BGI senior corporate comms manager Melissa McVeigh said Jenkins, who has been with the asset manager for more than eight years, would not be replaced.
McVeigh and senior media relations manager Esther Nass-Fetzmann remain BGI's only London PROs, reporting to San Francisco-based global PR MD Tom Taggart.
The restructuring of BGI's comms function comes a few months after the departure of London-based co-chief executive Andrew Skirton, whose responsibilities have been absorbed by co-CEO Blake Grossman in San Francisco.
BGI manages £834bn through index tracking and quantitative techniques (rather than stock picking methods). The group is part of Barclays, whose corporate affairs director Stephen Whitehead arrived in October with a remit to shake up group-wide comms.