At BlackRock, she was a managing director and head of the company's U.S. defined contribution business.
State Street spokeswoman Marie McGehee declined to comment.
Bobbie Collins, a spokeswoman for BlackRock, said Ms. Mitchem’s duties at the company have been absorbed by Frank Porcelli, head of the firm’s U.S. retail arm, and Robert Capaldi, head of the U.S. institutional business. Ms. Collins declined to comment on whether the firm intended to replace Ms. Mitchem.
Ms. Mitchem joined Barclays Global Investors in 2006 as managing director and head of the firm's U.S. defined contribution business. When BlackRock bought BGI last year, she was chosen to lead the combined unit, which represented $213.3 in billion in assets as of Dec. 31, 2008, the latest data available.
Before that, Ms. Mitchem spent nine years at Goldman Sachs, where she held a variety of roles, including leading the West Coast derivatives group and the U.S. transition services.
SSgA had been searching for an executive to lead its DC business for several months, according to the sources, who declined to be identified.
Ms. Mitchem could not be reached for comment.
Jessica Toonkel Marquez is a reporter at InvestmentNews, a sister publication of Pensions & Investments.