Study of MicroRNA Helps NIH Scientists Unlock Secrets of Immune Cells
June 3, 2010 - With the rapid and continuous advances in biotechnology, scientists are better able to see inside the nucleus of a cell to
unlock the secrets of its genetic material. However, what happens outside of the nucleus has, in many ways, remained a mystery. Now, researchers with the
National Institutes of Health are closer to understanding how activity outside of the nucleus determines a cell's behavior. They looked at mouse
immune cells and examined the types, amount, and activity of microRNAs, genetic components that help regulate the production of proteins.
Their study provides a map to the variety of microRNAs contained within mouse immune cells and reveals the complexity of cellular
protein regulation. The study appears online in the journal Immunity.
An organism is made up of cells containing genetic material in the form of deoxyribonucleic acid (DNA) residing within the nucleus. An organism's entire collection
of DNA is called its genome and consists of genes, short segments of DNA that code for proteins, and many long segments of DNA that do not contain genes. While
each cell contains the entire genome, not all of a cell's genes are making proteins all of the time. Which genes are turned on and which are turned off,
and when, determine the behavior of a cell, such as the type of cell it becomes, where it goes, and what it does.
"A plethora of cellular functions, ranging from development, differentiation, metabolism, and host defense, are impacted by protein levels," said Rafael
Casellas, Ph.D., the study's principal investigator from the Genomics and Immunity Group of the NIH's National Institute of Arthritis and Musculoskeletal and
Skin Diseases (NIAMS). " We were interested in discovering how microRNAs contribute to the regulation of these functions."
A cell makes proteins through a process called transcription, in which genes are copied from DNA into messenger ribonucleic acid (RNA), which travels from the
nucleus into the body of the cell. Not all RNA transcribed from DNA are messenger RNA, however. There are many other forms of RNA that do not code for
proteins. MicroRNAs (miRNAs), for example, are small strands of RNA that modulate the production of proteins from messenger RNA, thereby helping to
regulate protein levels in the cell. Previous studies have shown that cells are very sensitive to fluctuations in miRNA levels, which require
tight control in order to regulate protein activity effectively.
In the current study, the NIH scientists used a new microsequencing technology to comprehensively identify all of the different miRNAs existing in mouse immune cells.
In addition to increasing the number of known miRNAs, the scientists also discovered several cellular mechanisms that regulate miRNA abundance. The study found that
some miRNA constructs exist in a dormant state within the nucleus until they receive signals from the epigenome to become active. The epigenome regulates
transcription and comprises all of the non-genetic material in the nucleus. Other miRNAs, the researchers determined, are not hampered by these
epigenetic mechanisms and are controlled simply through transcription. However, for some of these miRNAs, abundance depends upon the amount
of target messenger RNA available in the cell.
According to NIAMS Director Stephen I. Katz, M.D., Ph.D., "The data generated from this study represent a useful tool for immunologists and cell biologists to use
for future studies on functional aspects of the immune system and basic miRNA biology."
More information about the NIAMS Genomics and Immunity section can be found
The mission of the National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS), a part of the U.S. Department of Health and Human Services'
National Institutes of Health, is to support research into the causes, treatment, and prevention of arthritis and musculoskeletal and skin diseases; the training
of basic and clinical scientists to carry out this research; and the dissemination of information on research progress in these diseases. For more information about
NIAMS, call the information clearinghouse at (301) 495-4484 or (877) 22-NIAMS (free call) or visit the NIAMS Web site at http://www.niams.nih.gov.
The National Institutes of Health (NIH) - The Nation's Medical Research Agency - includes 27 Institutes and Centers and is a component of the U.S.
Department of Health and Human Services. It is the primary federal agency for conducting and supporting basic, clinical and translational medical
research, and it investigates the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its
programs, visit www.nih.gov.
Source: NIH News: National Institutes of Health