Abstract
BackgroundN-ethyl-N-nitrosourea mutagenesis was used to induce a point mutation in C57BL/6 J mice. Pain-related phenotype screening was performed in 915 G3 mice. We report the detection of a heritable recessive mutant in meiotic recombinant N1F1 mice that caused an abnormal pain sensitivity phenotype with spontaneous skin inflammation in the paws and ears.MethodsWe investigated abnormal sensory processing, neuronal peptides, and behavioral responses after the induction of autoinflammatory disease. Single-nucleotide polymorphism (SNP) markers and polymerase chain reaction product sequencing were used to identify the mutation site.ResultsAll affected mice developed paw inflammation at 4–8 weeks. Histological examinations revealed hyperplasia of the epidermis in the inflamed paws and increased macrophage expression in the spleen and paw tissues. Mechanical and thermal nociceptive response thresholds were reduced in the affected mice. Locomotor activity was decreased in affected mice with inflamed hindpaws, and this reduction was attributable to the avoidance of contact of the affected paw with the floor. Motor strength and daily activity in the home cage in the affected mice did not show any significant changes. Although Fos immunoreactivity was normal in the dorsal horn of affected mice, calcitonin gene-related peptide immunoreactivity significantly increased in the deep layer of the dorsal horn. The number of microglia increased in the spinal cord, hippocampus, and cerebral cortex in affected mice, and the proliferation of microglia was maintained for a couple of months. Two hundred eighty-five SNP markers were used to reveal the affected gene locus, which was found on the distal part of chromosome 18. A point mutation was detected at A to G in exon 8 of the pstpip2 gene, resulting in a conserved tyrosine residue at amino acid 180 replaced by cysteine (Y180 C).ConclusionsThe data provide definitive evidence that a mutation in pstpip2 causes autoinflammatory disease in an N-ethyl-N-nitrosourea mutagenesis mouse model. Thus, our pstpip2 mutant mice provide a new model for investigating the potential mechanisms of inflammatory pain.
Highlights
N-ethyl-N-nitrosourea mutagenesis was used to induce a point mutation in C57BL/6 J mice
Genetic mapping indicated that the autoinflammation mice showed a point mutation in pstpip2/Mayp located on the distal part of chromosome 18 that caused an amino acid substitution from tyrosine to cysteine
Pain symptoms caused by a mutation of the pstpip gene have been reported in autoinflammatory disease (e.g., PAPA syndrome)
Summary
N-ethyl-N-nitrosourea mutagenesis was used to induce a point mutation in C57BL/6 J mice. Pain and hyperalgesia frequently result from peripheral tissue injury or nerve damage [1,2] These abnormal sensory events arise partially from the action of inflammatory mediators on peripheral terminals of nociceptive primary sensory neurons [3,4]. Numerous molecules, such as prostaglandins and bradykinin, are known to be produced by tissue damage or inflammation and considered responsible for the activation and sensitization of peripheral pain-signaling sensory neurons [5]. Identified mediators include various factors produced and released from non-neuronal cells, such as macrophages and immune cells These factors can act at numerous loci and play important roles in mediating persistent pain states [6,7]. In classic neuroimmune diseases, such as multiple sclerosis and acute disseminated encephalomyelitis, neuroantigenreactive lymphocytes escape immune tolerance, invade the central nervous system, and are responsible for tissue damage, demyelination, and axonal degeneration [15]
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