PPFIA2 and amyotrophic lateral sclerosis: Among the synaptic genes are PPFIA2, a scaffolding protein located in the presynaptic active zone33, SRGAP2C, a human-specific GTPase associated with synaptic development in excitatory and inhibitory neurons34, and Unc13, an essential protein for synaptic vesicle release in excitatory neurons35 and a known risk gene for ALS and Frontotemporal Dementia36.