Vision is required for cell type specification and function in the developing visual cortex

Abstract

Purpose : That visual experience is important for proper visual system development is known, but its molecular basis is poorly understood. This study examines the role of visual experience in wiring of the visual cortex during the visual critical period at the molecular level.

Methods : We performed single-nucleus RNA sequencing on mouse primary visual cortex during visual cortical development (P8 – P38) under a variety of visual experience perturbations: normal visual experience, dark rearing during the critical period (P21-28, 21-38), and dark rearing followed by light exposure (P21-28, followed by 8 hours of light). A total of 144,725 cells were clustered and parsed using machine learning to uncover novel cell types and map cell type specific transcriptomes across time. Single-cell fluorescent in-situ hybridization was used to examine in vivo localization of cell types. The function of one candidate cell surface protein selectively regulated by light during the critical period was studied in vivo in knockout mice through 2 photon imaging of the cortex in awake animals and by immunohistochemistry.

Results : We discovered three glutamatergic cell types form three sublayers in L2/3 of the visual cortex. Vision is required for the formation and maintenance of these cell types. By contrast, cell types in deeper layers are specified independent of vision. Cell types exhibit a transcriptomic continuum, defined by graded expression of genes that could be split into eight modules which vary dynamically with time. Cell surface proteins were encoded by many of these genes, and one (Igsf9b) stood out as having a layered distribution that increased during the critical period and was activity regulated. Mice lacking Igsf9b had reduced numbers of binocular cells, changes in their responses to visual stimuli and a reduction in inhibitory synapse proteins.

Conclusions : Vision is necessary for the specification of cell types in L2/3 of the visual cortex. Igsf9b, a homophilic cell adhesion molecule, is necessary for cortical wiring, formation of binocular cells, and the responses of excitatory neurons to visual stimuli. Our transcriptomic atlas of visual cortical development from synaptogenesis to the end of the critical period is an important resource for future studies on cortical development.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.