August 14, 2012
Mole And Shrew Differences Is In Their SOX
redOrbit Staff & Wire Reports - Your Universe Online
Talpidae is a family of small insectivores which includes the moles, shrew moles, and aquatic desmans. New research has found that the large size of the moles' digging front paws, compared to their feet, is controlled by altered timing of expression of the gene SOX9. This research is published in BioMed Central's open access journal EvoDevo.Adaption to burrowing underground has given Fossorial (digging) moles, which are closely related to shrews, specialized strong forelegs, and large, broad hands with a rotated palm. To help with digging, the moles also have an extra digit-like structure in both hands and feet (Os falciforme).
"SOX genes are transcription factors and consequently, when they bind to DNA, they regulate the expression of other genes. SOX9 is specifically involved in chondrocyte (cartilage) differentiation and is also involved in the development of the (Os falciforme)," according to the research.
When comparing the timing and pattern of SOX9 expression during development of the hands and feet of the Iberian mole (Talpa occidentalis), shrew (Cryptotis parva), and mouse (Mus musculus), the multinational team of researchers found that there was a difference in timing of SOX9 expression between the species. SOX9 is expressed sooner in the hands of moles than their developing feet but occurs at the same time during embryo development in front and hind paws for both mice and shrews
"This difference in timing of expression of a gene is called transcriptional heterochrony. It is an extreme example of adaption to an ecological niche, in this case digging, which has selected for animals with bigger front paws, who were better diggers and so on," explained Dr. Constanze Bickelmann, from the Paleontological Institute and Museum, University of Zurich.
Since moles evolutionary split from shrews about 70 million years ago, this selection process has led to a profound, but slow, change to the expression of a protein found in nearly all animal species.