IADR Abstract Archives
Dlx5-Augmentation in Neural Crest Cells Induced Calvarial Ectopic Cartilages.
Objectives: Distal-less homeobox (Dlx) genes are essential for craniofacial skeletal patterning. This research is to propose the Dlx5 functions in bone and cartilage development in the calvarium.
Methods: Wnt1-Cre;Rosa26Dlx5/+ (NCC-Dlx5) mice in which Dlx5 is continuously expressed in the neural crest cell (NCC) lineage were used. In situ hybridization (ISH), alizarin-red & alcian-blue skeletal staining, hematoxylin & eosin (H&E) staining, toluidine blue staining, and transmission electron microscopic (TEM) analyses were performed.
Results: Endogenous expression of Dlx5 in the distal part of mandibular arch, otic vesicle and some parts of the brain at the embryonic day (E) 10.5 wild-type mouse was confirmed by ISH. Then, it was first detected in a certain population of NCC-derived head mesenchyme between the surface ectoderm and the future meningeal mesenchyme at E11.5. In NCC-Dlx5 mice, low levels of expression of Dlx5 was found in NCC-derived mesenchyme in craniofacial subregions that normally lack Dlx5 expression. Subsequently, a striated ectopic cartilage formation was found in the frontal bone forming area from the lateral side of the head to the apex crossing the midline at E13.5. At E18.5, the apically expanded mineralized frontal bone and the ectopic cartilage overlapped at the posterior part of the frontal bone, prior to the coronal suture. Semi-thin sections and TEM observations demonstrated that the ectopic cartilage seemed to form in the dura mater layer of the meninges, underneath the developing frontal bone.
Conclusions: The augmented expression of Dlx5 in the NCC resulted in ectopic cartilage formation in a certain part of the meninges that covers the cerebral hemisphere. This observation suggests heterogeneity of head mesenchyme in response to Dlx5 expression.
Methods: Wnt1-Cre;Rosa26Dlx5/+ (NCC-Dlx5) mice in which Dlx5 is continuously expressed in the neural crest cell (NCC) lineage were used. In situ hybridization (ISH), alizarin-red & alcian-blue skeletal staining, hematoxylin & eosin (H&E) staining, toluidine blue staining, and transmission electron microscopic (TEM) analyses were performed.
Results: Endogenous expression of Dlx5 in the distal part of mandibular arch, otic vesicle and some parts of the brain at the embryonic day (E) 10.5 wild-type mouse was confirmed by ISH. Then, it was first detected in a certain population of NCC-derived head mesenchyme between the surface ectoderm and the future meningeal mesenchyme at E11.5. In NCC-Dlx5 mice, low levels of expression of Dlx5 was found in NCC-derived mesenchyme in craniofacial subregions that normally lack Dlx5 expression. Subsequently, a striated ectopic cartilage formation was found in the frontal bone forming area from the lateral side of the head to the apex crossing the midline at E13.5. At E18.5, the apically expanded mineralized frontal bone and the ectopic cartilage overlapped at the posterior part of the frontal bone, prior to the coronal suture. Semi-thin sections and TEM observations demonstrated that the ectopic cartilage seemed to form in the dura mater layer of the meninges, underneath the developing frontal bone.
Conclusions: The augmented expression of Dlx5 in the NCC resulted in ectopic cartilage formation in a certain part of the meninges that covers the cerebral hemisphere. This observation suggests heterogeneity of head mesenchyme in response to Dlx5 expression.