Multi functional studies of candidate dyslexia susceptibility genes in the rat

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The 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 our laboratories, we will transfect into young neurons in the ventricular zone short hairpin RNAs or over-expression constructs targeted against homologs in the rat of CDSG Dyxicl, Kiaa0319, or Dcdc2. We 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 (J.J. LoTurco, PI) will analyze Dyxicl's interaction with genes with known molecular pathways involved in process extension, nuclear movement, and cell adhesion, the domains on the Dyxicl critical to function. Project II (A.M. Galaburda, PI) will characterize anatomic changes (cortical architecture, cell identity, morphology, and connectivity) associated with knockdown or overexpression of CDSGs. Project III (H. Fitch, PI) 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.