A microRNA mechanism may lie at the heart of why some skin cell growth goes unchecked, according to a paper published today in Nature. The authors found that one microRNA regulates the differentiation of progenitor skin cells into the stratified outer layers of the skin.

Elaine Fuchs, from Rockefeller University, led the study and tracked the expression of each skin-associated microRNA from the early stages of embryonic development when the epidermis is forming, until the epidermis is completely formed. The researchers showed that microRNA-203 (miR-203) is expressed only in terminally differentiated cells, and that it downregulates a master regulator gene, p63, which maintains pluripotency in skin stem cells. By suppressing p63, miR-203 allows those pluripotent cells to differentiate into the stratified layers that make up the skin. The group also showed that evolutionarily, all land-dwelling vertebrates show a similar expression pattern of miR-203 and targeting of p63.

"If miR-203 becomes low in certain tissues, then absence of miR-203 might lead to abnormal growth," Rui Yi, first author of the paper told The Scientist. "In some of our other preliminary data we do observe low levels of this microRNA in squamous cell carcinoma in the lab."

"It will be interesting to see the consequences of the mir-203 knockout in mice and the consequences for tissue morphogenesis in stratified epithelial," Frank McKeon, from the Harvard Medical School, who was not involved in the study, told The Scientist in an Email. Because the paper used microRNA silencers and not knockout experiments to observe the effect of silencing miR-203, the full picture of miR-203's role may not have been revealed, McKeon added.