Deletion of an X-inactivation boundary disrupts adjacent gene silencing
Open Access
- Author:
- Horvath, Lindsay Marie
- Graduate Program:
- Genetics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 14, 2013
- Committee Members:
- Laura Carrel, Dissertation Advisor/Co-Advisor
Sergei A Grigoryev, Committee Member
Jeffery Thomas Sample, Committee Member
David Joseph Spector, Committee Member - Keywords:
- X chromosome
gene expression
domain boundary
boundary regulation
X-chromosome inactivation - Abstract:
- In mammalian females, genes on one X chromosome are largely silenced by X-chromosome inactivation (XCI), although some “escape” XCI and are expressed from both X chromosomes. Escape genes can closely juxtapose X-inactivated genes and provide a tractable model for assessing boundary function at epigenetically regulated loci. To delimit sequences at an XCI boundary, we examined female mouse embryonic stem cells carrying X-linked BAC transgenes derived from an endogenous escape locus. Previously we determined that large BACs, carrying escapee Kdm5c and flanking X-inactivated transcripts, are properly regulated. Here we identify two lines with truncated BACs that lack all or part of the distal Kdm5c XCI boundary. This boundary is not required for escape, since despite integrating into regions that are normally X inactivated, transgenic Kdm5c escapes XCI, as determined by RNA FISH and by structurally adopting an active conformation that facilitates long-range preferential association with other regions that escape XCI. Yet, XCI regulation is disrupted in the transgene fully lacking the distal boundary; integration site genes up to 350 kb downstream of the transgene now inappropriately escape XCI. Altogether, these results reveal two genetically separable XCI regulatory activities at Kdm5c. XCI escape is driven by a dominant element(s) retained in the shortest transgene that therefore lies within or upstream of the Kdm5c locus. Additionally, the distal XCI boundary normally plays an essential role in preventing nearby genes from escaping XCI.