Goldman Sachs is reported to be the "lead left" manager for Twitter's IPO, and JP Morgan Chase and Morgan Stanley are also reported to be part of the lead banks for the deal.
Here's a link to my prior post on Twitter - what is known at this point and what is speculation:
http://www.allenlatta.com/1/post/2013/09/twitter-files-for-its-ipo-what-we-know-for-certain-and-speculation.html
Link to The Wall Street Journal story (subscription required): http://online.wsj.com/article/SB10001424052702303464504579106151499047342.html
Link to Twitter IPO article on Quartz:
http://qz.com/129205/twitter-plans-to-make-its-ipo-filing-public-this-week/