Ontogeny of the spinal cord dorsal horn [Xenium]

An exquisite example of form serving function is the dorsal horn of the spinal cord, the gateway to the central nervous system for sensory information from the body. Each sensory input to the dorsal horn targets a specific address within its laminated arrangement of diverse neuronal populations. However, it is not known how this organization emerges during development from an apparently homogenous pool of neural progenitors. Here, we found that both the excitatory and inhibitory cell families of the mouse dorsal horn were born in successive waves as temporal cohorts. The excitatory families then settled into a chronotopic map that transformed their birth order into the dorsal laminae. Diversification of families into refined neuron types was mediated by a dorsal-ventral progenitor gradient of Zic transcription factors. This work uncovered fundamental temporal and spatial factors that establish the cell types and structure of the spinal cord dorsal horn. Spinal cords taken from E16.5 mouse embryos were examined using the 10X Xenium v1 spatial transcriptomics platform, using the 247 gene mouse brain probe panel and with 100 additional custom gene probes.