Friday, April 4, 2008

Sindromul Unertan - evolutia rasturnata

Af­ter two years in which he some­times tast­ed rid­i­cule, there is now some rec­og­ni­tion for a Turk­ish sci­ent­ist who claims ev­o­lu­tion may have gone back­ward in some un­usu­al coun­try­men of his. Phys­i­olo­g­ist Un­er Tan’s lat­est re­search on the peo­ple—who have walked on all fours life­long—is set to ap­pear in one of the most pres­tig­ious sci­en­tif­ic jour­nals.
In the re­search, Tan and col­leagues iden­ti­fy a gene linked to the con­di­tion, which they call Un­er­tan syn­drome.

Tan de­scribed him­self as “ex­tremely hap­py” about the pub­lica­t­ion. The find­ings are to ap­pear this week in the on­line early edi­tion of the U.S. jour­nal Pro­ceed­ings of the Na­tional Acad­e­my of Sci­ences. The jour­nal is of­ten cit­ed as one of the three most in­flu­en­tial sci­en­tif­ic jour­nals over­all by Thom­son Sci­en­tif­ic, a com­pa­ny that pub­lishes widely used jour­nal rank­ings.
The pub­lica­t­ion comes af­ter Tan, fac­ing skep­ti­cism and some­times hos­til­ity, had long dif­fi­cul­ties in get­ting his stud­ies on the syn­drome pub­lished in ma­jor jour­nals.

Con­tro­ver­sy fol­lowed Tan ev­er since he pro­posed his re­verse-ev­o­lu­tion the­o­ry, which along with the syn­drome it­self was first re­ported to the gen­er­al pub­lic in World Sci­ence. The the­o­ry—not dis­cussed in the Pro­ceed­ings pa­per—holds that the syn­dome may be a ge­net­ic throw­back to our ape-like an­ces­tors’ walk­ing style, and thus could shed light on it. Some sci­ent­ists have called the idea highly im­plau­si­ble. They ar­gue that any muta­t­ion caus­ing mod­ern peo­ple to walk on all fours must in­volve a sin­gle ge­net­ic change, where­as the ev­o­lu­tion­ary tran­si­tion to up­right walk­ing probably in­volved many changes.
Oth­ers who dis­a­gree with Tan have gone fur­ther and ac­cused him of slop­py schol­ar­ship and even er­rat­ic be­hav­ior. The sci­en­tif­ic de­bate has been com­pli­cat­ed by bit­ter, more per­son­al dis­putes be­tween Tan and some col­leagues, as well by what some ob­servers have called a circus-like at­mos­phere that sur­rounded the syn­drome’s dis­cov­ery in 2006.

Yet amid these con­tro­ver­sies, some re­search­ers called Tan’s re­verse-ev­o­lu­tion hy­poth­e­sis plau­si­ble and test­a­ble. Rev­erse ev­o­lu­tion—an or­gan­is­m’s re­turn to ge­net­ic char­ac­ter­is­tics of its an­ces­tors—has been doc­u­mented to oc­cur in some an­i­mals, such as fish that lose their eyes af­ter liv­ing in dark caves for genera­t­ions.
The new pa­per, co-authored with six of Tan’s col­leagues in­clud­ing his wife, Meliha, re­ports that a re­spon­si­ble muta­t­ion has been found in two of four fam­i­lies that by now have turned up af­fect­ed by “Uner­tan syn­drome.”
“Hu­man mo­lec­u­lar ge­net­ics in Tur­key is ‘on the map’ with this el­e­gant anal­y­sis,” said Mary-Claire King, a ge­net­icist at the Uni­ver­s­ity of Wash­ing­ton and an ed­i­tor of the Pro­ceed­ings.The muta­t­ion is thought to af­fect brain de­vel­op­ment, though how pre­cisely it may lead to the un­usu­al walk­ing style is un­clear. Or­gan­isms that move on all fours are called quadrupeds.

Since the in­tial re­port of the syn­drome, Tan and col­leagues have iden­ti­fied three more Turk­ish fam­i­lies af­fect­ed. The Pro­ceed­ings pa­per re­ports that mem­bers of two of the fam­i­lies suf­fer a muta­t­ion in a gene called VLDLR, which in­flu­ences how new brain cells find their way to the right place in the de­vel­op­ing brain. One brain re­gion af­fect­ed is the cer­e­bel­lum, which gov­erns bal­ance for walk­ing and stand­ing.
In a third fam­i­ly—that of the first dis­cov­ered cases of the syn­drome—Tan’s group con­firmed a pre­vi­ous study link­ing their muta­t­ion to a re­gion of a chro­mo­some called 17p. The re­gion is be­lieved to be one of the ar­eas of great­est dif­fer­ences be­tween hu­mans and chimps. Tan has said that this find­ing sup­ports his re­verse-ev­o­lu­tion idea. Al­though the new pa­per did­n’t go in­to that, he said he ex­pects fu­ture stud­ies to look at this issue. Probably “many genes are in­volved,” he added.