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Segmental duplications flank the multiple sclerosis locus on chromosome 17q
Daniel C Chen1, Janna Saarela, Royden A Clark
1Department of Human Genetics, David Geffen School of Medicine at UCLA, University of California, Los Angeles, California 90095, USA.
Genome Research
|July 17, 2004
Summary
Large chromosomal duplications flank a Multiple Sclerosis (MS) susceptibility locus. This unique genomic structure, including inversions, may influence gene activity and contribute to MS genetic risk.
Area of Science:
- Genomics
- Human Genetics
- Molecular Biology
Background:
- Large chromosomal rearrangements like duplications and inversions are common in mammalian genomes.
- A specific locus on human Chromosome 17q24 is associated with Multiple Sclerosis (MS) susceptibility.
- Understanding the genomic architecture around disease loci is crucial for identifying genetic risk factors.
Purpose of the Study:
- To investigate the DNA sequence features and structural organization of the region flanking the MS susceptibility locus on Chromosome 17q24.
- To identify potential mechanisms, such as segmental duplications, that could contribute to MS genetic susceptibility.
- To compare the genomic structure of this region across species.
Main Methods:
- Positional cloning and radiation hybrid mapping to define the 3-Mb MS locus.
- Fluorescence in situ hybridization (FISH) to detect copy number variations and duplications.
- Shotgun sequence comparisons to identify duplicated sequences within the 17q22-q24 region.
- Comparative genomics to analyze the orientation of the locus in human, chimp, and mouse genomes.
Main Results:
- Evidence for duplicated sequences in the 17q24 region, with several markers showing increased retention rates.
- FISH and sequence analyses confirmed the presence of segmental intrachromosomal duplications flanking the MS haplotype region.
- Highly homologous DNA sequences (>96% identity) were found at both ends of the MS haplotype.
- The 3-Mb DNA segment is inverted in the mouse genome relative to human and chimp genomes.
- Palindromic sequence stretches were identified flanking the MS locus.
Conclusions:
- The MS susceptibility locus on Chromosome 17q24 is characterized by extensive segmental duplication architecture.
- This duplication structure, potentially involving nonallelic homologous recombination, may impact the biological activity of genes in the region.
- The findings suggest a possible contribution of these genomic features to the genetic background of Multiple Sclerosis.