Jon Corzine, the chief executive of the now defunct trading firm MF Global, plans to tell Congress his involvement in the mechanics of his firm's operations was "limited," but he is nonetheless full of "great sadness" at the firm's undoing. "My sadness, of course, pales in comparison to the losses and hardships that customers, employees and investors have suffered as a result of MF Global’s bankruptcy," Corzine said in testimony prepared for his appearance before the House Agriculture Committee today. "Their plight weighs on my mind every day – every hour. And, as the chief executive officer of MF Global at the time of its bankruptcy, I apologize to all those affected." Corzine, a former senator and former governor of New Jersey, was subpoened to appear before Congress to testify on the collapse of MF Global, a player in many agriculture commodity markets, and the disappearance of an estimated $1.2 billion in client money. Many speculate that Corzine, 64, will invoke his Fifth Amendment Constitutional right against self-incrimination during questioning at the hearing. Corzine has stayed out of the public eye since MF Global filed for bankruptcy on Oct. 31.  [cnbc 12/8/11] (Read Jon Corzine's full prepared testimony here)