Transient transcriptional silencing alters the cell cycle to promote germline stem cell differentiation in Drosophila

Dev Biol. 2018 Feb 1;434(1):84-95. doi: 10.1016/j.ydbio.2017.11.014. Epub 2017 Dec 1.

Abstract

Transcriptional silencing is a conserved process used by embryonic germ cells to repress somatic fate and maintain totipotency and immortality. In Drosophila, this transcriptional silencing is mediated by polar granule component (pgc). Here, we show that in the adult ovary, pgc is required for timely germline stem cell (GSC) differentiation. Pgc is expressed transiently in the immediate GSC daughter (pre-cystoblast), where it mediates a pulse of transcriptional silencing. This transcriptional silencing mediated by pgc indirectly promotes the accumulation of Cyclin B (CycB) and cell cycle progression into late-G2 phase, when the differentiation factor bag of marbles (bam) is expressed. Pgc mediated accumulation of CycB is also required for heterochromatin deposition, which protects the germ line genome against selfish DNA elements. Our results suggest that transient transcriptional silencing in the pre-cystoblast "re-programs" it away from self-renewal and toward the gamete differentiation program.

Keywords: Cell cycle; Differentiation; Germ line; Heterochromatin; Stem cells; Transcriptional silencing.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Cell Differentiation / physiology*
  • Cyclin B / biosynthesis
  • Cyclin B / genetics
  • Drosophila Proteins / biosynthesis
  • Drosophila Proteins / genetics
  • Drosophila melanogaster
  • G2 Phase / physiology*
  • Gene Silencing / physiology*
  • Germ Cells / cytology
  • Germ Cells / metabolism*
  • Heterochromatin / genetics
  • Heterochromatin / metabolism
  • Stem Cells / cytology
  • Stem Cells / metabolism*

Substances

  • CycB protein, Drosophila
  • Cyclin B
  • Drosophila Proteins
  • Heterochromatin
  • bam protein, Drosophila