Imaging the human embryo
Live-imaging has uncovered major events driving early development, yet studies in human have been limited by restrictions on genetic manipulation and lack of imaging approaches. Working with IVF clinics and fertility experts, we overcome this barrier by combining fluorescent dyes with live-imaging to reveal the dynamics of chromosome segregation, compaction, polarization, and blastocyst formation in the human embryo.
Scanning dozens of thin confocal scans covering the whole embryo allows accurate segmentation of cell shape and position in 3D
Dynamics of human embryo compaction
Uncovering the dynamics of inner-outer lineage segregation in the human embryo
We also discovered that blastocyst expansion mechanically constrains trophectoderm cells causing nuclear budding and DNA shedding into the cytoplasm. This process of DNA loss is different from aneuploidies produced by chromosome segregation errors, which happen during mitosis instead of interphase. Importantly, it suggests multiple origins for aneuploidy, which is commonly found in preimplantation genetic testing (PGT) and associated with compromised fertility and pregnancy loss.
3D view of nuclear budding in a trophectoderm cell (stained for DNA and histones)
Segmenting the cell nucleus to identify nuclear buds
Imaging shows nuclear budding and DNA shedding. Similar to micronuclei produced by chromosome segregation errors during mitosis, the cytoplasmic DNA is inherited following cell division
Moreover, applying trophectoderm biopsy, a mechanical procedure performed clinically for genetic testing, increases DNA shedding
Example of DNA shedding captured via live-imaging after biopsy
Nuclear buds visualized using various DNA and chromatin markers
Domingo-Muelas*, Skory* et al. Human embryo live-imaging reveals nuclear DNA shedding during blastocyst expansion and biopsy.