Early Development: Invertebrates
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Transcript of Early Development: Invertebrates
Early Development: Invertebrates Brief overview of early developmental themes Early development of Sea Urchin Early development of Caenorhabditis elegans
Invertebrates? So what? Very easy to study Genetics and molecular events are highly
conserved
Cleavage initiation Maternal Factors Mitosis Promoting
Factor No Gaps at first Mid Blastula
transition-Gene activation from Zygote nucleus.
Cell and nuclear division Karyokinesis Cytokinesis Centrioles and axis
determination.
Patterns of Cell division
Gastrulation
Cell specification and Axis formation Cell-cell signaling or
acquisition of cellular factors
Bound to egg cytoplasm
Actively transported Associate with
centrioles
Sea Urchin: Initial Cleavage
Fate Mapping of Sea Urchin embryo
Global regulatory networks Maternal Factors Disheveled and b-catenin b-catenin and TCF- Micromere differentiation
Double Negative Gate
GeneA Gene B
Gene DGene C Gene E Gene F
Double Negative Gate: Micromere
Pmar1 HesC
ThrAlx1 Ets Delta
Otx/b-catenin
Double Negative Gate: Veg2 cell
Pmar1 HesC
ThrAlx1 Ets Delta
Specification of Vegetal Cells Wnt signaling; Early Signal (ES); Delta (Notch) b-catenin Blimp1 wnt autocrine;
Endoderm differentiation Pmar1 and HesC regulate ES, which leads to
mesoendoderm differentiation. Delta Mesoderm differentiation.
Axis specification Animal/Vegetal= Anterior/Posterior axis Nodal regulates Oral/Aboral axis
Gastrulation Blastula hatches from
Fertilization envelope. Skeletogenic mesenchyme
ingression. Vegetal plate involutes
beginning invagination.
Gastrulation
Gastrulation
Gastrulation
Caenorhabditis elegans
C. elegans and Initial Cleavage
Anterior-Posterior Axis Sperm Pronucleus location Cyk-4 activates GTPases
relocates PAR proteins to anterior
P-granules: Ribonucleoprotein complex RNA helicases Poly A polymerases Translation initiators
Dorsal-Ventral/Left-Right Axis formation
Specification: Autonomous Maternal cytoplasmic
factors SKN-1: EMS fate
determination. PAL-1: Differentiation
of P2 somatic descendents
PIE-1: placed into P blastomeres via PAR-1, inhibits SKN-1 and PAL-1 in P cells.
Specification: Conditional Cell-cell signaling (Juxtacrine) Paracrine signaling
Gastrulation