Toni Collette has joined the cast of British director Sam Mendes's untitled relationship comedy, says The Hollywood Reporter.

The Focus Features movie revolves around a couple who cross America looking for a place to start a family and lay down roots. Collette (Little Miss Sunshine) is to play a college professor who is a friend to the couple.

Dave Eggers and Vendela Vida penned the screenplay, which Mendes will shoot this month in Connecticut.

John Krasinski, Maya Rudolph and Cheryl Hines are already among the cast.