Agenesis of the corpus callosum is found in 1 in 4,000 individuals and is associated with a wide range of developmental defects and syndromes (Paul et al., 2007). Many affected patients have mental retardation, seizures, or autism spectrum disorders. There are many causes of callosal agenesis in humans, and it is commonly Adriamycin associated with cortical malformations or other midline defects, although it can also be an isolated finding in otherwise quite normal individuals. There are many identified genetic syndromes associated with callosal agenesis, some with identified genes and many others with still unidentified genes (Paul et al., 2007). One interesting, recently
identified callosal agenesis gene is the Zfhx1b (also called SMAD-interacting-protein 1 [Sip1]) transcription factor that has been identified as the etiology of Mowat-Wilson syndrome (Mowat et al., 2003). In mice, this transcription factor has been shown to be downstream of Bmp signaling in the cortex and to also integrate this pathway with Wnt signaling in cortical midline development
(Miquelajauregui et al., 2007). This is particularly interesting, considering our finding in this study that there are potent roles for both Bmp and Wnt signaling in regulating the development of the corpus callosum. It seems likely that other genes regulating these pathways Apoptosis inhibitor will turn out to be causative for callosal agenesis as some of the syndromes with unknown genes are identified. In addition, our discovery that an inherited form of callosal agenesis (the mutant phenotype in our mice) could be rationally targeted and successfully treated by replacing a
signaling molecule missing in the mutant mice is of potential significance for the future application of translational approaches to developmental disorders. It is possible that future application of reagents that regulate signaling at the appropriate developmental mafosfamide time could provide specific interventions, allowing treatment of patients with developmental phenotypes associated with specific defects in axon outgrowth. The individual alleles used in the study are detailed in the Supplemental Experimental Procedures. All mice were bred using standard mouse husbandry approaches to obtain the genotypes described in the text and according to UCSF IACUC standards and protocols. In addition, all procedures were performed with approval of the UCSF IACUC. This procedure was performed using a standard procedure with plasmids as described in the text. For all electroporation experiments, multiple litters (at least three) were obtained for each construct and high-expressing, properly targeted electroporations were collected. A minimum of n = 6 were examined, and the results were uniform. Standard techniques were used for all of this analysis and are described in detail in the Supplemental Experimental Procedures, as well as the sources for antibodies and materials.