No, but young Magneto witnessed his experiments:

"As a Nazi scientist, Mister Sinister worked along with geneticist Josef Mengele, earning the nickname “Nosferatu” from the captive children at Auschwitz after his pale skin. Working in the camps was a convenient opportunity for him to have easy access to large amounts of genetic samples by offering candy to children in exchange for their blood as a means of bribery. Back then, he used to play a piece by Franz Schubert. Young Max Eisenhardt witnessed "Nosferatu's" terrible experiments, aimed at catalyzing the mutator gene by deforming his victims.[8]"

But somewhere I read once magneto mentione sinister experiment on young magneto in camp depends who's writing comic