Problem Set Questions Exam 2 Development

Xenopus embryo split dorsal ventral

Produces two normal embryos because both halves receive dorsal determinants

Xenopus embryo split left right

Produces one normal and one ventralized embryo due to unequal determinant distribution

Is activin a morphogen?

Yes because different concentrations produce different mesodermal cell fates

Spemann Mangold experiment result

Transplanted organizer induces a secondary body axis

Organizer function

Secretes BMP inhibitors to induce dorsal and neural structures

FGF signaling pathway

FGF binds FGFR causing dimerization and phosphorylation activating transcription factors

Hedgehog signaling pathway

Hedgehog binds Patched allowing Smoothened to activate Ci transcription factor

Wnt signaling pathway

Wnt binds Frizzled stabilizing beta catenin which activates transcription

TGF beta signaling pathway

TGF beta binds receptor activating Smads to regulate gene expression

Delta Notch signaling

Delta binds Notch leading to cleavage and transcriptional activation

Beta catenin role

Acts as transcriptional activator in dorsal axis formation

Vg1 function

Vegetal ligand inducing mesoderm formation

BMP function

Promotes ventral cell fates

Smads function

Transduce TGF beta signals to nucleus

Brachyury role

Transcription factor required for mesoderm formation

Noggin function

BMP inhibitor promoting dorsal development

Cyp26 role

Enzyme degrading retinoic acid in anterior embryo

Cerberus function

Inhibits BMP Wnt and Nodal to promote head formation

Organizer signaling type

Non cell autonomous because it affects neighboring cells

Organizer protein types

Secreted inhibitors signaling ligands and transcription factors

Clock and wavefront model

Somite formation controlled by oscillating genes and morphogen gradients

Wavefront definition

Boundary where somites form between RA and FGF gradients

Somite derivatives

Sclerotome forms vertebrae myotome forms muscle dermatome forms dermis

Hox gene function

Determines anterior posterior identity of body segments

Hox misexpression effect

Anterior segments adopt posterior identities

Somite specification state

Somites are not fully determined and remain plastic

EMT definition

Process where epithelial cells become migratory mesenchymal cells

EMT cadherin change

Cadherins decrease reducing cell adhesion

EMT cytoskeleton role

Actin and myosin reorganize to enable movement

ECM role in EMT

Provides scaffold for migrating cells via integrins

Cytochalasin D effect

Blocks actin polymerization preventing cell migration

Neural tube adhesion

High adhesion maintains epithelial structure

Neural crest adhesion

Low adhesion allows migration

Neural tube movement

Cells undergo apical constriction without migration

Neural crest movement

Cells undergo EMT and migrate extensively