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Unequal exchange at the Charcot-Marie-Tooth disease type 1A recombination hot-spot is not elevated above the genome

L L Han1, M P Keller, W Navidi

  • 1Molecular Biology Program, Center for Computational and Experimental Genomics, University of Southern California, 835 West 37th Street, Los Angeles, CA 90089-1340, USA.

Human Molecular Genetics
|August 1, 2000
PubMed

Insights

Unequal recombination between Charcot-Marie-Tooth disease type 1A repeats occurs at the genome average rate, not a hotspot. This finding challenges previous assumptions about recombination hotspots in humans.

Area of Science:

  • Genetics
  • Molecular Biology
  • Human Disease

Background:

  • Micro-duplications and microdeletions, often caused by meiotic recombination between homologous repeats, are linked to numerous human diseases.
  • Charcot-Marie-Tooth disease type 1A (CMT1A) is the first identified microduplication syndrome, resulting from unequal crossing over between highly similar repeats (CMT1A-REPs) on chromosome 17.

Purpose of the Study:

  • To directly measure the frequency of unequal recombination within the proposed hotspot region of the CMT1A repeats.
  • To compare the recombination rate in the CMT1A hotspot to the average male genome recombination rate and other known hotspots.

Main Methods:

  • Direct measurement of unequal recombination frequency in the CMT1A hotspot region using sperm from four normal individuals.
  • Analysis of recombination rates in the context of homologous repeat alignment and comparison with yeast and human mini-satellite recombination data.

Main Results:

  • Contrary to previous suggestions of a hotspot, unequal recombination between CMT1A-REPs occurs at a rate similar to the average male genome rate (approximately 1 cM/Mb).
  • The recombination rate is consistent with equally aligned repeats, suggesting no significant enhancement.
  • The CMT1A hotspot contrasts with highly enhanced recombination hotspots like MS32, indicating unique mechanisms or characteristics.

Conclusions:

  • The CMT1A repeat region does not function as a recombination hotspot; its recombination rate is at the genome average.
  • This finding extends observations from yeast to humans, suggesting that recombination between distant repeats on the same chromosome can occur at similar frequencies to allelic recombination.
  • The CMT1A region may represent a region of average recombination potential within a larger recombination cold-spot.

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