Allan Bufferd in the coming year will retire as president and CIO of MIT Investment Management Co., which oversees $10 billion in endowment and defined benefit plan assets for the Massachusetts Institute of Technology, Cambridge, said Denise Brehm, spokeswoman. He is also stepping down as MIT treasurer. Mr. Bufferd said he will stay on at MIT Investment Management until a successor is found or through the end of the coming academic year, whichever comes first. MIT will hire an executive search firm to identify candidates, he said. Susan Hockfield, MIT president, has announced that the MIT treasurer and investment functions will be split into two positions with Mr. Bufferd's retirement, Ms. Brehm said.