November 8, 2012
Genetic Differences Help Explain Similarities And Differences Across Species
April Flowers for redOrbit.com - Your Universe OnlineAmerican Society of Human Genetics 2012 meeting, University of Chicago associate professor of human genetics Yoav Gilad, Ph.D. described the DNA factors that contribute to the differences.
Up to 40 percent of the differences in the expression of genes between humans, rhesus monkeys, and chimpanzees, according to Dr. Gilad, can be explained by regulatory mechanisms. These mechanisms determine whether and how a gene's recipe for a protein is transcribed to the RNA molecule that carries that recipe to the sites in cells where proteins are manufactured.
Studies such as this could have relevance to understanding human health and diseases, as well as improving scientific understanding of the uniqueness of humans.
"Through inter-species' comparisons at the DNA sequence and expression levels, we hope to identify the genetic basis of human specific traits and in particular the genetic variations underlying the higher susceptibility to certain diseases such as malaria and cancer in humans than in non-human primates," said Dr. Gilad.
Gilad and his team investigated gene expression in lymphoblastoid cell lines — laboratory cultures of immortalized white blood cells- from eight individuals from each species. The distinct gene expression patterns of the three species can be explained by corresponding changes in genetic and epigenetic regulatory mechanisms. These mechanisms determine when and how a gene's DNA code is transcribed to a messenger RNA (mRNA) molecule.
"These data allowed us to identify both conserved and species-specific enhancer and repressor regulatory elements, as well as characterize similarities and differences across species in transcription factor binding to these regulatory elements," Dr. Gilad said.
The promoter regions of DNA that initiated transcription of a particular gene are among the similarities of the three species. In all three, the team found that transcription factor binding and histone modifications were identical in over 67% of regulatory elements in DNA segments that are regarded as promoter regions.