Financial institutions lost billions when Reddit traders pumped money into stocks they had bet against. : A London-based hedge fund that took on heavy losses betting against GameStop in January has closed its doors, the Financial Times reported Tuesday, becoming one of the first casualties of retail traders’ piling into unpopular or heavily-shorted “meme stocks” that saw some financial mainstays lose billions. White Square Capital will close its main fund this month after a review raised concerns over the viability of its business model, head Florian Kronawitter wrote to investors, the FT reported.