Genetics And Genomics Of Neurobehavioral Disorders

To date, molecular geneticists have cloned many genes causing MR or LD: fragile X syndrome, FRAXE, myotonic dystrophy, a-thalassemia mental retardation (ATR-X syndrome), Rett syndrome, neurofibromatosis types 1 and 2, tuberous sclerosis 1 and 2, and other syndromal forms of XLMR. Researchers have also identified genes in regions containing microdeletions that are associated with other neurobehavioral disorders such as Prader-Willi syndrome/Angelman syndrome, Williams syndrome, and del22q11. Other genes related to nonsyndromal XLMR have also been discovered.

At the behavioral end of the genotype-phenotype spectrum, the development, refinement, and standardization of psychometric, clinical, and neuropsychometric instruments has led to greater precision and quantitative assessment of cognitive-behavioral phenotypes identified with neuro-behavioral disorders. Functional magnetic resonance imaging (fMRI) now permits noninvasive access to brain function during the performance of a variety of cognitive and memory tasks. The development of transgenic strategies in rodent models to emulate cognitive-behavioral features of human genetic mutations, for example, a-calcium-calmodulin kinase II, the fragile X mutation, neurofibromatosis type 1, has permitted scientists to examine neuroanatomical, neurobiological, and neurophysiological, functions that could not be investigated previously.

Given standardized instruments by which to assess the multidimensional-ity of behavior, molecular techniques by which deTermane the genetic causes of MR and LD, the development of mouse models to emulate cognitive impairment, and the knowledge of brain function obtained from many areas of investigation in neuroscience, researchers are now in a position to examine and provide a comprehensive analysis of many of the outstanding issues related to genetic and genomic etiologies of cognitive-behavioral dysfunction and their respective neurobiological and neurophysiological roles. Scientists are at a point where it is possible to weave the various molecular-genetic, genomic, neurobiological, neurophysiological, and neurobehavioral threads together into a cohesive fabric of genes, brain, and behavior in ways about which previous generations of scientists could only dream.

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