Figure 8
A stochastic model of tSC and vacancy mediated synapse elimination. According to the model, a vacant site or vacancy in an endplate of a muscle fiber forms randomly by a removing tSC or nerve terminal of an axon. The transition probability of a tSC to a vacancy and an axon to a vacancy are determined by measured relative areas of tSCs, vacancies, and axons. Subsequently, the vacancy is taken over by adjacent axons or tSCs. But the probability of its taking over by a specific axon is positively correlated with the axon’s relative contact area surrounding the vacancy. In other words, the greater the contact area of an axon surrounding the vacancy is, the greater the probability of its taking over the vacancy is. When the synaptic activity of an axon is greater than other axons in an endplate, the probability of the axon’s taking over is greater than other axons leading to acceleration of synapse elimination consistent with previous and other studies. Furthermore, our model newly predicts that as the relative area of the vacancy or tSC in an endplate increases synapse elimination speeds up raising a testable hypothesis that both the measurable relative areas of vacancies and tSCs are important structural correlates of the rate of synapse elimination.
