SURVEY OF MAXIMUM CTG CAG REPEAT LENGTHS IN HUMANS AND NONHUMAN-PRIMATES - TOTAL GENOME SCAN IN POPULATIONS USING THE REPEAT EXPANSION DETECTION METHOD/

Repeat Expansion Detection (RED) is an efficient and simple method for detecting repeat expansions in the human genome, including expansion mutations resulting in disease, Here we report the first population su rvey of CTG/CAG repeat lengths in humans using the RED method; we have determined maximum CTG/CAG repeat length in 244 individuals from six human populations: Danes, Chinese, Japanese, Rondonian Surui, Maya and Mbut/Biaka Pygmies, We have also sampled a number of non-human primat es including eight orang-utans (Pongo pygmaeus), seven gorillas (Goril la gorilla), seven pygmy chimpanzees (Pan paniscus), 13 common chimpan zees (Pan troglodytes) and three Hylobatidae (one Hylobates lar, one H .klossii, and one H.syndactylus). Our results demonstrate the existenc e of significant variation in the sizes and frequencies of the longest CTG/CAG repeat length seen per individual both within and between hum an populations, The population differences argue that overall mutation rates at CTG/CAG repeat loci are sufficiently low that mutation does not obliterate the effect of random genetic drift and clearly indicate that population stratification could occur in disease association stu dies using the RED method, No significant differences were detected am ong the non-human primates sampled, Our results also show that both co mmon chimpanzees and pygmy chimpanzees (bonobos) are polymorphic for m aximum length of any CTG/CAG repeats while no variation was found for gorillas and orang-utans.