Elevated expression of calcineurin subunits during active mineralization of developing mouse molar teeth

<jats:p>Calcineurin is a <jats:styled-content style="fixed-case">C</jats:styled-content>a<jats:sup>2+</jats:sup>/calmodulin‐dependent protein phosphatase consisting of two subunits – catalytic subunit <jats:styled-content style="fixed-case">A</jats:styled-content> (<jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">A</jats:styled-content>) and regulatory subunit <jats:styled-content style="fixed-case">B</jats:styled-content> (<jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">B</jats:styled-content>) – and plays a critical role in transducing <jats:styled-content style="fixed-case">C</jats:styled-content>a<jats:sup>2+</jats:sup> signals into cellular responses. In this study, we investigated the expression of calcineurin in the mouse developing tooth. In‐situ hybridization detected m<jats:styled-content style="fixed-case">RNA</jats:styled-content>s for the <jats:italic><jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">A</jats:styled-content>α</jats:italic> and <jats:italic><jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">A</jats:styled-content>β</jats:italic> isoforms of <jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">A</jats:styled-content> and for the <jats:italic><jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">B</jats:styled-content>1</jats:italic> isoform of <jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">B</jats:styled-content> in the upper molar tooth germ at embryonic day 15. Immunohistochemistry with antibodies specific for <jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">A</jats:styled-content>α, <jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">A</jats:styled-content>β, and <jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">B</jats:styled-content>1 showed strong immunoreactivity of these proteins in secretory‐stage ameloblasts and in odontoblasts during dentin formation. <jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">A</jats:styled-content>β and <jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">B</jats:styled-content>1 were strongly immunoreactive in ruffle‐ended ameloblasts at the enamel‐maturation stage. In ameloblasts and odontoblasts, we also noted different subcellular distributions of <jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">A</jats:styled-content>α and <jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">A</jats:styled-content>β. From these data, temporal profiles of calcineurin expression appear to correlate with active mineralization in tooth development. Furthermore, the distinct subcellular distribution of the two <jats:styled-content style="fixed-case">C</jats:styled-content>n<jats:styled-content style="fixed-case">A</jats:styled-content> subunits may reflect their distinct substrates or responsive sites within single cells, thus contributing to the diversity of calcineurin‐dependent cellular responses during active tooth mineralization.</jats:p>