When kids’ autis­tic brains can’t calm down

Sunday Trust - - NEWS HEALTH - Source: www.sci­encedaily.com

One third of chil­dren who have autism spec­trum dis­or­der also have epilepsy. It’s re­lated to a ma­jor autism risk gene, which is mu­tated in pa­tients with autism. But sci­en­tists didn’t know why the mu­ta­tion, cat­nap2, caused seizures.

Now North-west­ern Medicine sci­en­tists have dis­cov­ered the mu­ta­tion acts like a bad gar­dener in the brain. It shrinks the neu­rons’ tiny branches and leaves -- its den­drite ar­bors and synapses -- that en­able brain cells to re­lay vi­tal mes­sages and con­trol the brain’s ac­tiv­ity. The shrink­age causes a break­down in mes­sage de­liv­ery.

An im­por­tant mes­sage that gets lost? Calm Down!

In peo­ple with the mu­ta­tion, in­hibitory neu­rons -- whose job is to keep things tran­quil in the brain and slam the brake on ex­ci­ta­tory neu­rons -- don’t grow enough branches and leaves to com­mu­ni­cate their Zen-like mes­sage, the sci­en­tists found. That leads to seizures.

The mu­ta­tion, CNTNAP2 or “cat­nap2,” works as a team with an­other mu­tated gene, CASK, im­pli­cated in men­tal re­tar­da­tion. As a re­sult, sci­en­tists have a new tar­get for drugs to treat the dis­or­der.

The pa­per was pub­lished April 2 in Molec­u­lar Psy­chi­a­try.

“Now we can start test­ing drugs to treat the seizures as well as other prob­lems in autism,” said lead au­thor Peter Pen­zes, the Ruth and Eve­lyn Dun­bar Pro­fes­sor of Psy­chi­a­try and Be­hav­ioral Sciences at North­west­ern Uni­ver­sity Fein­berg School of Medicine. “Pa­tients with the mu­ta­tion also have lan­guage de­lay and in­tel­lec­tual dis­abil­ity. So a drug tar­get­ing the mu­ta­tion could have mul­ti­ple ben­e­fits.”

Next Pen­zes’s team will do high­through­put screen­ing of mol­e­cules with the goal of rev­ers­ing these ab­nor­mal­i­ties in pa­tients with autism.

Cat­nap2 is an ad­he­sive mol­e­cule that helps cells stick to­gether, in this case help­ing the synapses ad­here to the den­drites. It’s a dif­fi­cult mol­e­cule to tar­get with drugs, Pen­zes said.

But cat­nap2’s part­ner, CASK, is a so­cial but­ter­fly en­zyme that in­ter­acts with many other mol­e­cules. It can more eas­ily be in­hib­ited or ac­ti­vated with drugs. Pen­zes’s team will screen drugs to ac­ti­vate it be­cause that ap­pears to main­tain healthy den­drite branches. When sci­en­tists blocked CASK in the study, den­drites didn’t grow.

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