Japan’s key Nikkei stock index extended its losses to over 2 percent midmorning on Friday, as a stronger yen against the U.S. dollar and an overnight fall of U.S. technology shares prompted investors to lock in recent gains. The 225-issue Nikkei Stock Average was trading at 41,250 at 10 a.m., compared with its record-high close of 42,224.02 on Thursday.