Yanase Berlitz is the mother of Platinum.
Ruby and Sapphire Arc
Her first appearance was in a flashback of Norman's. She was one of the researchers assigned to study and control Rayquaza. She was the one to brief Norman, his wife and Prof. Birch on the cause for Rayquaza's eventual escape, which, unfortunately, led Norman to realize his son was the true reason for the incident.
In a flashback, she was seen discarding the gem meant to control the Legendary Pokémon that escaped, which would eventually be found by the main protagonist of the arc.
Diamond and Pearl Arc
At the end of the chapter, she appeared in a ship talking to her cellphone and signing something with her name.