Single microRNA fine-tunes innate immun...( Findings: A single microRNA microRNA...),Health

Findings: A single microRNA, microRNA-223, in mice controls the production and activation of granulocytes, white blood cells essential for host defense against invading pathogens.

Relevance: This is the first microRNA shown to play a crucial role in the innate immune response. Absence of microRNA-223 increased the production, differentiation and activation of granulocytes, causing tissue inflammation and damage. Increased production of microRNA-223 may reduce inflammatory conditions and thus the effects of inflammatory diseases such as acute lung respiratory disease syndrome.

CAMBRIDGE, Mass. (February 17, 2008) - Over the last few years scientists have discovered hundreds of microRNAstiny RNAs that regulate the expression of protein-coding genes. However, the functions of these novel molecules in mammals are largely unknown.

Now, scientists in the lab of Whitehead Fellow Fernando Camargo have discovered the first microRNA shown to play a key role in the immune systems early warning systemthe innate immune response. The research, published online on February 17 by Nature, reveals that microRNA-223 controls the production and activation of granulocytes, white blood cells essential for host defense against invading pathogens. The findings may have implications for the treatment of inflammatory conditions as well as leukemia.

MicroRNA-223 is unique because its expression is entirely restricted to a specific branch of the immune system, says Camargo. We found that microRNA-223 is crucial for the development and function of the innate branch of the immune system. Our work suggests that microRNA-223 physiologically fine-tunes both the generation and function of granulocytic cells, delimiting their production and dampening their activation.

The study indicated that microRNA-223 targets Mefc2, a transcription factor that promotes the expansion of granulocyte cell progenitors. (Transcription factors are proteins that reg
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