Kubota et al. (2002) found that expression of a mutant HRG4 protein in the photoreceptor synapses of their transgenic mouse model had intrasynaptic and transsynaptic effects. They noted a decrease in 3 synaptic vesicle proteins, an increase in 5 cytoplasmic and plasma membrane proteins, and a significant reduction in thickness in the inner plexiform layer. These data supported a close relationship of HRG4 with other participants in synaptic vesicle function but noted that the interaction was not mediated by a direct coupling of HRG4 with any of the tested synaptic proteins, but possibly through interaction with a 23-kD protein