Rentech's CIOs are all ex-computer scientists and mathematicians (Dr. James Simons, Robert Mercer, Peter Brown). Visitors have described them as having the "best math department in the world".

From my understanding Renaissance has completely automated the process of signal discovery. They don't hire researchers to manually derive novel insights or trading models from data, and they don't really bother with exclusive sources of data. Instead, they hire researchers to improve methods for automatically processing vast amounts of arbitrary data and extracting profitable trading signals from it. And that's what differentiates them from other quant funds (D.E Shaw, Two Sigma) who still relies heavily on fundamentals.

You can take a look here: https://www.rentec.com/Careers.action?computerProgrammer=true