Wayne Pivac handed a surprise Six Nations call-up to Saracens centre Nick Tompkins on Wednesday, while 18-year-old Gloucester wing Louis Rees-Zammit was also included in the Wales squad for the first time.
Stuart Hogg was named Scotland captain on Wednesday as coach Gregor Townsend announced his 38-man squad for the Six Nations.
Eddie Jones has revamped his England backroom staff ahead of the 2020 Six Nations.
Interim Italy coach Franco Smith has named a 35-man squad for next month's Six Nations, handing call-ups to three uncapped players.
Exeter Chiefs second-row Sam Skinner is set to be fit for Scotland's Six Nations campaign, having been out for five months with a hamstring injury.
Munster and Ireland fly-half Joey Carbery will miss the 2020 Six Nations after surgery on a wrist injury.