Afadin, a Ras/Rap effector that controls cadherin function, promotes spine and excitatory synapse density in the hippocampus.
Many molecules regulate synaptogenesis, but intracellular signaling pathways required for their functions are poorly understood. Afadin is a Rap-regulated, actin-binding protein that promotes cadherin complex assembly as well as binding many other cell adhesion molecules and receptors. To examine its role in mediating synaptogenesis, we deleted afadin (mllt1), using a conditional allele, in postmitotic hippocampal neurons. Consistent with its role in promoting cadherin recruitment, afadin deletion resulted in 70% fewer and less intense N-cadherin puncta with similar reductions of β-catenin and αN-catenin puncta densities and 35% reduction in EphB2 puncta density. Its absence also resulted in 40% decreases in spine and excitatory synapse densities in the stratum radiatum of CA1, as determined by morphology, apposition of presynaptic and postsynaptic markers, and synaptic transmission. The remaining synapses appeared to function normally. Thus, afadin is a key intracellular signaling molecule for cadherin recruitment and is necessary for spine and synapse formation in vivo.
Department of Physiology, University of California, San Francisco, San Francisco, California 94158, USA.
Gerard M J
GM
Beaudoin
Claude M
CM
Schofield
Tulip
T
Nuwal
Keling
K
Zang
Erik M
EM
Ullian
Bo
B
Huang
Louis F
LF
Reichardt
D000818:Animals; D056547:CA1 Region, Hippocampal / Q000254:growth & development / Q000378:metabolism* / Q000648:ultrastructure; D015820:Cadherins / Q000502:physiology*; D002460:Cell Line; D049229:Dendritic Spines / Q000378:metabolism* / Q000648:ultrastructure; D019706:Excitatory Postsynaptic Potentials / Q000502:physiology*; D005260:Female; D055879:Gene Knock-In Techniques / Q000379:methods; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008817:Mice, Mutant Strains; D008840:Microfilament Proteins / Q000172:deficiency / Q000235:genetics*; D009924:Organ Culture Techniques; D013570:Synaptic Membranes / Q000378:metabolism* / Q000648:ultrastructure
D015820:Cadherins; D008840:Microfilament Proteins; C108835:afadin