Length-sensitive partitioning of Caenorhabditis elegans meiotic chromosomes responds to proximity and number of crossover sites.

Sensing and control of size are critical for cellular function and survival. A striking example of size sensing occurs during meiosis in the nematode Caenorhabditis elegans. C.

Phosphoregulation of DSB-1 mediates control of meiotic double-strand break activity.

In the first meiotic cell division, proper segregation of chromosomes in most organisms depends on chiasmata, exchanges of continuity between homologous chromosomes that originate from the repair of programmed double-strand breaks (DSBs) catalyzed by the Spo11 endonuclease. Since DSBs can lead to irreparable damage in germ cells, while chromosomes lacking DSBs also lack chiasmata, the number of DSBs must be carefully regulated to be neither too high nor too low. Here, we show that in , meiotic DSB levels are controlled by the phosphoregulation of DSB-1, a homolog of the yeast Spo11 cofactor Rec114, by the opposing activities of PP4 phosphatase and ATR kinase.

Nematode chromosomes.

The nematode Caenorhabditis elegans has shed light on many aspects of eukaryotic biology, including genetics, development, cell biology, and genomics. A major factor in the success of C. elegans as a model organism has been the availability, since the late 1990s, of an essentially gap-free and well-annotated nuclear genome sequence, divided among 6 chromosomes.

Sequential peripheral enrichment of H2A.Zac and H3K9me2 during trophoblast differentiation in human embryonic stem cells.

During the transition from pluripotency to a lineage-committed state, chromatin undergoes large-scale changes in structure, involving covalent modification of histone tails, use of histone variants and gene position changes with respect to the nuclear periphery. Here, using high-resolution microscopy and quantitative image analysis, we surveyed a panel of histone modifications for changes in nuclear peripheral enrichment during differentiation of human embryonic stem cells to a trophoblast-like lineage. We found two dynamic modifications at the nuclear periphery, acetylation of histone H2A.