CA8 Variants: New Mechanisms Underlying Transitions to Persistent Pain Syndromes

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DESCRIPTION (provided by applicant): Over $150 billion is spent annually on over 30 million Americans suffering with unrelieved pain. Inadequate persistent pain treatments lead to poor quality of life, and social and emotional dysfunctioning. It is now generally accepted that susceptibility to persistent pain is a complex heritable trait influenced by multiple genes. Recently, common inherited genetic polymorphisms have been shown to cause individual differences in pain perception, and may underlie the transition from acute to persistent pain. However, these variants explain very little of the underlying genetic effect and most of the functional genetic variants are unknown. Pinpointing genes and associated variants that better define the variable biologic pathways underlying the transition from acute to persistent pain can yield a mechanistic understanding of how some forms of persistent pain develop facilitating more effective interventions greatly impacting these patients and this field. We have recently shown that variation in neuronal carbonic anhydrase 8 (CA8) is associated with variable nociception and persistent pain in mice. Additionally, biologic variability in human CA8 is associated with multiple prevalent persistent pain syndromes, suggesting biologic variability at the CA8 locus could play an important pleiotropic role in predisposing to these difficult to treat syndromes. CA8 is an allosteric inhibitor of neuronal inositol triphosphate receptor-1 (IP3R1) that is an intracellular IP3-gated Ca2+ channel. CA8 regulates diverse calcium-dependent neuronal activities such as cellular secretion, contraction, synaptic functioning, and membrane excitability. In this project, we will identify and validate functional CA8 variants that underlie susceptibility to one or more common persistent pain syndromes including temporomandibular disease (TMD), TMD with widespread pain, sciatica, post-herpetic neuralgia (PHN), neuropathic pain after spinal cord injury (SCI), and osteoarthritis (OA). We will use state-of-the-art exome arrays comprising exonic single nucleotide polymorphisms (SNPs) in annotated genes (including CA8 pathway genes) to identify SNPs associated with persistent pain, stiffness and emotional and social functioning in a large OA cohort. This will be followed by the selection of putative functional variants using the latest bioinformatics techniques. Presumed functional SNPs associated with the OA phenotype will then be genotyped in our replication cohorts including TMD, sciatica, PHN, and SCI to test for association with the persistent pain. The biologic role of SNPs meeting our replication criteria in the other persistent pain syndromes will then be established using functional genomics in vitro. We have assembled an outstanding collaborative team with great expertise in basic and clinical pain research and the genetic dissection of complex traits, with the ability to pursue this innovative and highly relevant state-f-the-art scientific plan related to the identification and functional validation of CA8 pathway variants in persistent pain. The results of this Collaborative Research on Transitions From Acute to Chronic Pain will lead to improved biomarkers of susceptibility and therapeutic response, and better interventions for persistent pain syndromes.