NBA center Jason Collins came out as gay in an essay written for an upcoming issue of Sports Illustrated, and celebrities and professional athletes have taken to their Twitter accounts to post their support.

“I didn’t set out to be the first openly gay athlete playing in a major American team sport,” the 12-year veteran writes. “But since I am, I’m happy to start the conversation.”

theGrio: NBA center Jason Collins: ‘I’m black and I’m gay’

Collins started his career with the New Jersey Nets in 2001 and most recently played for the Washington Wizards.

Past and current NBA players, including his twin brother Jarron Collins, as well as celebrities, athletes and organizations have tweeted their support for Collins, who is currently a free agent.

NBA commissioner David Stern released a statement of support, saying:

As Adam Silver and I said to Jason, we have known the Collins family since Jason and Jarron joined the NBA in 2001 and they have been exemplary members of the NBA family,” Stern said. “Jason has been a widely respected player and teammate throughout his career and we are proud he has assumed the leadership mantle on this very important issue.

Former president Bill Clinton and daughter Chelsea Clinton both tweeted their support.  Collins and Chelsea Clinton attended Stanford University together.

Follow Carrie Healey on Twitter @CarrieHeals