Cerebral Hemispheres 2

NEUROSCIENTIFICALLY CHALLENGED

NEUROSCIENCE MADE SIMPLER

microRNAs and Schizophrenia

May 19, 2008


Over the past twenty years, our understanding of gene expression has grown tremendously. As is often the case, however, with that increased level of comprehension has come a realization that the process is even more complex than originally thought. Thus, the relatively simple model of mRNA being transcribed from DNA, then traveling to ribosomes where it is translated into proteins (with the help of tRNA and rRNA), is now thought to be just a rough summary of the process. A number of other molecules, such as transcription factors (TFs) and microRNAs (miRNAs), are also involved in the expression of genes.

TFs are proteins that bind to sections of DNA and control the transfer of genetic information from DNA to RNA. They are integral to development, management of the cell cycle, responding to environmental changes, and intercellular communication. miRNAs are small, single-stranded RNA molecules that are transcribed by DNA but not translated into proteins. They are complementary to a particular section of mRNA, and by binding to mRNA can suppress gene expression. TFs and miRNAs can control anywhere from dozens to hundreds of genes in the human genome, with some estimates being much higher.

Fully understanding the role of TFs and miRNAs is essential for uncovering the etiology of genetically based disorders. Recently researchers at Columbia University Medical Center (CUMC) found that changes in miRNA levels can result in cognitive and behavioral deficits. They believe miRNAs could be involved in the development of schizophrenia in humans.

In the past, a higher incidence of schizophrenia has been correlated with a deletion of a small part of chromosome 22, at a location designated as q11.2. One of the genes in that chromosomal section is called Dgcr8. It plays an integral role in miRNA production. Thus, the researchers at CUMC hypothesized that the absence of Dgcr8 and the resultant reduction in miRNAs might be part of the etiology of schizophrenia.

They engineered a strain of mice that lacked the Dgcr8 gene. As they predicted, the mice were found to exhibit the same behavioral and neuroanatomical deficits seen in people with schizophrenia.

While this is an important step in understanding one of the most perplexing disorders medicine has ever had to confront, it is not exactly heartening. miRNAs have widespread effects on gene expression throughout the brain. This may help to explain why schizophrenia has been so difficult to decipher, as it is probably the result of a number of genetic aberrations. Unfortunately, though, it is further indication that schizophrenia is very complex, and much more investigation will be needed to fully comprehend its origin.

YOUR BRAIN, EXPLAINED

Sleep. Memory. Pleasure. Fear. Language. We experience these things every day, but how do our brains create them? Your Brain, Explained is a personal tour around your gray matter. Building on neuroscientist Marc Dingman’s popular YouTube series, 2-Minute Neuroscience, this is a friendly, engaging introduction to the human brain and its quirks using real-life examples and Dingman’s own, hand-drawn illustrations.

  • An informative, accessible and engaging book for anyone who has even the slightest interest in how the brain works, but doesn’t know where to begin. - Dean Burnett, PhD, author, Happy Brain and Idiot Brain

  • Dingman weaves classic studies with modern research into easily digestible sections, to provide an excellent primer on the rapidly advancing field of neuroscience. - Moheb Costandi, author, Neuroplasticity and 50 Human Brain Ideas You Really Need to Know

  • ...a highly readable and accessible introduction to the operation of the brain and current issues in neuroscience... a wonderful introduction to the field. - Frank Amthor, PhD, Professor of Psychology, The University of Alabama at Birmingham, author, Neuroscience for Dummies

  • Reading like a collection of detective stories, Your Brain, Explained combines classic cases in the history of neurology with findings stemming from the latest techniques used to probe the brain’s secrets. - Stanley Finger, PhD, Professor Emeritus of Psychological & Brain Sciences, Washington University (St. Louis), author, Origins of Neuroscience