Soutenance de thèse de Claire GOUNY

The diversity between GABAergic cells appears to be in part predefined by a developmental program. The proliferative area in which interneurons are generated from precursors (spatial embrryonic origin) shapes the morphological and physiological properties that interneurons will exhibit in adult circuits (Butt et al., 2005). Together with the spatial origin, the temporal origin during embryogenesis is another important factor determining the fate of GABAergic cells. For example, neuronal birth date shapes the features that parvalbumin-expressing neurons will display in adulthood: parvalbumin-positive basket cells are generated earlier than axo-axonic cells (Inan et al., 2012; Taniguchi et al., 2013); additionally, parvalbumin-positive cells display different forms of plasticity upon learning that depend on their birth date (Donato et al., 2015). Our group discovered that neurons generated early in neurogenesis act as ‘hub’ neurons in the CA3 area of the neonatal (P5-P7) mouse hippocampus, suggesting that an early birth date endows GABAergic neurons with a unique role during postnatal development. Early born GABAergic cells (ebGABA) cells are not a transient developmental phenomenon because they persist in adulthood. At least some of these cells form a population of GABAergic projection neurons innervating the medial septum (Villette et al., 2016). This indicates that an early birth date could lead to distinct morphophysiological properties even in adulthood.

The diversity between GABAergic cells appears to be in part predefined by a developmental program. The proliferative area in which interneurons are generated from precursors (spatial embrryonic origin) shapes the morphological and physiological properties that interneurons will exhibit in adult circuits (Butt et al., 2005). Together with the spatial origin, the temporal origin during embryogenesis is another important factor determining the fate of GABAergic cells. For example, neuronal birth date shapes the features that parvalbumin-expressing neurons will display in adulthood: parvalbumin-positive basket cells are generated earlier than axo-axonic cells (Inan et al., 2012; Taniguchi et al., 2013); additionally, parvalbumin-positive cells display different forms of plasticity upon learning that depend on their birth date (Donato et al., 2015). Our group discovered that neurons generated early in neurogenesis act as ‘hub’ neurons in the CA3 area of the neonatal (P5-P7) mouse hippocampus, suggesting that an early birth date endows GABAergic neurons with a unique role during postnatal development. Early born GABAergic cells (ebGABA) cells are not a transient developmental phenomenon because they persist in adulthood. At least some of these cells form a population of GABAergic projection neurons innervating the medial septum (Villette et al., 2016). This indicates that an early birth date could lead to distinct morphophysiological properties even in adulthood.