A large central muscle (adductor muscle) serves to close the valve against the pull of the ligament.
Furthermore, FDI and DM have overlapping central muscle representations, suggesting coordination in control of these muscles [18].
However, additional factors may restrict synapses to central muscle zones [28], [29].
We propose that AChR prepatterning and axonal guidance are spatio-temporally coordinated through common unplugged/MuSK signals, and that additional factor(s) restrict unplugged/MuSK signaling to a central muscle zone critical for establishing mid-muscle synaptogenesis.
Using the same transgenic approach, we expand the unplugged/MuSK expression domain to the entire muscle surface, but find that AChR prepattern and synapses remain restricted to the central muscle region, consistent with the idea that in vivo additional, extrinsic and/or muscle intrinsic mechanisms restrict unplugged/MuSK signaling to the mid-muscle region.
The data presented here suggest that the early Wnt dependent function of unplugged/MuSK to establish a central muscle zone for AChR prepatterning and motor axons is temporally restricted, while its later, Agrin dependent function to induce neuromuscular synapses, is temporally less restricted.
Although we have not examined unplugged/MuSK signaling directly, i.e. by assessing receptor phosphorylation, the data is consistent with our model that unplugged/MuSK signaling through dishevelled primarily functions to organizes a central muscle zone to which AChR prepatterning and growth cone guidance is restricted [15].
IntraMF has been correlated with deficits in central muscle activation [ 46], increased risk of future mobility loss [ 47, 48], and insulin resistance [ 49] in the elderly population.
The central muscle of the gastrocnemius was taken and divided into three parts, placed into cryopreservation tubes and quickly placed into liquid nitrogen (−196°C) for preservation.
A regression line between volume of the thigh muscle and the central muscle area estimated that: muscle volume of the thigh (cm)=(12.1×central cross-sectional muscle area−9.66)×distance between the greater trochanter and the patella.
