Jacques Nienaber had previously served as Rassie Erasmus' assistant with South Africa and has now taken the top job.
The mercurial Finn Russell has been punished for a breach of team protocol just nine days before Scotland's first Six Nations game.
Steff Evans was linked with a move to the Top 14, but the Wales flyer has decided to remain with his home region.
Louis Rees-Zammit, the 18-year-old Gloucester flyer, could make his Wales debut in the Six Nations in a new era under Wayne Pivac.
Gregor Townsend has turned to Stuart Hogg to lead Scotland in the Six Nations following Greig Laidlaw's international retirement.
The Six Nations kicks off next month and England will have a new coaching line-up in place for the tournament.
Joey Carbery has suffered another injury blow and will play no part in Ireland's bid to regain the Six Nations title.
Charles Ollivon only has 11 caps to his name but the Toulon back-row will captain a new-look France during the Six Nations.
Ian Foster's New Zealand coaching staff has been finalised with the appointment of Scarlets boss Brad Mooar, who will head home in June.
Fly-half Greig Laidlaw said it was an "incredibly hard" decision to retire from international rugby.