Spinal cord genes enriched in rat dorsal horn and induced by noxious stimulation identified by subtraction cloning and differential hybridization

Persistent nociceptive input increases neuronal excitability and induces a program of gene expression in the dorsal spinal cord. The alteration in gen e expression commences with phosphorylation and induction of immediate earl y genes and proceeds to target genes. Only a few target genes have been ide ntified as yet. The present report uses a polymerase chain reaction-based s ubtraction cloning procedure to obtain an "anatomically focused" complement ary DNA library enriched in transcripts related to sensory spinal cord (rat dorsal horn minus ventral horn). A subset of clones from this library (n = 158) was screened to verify dorsal horn enrichment and to identify those r egulated by carrageenan-induced peripheral inflammation. Molecular classes which displayed enriched expression included a proto-oncogene not previousl y associated with sensory processes, two regulators of the Rho/Rac pathway which controls cell shape, and three genes involved in cytoskeletal regulat ion and scaffolding. Additional transcripts coded for proteins involved in intercellular communication or intracellular function. Within the set of 15 8 transcripts, one known and two unknown genes were induced by persistent n oxious input. The known gene codes for the secreted cysteine proteinase inh ibitor, cystalin C, suggesting that modulation of extracellular proteolytic activity occurs. Since it is secreted, cystatin C may also provide a cereb rospinal fluid bio-marker for persistent pain states. Using a combined anatomical and functional approach, we have extended the m olecular repertoire of genes expressed and induced in second-order neurons or supporting glial cells in several new directions, with particular emphas is on regulation of cell morphology and plasma membrane dynamics. Some of t hese proteins reveal new pathways for information signaling in the sensory half of the spinal cord and require further research to understand their ro le in the adult spinal cord. The induced genes may provide new molecular ta rgets for therapeutic development and provide new probes for investigating the dynamic state of cellular activity that occurs during persistent pain s tates. Published by Elsevier Science Ltd on behalf of IBRO.