title: Genome-wide analysis of the maternal-to-zygotic transition in Drosophila primordial germ cells.
abstract: BACKGROUND
  During the maternal-to-zygotic transition (MZT) vast changes in the embryonic transcriptome are produced by a combination of two processes: elimination of maternally provided mRNAs and synthesis of new transcripts from the zygotic genome. Previous genome-wide analyses of the MZT have been restricted to whole embryos. Here we report the first such analysis for primordial germ cells (PGCs), the progenitors of the germ-line stem cells.
  
  
  RESULTS
  We purified PGCs from Drosophila embryos, defined their proteome and transcriptome, and assessed the content, scale and dynamics of their MZT. Transcripts encoding proteins that implement particular types of biological functions group into nine distinct expression profiles, reflecting coordinate control at the transcriptional and posttranscriptional levels. mRNAs encoding germ-plasm components and cell-cell signaling molecules are rapidly degraded while new transcription produces mRNAs encoding the core transcriptional and protein synthetic machineries. The RNA-binding protein Smaug is essential for the PGC MZT, clearing transcripts encoding proteins that regulate stem cell behavior, transcriptional and posttranscriptional processes. Computational analyses suggest that Smaug and AU-rich element binding proteins function independently to control transcript elimination.
  
  
  CONCLUSIONS
  The scale of the MZT is similar in the soma and PGCs. However, the timing and content of their MZTs differ, reflecting the distinct developmental imperatives of these cell types. The PGC MZT is delayed relative to that in the soma, likely because relief of PGC-specific transcriptional silencing is required for zygotic genome activation as well as for efficient maternal transcript clearance.
authors.affiliation: Department of Molecular Genetics, University of Toronto, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8.
authors.forename: Najeeb U
authors.initials: NU
authors.lastname: Siddiqui
authors.forename: Xiao
authors.initials: X
authors.lastname: Li
authors.forename: Hua
authors.initials: H
authors.lastname: Luo
authors.forename: Angelo
authors.initials: A
authors.lastname: Karaiskakis
authors.forename: Huayun
authors.initials: H
authors.lastname: Hou
authors.forename: Thomas
authors.initials: T
authors.lastname: Kislinger
authors.forename: J Timothy
authors.initials: JT
authors.lastname: Westwood
authors.forename: Quaid
authors.initials: Q
authors.lastname: Morris
authors.forename: Howard D
authors.initials: HD
authors.lastname: Lipshitz
mesh_terms: D000818:Animals; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics; D047108:Embryonic Development / Q000235:genetics*; D053595:Embryonic Stem Cells / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells / Q000378:metabolism; D020543:Proteome / Q000235:genetics; D023121:RNA, Messenger, Stored / Q000235:genetics / Q000378:metabolism*; D059467:Transcriptome / Q000235:genetics; D015053:Zygote / Q000378:metabolism*
chemical_list: D020543:Proteome; D023121:RNA, Messenger, Stored