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| Status |
Public on Jun 17, 2022 |
| Title |
Precocious expression of Zelda does not initiate early zygotic genome activation |
| Organism |
Drosophila melanogaster |
| Experiment type |
Expression profiling by high throughput sequencing
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| Summary |
During the first stages of development, the fertilized germ cells rapidly transition to totipotency. Maternally deposited mRNAs encode the proteins necessary for reprogramming the transcriptionally quiescent zygotic genome during this maternal-to-zygotic transition (MZT). The transcription factor Zelda is essential for this reprogramming in the Drosophila embryo. Zelda is necessary for transcriptional activation of the zygotic genome, and the absence of Zelda leads to embryonic lethality during the MZT. Excess Zelda activity is also lethal to the embryo, demonstrating that Zelda levels must be precisely controlled during early development. Because Zelda is encoded by a maternally deposited mRNA, Zelda levels in the embryo are controlled at the level of translation. To understand how levels of this essential reprogramming factor were regulated to allow for embryonic development and zygotic genome activation, we investigated the factors that regulated translation of zelda. Brain Tumor (BRAT) is a translational regulator that was previously shown to bind to zelda mRNA in the embryo. We showed that BRAT functions to repress zelda translation, as embryos deficient for maternal BRAT activity prematurely express Zelda. We further showed that in the larval brain, BRAT similarly regulates Zelda levels and identified specific BRAT-binding sites that mediate these effects. Thus, BRAT regulates Zelda in multiple tissues. Because both too little and too much Zelda are lethal to the embryo, we hypothesized that precocious expression of this transcriptional activator might be capable of driving precocious activation of the zygotic genome, leading to embryonic lethality. To test this hypothesis, we performed single embryo RNA-seq at distinct nuclear cycles throughout zygotic genome activation (NC10, NC12, NC13, and NC14) in control and brat-mutant embryos. Our results conclusively demonstrated that in embryos lacking functional BRAT, Zelda target genes were not prematurely activated. Rather, these genes were expressed normally, but become significantly upregulated at nuclear cycle 14, when the division cycle slows. Our data support a model in which zygotic genome activation requires precise coordination between expression of reprogramming factors, such as Zelda, and the slowing of the cell cycle.
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| Overall design |
RNA-seq from single late stage oocytes and single embryos (NC10, NC12, NC13, early NC14 and later NC14) colleted in triplicate or quadruplicate from bratDf/fs1, brat Df or brat fs1, and His2AVRFP flies.
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| Contributor(s) |
Larson ED, Komori H, Fitzpatrick ZA, Krabbenhoft SD, Lee C, Harrison MM |
| Citation(s) |
35876878 |
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| Submission date |
Feb 28, 2022 |
| Last update date |
Sep 15, 2022 |
| Contact name |
Melissa M Harrison |
| E-mail(s) |
[email protected]
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| Organization name |
University of Wisconsin Madison
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| Department |
Biomolecular Chemistry
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| Lab |
1135 Biochemical Sciences Bldg
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| Street address |
420 Henry Mall
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| City |
Madison |
| State/province |
WI |
| ZIP/Postal code |
53706 |
| Country |
USA |
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| Platforms (1) |
| GPL19132 |
Illumina NextSeq 500 (Drosophila melanogaster) |
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| Samples (62)
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| Relations |
| BioProject |
PRJNA811124 |
| Supplementary file |
Size |
Download |
File type/resource |
| GSE197582_GEO_count_table.txt.gz |
1.0 Mb |
(ftp)(http) |
TXT |
SRA Run Selector |
| Raw data are available in SRA |
| Processed data are available on Series record |
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