Variable gene expression seen in different ethnic groups

Research published in the journal Nature Genetics last week showed that variation between different ethnic groups, such as susceptibility to certain diseases, may be explained by variable gene expression.

Samples collected for the International HapMap Project were used in the study. The HapMap was published last year and maps the frequency of single base pair differences (called SNPs or single nucleotide polymorphisms) in different human populations.

Richard Spielman, Vivian Cheung and their team at the University of Pennsylvania in Philadelphia examined expression levels of more than 4000 genes in 142 banked cell lines taken from individuals of European and Asian descent. They found that 25 per cent of the genes had expression patterns with statistically significant, although often small, differences depending on whether they came from a European or Asian sample. Of this 25 per cent, 35 genes had expression levels that differed, on average, as much a twofold. The team were initially taken aback by the large number of genes whose expression varied. Spielman told Nature 'It comes as somewhat of a surprise'. However, when the comparison was repeated with twenty four Asian residents of Los Angeles the results were almost identical to the pattern of expression seen in the Asian cell lines, showing the differences were due to genetically determined characteristics rather than environmental factors.

It is unclear whether the differences observed between the ethnic groups are due to nearby regulatory regions of DNA which control the gene's level of expression or due to differences in SNPs located near the genes of interest. Many other types of genetic variation also distinguish individuals and ethnic groups, such as additions or deletions of large pieces of DNA as well as SNPs. The extent to which this information can be of clinical interest is still unclear, however it may help determine disease risks associated with certain genetic variants.