This proposed program project is to study a unique rat model of developmental learning disability that uses methods of developmental neurobiology, structural anatomy, and behavior to analyze the functions of three candidate dyslexia susceptibility genes (CDSGs). Neuropathologic studies in human dyslexic brains and previous animal models have underscored the importance of focal neuronal migration defects and developmental plasticity for some of the dyslexic deficits. The discovery of CDSGs challenges us to analyze the effects of this genetic variation on brain development, structure, and behavior with respect to learning disability. Using an in utero electroporation method developed in their laboratories, the investigators will transfect into young neurons in the ventricular zone short hairpin RNAs or overexpression constructs targeted against homologs in the rat of CDSG Dyx1c1, Kiaa0319, or Dcdc2. They have already seen that this procedure leads to abnormal neuronal migration, alters neuronal morphology, and causes secondary effects in untouched neighboring neurons, thus producing a picture reminiscent of dyslexic brains. Interesting behavioral alterations are also seen. Project I will analyze Dyx1c1's interaction with genes with known molecular pathways involved in process extension, nuclear movement, and cell adhesion, the domains on the Dyx1c1 critical to function. Project II will characterize anatomic changes (cortical architecture, cell identity, morphology, and connectivity) associated with knockdown or overexpression of CDSGs. Project III will uncover behavioral consequences of CDSG disruption (auditory processing and learning), and will attempt to ameliorate the effects of these genetic manipulations by behavioral interventions. The three interactive projects will be supported by an Administrative Core, an in utero Electroporation Core, and a Neurohistology, Morphometry, and Data Processing Core. A better understanding of the functions of CDSGs will shed a broader light on mechanisms of normal brain development and on the abnormalities seen in developmental dyslexia, but also offering the possibility of earlier detection, biologically-based subtyping, and improved treatment.
Animal models of human disorders have traditionally been helpful for moving the field forward and leading to better diagnostic and treatment approaches. There are few animal models for learning disorders in general, and only one for dyslexia. Results from the proposed work are apt to help us understand human dyslexia more fully, diagnose it more accurately, and define better treatment modalities.
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