Nuveen Investments ceo Timothy Schwertfeger has left the firm amidst the company’s search for an independent director to lead its funds, the Chicago Tribune reports. Schwertfeger spearheaded the sale of the firm to buyout company Madison Dearborn Partners.

“He has retired from the firm,” a spokeswoman said, calling the move a “natural progression.” She added that the move was not tied to performance and that Madison was not behind the shift. This comes after his June 2007 announcement that upon completing the sale to Madison, he would resign as ceo but remain chairman, having president John Amboian succeed him as ceo.

In a letter filed with regulators this week, Schwertfeger said, “Nuveen and your fund's board determined that fund shareholders would be best served by having an independent director serve as the new chairman of the fund’s board.” Robert Bremner replaced him as chairman, who has been on the board since 1997 and is a management consultant.