* Ex-dividend effect shaves off about 90 points from Nikkei - traders * Aeon rises on tender offer to become top shareholder of Daiei By Ayai Tomisawa TOKYO, March 27 (Reuters) - Japan's Nikkei average edged down on Wednesday in directionless trade after many shares went ex-dividend, offsetting a boost to sentiment after Wall Street gained on strong U.S. economic data. Traders said the effect of shares going ex-dividend - Tuesday was the deadline for investors to buy shares and be eligible to receive dividends for the current financial year - took about 90 points off the Nikkei and about 9 points off the Topix. The Nikkei was down 0.2 percent at 12,443.12 in midmorning trade after opening a tad higher. The index is 1.7 percent below a 4-1/2 year high of 12,650.26 struck last Thursday. Analysts said that investor sentiment remained positive on the back of expectations for aggressive easing by Japan's central bank but that trading may stay choppy on Wednesday. "If you take ex-dividend price declines into account, overall gains will likely be limited at the end of the day," said Toshihiko Matsuno, a senior strategist at SMBC Friend Securities. He added that the market remained nervous about the euro zone's debt problems due to the negative implications of a rescue plan for Cyprus. "In terms of global market news, there is a mix of both positives and negatives, so most investors may stay on the sidelines for now," Matsuno said. The broader Topix shed 0.1 percent at 1,043.27. The Dow Jones industrial average on Tuesday climbed to another record close and the S&P 500 came within striking distance of its all-time closing high, as strong data on home prices and manufacturing fed optimism about the economy. On Wednesday, Aeon Co rose 5.5 percent after sources told Reuters that the company would raise its stake in Daiei Inc to more than 40 percent through a tender offer to become the supermarket operator's top shareholder after acquiring 24 percent from Marubeni Corp. Daiei dropped 11 percent. Real estate companies gained on hopes for the government's reflationary policy, with Mitsui Fudosan rising 2.2 percent and Mitsubishi Estate adding 1.7 percent. "If the dollar trades above 95 yen, we may even see the index climb back to near a recent high quickly on exporters' gains," said Naoki Fujiwara, a fund manager at Shinkin Asset Management. The dollar last traded at 94.54 yen.