Ancient Somatosensory Circuit Architectures Employ Flexible Molecular Strategies

The extent to which shared molecular specification programs govern conserved neural circuit architectures remains uncertain. To investigate this, researchers studied the somatosensory system of the little skate, Leucoraja erinacea, an early-diverging vertebrate that preserves ancestral features of both finned and limb-based body plans.

Their findings revealed that core elements of somatosensory circuit organization, such as the laminar structure of the spinal cord and the restricted targeting of sensory afferents to the dorsal region, are deeply conserved across species. However, an unexpected divergence was observed in the molecular programs that determine the identity of sensory neurons within the dorsal root ganglion (DRG).

While the dependence on target-derived cues for specifying DRG neuron subtypes and establishing spinal connectivity remains consistent with mammals, skates utilize unique neurotrophin receptor and transcription factor identity codes. These results support a model wherein conserved spinal circuit architectures serve as a stable foundation, utilizing flexible sensory neuron specification programs to enable the evolutionary diversification of vertebrate somatosensory systems.