Mark Leung and Jason Sippel will run the equities business, as former head Throsby moves to Barclays.
O'Hara has quit the bank after serving only 10 months in the role, as the bank's restructuring programme continues to hit key businesses.
Andrej Bolkovic will lead the Dutch bank's US operations, replacing industry veteran John Ruth.
Wilkins will run GH Financials listed derivatives sales and execution desk following the departure of its head of brokering.
The charge for cash used as initial margin for listed derivatives trades will affect around 60 clients.
ING appoints head of ECM and new MD, both from ABN Amro.
State Street announced the closure of its derivatives clearing business in March as it looks to refocus on core businesses.
Grant will replace John Ragan, who retires after 23 years with the broker-dealer.
Credit Suisse plans to further downsize its derivatives portfolio in a bid to avoid higher capital charges.
Bank of America Merrill Lynch hires economics expert from HSBC after Bank of Japan's liquidity warning.