John Sykes, president of network development at MTV Networks and part of the executive team that developed and launched MTV, is leaving the company at month's end.

An MTVN spokesman on Tuesday confirmed Sykes' imminent departure.

Sources said it was his own decision to leave the company, where he had been charged three years ago with overseeing the development and launch of new platforms, including cable networks and broadband sites, for 35- to 50-year-olds.

But that initiative ultimately didn't fit with the plans of parent Viacom, which instead is putting the focus on strengthening its existing brands in various platforms as well as superserving those brands' core demos, sources said.

It's understood that MTV Networks will not be replacing his position. It's also unclear what Sykes' plans are after he leaves the company.

In an internal memo sent to employees Wednesday, MTVN chairman and CEO Judy McGrath praised Sykes.

"Many have left their indelible mark on MTV Networks over the years, but John's creative leadership, bold thinking, and social responsibility – not to mention the world's greatest A-list relationships - truly shaped our company," McGrath wrote. "John isn't just in tune with popular culture, he isn't satisfied unless he is defining it."

Sykes was part of the original executive team that developed and launched MTV in 1981 and sister channel VH1 four years later. After early 1990s stints at Chrysalis Records North America and later EMI Music, which acquired Chrysalis, Sykes rejoined MTVN in 1994, serving for eight years as president of VH1, where he instituted the "Save the Music" program. Under his leadership, VH1 debuted such series as "Behind the Music," "Storytellers" and "Pop Up Video." In 2002, Sykes joined Viacom's radio division, Infinity Broadcasting, as chairman and CEO. He took his current post three years later.