On the heels of the announcement that SEC Chairman Mary Schapiro would be leaving the agency on Dec. 14, otherofficials followed suit.

SEC Chief of Staff Didem Nisanci left at the end of week of Dec.10, the agency said. Schapiro named her to the post in March 2009.Nisanci served as senior advisor to Schapiro on policy, managementand regulatory issues, played an integral role in the SEC's effortsin the passage of the Dodd-Frank Act and also served as an SEC deputy to theFinancial Services Oversight Council.

General Counsel Mark Cahn will leave the agency at the end ofthe year to return to the private sector, the SEC said.

Cahn has served as the SEC's General Counsel since February 2011and counseled the commission on issues ranging from enforcementactions, rulemakings, other administrative proceedings and appealsthroughout the country and in the Supreme Court. Prior to becominggeneral counsel, Cahn served as the SEC's deputy general counselfor two years.

Robert Cook, director of the SEC's Division of Trading andMarkets, is also planning to leave the agency soon, the SEC said.Since joining the SEC in January 2010, Cook has led the division'sbroad regulatory policy program that includes oversight ofsecurities exchanges and markets, broker-dealers, clearingagencies, and the Financial Industry Regulatory Authority.

Cook also oversaw the implementation of significant rulemakingand other responsibilities assigned to the Division under theDodd-Frank Wall Street Reform and Consumer Protection Act and theJumpstart Our Business Startups Act, the SEC said.

Meredith Cross, director of the Division of Corporation Finance,will also leave the SEC at the end of the year to return to theprivate sector, according to the agency.

Cross has served as the division's director since June 2009. Shejoined Schapiro's senior leadership team in the wake of thefinancial crisis and played a key role in the chairman'sinitiatives to rebuild the agency's credibility, improve overalloperations at the SEC, and build a more resilient, integratedprogram designed to foresee and reduce the likelihood of futurecrises in the securities markets, the SEC said.

SEC Commissioner Elisse Walter has been tapped to succeed Schapiro.