Threadneedle Investments has appointed Diane Sobin as co-manager of its £358 million (about $578 million) American Smaller Companies fund.

Sobin joined the firm in September last year and will run the fund alongside Cormac Weldon, who is head of US equities.

Weldon said Sobin has extensive experience in analysing and selecting small- and mid-cap stocks, and has supported the firm's bottom-up investment approach.

Last month Threadneedle announced it was set to launch an online tool for staff members that will cover account information, valuations and dealings with existing clients.