However, the function of PMLNBs varies widely between cell types and has not been investigated in neurons, so it is not yet known whether modifying PML-NB formation affects synaptic plasticity. Additionally, the molecular mass of Arc is near the size cutoff for passive diffusion into the nucleus through the nuclear pore complex, so it is not clear if the high level of Arc nuclear localization is due to active transport or simple diffusion and nuclear retention.