Nimblegen Systems Inc., a Madison, Wis.-based maker of microarrays for the life sciences market, has filed for a $75 million IPO. It plans to trade on the Nasdaq under ticker symbol NMBL, with JPMorgan serving as lead underwriter. The company has raised around $66 million in VC funding since 2000, from firms like Skyline Ventures (14.04% pre-IPO stake), Cargill Ventures (13.37%), Schott AG (12.71%), Brookside Capital Partners (7.77%), Venture Investors LLC (6.55%), the State of Wisconsin Investment Board and Baird Venture Partners. www.nimblegen.com