Biologie cellulaire et du développement
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The Expression of Procalcitonin in the Central Nervous System of the Rat Embryo

Jesus Canudas, Victor Sorribas, Ana M Lacosta and Manuel Sarasa

Procalcitonin mRNA is abundantly synthesized in the thyroid gland in mammals. In recent years, procalcitonin or its posttranslational product calcitonin, has been identified in numerous non-thyroidal adult tissues. Nevertheless, little is known about the implications of procalcitonin in development. We have previously discovered that chick embryo expresses procalcitonin in the developing floor plate and the dorsal rhombencephalon from the early stages of embryogenesis. This finding focused our attention on investigating whether procalcitonin is present in the nervous system of mammalian embryos. In a previous study by our laboratory, the central expression of calcitonin was not found in rat embryos when isotopic deoxyoligonucleotides were used as probes for in situ hybridization analyses. In this study, the expression of procalcitonin mRNA was detected in rat embryos from 11 to 18 days post-coitum when analyzed using techniques such as RT-PCR. In situ hybridization histochemistry with riboprobes revealed the expression of procalcitonin mRNA in the roof of the diencephalon from 12 to 16 days post-coitum and this expression was quantified by Ribonuclease Protection Assay technique. The immunohistochemical analysis confirmed the presence of the protein in this region and in the roof (velum medullare) of the rhombencephalon. Notably, numerous microglial cells were present in the developing diencephalon only during the period during which the expression of procalcitonin was detected. These findings suggest roles for procalcitonin not only in diencephalon development but also in the process of microglial colonization of the central nervous system.