Axial interactions during neurogenesis in dysraphic mice

The spatial relationships of midline axial structures were compared in normal and dysraphic embryos of the loop-tail (Lp) mutant mouse at 9 days of gestation, and the distribution of two glycoproteins, fibronectin and laminin, was determined in this region by means of immunofluorescence histochemistry. At various levels of the trunk in abnormal embryos, the notochord, ventral midline of the neural folds, dorsal aorta(e) and/or gut were variably separated from one another, in contrast to the closer contact that occurred among these midaxial structures at comparable trunk levels in normal embryos. Positive anti-fibronectin and anti-laminin reactions were noted within areas of contact in the normal embryos and at the interfaces of tissue separation in the abnormal embryos. Although the intensity of the immunofluorescent reaction could not be assessed or compared quantitatively, the presence and distribution of fibronectin and laminin in the abnormal embryos suggest that these two glycoproteins may not be causally or fundamentally involved in producing the abnormal spatial relationships and separation of the midaxial structures.