Stage-specific transcriptional repression directs selective gene activation in an adult stem cell lineage
Abstract/Contents
- Abstract
- A single fertilized embryo gives rise to more than 200 distinct cell types in the human body. Regulation of cell type specific gene expression is one of the most critical molecular processes in specifying and maintaining these diverse cell fates. Here we show that cell type specific transcriptional repressors, along with activators, play key roles in selective gene expression in cell fate determination. In the Drosophila male germ line stem cell lineage, when progenitor cells cease mitotic proliferation and initiate terminal differentiation, they turn on one of the most dramatic cell type specific transcriptional programs in Drosophila. To investigate how this dramatic cell type specific gene expression is set up, I developed an in vivo synchronous differentiation system to identify the first transcripts turned up, with the idea that these early expressed genes may include "first regulators" that help initiate the terminal differentiation program. Progenitor mitotic spermatogonia that accumulated in bam-/- mutant testes were triggered to differentiate by a single heat shock pulse of expression of Bam. Global gene expression profiling by microarray and RNA-seq across time as spermatogonia synchronously differentiate into spermatocytes identified three distinct steps - 'downregulation', 'initiation', and 'terminal differentiation' -- in the gene expression cascade in the switch. Functional knock down of the first 39 upregulated genes identified 16 new genes required for proper differentiation, 6 of which exhibited particularly strong and early defects. One of the newly identified early genes, tZnF, encodes a multiple zinc finger spermatocyte-specific nuclear protein, required for repressing gene expression of somatic transcripts in male germ cells. Results from double mutant analysis suggest that tZnF is required in spermatocytes to prevent promiscuous activation of somatic transcripts by the testis-specific Meiotic Arrest Complex (tMAC) when it activates testis specific transcripts required for spermatocyte differentiation My results demonstrate how a cell can prevent collateral activation by a promiscuous activator to ensure correct differentiation of a specific cell type. In chapter 4, I characterize five additional genes identified from the early regulator screen. The products of the five genes --testis-specific ATP synthase [beta] chain (CG5389); B9 domain (CG14870); pipsqueak type homeodomain like domain (CG30401); smooth or hnRNP-L, RNA binding domain (CG9218); and tBRD-1, bromodomain (CG13597) -- have diverse molecular functions, ranging from signaling, transcription, and RNA-processing, suggesting that terminal differentiation into spermatocytes is a complicated process involving complex regulatory mechanisms.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2015 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Kim, Jongmin | |
|---|---|---|
| Associated with | Stanford University, Department of Chemical and Systems Biology. | |
| Primary advisor | Fuller, Margaret | |
| Thesis advisor | Fuller, Margaret | |
| Thesis advisor | Chen, James | |
| Thesis advisor | Ferrell, James Ellsworth | |
| Thesis advisor | Khavari, Paul A | |
| Thesis advisor | Lipsick, Joseph Steven, 1955- | |
| Advisor | Chen, James | |
| Advisor | Ferrell, James Ellsworth | |
| Advisor | Khavari, Paul A | |
| Advisor | Lipsick, Joseph Steven, 1955- |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Jongmin Kim. |
|---|---|
| Note | Submitted to the Department of Chemical and Systems Biology. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2015. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2015 by Jongmin Kim
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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