Rex Williams Ph.D.


Rex Williams
Undergraduate Institution: Texas A&M University
Department: Genetics
PI: Terry Magnuson
Research Summary The relationship between three-dimensional conformation of chromosomes and the regulation of gene expression is an important emerging concept in the field of epigenetics.   Several recent studies using technologies based on Chromosome Conformation Capture (3C) have demonstrated that sequences separated by greater than hundreds of kilobases on the same chromosome can be positioned in close proximity via chromosome looping. Furthermore, these studies show evidence that changes in chromosome conformation are correlated with changes in gene expression, suggesting that the three-dimensional architecture of chromosomes has functional relevance. X-chromosome inactivation (XCI) is an epigenetic process that inactivates one X-chromosome in every mammalian female somatic cell. Once chosen for inactivation, the Xi becomes enriched for epigenetic modifications associated with transcriptional silencing and adopts a structure consistent with compact heterochromatin. While histone modifications required for XCI have been identified, the Xi-specific sequences that mediate the long-range intrachromosomal interactions required for XCI are largely unknown.   My research involves combining 3C and next-generation sequencing (Hi-C) with chromatin immunoprecipitations (ChIP) to generate a map of Xi-specific long-range genomic sequence interactions that are associated with the histone modifications that are required for XCI. In this study, my goal is to generate a map of the higher-order three-dimensional architecture of the Xi and to identify long-range sequence interactions that may be required for the establishment and maintenance of XCI.