, 2006). Interestingly, RhoA depletion affects both the stability of the actin and tubulin cytoskeleton with increased levels in G-actin and tyrosinated tubulin. These alterations result in double cortex formation due to profound defects in RG as clearly demonstrated by electroporation and migration data presented here. Notably, scattering of progenitor cells (and hence RG) is also observed in the TISH rat and HeCo mice, both still
unknown mutations, but causing SBH GDC-0068 price similar to the phenotype observed in the RhoA cKO mice (Croquelois et al., 2009, Fitzgerald et al., 2011 and Lee et al., 1997). Heterotopic cortical masses can be also generated by overexpression of wnt ligands due to accumulation
of newly generated neurons in the intermediate zone (Munji et al., 2011). Given that scattering of progenitors is not only in the RhoA cKO mice but also in other cases linked to the phenotype of SBH, we propose that defects in the RG scaffold, rather than in migrating neurons themselves, may also account for some other cases of SBH formation caused by mutation of distinct genes. This view on the etiology of “migrational” disorders has also profound implications for such disorders in human patients as it may help to explain the often rather divergent phenotypes observed in patients and mouse models, as e.g., upon Lis1 or Dcx mutations (Götz, 2003 and Kerjan and Gleeson, 2007). Given the profound differences in the RG scaffold in rodent and human cerebral cortex with additional glial cells inserted into the outer SVZ (Fietz et al., 2010, Hansen et al., 2010, check details Reillo et al., 2010 and Smart et al., 2002), which exist only in small numbers in the lissencephalic rodent cerebral cortex (Shitamukai et al., 2011 and Wang et al., 2011), a role in RG may well explain
these differences in phenotypes observed in rodents and humans. Indeed, the RG cells in the outer SVZ may be involved in gyrification (Fietz et al., 2010 and Reillo et al., 2010), consistent with the concept that defects in their process formation or maintenance may interfere with gyrification and hence result in lissencephalic brains in human patients. Thus, our data prompt a model for lissencephaly and double Phosphoprotein phosphatase cortex formation by proposing a key role of the stabilized forms of the tubulin and actin cytoskeleton for RG process maintenance. Homozygous RhoAfl/fl ( Jackson et al., 2011) were crossed to Emx1::Cre/RhoAfl/+ mice (day of plug = E0) to obtain the Emx1::Cre/RhoAfl/fl (cKO) and littermate controls phenotypic WT embryos (RhoAfl/fl or Emx1::Cre/RhoAfl/+). Genotyping was performed by polymerase chain reaction (PCR), and each phenotypic analysis was done with at least three independent litters. Immunohistochemistry was performed as described previously (Cappello et al.