Tom Slater, co-manager of the £3.6bn Scottish Mortgage trust, will take over the role of head of the North American team at Baillie Gifford.
Weisser joins from Standard Chartered Bank
Previous roles at L&G and Skandia
Will remain as non-exec director
Brockman becomes head of intermediary distribution
MacIntyre to join in January 2016
Jayne Styles will remain at insurer