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Evelyne SernagorEARLY NEURAL ACTIVITY DURING THE DEVELOPMENT OF RETINAL CIRCUITRY IN HEALTH AND DISEASE. Séminaire labelisé INB / Ecole doctorale / Axe Neurobiologie

Abstract :


Retinal circuitry is immature at birth.
However, the developing retina is not “silent” before the emergence of visual experience. Indeed, spontaneous waves of activity spread across the ganglion cell (GC) layer, while visual connections become established. In this talk, I will review our studies on developmental changes in wave dynamics and on how early neural activity influences developing GC dendrites and receptive fields. Waves slow down and shrink with development, disappearing during the first postnatal month, while light responses mature. The maturation of retinal circuitry is controlled by complex interactions between several neurotransmitters. Special emphasis will be given to the maturation of GABAergic inhibition, showing that GABAA responses are initially excitatory, and that the gradual shift to mature inhibition, through upregulation of the anionic transporter KCC2, underlies changes in activity patterns. I will also introduce recent studies on early neural activity patterns in the transgenic blind Cone-Rod homeoboX (CRX) mouse, an animal model of retinal dystrophy (retinitis pigmentosa). Waves disappear earlier than normal, becoming replaced by large slow oscillations and strong bursting, persisting beyond the onset of degeneration. Moreover, an abnormally high proportion of GCs are intrinsically photosensitive, generating sustained firing in response to blue light. These results demonstrate that the retina is capable of developing compensatory mechanisms to counteract visual experience impairment during the critical wiring period of visual connections. 

Selected publications

Mehta V, Sernagor E (2006) Receptive field structure-function correlates in developing turtle retinal ganglion cells. Eur J Neurosci 24:787-794.
Mehta V, Sernagor E (2006) Early neural activity and dendritic growth in turtle retinal ganglion cells. Eur J Neurosci 24: 773-786.
Sernagor E (2005) Retinal development: second sight comes first. Curr Biol. 15(14): R556-9
Leitch E, Coaker J, Young C, Mehta V, Sernagor E (2005) GABA type-A activity controls its own developmental polarity switch in the maturing retina. J Neurosci 25: 4801-5.
Sernagor E, Young C, Eglen SJ (2003) Developmental modulation of retinal waves dynamics: shedding light on the GABA saga. J Neurosci 23: 7621-7629.