Mutation may help explain human uniqueness

Mutation may help explain human uniqueness

May 8, 2007
Courtesy John Wiley & Sons, Inc.
and World Science staff

Sci­en­tists have iden­ti­fied a mu­ta­tion that they say could help ex­plain why hu­man cog­ni­tive abil­i­ties are so dif­fer­ent from those of other an­i­mals.

Past searches for such gene­tic chan­ges have had spot­ty suc­cess. A study last year did find mu­ta­tions unique to hu­mans in a gene called HAR1F, tied to brain de­vel­op­ment and pos­si­bly brain size. But it did­n’t clar­i­fy for cer­tain wheth­er the gene al­so en­hances men­tal ca­pac­i­ties. An­other gene, called FOXP2, has been linked to lang­uage abil­i­ties.

The new study found that hu­man brains have a unique form of a mol­e­cule im­pli­cat­ed in learn­ing and mem­o­ry, called neu­ro­p­sin.

This new form would have orig­i­nat­ed less than five mil­lion years ago—lat­er than when the hu­man line­age split off in ev­o­lu­tion from its clos­est an­ces­tors, chimps, some six mil­lion years ago. Hu­mans and chimp genomes vary by an es­ti­mated 1.2 per­cent.

The study is to ap­pear in an up­com­ing on­line is­sue of the re­search jour­nal Hu­man Mu­ta­tion.

Bing Su of the Chin­ese Acad­e­my of Sci­ences in Kun­ming, Chi­na and col­leagues an­a­lyzed hu­mans and sev­er­al spe­cies of apes and mon­keys. They found that hu­mans alone had a particularly long form of the neu­ropsin mol­e­cule called type II neu­ropsin. Al­though the pre­cise func­tion of neu­ropsin, a pro­tein, re­mains un­clear, it has been found in mice to help con­trol a pro­cess that un­der­lies learn­ing and mem­o­ry for­ma­tion. In this pro­cess, called long-term po­ten­ti­a­tion, new infor­ma­tion prompts brain cells to grad­u­al­ly change their ten­den­cies to pass along sig­nals to oth­er cells.

The change in the protein, Su and colleagues said, was in turn due to a change in a so-called splic­ing site of the gene that codes for its pro­d­uct­ion. This in es­sence means the gene’s code is edited dif­fer­ently as it’s used to create a fin­ished mol­e­cule. The find­ings “un­der­score the po­ten­tial im­por­tance of the cre­a­tion of nov­el splic­ing forms in the cen­tral nerv­ous sys­tem in the emer­gence of hu­man cog­ni­tion,” the re­search­ers wrote. They added that fu­ture re­search will have to clar­i­fy fur­ther what type II neu­ro­p­sin does.