In vivo human embryonic spinal cord atlas validates stem cell–derived human dorsal interneurons and reveals ASD spinal signatures

Abstract Restoring somatosensory function after spinal cord injury (SCI) faces fundamental challenges: neuronal subtypes must match both axial position and circuit identity, yet the developmental patterning of human dorsal spinal interneurons (dIs) remains incompletely defined. Here, we integrate six single-cell transcriptomics datasets derived from human embryonic spinal cord tissue spanning gestational weeks 4-25 to generate a reference atlas of early human somatosensory circuit development. The atlas reveals molecular signatures underlying expansion and specialization of dI4 and dI5 interneuron populations associated with mechanosensory and nociceptive processing. Guided by this resource, we established a neuromesodermal progenitor–based differentiation approach that generates dorsal interneurons spanning anterior–posterior identities. Comparison of in vivo and in vitro dI4/dI5 subclasses identified conserved gene networks associated with sensory modalities and revealed enrichment of autism spectrum disorder–associated genes within mechanosensory interneuron populations. Together, these findings clarify how human dorsal spinal interneuron diversity is established.