Exploring the neural basis of touch through selective and stable genetic tagging in the chick somatosensory system

The assembly of circuitries for somatosensory perception relies on a complex interplay of neuronal diversification, specification, phenotypic modulation and establishment of precise connectivity patterns during embryogenesis. However, little is known about the molecular mechanisms controlling the establishment of well-defined somatosensory connectivity, which is to a large part due to the limitation of sensory neuron subtype-specific molecular markers. This study aimed at the identification of novel genetic markers for distinct somatosensory neuron subtypes to provide more detailed insights into primary somatosensory circuit formation, organization and function. These aims were addressed by a newly established in silico-to-in vivo screen for neuron subtype-specific enhancer activities in the chick at late-gestation stages. This study designed a simple screening strategy that permits rapid, efficient and stable genetic tagging of sensory neuron subtypes in vivo, which thus provides the basis for the systematic discovery of late-onset sensory neuron subtype-specific gene regulatory activities. Thereby, a novel molecularly defined subclass of touch receptor neurons was uncovered, thus providing the utility of the system for uncovering the neural basis of discrete sensory modalities relayed by the primary somatosensory system. In addition, the system facilitated stable cell fate-tracking, which unraveled outstanding features of the primary somatosensory neuron lineage. Besides facilitating the genetic dissection of the somatosensory system, the strategy also offers an effective pre-screening platform for targeting genetically identified neuronal subtypes in other vertebrate species