Tesla Inc. TSLA, -5.59% said late Thursday that Hiromichi Mizuno has joined the Silicon Valley car maker's board of directors, effective immediately. With Mizuno's arrival, Tesla's board increases to 10 members. Mizuno most recently served as executive managing director and chief investment officer of Japan's Government Pension Investment Fund, which Tesla said is the largest pension fund in the world with about $1.5 trillion in assets. "During his time there, Hiro emphasized the importance of environmental considerations in portfolio management and became a global thought leader in sustainable and responsible investment," Tesla said. "He also challenged many established market practices, including short-selling, to promote long-term value creation by corporations." Other Tesla board members include Chair Robyn M. Denholm, a telecommunications executive, and Chief Executive Elon Musk. Shares of Tesla were up a fraction in the extended session after ending the regular trading day down 3.6%.