Antibody analyses revealed that nucleosomal core histones on transgenes in normal germ cells are underacetylated relative to those on chromosomes. In contrast, transgene histones in sig-2 germ cells are detectably hyperacetylated. Interestingly, fluorescence light microscopy of DAPI stained sig-2 germ cells also indicates dysfunctional synapsis or pairing of meiotic chromosomes. These data suggest that normal SIG-2 function is required for some aspect of germ cell chromatin assembly that affects both meiotic synapsis and genetic silencing. These findings may shed light on a role for chromatin regulation in the maintenance of germ cell totipotency during development.
Germ cells are the progenitors of all cell types in metazoan organisms.
The mechanisms that allow germ cells to retain totipotency throughout development are poorly understood. Understanding fundamental characteristics that differ between germ cells and all somatic tissues may point to aspects of germ cell biology that affect totipotency. One obvious difference between the soma and germ cells in C. elegans is that transgene expression is strongly suppressed in the germ line, but not in the soma1. This indicates that germ line silencing mechanisms are essential for germ cell function. One potential role is in chromatin organization.