CBI has filed its chargesheet against National Stock Exchange's (NSE) ex-MD and CEO Chitra Ramkrishna and ex-Group Operating Officer Anand Subramanian in connection with the co-location scam case. In the chargesheet, CBI has accused Ramkrishna of allegedly abusing her official position in key decisions. SEBI had earlier charged her with alleged governance lapses in Subramanian's appointment.