Biology subjects

Cavazza, T.

Publications and source records attributed to Cavazza, T..

2 recordsLinked to original sources

bioRxiv2026

Restoring Shugoshin 1 reduces chromosome errors in human eggs

Aneuploidy in human eggs, which rises sharply with age, is a leading cause of infertility, IVF failure, and miscarriage. This age-related aneuploidy is primarily driven by premature sister chromatid separation (PSSC), resulting from loss of the cohesin complex that holds chromatids together. How cohesin is destabilized in the long-lived mammalian oocyte is poorly understood. Here, we show that in mouse oocytes, pericentromeric transcription is essential for maintaining the cohesion protector Shugoshin 1 (SGO1) and PP2A at centromeres, which together safeguard the cohesin subunit REC8. With age, mouse oocytes lose pericentromeric transcription, SGO1, and PP2A, leading to destabilized cohesion and increased PSSC. Supplementing aged mouse oocytes with Sgo1 restores centromeric protection, and reduces PSSC to youthful levels. Aged human oocytes also show reduced SGO1, and SGO1 supplementation reduces the fraction of human eggs with PSSC by approximately half. These findings establish SGO1 supplementation as a potential strategy to preserve chromatid cohesion in aging oocytes.

cell biology↗

bioRxiv2020

Parental genome unification is highly erroneous in mammalian embryos

The vast majority of human embryos are aneuploid. Aneuploidy frequently arises during the early mitotic divisions of the embryo, but the origin of this remains elusive. Using bovine embryos as a model for human embryos, we identify an error-prone mechanism of parental genome unification which often results in aneuploidy. Surprisingly, genome unification initiates hours before breakdown of the two pronuclei that encapsulate the parental genomes. While still within intact pronuclei, the parental genomes polarize towards each other, in a process driven by centrosomes, dynein, and microtubules. The maternal and paternal chromosomes eventually cluster at the pronuclear interface, in direct proximity to each other. Parental genome clustering often fails however, leading to massive chromosome segregation errors, incompatible with healthy embryo development. Nucleoli, which associate with chromatin, also cluster at the pronuclear interface in human zygotes. Defects in nucleolar clustering correlate with failure in human embryo development, suggesting a conserved mechanism.

developmental biology↗