Twitter's design and culture exec Elizabeth Weil has left the company to take a new high-profile spot at Andreessen Horowitz.

As the venture firm's partner, Weil will be in charge of social strategy, AllThingsD reports. She will work closely with veteran tech executive Mark Cranney, the firm's partner for marketing development, who joined the firm last year.

Weil Tweeted about her new job on Friday: "3 years at Twitter have flown by. Honored to have worked alongside this amazing crew. Thrilled to be joining the Andreessen Horowitz team." 

An investor in technology start-ups since its founding in 2009, the Menlo Park-based Andreesen Horowitz most recently invested $15 million in lyrics site Rap Genius. The firm has invested in companies, including Instagram, Pinterest, Skype and Foursquare. Last year, the firm bought $80 million in Twitter stock.

At Twitter, Weil directed the company's first advertisement products and oversaw the acquisitions of start-ups like Tweetie and DabbleDB, notes AllThingsD. Her husband, Kevin Weil, is Twitter's director of revenue products.

Twitter bade farewell to several other employees in recent weeks, according to AllThingsD. Departures include product manager Cynthia Johanson and engineering managers Ori Allon and Mark McBride.