Indie darling Greta Gerwig (Mistress America) has landed a role in Jackie, according to Variety.

Academy award winner Natalie Portman (Black Swan) will headline the biopic following Jacqueline Kennedy in the first four days after her President John F. Kennedy, Jr. was assassinated. Gerwig will play one of the former First Lady’s aides. Peter Sarsgaard (Experimenter) has just been cast as as one of JFK’s brothers, Robert Kennedy. Production on the title is expected to begin at the end of the year. Gerwig previously co-starred in Portman’s 2011 comedy No Strings Attached.

Chilean director Pablo Larraín (No, Oscar-nominated for Best Foreign Film in 2013) will helm the project, which previously had Oscar-nominated director Darren Aronofsky (Black Swan) attached. Instead, Aronofsky will produce the film, along with Scott Franklin at Protozoa Pictures and Juan de Dios Larrain of Chile’s Fabula. Noah Oppenheim (The Maze Runner) penned the screenplay. International rights for the film were sold at Cannes. Domestic rights are still being shopped around by CAA.

Gerwig has written and starred in a string of critically well-received indie flicks, including 2012’s Frances Ha for which she received a Golden Globe Best Actress nomination. She will be seen next in the titular role of Rebecca Miller’s comedy Maggie’s Plan, set to bow on May 20. She will also be in another comedy scheduled for release next year, Todd Solondz’s (Dark Horse) Weiner-Dog, alongside Brie Larson, who can currently be seen in the critically-acclaimed Room.