Scientists will also be able to study cell lines that are genetically encoded for specific diseases--perhaps one of the most promising near-term uses of embryonic stem cells. (None of the Bush-approved lines have these qualities.) "One of the clear opportunities that has not been available are lines generated from embryos that carry mutations for Huntington's disease, amyotrophic lateral sclerosis (ALS), and cystic fibrosis," says Story Landis, director of the National Institute for Neurological Disorders and Stroke, in Bethesda, MD, and chair of the NIH's Stem Cell Task Force. These cells provide unprecedented access to the molecular processes underlying disease; they can be prodded to develop into the cell type affected in a specific disease, such as motor neurons in ALS, so that scientists can watch the disease unfold at a cellular level. These cells can also be used to screen new drugs.

Scientists and policy makers are still guessing as to when and how President Obama will reverse the restrictions--whether he will issue an executive order, or let Congress decide the matter. But according to White House press reports last week, the president promised the former. Prior to Obama's presidency, Congress twice passed a bill reversing the restrictions, the Stem Cell Research Enhancement Act, which Bush twice vetoed.

It's not yet clear how quickly the field will rebound from the funding limits. Many scientists were discouraged from studying embryonic stem cells during the past eight years because they couldn't secure private funds, or because they or their universities did not want to deal with the extensive accounting required. "The effect of the restrictions was to create a few centers going forward, like mine and like Harvard, Stanford, and UCSF, which had access to private and state money," says Loring. "Now there will be more room for people to get involved, but they'll be eight years behind."

The field has changed dramatically since President Bush's edict, especially in the past two years, which may make new funding freedom less significant. A newly developed technique to create stem cells--called induced pluripotent stem (iPS) cell reprogramming--does not require the destruction of human embryos, and scientists hesitant to take on embryonic stem cells have been flocking to the new approach in droves.

Researchers have been able to do many of the same experiments with these iPS cells as they have with embryonic stem cells. However, they caution that these cells have not been shown to carry all the power of embryonic cells--for example, they cannot differentiate into as many cell types. "It's very important that labs be able to do experiments with both kinds of cells side by side," says Kriegstein. "Relaxing presidential policies will make this much easier to accomplish."

One area of research that won't change with removal of the restrictions is therapeutic cloning. In therapeutic cloning (also called somatic cell nuclear transfer), scientists transplant DNA from an adult skin cell into an egg that has had its DNA removed. Unknown factors in the egg reprogram the adult DNA to resemble embryonic DNA, and, in theory, the cell begins to develop like a normal embryo. Scientists would like to create stem cells from cloned human embryos, both for research and potentially for therapy: the cells would be genetically matched to their human donors and thus could be transplanted without fear of rejection. But no one has yet accomplished this with human cells and eggs. Research that involves destruction of human embryos, which includes both cloning and derivation of new stem-cell lines, is prohibited from federal funding under the Dickey Amendment, a rider to the appropriations bills that have been passed in Congress over the past several years.