This implies that a complete prohibition of nerve- or germ-cell generation in animals might not be necessary.
The H3K36me patterns maintained by MES-4 reflect the transcriptional activity that occurred in the germ line of the preceding generations, and stable maintenance of these patterns between generations is essential for germ cell function within each generation.
This template creates a chromatin signature that may be sufficient to maintain accessibility of promoters to basal transcription machinery, obviating the need for the induction of specific transcription factors to drive germ cell specification at each generation.
The clustering of two confined cases and, possibly, a third case, of germ cell neoplasms in three generations of the same family pointed to a genetic component in the aetiology of some of these neoplasms.
Further, roles for the H3K4 demethylases rbr-2 and spr-5 were detected in germ cell maintenance over the generations under conditions of high temperature stress, which was exacerbated in strains where function of both genes was reduced.
In the most recent study, Skinner and colleagues [ 102] showed that maternal exposure to vinclozolin during pregnancy altered methylation patterns and gene expression of primordial germ cells in F3 generation male fetuses, compared with the F3 generation control offspring.
Transient expression of such transgenes in germ cells can impart a transgenerationally stable epigenetic memory: H3K4me2 that was incorporated into the transgene chromatin during its expression in germ cells is maintained for many (>20) generations thereafter, irrespective of its lack of germ cell expression in the later generations.
Gene ontology (GO) term enrichment analysis also highlighted the signature of gametogenesis with enrichment of GO terms related to gametogenesis (Additional file 3) including "cellular process involved in reproduction in multicellular organism" (GO 0022412), "gamete generation" (GO 0007292), "germ cell development" (GO 0007281), and "regulation of cell cycle" (GO 0051726).
The effects of maternal vinclozolin on germ cells in F3 generation adult female offspring also have been explored, and 43 differentially methylated genes were identified [ 100].
