November 10, 2000

Tiny RNA may regulate development in animals

A group of MGH researchers has discovered a tiny RNA gene that may control developmental timing in creatures as diverse as fish, sea urchins, mollusks, marine worms, flies, nematodes and humans. The team, led by Gary Ruvkun, PhD, of the MGH Molecular Biology Department, showed that a tiny regulatory RNA that controls the transition from larva to adult in the C. elegans nematode worm is present in the genomes of a wide variety of animals.

While most genes carry instructions for production of proteins, an RNA gene codes for production of the single-strand molecule RNA. Most commonly thought of as an intermediary in the process leading from double-stranded DNA to proteins, RNA is believed to have been the dominant informational molecule during the earliest stages of life, an era that has been called the "RNA World." Some of these ancient RNA genes are preserved in modern species, in which they may control very basic functions.

Earlier this year members of the Ruvkun lab published their discovery of the RNA gene called let-7 and its role in C. elegans development. The current study shows that let-7 also is found in animals ranging from fruitflies to mammals, including humans, but not in very primitive animals like sponges and coral nor in plants. Although mammals do not have larval stages, it is possible that let-7 may regulate such developmental transitions as the "molting" of baby teeth or changes associated with puberty. Defects in developmental timing could figure in a variety of human birth defects.

The study, which appeared in the Nov. 2 issue of Nature, was conducted by Amy Pasquinelli, PhD, and Brenda Reinhart, PhD, postdoctoral fellows in the Ruvkun lab, in collaboration with a group of biologists from around the world.