In the wee hours of Monday morning, a few scientists will get a phone call from the Karolinska Institute in Stockholm, Sweden to let them know that they’ve just won the Nobel Prize in Physiology or Medicine. Last year’s honors went to UCSF’s Elizabeth Blackburn, Johns Hopkins’ Carol Greider and Harvard’s Jack Szostak for describing how telomeres protect DNA.

Who’s likely to get the call this year? According to Thompson Reuters, the leading contenders fall into three groups:

• Douglas Coleman (Jackson Laboratory) and Jeffrey Friedman (Rockefeller University/Howard Hughes Medical Institute) for discovering the hormone leptin, which is involved in a host of metabolic functions, including regulation of appetite. (Coleman and Friedman also won this year’s Lasker awards and wrote commentaries about the discovery for Nature Medicine.)

• Ernest McCulloch (Ontario Cancer Institute) and James Till (Ontario Cancer Institute) for the initial discovery of stem cells, plus Shinya Yamanaka (Kyoto University) for figuring out how to induce pluripotent stem cells from adult mouse fibroblasts. (Yamanaka won last year’s Lasker and wrote about it for the journal, too.)

• Ralph Steinman (Rockefeller University) for discovering key immune regulators called dendritic cells. (Steinman — yes, you guessed it — won the 2007 Lasker. Read his commentary here.)

Last year, Thomson Reuters also predicted that James Rothman (Yale University) along with Randy Schekman (University of California, Berkeley) had a strong chance for their discovery of cellular membrane trafficking.

Our dark horse in this race is Craig Venter, for his work in creating a synthetic bacterium and sequencing the human genome. Back in 2005, Thomson Reuters touted Venter, along with Francis Collins and Eric Lander, as front runners for the prize, so Venter has been waiting a long time for another accolade to add wind to his sails.

Feel free to speculate on any other likely contenders in the comments!