Spatial organization of transcribing loci during early genome activation in Drosophila.

TitleSpatial organization of transcribing loci during early genome activation in Drosophila.
Publication TypeJournal Article
Year of Publication2021
AuthorsHuang, S-K, Whitney, PH, Dutta, S, Shvartsman, SY, Rushlow, CA
JournalCurr Biol
Volume31
Issue22
Pagination5102-5110.e5
Date Published2021 Nov 22
ISSN1879-0445
Abstract

The early Drosophila embryo provides unique experimental advantages for addressing fundamental questions of gene regulation at multiple levels of organization, from individual gene loci to the entire genome. Using 1.5-h-old Drosophila embryos undergoing the first wave of genome activation, we detected ∼110 discrete "speckles" of RNA polymerase II (RNA Pol II) per nucleus, two of which were larger and localized to the histone locus bodies (HLBs). In the absence of the primary driver of Drosophila genome activation, the pioneer factor Zelda (Zld), 70% fewer speckles were present; however, the HLBs tended to be larger than wild-type (WT) HLBs, indicating that RNA Pol II accumulates at the HLBs in the absence of robust early-gene transcription. We observed a uniform distribution of distances between active genes in the nuclei of both WT and zld mutant embryos, indicating that early co-regulated genes do not cluster into nuclear sub-domains. However, in instances whereby transcribing genes did come into close 3D proximity (within 400 nm), they were found to have distinct RNA Pol II speckles. In contrast to the emerging model whereby active genes are clustered to facilitate co-regulation and sharing of transcriptional resources, our data support an "individualist" model of gene control at early genome activation in Drosophila. This model is in contrast to a "collectivist" model, where active genes are spatially clustered and share transcriptional resources, motivating rigorous tests of both models in other experimental systems.

DOI10.1016/j.cub.2021.09.027
Alternate JournalCurr Biol
PubMed ID34614388
PubMed Central IDPMC8612988
Grant ListR01 GM063024 / GM / NIGMS NIH HHS / United States
R01 GM134204 / GM / NIGMS NIH HHS / United States
T32 HD007520 / HD / NICHD NIH HHS / United States