To use Nikon F-mount lenses, Nikon 1 series require an adapter.
Moreover, the flash unit mount is a custom one too and it seems that there is no adapter at all, but maybe I'm wrong.
What is the technical reason to use custom mounts for this new brand, while there are obvious disadvantages of not keeping the mount which already exists for a half of a century, and the hot shoe which is largely compatible with most manufacturers?