FORTUNE — The University of California is without a chief investment officer for its $80 billion endowment, following the sudden resignation of longtime CIO Marie Berggren for what are being referred to as “personal reasons.”

A source familiar with the situation says that Berggren gave no notice for her decision, informing the UC Regents just one or two days before leaving for good on July 2. In addition to her CIO role, she also had been acting treasurer and vice president for investments.

Berggren originally joined UC in 2002, after having led venture capital investing for Bank One Corp. She was promoted to CIO four years later, and recently oversaw significant asset allocation changes that included a large long-term increase in alternative asset exposure at the expense of both public equities and fixed income.

UC Regents are expected to name an acting CIO during its regular monthly meeting, which begins today and runs through Thursday. And, if history is any guide, it also will hire an outside search firm to identify a permanent replacement.

UC Regents did publish a statement on its website about the resignation, but it does not appear to have been picked up by any media outlets outside of a campus newspaper. Berggren’s emails do not bounce back with any out-of-office reply, and calls are still transferred to her assistant without mention of the resignation.

Sign up for my daily email newsletter on deals and deal-makers: