The Origin and Evolution of Synapses Flashcards
What is a protosynapse? What is its significance?
ancestoral molecular machinery that existed in unicellular organisms
existed before the evolution of neurons
challenges existing views on the origins of the brain
How should we study evolution of the brain?
examine the phylogeny of the molecular components of the synapse
Define Postsynaptic proteome
the complete set of proteins currently identified at the postsynaptic side of the synapse
The fundamental mechanisms of synaptic transmission and plasticity are __________ across a range of animal species
highly conserved
What 3 experimental methods have been recently used to study the evolution of the synapse?
proteomics + genomics + molecular phylogenetics
What is Proteomics?
studying the protein constituents of the synapse
What is MAGUK (Membrane Associated Guanylate Kinase)?
proteins that act as scaffolds for the clustering of receptors, ion channel,s and associated signalling proteins at postsynaptic sites
traffic NMDA and AMPA receptors to the synapse
Define Ursynapse
the last common ancestor of all synapses
the platform from which diversity of synaptic proteins between different organisms and different types of synapses has evolved
Define Protosynapse
the synaptic components that were present before the emergence of synapses and most likely contributed to their evolution
Name 2 protosynaptic organisms (organisms in which the protosynaptic mechanisms have been conserved)
yeast and amoeba
What two protosynaptic mechanisms were found in Yeast and Ameoba that still play a fundamental role in synaptic transmission in animals today?
PMCA (plasma membrane calcium ATPase) and PKC (protien kinase C)
Who is the closest unicellular relative of mulitceullular metazoans?
Choanoflagellates
Name the multicellular organism that lacks a nervous system that is a candidate for identification of protosynaptic components?
Porifera (sponges)
Who are Bilaterians? Name the two major divisions of this phylum
clade of animals who exhibit bilateral symmetry and possess complex nervous systems
2 major division of Phylum Bilatera:
- protostomes
- deuterostomes
Protosynaptic proteins represent a pre adaptation that later _____________ for synaptic function and may have contributed to development of ____________
co-opted, the first synapses
What is a pitfall that has accompanied the evolution of human behaviour?
positive selection of synaptic proteins has lead to increased human susceptibility to psychiatric diseases
Could synapses have existed before axons and dendrites? explain.
yes. synapses might have evolved before axons and dendrites.
an organism with a small number of neurons wouldn’t need axonal projections for neuron to neuron communicaiton
why is snypase formation an exception to the general rule that: “Ontogeny recapitulates phylogeny”?
synapses evolved before axons and dendrites
Explain the “Synapse-First Model”
the evolution of synapses lead to the evolution of neurons
this is because a neuron is defined by its synaptic connections, and therefore, the synapse must exist first
Name some future improvements that can be made in the study of synaptic evolution?
- studies should be expanded to include all presynaptic and postsynaptic proteins
- loss-of-function experiments should be done on ancient and mammalian specific genes in order to determine their physiological function
- Gain-of-function studies should be done on organisms who lack synapses in order to determine what combinations of synaptic proteins resulted in the origin of the synapse
- current studies mostly use mice as subjects. human subjects should be used in the future
