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Mechanisms of Xist-Mediated Gene Silencing During the Initiation and Maintenance of X Chromosome Inactivation


Strehle, Mackenzie (2024) Mechanisms of Xist-Mediated Gene Silencing During the Initiation and Maintenance of X Chromosome Inactivation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/nxq5-hj97.


X chromosome inactivation (XCI) is a critical development process during which one of the two X chromosomes in female mammals is silenced to balance gene expression with males. XCI is initiated by upregulation of the long noncoding RNA (lncRNA) Xist from the future inactive X chromosome (Xi), which recruits a variety of proteins in cis to mediate transcriptional repression that is maintained throughout the lifetime of the organism. Recent studies have demonstrated that silencing following Xist expression is dependent on direct recruitment of the transcriptional silencing protein SHARP (also known as SPEN); however, the mechanism underlying formation of the Xi silencing compartment has remained poorly defined. Similarly, it has long been thought that maintenance of XCI occurs independently of Xist and depends on differential DNA methylation enrichment on the Xi, but the evidence in support of these views is lacking. Here, we show how low copy numbers of Xist can recruit SHARP in super-stoichiometric excess to initiate gene silencing on the X and mediate formation of the silent Xi compartment. We also provide preliminary evidence suggesting that maintenance of XCI is Xist independent, but dependent on DNA methylation and histone deacetylation. Together, these results offer a more holistic view of the molecular mechanisms underlying both initiation and maintenance XCI, as well as provide a framework for further investigation into lncRNA biology and epigenetic regulation more broadly.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:molecular biology; RNA; noncoding RNA; genomics; X chromosome inactivation; gene regulation
Degree Grantor:California Institute of Technology
Division:Biology and Biological Engineering
Major Option:Molecular Biology and Biochemistry
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Guttman, Mitchell
Thesis Committee:
  • Sternberg, Paul W. (chair)
  • Zernicka-Goetz, Magdalena
  • Chong, Shasha
  • Guttman, Mitchell
Defense Date:29 March 2024
Funding AgencyGrant Number
NIH 4DN ProgramU01 DA040612
NIH 4DN ProgramU01 HL130007
New York Stem Cell FoundationNYSCF-R-I13
NIH Directors’ Transformative Research AwardR01 DA053178
California Institute of TechnologyUNSPECIFIED
Record Number:CaltechTHESIS:04182024-125718373
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 1: Xist drives spatial compartmentalization of DNA and protein to orchestrate initiation and maintenance of X inactivation adapted for Chapter 2: Xist spatially amplifies SHARP/SPEN recruitment to balance chromosome-wide silencing and specificity to the X chromosome
Strehle, Mackenzie0000-0003-1410-8701
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16358
Deposited By: Mackenzie Strehle
Deposited On:01 May 2024 19:54
Last Modified:04 Jun 2024 23:07

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