TAILIEUCHUNG - DEVELOPMENTAL NEUROBIOLOGY - PART 3

Ở những con chuột, số phận của di cư tế bào mào thần kinh sọ não đã được theo sau bằng cách sử dụng công nghệ biến đổi gen của Cre-Lox để kích hoạt cấu-galactosidase biểu hiện dưới sự kiểm soát của promoter Wnt1 (Chai et al, 2000). | Neural Crest and Cranial Ectodermal Placodes Chapter 4 79 injected into individual neural crest cell precursors and migrating neural crest cells in vivo allowing the progeny of single cells to be followed during development Bronner-Fraser and Fraser 1988 1989 Fraser and Bronner-Fraser 1991 . Retroviral-mediated gene transfer has also enabled the clonal analysis of the progeny of single neural crest cells in vivo Frank and Sanes 1991 . In mice the fate of migrating cranial neural crest cells has been followed by using Cre-Lox transgenic technology to activate constitutive p-galactosidase expression under the control of the Wnt1 promoter Chai et al. 2000 . Together these different cell-labeling approaches have enabled a detailed picture to be drawn of the migration pathways followed by neural crest cells through the periphery. Migration Pathways of Cranial Neural Crest Cells Cranial neural crest cells migrate beneath the surface ectoderm above the paraxial cephalic mesoderm see Figs. 3 and 4B although a few cells penetrate the paraxial mesoderm. Pharyngeal arches 4th 3rd 2nd FIGURE 3. Schematic lateral views of a generalized 20-30 somite-stage amniote embryo with the surface ectoderm removed except to show the positions of the cranial ectodermal placodes . Each tissue type from the embryo at the top is shown separately below illustrating the relative positions of the migrating neural crest placodes filled black circles axial structures paraxial mesoderm arteries and pharyngeal endoderm. The olfactory placodes cannot be seen in this view. The vertical lines indicate which regions are in register with each pharyngeal arch. Redrawn from Noden 1991 . art. artery fb forebrain gen geniculate ln lens mb midbrain mmV maxillomandibular trigeminal nod nodose opV ophthalmic trigeminal pet petrosal. 80 Chapter 4 Clare Baker FIGURE 4. Cranial neural crest migration streams in the axolotl visualized by in situ hybridization for the AP-2 gene. A Stage 29 16-somite stage axolotl .

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