Led by Eddy Rubin, the Director of Berkeley Lab's Genomics Division and the U.S. Department of Energy Joint Genome Institute, a research team introduced the human-accelerated conserved noncoding sequence 1 (HACNS1) into a mouse embryo system.
The researchers observed that the human sequence could influence the molecular machinery to yield human limb and thumb development patterns.
According to them, the sequence enhanced gene expression in limb and brain, which meant a gain of function.
Rubin says that the next question before the research team was if the human and chimp elements have sequence differences, why they still function similarly.
For determining this, they placed the chimp version of the gene sequence in mice, and found that the human and chimp sequences have very different expression properties.
"Our results led us to believe that HACNS1 has contributed to uniquely human aspects of digit and limb patterning. We suspect the gain of function in HACNS1 may have influenced the evolution of these or other human limb features by altering the expression of nearby genes during limb development," Rubin said.
The researchers concede that they have yet to define the precise molecular mechanism by which the substitutions in HACNS1 confer the human expression patterns.
"To get a more complete picture of our HACNS1 factors into human morphological evolution will require additional studies. If this really is deterministic, you should see some type of change. But it will be a long, hard path forward," according to Rubin," Rubin said.
The study reinforces the conclusion that certain regions of genomes can have a powerful regulatory influence on gene expression or the production of proteins.
"The study points to how human nucleotide substitutions can alter the regulation of genes in humans distinct from that of non-human primates, such as chimps. This highlights a strategy that could be applied across the genome to understand at a molecular level what leads to differences between humans and non-human primates," said Rubin.
The study has been published in the online edition of the journal Science.