Pacific Investment Management Co., the big bond fund shop that boasts legendary bond guru Bill Gross as chief investment officer, announced that Mohammed El-Erian will become sole CEO of the company following the year-end retirement of long-time CEO Bill Thompson. El-Erian, 50, was named co-CEO along with Thompson, 63, of the company known as PIMCO in January, following his return to the Newport Beach, California-based company from Harvard University, where he had managed the school’s endowment. El-Erian will remain co-CIO along with Gross of the company, which had 1,053 employees and $829 billion in assets as of June 30. Gross’s flagship PIMCO Total Return Fund has $129 billion of that toal. When Thompson joined PIMCO 15 years ago when the firm, which was founded in 1971, had 125 employees and $40 billion in assets.