Acute phase response in amputated tail stumps and neural tissue-preferential expression in tail bud embryos of the Xenopus neuronal pentraxin I gene.

Regeneration of lost organs involves complex processes, including host defense from infection and rebuilding of lost tissues. We previously reported that Xenopus neuronal pentraxin I (xNP1) is expressed preferentially in regenerating Xenopus laevis tadpole tails. To evaluate xNP1 function in tail regeneration, and also in tail development, we analyzed xNP1 expression in tailbud embryos and regenerating/healing tails following tail amputation in the 'regeneration' period, as well as in the 'refractory' period, when tadpoles lose their tail regenerative ability. Within 10 h after tail amputation, xNP1 was induced at the amputation site regardless of the tail regenerative ability, suggesting that xNP1 functions in acute phase responses. xNP1 was widely expressed in regenerating tails, but not in the tail buds of tailbud embryos, suggesting its possible role in the immune response/healing after an injury. xNP1 expression was also observed in neural tissues/primordia in tailbud embryos and in the spinal cord in regenerating/healing tails in both periods, implying its possible roles in neural development or function. Moreover, during the first 48 h after amputation, xNP1 expression was sustained at the spinal cord of tails in the 'regeneration' period tadpoles, but not in the 'refractory' period tadpoles, suggesting that xNP1 expression at the spinal cord correlates with regeneration. Our findings suggest that xNP1 is involved in both acute phase responses and neural development/functions, which is unique compared to mammalian pentraxins whose family members are specialized in either acute phase responses or neural functions.