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Analysis of Genomic Structures Involved in Chromosome 22q Deletion Syndrome
Start Date: 12/3/2018Start Time: 1:00 PM
End Date: 12/3/2018End Time: 3:00 PM

Event Description
BIOMED PhD Thesis Defense

Title:
Analysis of Genomic Structures Involved in Chromosome 22q Deletion Syndrome

Speaker:
Steven Pastor, PhD Candidate
School of Biomedical Engineering, Science and Health Systems 
Drexel University

Advisor:
Ming Xiao, PhD
Associate Professor
School of Biomedical Engineering, Science and Health Systems
Drexel University

Abstract:
Chromosome 22q11.2 Deletion Syndrome (22q11DS) is the most common microdeletion disorder in humans. The disease demonstrates wide phenotypic variability with affected individuals exhibiting significant medical problems. In roughly 90% of affected individuals, a de novo heterozygous ~3 million base pair deletion occurs from an aberrant recombination mediated by low copy repeats (LCRs) in the chromosome 22q11.2 region. The combination of large, near-identical segments makes the LCRs substrates in non-allelic homologous recombination (NAHR), leading to genomic rearrangements. Unfortunately, these same characteristics make the LCRs difficult to reliably sequence and identify rearrangement breakpoints within the homologous chromosome 22 LCRs in individuals with 22q11DS.

By leveraging the increased sensitivity afforded by long single DNA molecule optical mapping on nanochannel arrays, coupled with 10XGenomics whole-genome sequencing, and CRISPR-Cas9 labeling, this thesis reveals the previously unmapped structure and variation of the chromosome 22 LCRs and surrounding regions. These approaches provide enhanced insight into the role of LCRs in producing the 22q11DS.

Through the optical mapping of 154 healthy genomes, results indicate unprecedented variability in LCR structure. Further, optical mapping of 6 trios each consisting of 2 healthy parents and 22q11DS-affected probands, reveals direct evidence of NAHR, observed for the first time. Finally, methods developed to provide resolution below the level of optical maps reduce the ambiguous breakpoint regions and indicate 2 possible recombination signatures. The approaches developed here will likely represent a paradigm, providing resources for the analysis of numerous other significant regions of the genome that have failed accurate elucidation because of the presence and complexity of other LCRs, many of which cause disease.
Contact Information:
Name: Ken Barbee
Phone: 215-895-1335
Email: barbee@drexel.edu
Steven Pastor
Location:
One Drexel Plaza, Room 34, located at 3025 Market Street.
Audience:
  • Undergraduate Students
  • Graduate Students
  • Faculty
  • Staff

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