Anatomical, functional and behavioral characterization of a duplicated whisker representation in two murine models of gray matter heterotopia
Aurélien Fortoul
Team Cortical development

Abstract
Gray matter heterotopia (GMH) are characterized by masses of ectopic neurons (or heterotopia) accumulated under the cortex, forming an apparent duplicated cortex. In humans, GMH cause altered cortical functions and epilepsy. During my PhD, I studied two mouse models exhibiting large heterotopia located under the somatosensory cortex. In rodents, a large portion of this cortex is dedicated to cortical whisker representation, essential for exploring their environment. It is organized topographically forming the ‘barrel field’ where each barrel is characterized by aggregates of layer 4 neurons innervated by thalamocortical axons. During my Phd, I investigated the impact of GMH on the development of cortical whisker representation and sensory integration. I used two mouse models of GMH resulting from conditional knockout (cKO) specifically in the dorsal telencephalon of the Eml1 or RhoA genes reproducing two subtypes of GMH: respectively subcortical band heterotopia and periventricular nodular heterotopia. Combining immunohistochemistry, viral tracing, and electrophysiological recordings, I showed in both models that ectopic barrels are present in the heterotopia and that they respond topographically to whisker stimulation, just like normally positioned barrels in the cortex. I also showed that this duplicated representation of the whiskers has little impact on learning a whisker-guided foraging task but rather on locomotion speed in the RhoAcKO model.

Jury
Laurent Nguyen, Rapporteur – GIGA Institute, University of Liège, Belgique
Alessandra Pierani, Rapportrice – Institut Imagine, Paris
Isabelle Ferezou, Examinatrice – Institut NeuroPSI, Saclay
Sophie Chauvet, Présidente – IBDM, Marseille
Jean-Bernard Manent, Directeur de thèse – INMED, Marseille
Françoise Watrin, Co-directrice de thèse – INMED, Marseille
David Robbe, Membre invité – INMED, Marsaille

Monday, 22 september at 2pm, INMED Conference room