Study: Human, Chimps Share Similar DNA But Different Gene Regulatory Mechanism

The researchers at the University of Chicago have provided a scientific understanding of the uniqueness of humans. They say that humans and their primate cousin have nearly 90 percent of the similar DNA. But their expression or activity patterns of genes differ across species in ways that help explain each species' distinct biology and behavior.

According to Yoav Gilad, Ph.D., associate professor of human genetics at the University of Chicago, upto 40 percent of the differences in the expression or activity patterns of genes between humans, chimpanzees and rhesus monkeys can be explained by regulatory mechanisms. It is this mechanism that determines whether and how a gene's recipe for a protein is transcribed to the RNA molecule that carries the recipe instructions to the sites in cells where proteins are manufactured.

Such a study conducted by Dr. Gilad and colleagues could have relevance to human health and disease.

"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.

For the study, the team studied gene expression in lymphoblastoid cell lines, laboratory cultures of immortalized white blood cells, from eight humans, eight chimpanzees and eight rhesus monkeys.

On doing so they noticed that the distinct gene expression patterns of the three species can be explained by matching changes in genetic and epigenetic regulatory mechanisms that determine when and how a gene's DNA code is transcribed to a messenger RNA (mRNA) molecule.

According to Dr. Gilad, the epigenetics process known as histone modification also differs in the three species. The presence of histone marks during gene transcription indicates that the process is being prevented or modified.

"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.

What were similar among the three species are the promoter regions of DNA that initiated transcription of a particular gene.

It is surprising when Dr. Gilad's lab found that transcription factor binding and histone modifications were identical in over 67 percent of regulatory elements in DNA segments that are regarded as promoter regions.

The presentation titled, "Genome-wide comparison of genetic and epigenetic regulatory mechanisms in primates." were described on Nov. 6 at the American Society of Human Genetics 2012 meeting by Yoav Gilad