The developing spinal cord has long been a classic model for understanding neurodevelopmental mechanisms
yet linking developmental cell types to their adult counterparts has proved elusive. Developmental transcription
factors are required for the differentiation and specification of cell types during embryogenesis and are expressed
in discrete domains in the developing spinal cord. Yet in the adult, expression of these developmental
transcription factors is lost making it difficult to connect embryonic progenitor domains to their adult cell types
and function. We will address this gap in knowledge by tracking developmental lineages over time using
genetic lineage tracing of molecularly-defined progenitor domains and assaying the changes in
transcription, epigenome, and anatomical distribution. Comprehensive understanding of the developmental
lineages will reveal true structural and functional complexity of spinal cord circuits that are not reflected in single-
cell transcriptomics of adult tissue. We will focus on the developing dorsal progenitor domains that give rise to
adult cell types of the dorsal to intermediate spinal cord. The dorsal spinal cord is the primary area for integration
of somatosensory stimuli from the periphery and consists of the senses of nociception (pain), thermosensation
(temperature), mechanosensation (touch), pruriception (itch), and proprioception (limb and body position).
The goal of this proposal is to generate three types of mouse atlases. In Aim 1, we will generate a molecular
signature developmental atlas that catalogs the transcriptional and epigenomic changes of dorsal progenitor
domain lineages using the 10x Genomics Multiome platform. We have identified five CRE-recombinase mouse
lines that together will isolate progenitor domains of the developing spinal cord. We will use these lines to assay
the molecular signatures of these lineages at three major time points across the lifetime of the animal and along
the rostral-caudal axis. In Aim 2, we will generate an anatomical phenotype developmental atlas to understand
the distribution of the molecular signatures using standard histological techniques and a multiplexed spatial
transcriptomics platform, MERSCOPE. In Aim 3, we will create a molecular lineage 3-dimensional atlas of all
five CRE-lineages at adult stages using the TissueCyte platform.
Altogether, these three atlases will provide an invaluable resource for the spinal cord and somatosensory
neuroscience community. Comprehensive cell profiling of the dorsal spinal cord will catalog spinal cell types in
native states that can be compared to injured or diseased states. It will also serve as a reference for the cell type
profiling of the spinal cord in other species. Furthermore, by adding on a layer of developmental lineage, we will
answer long standing questions about the development of the spinal cord. Understanding this developmental
relationship will provide insight into whether a particular adult cell type is constrained by its developmental
lineage, how discrete progenitor domains generate the diversity of cell types in the adult spinal cord and lay the
necessary foundation for cell-type regeneration and engineering efforts for spinal cord tissue.