Neurulation BIO361 PDF

The Nervous System Pax7 Pax6 Olig2 Nkx2.2 FoxA2  Major distinguishing features of chordates Notochord Hollow dorsal nerve cord Neurulation Pharyng...

The Nervous System Pax7 Pax6 Olig2 Nkx2.2 FoxA2  Major distinguishing features of chordates Notochord Hollow dorsal nerve cord Neurulation Pharyngeal slits (arches & pouches in vertebrates) Endostyle (Thyroid in vertebrates?) Neurulation refers to a folding process in vertebrate embryos, which includes the transformation of the neural plate into the neural tube. The embryo at this stage is termed the neurula. Major derivatives of the ectoderm germ layer Two views of primary neurulation in an amphibian embryo, showing early, middle, and late neurulae in each case Primary and secondary neurulation and the transition zone between them Primary neurulation: neural tube formation in the chick embryo Primary neurulation: neural tube formation in the chick embryo (Part 1) Primary neurulation: neural tube formation in the chick embryo (Part 2) Primary neurulation: neural tube formation in the chick embryo (Part 3) Primary neurulation: neural tube formation in the chick embryo (Part 4) Morphogen regulation of hinge point formation Primary neurulation: neural tube formation in the chick embryo (Part 5) Mechanisms of Primary Neurulation: Variations in how you roll up Xenopus Chick brain Chick spinal cord Zebrafish brain and trunk region Segments of the mouse Region of the mouse Region of the mouse spinal cord posterior neuropore (20 posterior neuropore (12 Xenopus somites) somites) Lowery and Sive (2004) Mech Dev 121:1189–1197 Activated BMP signaling leads to neural tube defects BMP prevents MHP formation by regulating apical-basal polarity  Transition from E-cadherin to N-cadherin expression Nakaya et al. (2008) Nat Cell Bio 10:765-775 Gilbert 9th Ed., Fig. 9.6 Mechanisms of Secondary Neurulation: Variations in how to condense cells Lowery and Sive (2004) Mech Dev 121:1189–1197 Planar cell polarity pathway is required for NT closure  Planar cell polarity pathway is required for NT closure This whole thing represents DISHEVELLED PDZ domain (PSD95, Dlg1 and Zo-1 domain) DEP domain (Dishevelled, Egl-10 and Pleckstrin domain) Xdd1 (DPDZ) Xdsh-D2 (DDEP) Canonical Wnt Planar Cell Polarity only signaling and Planar Cell Polarity Sokol (1996) Curr Biol 6:1456–1467  Planar cell polarity pathway is required for NT closure Xdd1 disrupts Canonical and PCP pathways DPDZ Xdsh-D2 disrupts PCP pathway only DDEP Wallingford and Harland (2002) Dev 129:5815-5825  Defective PCP pathway = Defective neural tube closure Craniorhachischisis: Vangl  Binds to dishevelled complete failure of Bottom line: Mutations in neural tube closure vangl cause NT defects because they interfere with PCP pathway Torban et al. (2008) PNAS 105:3449–3454 Neural tube defects