By Rob Lenihan An important U.S. regulator raises concerns about ‘fraudulent and manipulative acts and practices.’ Cathie Wood took a hit on Friday when the U.S. Securities and Exchange Commission (SEC) turned down an application for a spot bitcoin exchange-traded fund EFT from the star investor’s Ark 21Shares. Basically, the firm wanted the market watchdog to approve spot exchange-traded funds, or ETFs, based on actual bitcoin holdings. ‘Protect Investors and the Public Interest’Cboe BZX Exchange filed an application to allow for a rule change, but the SEC said that BZX did not meet its burde…