(UPDATED: See below.)

Stem-cell proponents have long told anyone who will listen that U.S. restrictions on the research will lead to a “brain drain” of scientists emigrating to other countries where the work can proceed without limits.

The prospect of the brain drain, though, was always somewhat overblown, as only a handful of scientists have emigrated specifically to escape federal limits on stem-cell research. Among them were Roger Pedersen, the UCSF biologist who in 2001 decamped to the University of Cambridge in the U.K. and two husband-and-wife scientists — Neal Copeland and Nancy Jenkins of the NIH and Edward Holmes and Judith Swain of UCSD — who left for Singapore last year. (Holmes’ decision to move is especially hard to paint as a “brain drain,” since he sat on the powerful committee that oversees California’s $3 billion stem-cell program.)

These days, it’s equally tempting to suggest that the brain drain — to the extent that it ever existed — has been reversed into a “brain gain.” Several California universities have boosted their hiring of stem-cell researchers and administrators from elsewhere in the U.S., and now some foreign scientists seem willing to pull up roots for the Golden State as well.

Yesterday, for instance, the Gladstone Institute of Cardiovascular Disease, a research organization affiliated with UCSF, announced that it had hired Shinya Yamanaka, a Japanese researcher who recently demonstrated a way to revert ordinary skin cells back into a stem-cell like state. (See our coverage here (first item); Yamanaka is pictured to the left.) It’s a homecoming of sorts for Yamanaka, a Kobe University researcher who was a postdoc and then a staff research investigator at Gladstone in the mid-1990s. Arlene Chiu, interim chief scientific officer for the California stem-cell program, called the move “a great coup for Gladstone and for California.” Gladstone, apparently hoping to maximize the publicity effect, has already put up a bio page for Yamanaka.

The move is certainly a coup for California’s still-nascent stem-cell effort, especially since as recently as two months ago, Yamanaka had disavowed any desire to leave his native Japan. As a harbinger of a reverse brain drain, however, it’s still pretty weak beer. That’s particularly true since Yamanaka is only going to be spending one week a month in San Francisco for the next year or two, according to the WSJ health blog, although the institute’s head said he hopes to bring the Japanese scientist on full-time in two years.

For more background on Yamanaka, try this WSJ column by Peter Landers.

UPDATE: David Jensen over at the California Stem Cell Report runs with a list of the nearly 50 stem-cell researchers who have come to California since the state’s stem-cell program was approved by voters. Two caveats: The list was produced by the stem-cell agency itself, and it doesn’t include names of scientists who have moved out of the state, so it’s a fairly one-sided perspective on the question. Still, it’s worth a look if this sort of thing interests you.