Impact of Zika virus infection on cortical GABAergic interneurons development

Two main neuronal populations compose the cerebral cortex: pyramidal projecting glutamatergic neurons and GABAergic interneurons. These populations' development impacts brain function through neurochemical inhibition/excitation balance. Diverse factors can disrupt the steps of neuronal development (proliferation, migration and positioning, differentiation), such as viral infections during pregnancy. Zika virus infection has been shown to lead to diverse brain developmental alterations, resulting in severe impacts on children's development. Previous studies of our lab showed a higher susceptibility to seizures in animals infected with the virus, pointing to a neurochemical imbalance. We focused our studies on the impact of Zika virus infection on steps of cortical GABAergic interneurons development. We used in vitro (E14 brain slices or MGE dissociated cells cultured for 5-7 days) and in vivo (intracerebroventricular injections in E13 or P0 mice or intraperitoneal injections in P0 mice) assays. Control groups were inoculated with Vero cells supernatant (MOCK). Brain slices of in vivo models were analyzed at P0, P14 or P60.  We examined the development steps through immunohistochemical assays, in which primary antibodies used were against calbindin, somatostatin, parvalbumin (GABAergic subpopulations markers), caspase (cell death), 4G2 (viral protein) and PH3 combined with EdU assay (proliferation). We used Student’s t-test for statistical comparisons between groups. In our in vitro model of dissociated cells, we didn't observe a difference between the groups on caspase. Proliferatin assays point to a reduced proliferation on ZIKA virus infected slices. In vivo models pointed to disturbances in calbindin+  interneurons positioning on cerebral motor and somatosensorial cortical layers at different ages. Congenital ZIKA virus infection doesn't seem to interfere with GABAergic progenitors' death but seems to impact proliferation and cell positioning on the cortical wall.