Chromosome segregation during male meiosis is tailored to rapidly generate multitudes of sperm. Little is known about mechanisms that efficiently partition chromosomes to produce sperm. Using live imaging and tomographic reconstructions of spermatocyte meiotic spindles in , we find the lagging X chromosome, a distinctive feature of anaphase I in males, is due to lack of chromosome pairing. The unpaired chromosome remains tethered to centrosomes by lengthening kinetochore microtubules, which are under tension, suggesting that a 'tug of war' reliably resolves lagging. We find spermatocytes exhibit simultaneous pole-to-chromosome shortening (anaphase A) and pole-to-pole elongation (anaphase B). Electron tomography unexpectedly revealed spermatocyte anaphase A does not stem solely from kinetochore microtubule shortening. Instead, movement of autosomes is largely driven by distance change between chromosomes, microtubules, and centrosomes upon tension release during anaphase. Overall, we define novel features that segregate both lagging and paired chromosomes for optimal sperm production.
Department of Molecular, Cellular, and Biomedical Sciences, Sophie Davis School of Biomedical Education, City University of New York School of Medicine, New York, NY, USA; Graduate Program in Biology, City University of New York Graduate Center, New York 10091, USA.
One possible reason for failure in achieving optimal glycemic control in patients with type 2 diabetes (T2D) is that less attention has been paid to the brain, a fundamental player in glucose homeostasis, that consumes about 25% of total glucose utilization. In addition, animal and human studies indicate that nitric oxide (NO) is a critical player in glucose metabolism. NO synthesis from L-arginine is lower in patients with T2D, and endothelial NO synthase (eNOS)-derived NO bioavailability is lower in T2D.
Incomplete sister centromere decatenation results in centromeric ultrafine anaphase bridges (UFBs). PICH (PLK1-interacting checkpoint helicase), a DNA translocase, plays a crucial role in UFB resolution by recruiting UFB-binding proteins and stimulating topoisomerase IIα. However, the involvement of distinct PICH functions in UFB resolution remains ambiguous.
The kinesin family member 18A () is an essential regulator of microtubule dynamics and chromosome alignment during mitosis. Functional dependency on KIF18A varies by cell type and genetic context but the heritable factors that influence this dependency remain unknown. To address this, we took advantage of the variable penetrance observed in different mouse strain backgrounds to screen for loci that modulate germ cell depletion in the absence of KIF18A.
Cultured pluripotent stem cells are unique in being the only fully diploid immortal human cell lines. However, during continued culture they can acquire significant chromosome abnormalities. Chromosome 12 trisomy is the most common whole-chromosome abnormality found during culture of human induced pluripotent stem cells (iPSCs).
The mammalian kinetochore is a multi-layered protein complex that forms on the centromeric chromatin. The kinetochore serves as the attachment hub for the plus ends of microtubules emanating from the centrosomes during mitosis. For karyokinesis, bipolar kinetochore-microtubule attachment and subsequent microtubule depolymerization lead to the development of inter-kinetochore tension between the sister chromatids.
