cortical interneuons also activel avoid enterint the POA and striatum. Sema3a and sema3d are largely responsible for the chemorepulsive activity present in the striatum sensed by cortical interneuron through Neuropilin receptors. Expression of Neuropilin receptors in migrating cortical interneuonrs requires the repression of Nkx2-1 in these cells, via mechanisms that involve expression of transcription factor Zfhx/Sip1.
Molecular mechanisms for controlling tangential migration of CGE and POA interneurons to cortex are not well known
after they get to cortex, interneurons avoid cortical plate and disperese though a set of typical routes: maringal zone, subplate or a region overlapping with the cortical subventricular zone. not year clear if some interneurons prefer certain migratory pathways. The chemoline Cxcl12 has been ifentified as playing an important role in this process cia the G-protein coupled receptors Cxcr4 and Cxcr7. Interneuron preferentially use the routes marked with Cxcl12 to disperse tangentially through the cortex.
Once interneurons have reached an appropriate coordinate within the cerebral cortex they integrate into specfiec cortical layers. Not clear what mechanisms trigger the tangential to radial switch in the migration but timeing of exit seems to correlate with a loss o responsiveness to Cxcl12. When interneuons are allowed to leave migratory streams prematurely as observed in Cxcr4 and Cxcr7, they distribute abnormally.
Interneurons have relatively restricted laminar patterns, most evidence to date suggests that these cells follow specific classes to pyramidal cells to their final destination. This hypothesis holds that interneurons would follow cues procided by infragranular pyramidal cells (layers V-V1) while late born interneurons would preferntially interact with supgranular pyramidal cells *layers 2-4(. similar mechanisms may account for the layering of all cortical interneurons independe of their origin.