Trubuil, A. | bioRxiv Science

bioRxiv2026

Bovine in vitro blastocysts with distinct morphokinetic patterns show transcriptomic differences at genome activation

Bovine embryo in vitro production (IVP) is characterised by low efficiency and variable outcomes. Monitoring early embryonic development by videomicroscopy revealed substantial morphokinetic heterogeneity in the first four embryonic cycles (EC, conventionally referred to as the 2-, 4-, 8- and 16-cell stages). Morphokinetic analysis offers a promising approach to characterize divergent developmental trajectories and provide a better understanding of underlying molecular mechanisms. We developed a Random Forest classification system (Bovine Embryo Analyser based on Morphokinetics: BEAM) to predict embryo phenotype. It is based on morphokinetic variables collected from the 1st to the 4th EC and predicts four blastocyst categories (EHB: Early Hatching Blastocyst, HB: Hatching Blastocyst, SSB: Subtle Developmental Shift Blastocyst, ADB: Arrhythmic Development Blastocyst). Classification performance on an independent dataset was good (F1 score = 0.59; Accuracy = 0.78), indicating that the BEAM can be useful for embryo development studies. The BEAM was further applied to embryos submitted to 4.3 days of culture and having completed the 4th EC (16-32 cells). RNA sequencing was performed on sixteen samples (4 x 8 pooled embryos/category). The ADB category was significantly enriched in transcripts involved in the regulation of transcriptional activity compared to the EHB category. In addition, in the ADB category, 22.7% (n = 185/816) of the upregulated genes were of maternal origin while only 6.2% were of embryonic origin (n = 54/816). In conclusion, despite being at a comparable developmental stage and transcriptionally competent, the ADB category showed delayed maternal transcript degradation suggesting delayed transition to embryonic transcriptional autonomy. Illustrated Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC="FIGDIR/small/733532v1_ufig1.gif" ALT="Figure 1"> View larger version (45K): org.highwire.dtl.DTLVardef@13a0958org.highwire.dtl.DTLVardef@13b88a1org.highwire.dtl.DTLVardef@18707c9org.highwire.dtl.DTLVardef@105759_HPS_FORMAT_FIGEXP M_FIG C_FIG Summary SentenceIn vitro produced bovine embryo morphokinetic patterns allow prediction of four blastocyst categories (up to the 4th embryonic cycle) and are associated with distinct transcriptomic profiles at embryonic genome activation in competent embryos.

Developmental Biology↗

bioRxiv2022

Large-scale analysis and computer modeling reveal hidden regularities behind variability of cell division patterns in Arabidopsis thaliana embryogenesis

Noise plays a major role in cellular processes and in the development of tissues and organs. Several studies have examined the origin, the integration or the accommodation of noise in gene expression, cell growth and elaboration of organ shape. By contrast, much less is known about variability in cell division plane positioning, its origin and links with cell geometry, and its impact on tissue organization. Taking advantage of the first-stereotyped-then-variable division patterns in the embryo of the model plant Arabidopsis thaliana, we combined 3D imaging and quantitative cell shape and cell lineage analysis together with mathematical and computer modeling to perform a large scale, systematic analysis of variability in division plane orientation. Our results reveal that, paradoxically, variability in cell division patterns of Arabidopsis embryos is accompanied by a progressive reduction of cell shape heterogeneity. The paradox is solved by showing that variability operates within a reduced repertoire of possible division plane orientations that is related to cell geometry. We show that in several domains of the embryo, a recently proposed geometrical division rule recapitulates observed variable patterns, thus suggesting that variable patterns emerge from deterministic principles operating in a variable geometrical context. Our work highlights the importance of emerging patterns in the plant embryo under iterated division principles, but also reveal domains where deviations between rule predictions and experimental observations point to additional regulatory mechanisms.

developmental biology↗