Molecular signatures of neural connectivity in the olfactory cortex.

Assunta Diodato,Nicolas Derian,Sonia Garel,Alexander Fleischmann,Yeong Shin Yim,Marion Ruinart De Brimont,Sandrine Perrin,David Klatzmann,Juliette Pouch,Gloria B Choi

doi:10.1038/ncomms12238

Abstract

The ability to target subclasses of neurons with defined connectivity is crucial for uncovering neural circuit functions. The olfactory (piriform) cortex is thought to generate odour percepts and memories, and odour information encoded in piriform is routed to target brain areas involved in multimodal sensory integration, cognition and motor control. However, it remains unknown if piriform outputs are spatially organized, and if distinct output channels are delineated by different gene expression patterns. Here we identify genes selectively expressed in different layers of the piriform cortex. Neural tracing experiments reveal that these layer-specific piriform genes mark different subclasses of neurons, which project to distinct target areas. Interestingly, these molecular signatures of connectivity are maintained in reeler mutant mice, in which neural positioning is scrambled. These results reveal that a predictive link between a neuron's molecular identity and connectivity in this cortical circuit is determined independent of its spatial position.

Highlights

The ability to target subclasses of neurons with defined connectivity is crucial for uncovering neural circuit functions
While limitations in the efficiency of cholera toxin B subunit (CTB) uptake and the large number of potential molecular markers and piriform target areas preclude a complete, quantitative analysis of gene expression patterns and connectivity, our experiments suggest that the molecular identities of subclasses of piriform projection neurons can provide a predictive link with their connectivity, independent of whether they are segregated into distinct piriform layers or intermingled within a given layer
We have identified genes expressed in subpopulations of piriform neurons that segregate into distinct layers and sub-layers of the piriform cortex

Summary

Introduction

The ability to target subclasses of neurons with defined connectivity is crucial for uncovering neural circuit functions. The olfactory (piriform) cortex is thought to generate odour percepts and memories, and odour information encoded in piriform is routed to target brain areas involved in multimodal sensory integration, cognition and motor control. It remains unknown if piriform outputs are spatially organized, and if distinct output channels are delineated by different gene expression patterns. Neural tracing experiments reveal that these layer-specific piriform genes mark different subclasses of neurons, which project to distinct target areas. These molecular signatures of connectivity are maintained in reeler mutant mice, in which neural positioning is scrambled. Our results begin to reveal a molecular code of connectivity in the olfactory cortex and provide important new means of access into the functional and genetic dissection of olfactory circuits

Methods

Results

Conclusion