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Bistratified starburst amacrine cells in the Sox2 conditional knockout mouse retina display ON and OFF responses.

J Neurophysiol. 2018 Aug 08;:

Authors: Stincic TL, Keeley PW, Reese BE, Taylor WR

Abstract
Cell-intrinsic factors, in conjunction with environmental signals, guide migration, differentiation and connectivity during early development of neuronal circuits. Within the retina, inhibitory starburst amacrine cells (SBACs) comprise ON-types with somas in the ganglion cell layer (GCL) and dendrites stratifying narrowly in the inner half of the inner plexiform layer (IPL), and OFF-types with somas in the inner nuclear layer (INL) and dendrites stratifying narrowly in the outer half of the IPL. The transcription factor Sox2 is crucial to this subtype specification. Without Sox2, many ON-type SBACs destined for the GCL settle in the INL while many that reach the GCL develop bi-stratified dendritic arbors. This study asked whether ON-type SBACs in Sox2-conditional knockout retinas exhibit selective connectivity only with ON-type bipolar cells, or whether their bi-stratified morphology allows them to connect to both ON and OFF bipolar cells. Physiological data demonstrate that these cells receive ON and OFF excitatory inputs, indicating that the ectopically stratified dendrites make functional synapses with bipolar cells. The excitatory inputs were smaller and more transient in Sox2-conditional knockout compared to wild-type, however inhibitory inputs appeared largely unchanged. Thus, dendritic stratification, rather than cellular identification, may be the major factor that determines ON versus OFF connectivity.

PMID: 30089022 [PubMed – as supplied by publisher]