Linkage disequilibrium in human populations.

Area of Science:

• Population Genetics
• Human Evolutionary Biology
• Genomic Mapping

Background:

• Human linkage maps show population constancy, but linkage disequilibrium (LD) maps vary significantly.
• Differences in LD maps correlate with population history, particularly between sub-Saharan African and non-African populations.
• Major bottlenecks in African-derived populations altered heterozygosity and LD parameters (Malecot parameters M and epsilon).

Purpose of the Study:

• To validate the use of a cosmopolitan LD map for diverse populations.
• To establish a method for creating regional LD maps by fitting local data to a global map.
• To assess the information recovery and efficiency of LD mapping across different ethnic groups.

Main Methods:

• Development of a cosmopolitan LD map using a large, high-density typed sample.
• Fitting sample LD data to the cosmopolitan map to estimate Malecot parameters.
• Scaling cosmopolitan maps using estimated epsilon values to assess information recovery.

Main Results:

• A cosmopolitan LD map effectively represents diverse populations.
• Fitting local LD data to the cosmopolitan map allows for regional map creation.
• Scaled cosmopolitan maps recover substantial information compared to local maps, with varying scaling factors for European, Yoruba, and African American populations.
• Scaling factors suggest a common bottleneck around 173,500 years ago, distinct from the ~100,000-year-old migration out of Africa bottleneck.

Conclusions:

• Cosmopolitan LD maps are valuable tools for genetic studies across diverse human populations.
• Eurasian populations are efficient for genome-wide scans, while populations of recent African origin excel at identifying causal polymorphisms.
• The findings support evolutionary models involving ancient population bottlenecks and migrations.