In mical mutants, synaptic boutons do not sprout normally over the muscle surface and tend to form clusters along synaptic branches and at nerve entry sites.
The density of VAMP1 and VAMP2 boutons did not differ between TeNT-injected animals and controls, nor between CA1c and CA1a areas (data not shown).
In other models of either Wallerian degeneration in the CNS or chronic degeneration, the synaptic boutons do not appear to be enveloped by microglia processes (Adalbert et al., 2009; Scott et al., 2010).
S6K and TSC complex have recently been show to play a role in regulating Drosophila NMJ development (Cheng et al., 2011; Natarajan et al., 2013), affecting bouton size and number while knockdown of Tor does not appear to modulate bouton number (Penney et al., 2012).
Consistent with these observations, RNAi knock down of Marf in MN, muscles, glia and MN and muscle does not affect bouton number or size at NMJs.
Quantification of bouton densities from BDA-tracing experiments does not allow comparative analysis between animals.
Moreover, knockdown of Marf in neuron, muscle or glia does not recapitulate the bouton phenotype observe in Marf mutants, suggesting a unique cell non-autonomous requirement of Marf for proper NMJ morphology.
Defects in bouton size do not follow this general trend.
Interestingly, the number of AZs per bouton type did not differ between the genotypes (data not shown).
Rescue of the bouton size did not seem to be additive since knockdown of these genes on their own (Fig. 3G, bottom panel), did not give rise to smaller boutons.
