Biology subjects

Bekele, H.

Publications and source records attributed to Bekele, H..

2 recordsLinked to original sources

bioRxiv2026

A cohesion optimum underlies chromosome segregation fidelity in oocytes

Chromosome segregation is compromised in eggs from women of both early and advanced reproductive ages. Deteriorating cohesion causes premature separation of sister-chromatids in eggs from older females. We show that the converse is true for oocytes of adolescents, with excessive cohesion impeding segregation. Oocytes from juvenile mice show severe chromosome lagging in anaphase I, leading to nondisjunction or, in extreme cases, failure of the first meiotic division. These defects are suppressed by experimentally weakening cohesion or enhancing its resolution during anaphase I. By contrast, lagging and nondisjunction are rare in the oocytes of young adults because cohesion is inherently weaker. Thus, relative cohesion strength underlies both the frequency and type of segregation errors observed in eggs throughout the female reproductive lifespan. One-Sentence SummaryIn eggs, errors in chromosome segregation arise from age-dependent imbalances in how tightly chromosomes are held together.

cell biology↗

bioRxiv2024

Two retrotransposon-derived capsid genes PNMA1 and PNMA4 maintain reproductive capacity

The human genome contains 24 gag-like capsid genes derived from deactivated retrotransposons conserved among eutherians. Although some of their encoded proteins retain the ability to form capsids and even transfer cargo, their fitness benefit has remained elusive. Here we show that the gag-like genes PNMA1 and PNMA4 support reproductive capacity. Six-week-old mice lacking either Pnma1 or Pnma4 are indistinguishable from wild-type littermates, but by six months the mutant mice become prematurely subfertile, with precipitous drops in sex hormone levels, gonadal atrophy, and abdominal obesity; overall they produce markedly fewer offspring than controls. Analysis of donated human ovaries shows that expression of both genes declines normally with aging, while several PNMA1 and PNMA4 variants identified in genome-wide association studies are causally associated with low testosterone, altered puberty onset, or obesity. These findings expand our understanding of factors that maintain human reproductive health and lend insight into the domestication of retrotransposon-derived genes.

genetics↗