I met Mark when he visited UC Berkeley to decide whether or not to accept the invitation to join the grad program. He joined the Rubin lab, and we ended up sharing adjacent benches and becoming close friends. He had a great mind, and even greater heart and sense of humor. I will miss our fun and deep conversations over beer, in the lab, and on walks. I will miss you greatly.

I interned in Dr. Fortini's lab for a summer in college. He gave me an opportunity to do research when I had limited bench experience. Not only was he a perceptive and intelligent scientist, but he was also a kind mentor. I left a longer tribute in the stories section. Many other scientists who knew Dr. Fortini have posted tributes on Twitter as well. He was so appreciated.

I met Mark in 1986 when I went to Berkeley for postdoctoral research.  We had adjacent benches, and so for two years we worked about 3 feet apart.  I don't ever remember a harsh word exchanged, only his clever advice, his collection of Imperial Russian banknotes, and his St. Petersburg memories. He went on to make many significant scientific contributions.  It's so sad he is gone so young.

As fellow grad students in the Rubin lab, I always appreciated Mark's serious approach to his work, accompanied by the twinkle in his eye as he found humor in many things and shared related amusing thoughts. Curious and having diverse (sometimes obscure!) interests, he was always fun to talk to. He will be remembered fondly.