Although the root cause(s) of stuttering remain unknown, evidence has accumulated from twin and adoption studies that genetics plays a role. Dennis Drayna, a geneticist at the National Institute on Deafness and other Communication Disorders (NIDCD), undertook a study to identify the genes involved in the disorder with the ultimate goal to elucidate poorly defined neural structures and functions regulating human speech. Results from the study were reported recently in the New England Journal of Medicine [1].

The study focused on a Pakistani family in whom previous work had determined that stuttering was linked to the long arm of chromosome 12 (chromosome 12q). In addition to the affected and unaffected members of these families, the study also included 123 Pakistani stutterers who were unrelated and 270 stutterers from the United States and England. Children under the age of eight were excluded, as they often recover from stuttering, as were people with neurologic or psychiatric symptoms. The control group (non-stutterers) consisted of 96 Pakistanis and 276 North American whites.

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Researchers at the National Institutes of Health have identified DNA variants in mothers and fetuses that appear to increase the risk for preterm labor and delivery. The DNA variants were in genes involved in the regulation of inflammation and of the extracellular matrix, the mesh-like material that holds cells within tissues.

“A substantial body of scientific evidence indicates that inflammatory hormones may play a significant role in the labor process,” said Alan E. Guttmacher, M.D., acting director of the NIH’s Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). “The current findings add evidence that individual genetic variation in that response may account for why preterm labor occurs in some pregnancies and not in others.”

The central dogma of molecular biology deals with the detailed residue-by-residue transfer of sequential information. It states that such information cannot be transferred from protein to either protein or nucleic acid. The irreversible flow of information is from DNA to RNA to protein; DNA is transcribed into messenger RNA (mRNA) and subsequently translated into protein. However, in recent years it has become clear that additional genetic information exists in the human genome. Non-protein coding RNA (ncRNA) refers to mRNA that is transcribed from DNA but is not translated into protein. These sequences, once thought of as “junk DNA” – portions of the DNA sequence of the genome that don’t have a function – are being found to have crucial roles in human development, physiology and disease. Indeed, recent studies suggest that there are thousands of ncRNAs in the human genome [1-2].

Non-coding RNAs include a class of molecules called microRNAs (miRNAs or miRs). MicroRNAs are highly expressed in normal tissues and are being found to have critical roles in gene regulatory processes during cellular development and differentiation. MicroRNAs are small ncRNAs ~21-nucleotides long that regulate gene expression at the post-transcriptional level. MicroRNAs function by binding target mRNA molecules and either inhibiting translation into protein or targeting them for degradation. Abnormal microRNA expression has been linked to many human diseases, including schizophrenia, autism and cancer.
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