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Combining Measures of Senescence with Genomic Data for Isolated African Populations.


Brenna Henn
Carlos Bustamente

 This seed grant aimed to verify the ages of elderly individuals in a sample of Khomani San “Bushmen” from South Africa. With verified data, the researchers then aim to identify genetic loci associated with longevity in their sample. In November 2011, the researchers returned to South Africa and conducted follow-up interviews with 60 subjects; additionally they were able to enroll 41 new subjects in the study for a total of 101 subjects. They confirmed that half of their sample exceeded 50 years of age (up to age 98). Additionally, 140 Khoe-speaking Nama from the Richtersveld were also enrolled in the study including many individuals identifying as 70-100 years old. From collected saliva samples, 78 high-coverage exomes have been successfully sequenced; the next-generation sequence data is currently in preparation to investigate genetic diversity at genes previously associated with longevity. Fifty-eight individuals were also typed on Illumina 450K methylation arrays. The researchers were able to verify a strong correlation between age and hyper-methylation; that is, as individuals aged they accumulated epigenetic methyl modifications. Patterns of hyper-methylation occurred for specific classes of methylation (e.g. enrichment in CpG islands and shores). The Khomani San sample displayed significantly more methlyation than a second sample of hunter-gatherer individuals (Baka from Cameroon) with ages 20-60 years. This result, along with their demographic interviews, suggests that many individuals in their Khomani San sample exceed the age distribution of 20-60 years. The researchers are currently preparing a report on the ethnographic information for the reported ages in the Khomani San and Nama, and writing a manuscript on patterns of methylation as associated with aging using the first African sample of elderly individuals.