John Gabriel, the salt-and-pepper-haired actor-singer famed for playing domineering Dr. Seneca Beaulac on ABC’s soap opera "Ryan’s Hope" for more than a decade, has died. The Daytime Emmy nominee was 90.

His daughter, "Lost" actress Andrea Gabriel, confirmed his passing — although no cause of death has been revealed at this time.

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"It is with an unspeakably heavy heart that I share the news of my father’s passing," Andrea, 42, posted to Instagram. "John Gabriel was my hero, my role model, and my champion, but above all, my daddy … I will love you forever."

Gabriel was born Jack Monkarsh on May 25, 1931 in Niagara Falls to immigrant parents. His father was born in then-Mandatory Palestine, now Israel, to Polish Jewish parents. His mother was of Polish Jewish/Russian Jewish descent.

The veteran actor’s stage and screen career spanned six decades, but he was best-known as as Dr. Beaulac from 1975 and 1985, and again in 1988 and 1989. He earned his Emmy nod for the part in 1980. However, long before his soap career gave him household name status among daytime devotees, Gabriel was already a footnote in pop culture history: He played the "Professor" in the unaired pilot of "Gilligan’s Island" in 1964.

"It was the first time in my adult life that I remember weeping," he once said of losing the role to Russell Johnson, according to his IMDB.com profile. "And I think part of that has to do with the fact that I built this thing up to such a degree it was going to be my breakthrough."

The veteran actor’s stage and screen career spanned six decades, but he was best-known as as Dr. Beaulac from 1975 and 1985, and again in 1988 and 1989. He earned his Emmy nod for the part in 1980. However, long before his soap career gave him household name status among daytime devotees, Gabriel was already a footnote in pop culture history: He played the "Professor" in the unaired pilot of "Gilligan’s Island" in 1964.

RYAN'S HOPE - Show Coverage - Shoot Date: January 20, 1981.  (Getty)

"It was the first time in my adult life that I remember weeping," he once said of losing the role to Russell Johnson, according to his IMDB.com profile. "And I think part of that has to do with the fact that I built this thing up to such a degree it was going to be my breakthrough."

His film credits include the 1966 John Wayne film "El Dorado," for which he also wrote the title song, under the famed baton of bandleader Nelson Riddle. His Broadway credits include Kander and Ebb’s 1968 musical "The Happy Time" and "Applause," opposite Lauren Bacall in 1972.

His last credited role was a voiceover part in the popular video game "Red Dead Redemption" in 2010.

Gabriel also carved out a career as an accomplished singer, performing on top talk shows of the day such as "The Ed Sullivan Show," "The Merv Griffin Show," "The Mike Douglas Show" and "Regis and Kathie Lee."

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In 1995, Gabriel moved behind the scenes to produce the late actor-turned-political commentator Charles Grodin’s eponymous talk show for CNBC.

Gabriel is survived by his his wife, actress Sandy Gabriel ("All My Children"), his daughter Andrea and Melissa, and two grandsons.

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