Stephen Skybell will become The Exact Center of the Universe for Frances Sternhagen, when the actor joins the cast of the Off-Broadway production on Dec. 14. He replaces the departing Reed Birney.

Joan Vail Thorne's comedy had a critically embraced, nonprofit April 1999 run at Women's Project & Productions Theatre, before beginning its run at the Century Theatre Sept. 8.

The rest of the WPP cast, including Marge Redmond, Tracy Thorne and Sloane Shelton, remains the same. Bethel Leslie, an original cast member, recently passed away.

Skybell's recent credits include Dream True Off-Broadway and The First Picture Show at the Mark Taper Forum in L.A.

Vain Thorne's warm, Southern-fried family comedy, with Sternhagen as a matron unsettled by her son's romance, plays at the Century Theatre at the Century Center for the Performing Arts (previous home to Snakebit). John Tillinger recreates his WPP direction. Sternhagen, who has won two Tonys over her long career, plays Vada Love Powell, a matriarch from the Deep South whose small world is rocked when her son, Apple (played by Birney), marries without her consent. Gossip flares, barbs are tossed and secrets are revealed.

Among Sternhagen's most recent credits is the award-winning Lincoln Center Theatre revival of The Heiress starring Cherry Jones.

The initial non-profit run was produced by Women's Project & Productions March 30-May 2 at WPP Theatre (formerly Theater Four) on West 55th Street. Elsa Daspin Haft and Martin Markinson are producers of the commercial run.

Designers for Exact Center of the Universe are Michael Brown (sets), Carrie Robbins (costumes), Brian McDevitt (lighting) and Laura Grace Brown (sound).

Playwright Thorne's latest project is the libretto for the world premiere of Summer, for Berkshire Opera Company.

The Century Theatre is at 111 East 15th Street. Tickets are $17.50 $47.50. Call (212) 239-6200 for information.

--By Robert Simonson