Neuroscience – Evolution of the brain
Nervous system; an information exchange system in multicellular organisms
Information exchange is mediated by neurons. A neuron:
• Receives information
• Sends information
• Transmits information in contact points: synapses
• Forms networks
• Processes information
• Sens electrical signals: action potentials
• Characteristic form: axons and dendrites
PAPER RYAN & GRANT
Main items of this paper:
• Proteomic and genomic research of the synapse.
• protosynapse - ursynapse – synapse
• Postsynaptic proteins are present in protosynaptic organisms, they register
external stimuli
• Sponges (multicellular organism without a nervous system) and
choanoflagellate (single cellular organism that forms colonies) are model
systems to investigate the origin of the synapse.
• Glutamate receptors mark the first organisms with a nervous system.
• Gene duplication (paraloges) in complex organisms.
• Proteins with many interactions are likely being conserved in evolution
• Synapses have appeared before dendrites or axons: without synapses
these have no function. Hence, no synapse no neuron no nervous system.
Terms;
Homolog; genes or proteins that share a common ancestor
Ortholog; genes and proteins that share a common function
or structure in different species
Paralog; multiple variants of a similar protein or gene in one
species
Evolution of the synapse;
Eukaryotes (no synapse (protosynaptic), so no nervous system present)
Metazoans (no synapse (protosynaptic), so no nervous
system present)
Ursynapse (first synapse is detected, so they have
nervous system ± 1 billion years ago)
Eumatazoans (synapse, so they have nervous system)
Bilaterian (synapse, so they have nervous system)
Deuterostomes (synapse, so they have nervous system)
, Evolutionary older (protosynapse; protein complexes in organisms without a
nervous system – NO nervous system)
Eukaryotes;
Single cell organism
S. cervisea (yeast) and D. Discoideum (amoeba) express already things important for
nervous system:
• Calcium pumps: important for secretion of neurotransmitter
• Protein kinase C (metabotropic receptors), which are important for synapse
function
S. cervisae (yeast) contains 25% post-synaptic density (PSD) ortholog genes, that
regulate its response to external stimuli
Choanaflagellata;
Complex single cell organism.
New protsynapse genes:
• Cadherins & catenins: cell adhesion (synapses are closely adherent
structures, so first steps in forming synapses)
• Tyrosine kinase receptors: response to external stimuli (synaptic plasticity in
later organisms)
Demospongiae (sponge);
Multicellular organisms.
They can change its size, move flagella, contract and relax to allow the inflow and
outflow of sea water and this is the way how they get their nutrients
New protosynapse genes:
• Neurexin; cellular adhesion molecule
• GABA receptors
• Metabotropic glutamate receptors
• Ca/calmodulin-dependent kinase (CaMKII); important
kinase for synaptic plasticity
Between evolutionary older and younger is the ursynapse
Evolutionary younger (synapse – nervous system)
Ctenophora (comb jellies) and cnidaria (jelly fish);
First organism with a nervous system
New synapse proteins;
• Neuroligin (binds to neurexin, synapse adhesion)
• Glutamate receptors (AMPA & NMDA)
Nervous system; an information exchange system in multicellular organisms
Information exchange is mediated by neurons. A neuron:
• Receives information
• Sends information
• Transmits information in contact points: synapses
• Forms networks
• Processes information
• Sens electrical signals: action potentials
• Characteristic form: axons and dendrites
PAPER RYAN & GRANT
Main items of this paper:
• Proteomic and genomic research of the synapse.
• protosynapse - ursynapse – synapse
• Postsynaptic proteins are present in protosynaptic organisms, they register
external stimuli
• Sponges (multicellular organism without a nervous system) and
choanoflagellate (single cellular organism that forms colonies) are model
systems to investigate the origin of the synapse.
• Glutamate receptors mark the first organisms with a nervous system.
• Gene duplication (paraloges) in complex organisms.
• Proteins with many interactions are likely being conserved in evolution
• Synapses have appeared before dendrites or axons: without synapses
these have no function. Hence, no synapse no neuron no nervous system.
Terms;
Homolog; genes or proteins that share a common ancestor
Ortholog; genes and proteins that share a common function
or structure in different species
Paralog; multiple variants of a similar protein or gene in one
species
Evolution of the synapse;
Eukaryotes (no synapse (protosynaptic), so no nervous system present)
Metazoans (no synapse (protosynaptic), so no nervous
system present)
Ursynapse (first synapse is detected, so they have
nervous system ± 1 billion years ago)
Eumatazoans (synapse, so they have nervous system)
Bilaterian (synapse, so they have nervous system)
Deuterostomes (synapse, so they have nervous system)
, Evolutionary older (protosynapse; protein complexes in organisms without a
nervous system – NO nervous system)
Eukaryotes;
Single cell organism
S. cervisea (yeast) and D. Discoideum (amoeba) express already things important for
nervous system:
• Calcium pumps: important for secretion of neurotransmitter
• Protein kinase C (metabotropic receptors), which are important for synapse
function
S. cervisae (yeast) contains 25% post-synaptic density (PSD) ortholog genes, that
regulate its response to external stimuli
Choanaflagellata;
Complex single cell organism.
New protsynapse genes:
• Cadherins & catenins: cell adhesion (synapses are closely adherent
structures, so first steps in forming synapses)
• Tyrosine kinase receptors: response to external stimuli (synaptic plasticity in
later organisms)
Demospongiae (sponge);
Multicellular organisms.
They can change its size, move flagella, contract and relax to allow the inflow and
outflow of sea water and this is the way how they get their nutrients
New protosynapse genes:
• Neurexin; cellular adhesion molecule
• GABA receptors
• Metabotropic glutamate receptors
• Ca/calmodulin-dependent kinase (CaMKII); important
kinase for synaptic plasticity
Between evolutionary older and younger is the ursynapse
Evolutionary younger (synapse – nervous system)
Ctenophora (comb jellies) and cnidaria (jelly fish);
First organism with a nervous system
New synapse proteins;
• Neuroligin (binds to neurexin, synapse adhesion)
• Glutamate receptors (AMPA & NMDA)
