Both firms are replacing Monsanto (NYSE:MON) in the respective indexes, with Monsanto's acquisition by Bayer imminent.
RGNX is up 0.7% after hours in what looks to be thin trading. Shares declined 6.8% today.
All moves are effective prior to Thursday's open.
After hours: NFLX -0.2%.
Updated 5:27 p.m.: Twitter shares are up 3.6% after hours.
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