Lecture evolution and development
Why Evo-Devo
- Fundamental part of developmental biology
- High level integration
- History of life
Examples Evo-Devo: Wing diversity in the Hawaiian Drosophila: Radiation of species on
volcanic islands and modern human skull shape are influenced by Neanderthal
introgression.
Metazoans: Evolution of gastrulation in bilaterians
Almost all eumetazoans (meercelligen) develop from germ layers and undergo gastrulation.
How can gastrulation evolve?
- Radially symmetrical: two germ layers: ectoderm and endoderm
- Bilateria: three germ layers: ectoderm, endoderm and mesoderm
- D-V axis”: inverted during gastrulation
Simplest extant eumetazoa: trichoplax adhaerens
- Four cell types: flat disc of cells, two epithelial layers, in between fiber cells
- No apparent body axed other than top-bottom. periphery versus interior
- Reproduction by fission in culture
- Complex genome with developmental genes
Brachyury helps with mesoderm induction and is in the
marginal zone. Is specific for Bilaterians.
Origin of multicellularity and gastrulation unknown
Hypothetical model for development of the gastrula
Modern unicellular eukaryotes, many features of
development already present
- Cell adhesion, signaling
- Cell differentiation , stress response, meiosis
- Colony formation
, What happened to gastrulation?
Dorsal-ventral axis inverted in protostomes versus deuterostomes
Genes involved in D-V axis formation, heart development are conserved
Inverted D-V axis in insects relative to vertebrates
Gene expression patterns are also inverted
Drosophila:
Dpp: Decapentaplegic (dorsal), related to vertebrate BMP4 (ventral)
Sog: Short gastrulation (ventral), related to chordin (BMP inhibitor, dorsal)
BMP and Wnt inhibitors are in the organizer.
Don’t know how this happened, but do know that the same genes are involved.
Why Evo-Devo
- Fundamental part of developmental biology
- High level integration
- History of life
Examples Evo-Devo: Wing diversity in the Hawaiian Drosophila: Radiation of species on
volcanic islands and modern human skull shape are influenced by Neanderthal
introgression.
Metazoans: Evolution of gastrulation in bilaterians
Almost all eumetazoans (meercelligen) develop from germ layers and undergo gastrulation.
How can gastrulation evolve?
- Radially symmetrical: two germ layers: ectoderm and endoderm
- Bilateria: three germ layers: ectoderm, endoderm and mesoderm
- D-V axis”: inverted during gastrulation
Simplest extant eumetazoa: trichoplax adhaerens
- Four cell types: flat disc of cells, two epithelial layers, in between fiber cells
- No apparent body axed other than top-bottom. periphery versus interior
- Reproduction by fission in culture
- Complex genome with developmental genes
Brachyury helps with mesoderm induction and is in the
marginal zone. Is specific for Bilaterians.
Origin of multicellularity and gastrulation unknown
Hypothetical model for development of the gastrula
Modern unicellular eukaryotes, many features of
development already present
- Cell adhesion, signaling
- Cell differentiation , stress response, meiosis
- Colony formation
, What happened to gastrulation?
Dorsal-ventral axis inverted in protostomes versus deuterostomes
Genes involved in D-V axis formation, heart development are conserved
Inverted D-V axis in insects relative to vertebrates
Gene expression patterns are also inverted
Drosophila:
Dpp: Decapentaplegic (dorsal), related to vertebrate BMP4 (ventral)
Sog: Short gastrulation (ventral), related to chordin (BMP inhibitor, dorsal)
BMP and Wnt inhibitors are in the organizer.
Don’t know how this happened, but do know that the same genes are involved.
