Abnormal development of the notochord and perinotochordal sheath in duplicitas posterior, patch and tail-short mice.

Interest in developmental interactions involving the notochord and perinotochordal sheath led to a comparative investigation of these structures in three mouse mutants. Alcian blue or periodic acid-Schiff staining of 9 1/2-13 days' gestational age embryos revealed a supernumerary notochordal-like mass of cells or a deflected notochord in association with duplication of the neural tube in mice of the duplicitas posterior stock. The perinotochordal sheath and basement membrane of the accessory notochordal masses were frequently defective. Patch and Tail-short embryos were also utilized for study by means of light microscopy using Alcian blue staining. In Patch embryos, although the notochord was sometimes compressed dorso-ventrally, it had an intact perinotochordal sheath and a defined, but undulated, basement membrane. Mesenchymal cells between the notochord and neural tube were occasionally replaced by cell-free space. In contrast, in Tail-short embryos a poorly formed, lightly staining or totally absent notochordal sheath was revealed. Indeed, it was sometimes difficult to distinguish the notochord from surrounding mesenchymal cells. In both the Patch and Tail-short embryos the notochord was also deflected from its medial position. In the three mutants studied, the direct or indirect effect of gene action appeared to be on the notochord and perinotochordal sheath, and the important role of these structures in abnormal axial development was established.