic and gynogenetic blastomeres within the same embryo proofs the existence of heterogoneic division. We deduced distinct segregation mechanisms and demonstrate these genome-wide segregation errors to persist to the blastocyst stage in both human and cattle. Genome-wide zygotic segregation errors contribute to the high incidence of embryonic arrest and provide an overarching paradigm for the development of mixoploid and chimeric individuals and moles.

developmental biology↗

bioRxiv2020

The composition of the microbiota in the full-term fetal gut and amniotic fluid: a bovine caesarean section study

The fetal development of the intestinal immune system is stimulated by the maternal microbiota, but it is still unclear whether viable bacteria exist in the healthy fetus. Analysis of such low microbial biomass environments are challenging due to contamination issues. The aims of the current study were to assess the bacterial load and characterize the bacterial composition of the amniotic fluid and meconium of full-term calves, leading to a better knowledge of prenatal bacterial seeding of the fetal intestine. Amniotic fluid and rectal meconium samples were collected during and immediately after elective caesarean section, performed in 25 Belgian Blue cow-calf couples. The samples were analyzed by qPCR, bacterial culture using GAM agar and 16S rRNA gene amplicon sequencing. To minimize the effects of contaminants, we included multiple technical controls and stringently filtered the 16S rRNA gene sequencing data to exclude putative contaminant sequences. The meconium samples contained a significantly higher amount of bacterial DNA than the negative controls and 5 of 24 samples contained culturable bacteria. In the amniotic fluid, the amount of bacterial DNA was not significantly different from the negative controls and all samples were culture negative. Bacterial sequences were identified in both sample types and were primarily of phyla Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria, with some individual variation. We conclude that most calves encounter in utero maternal-fetal transmission of bacterial DNA, but the amount of bacterial DNA is low and viable bacteria are rare.

microbiology↗