The Arc Gene and Mem­ory

In his 1923 vol­ume The Pris­oner, (and in 1998 Alex Proyas movie Dark city) Where French nov­el­ist Mar­cel Proust describes mem­ory as a “…sort of chem­i­cal lab­o­ra­tory.” This apt def­i­n­i­tion was ahead of its time, as sci­en­tists were just learn­ing about the brain’s anatomy. Nearly a cen­tury later, neu­ro­sci­en­tists are begin­ning to dis­cover the chem­i­cal and mol­e­c­u­lar path­ways respon­si­ble for cre­at­ing and recall­ing mem­o­ries.
At Rut­gers Uni­ver­sity, Tim­o­thy Otto and his col­leagues are delv­ing into the brain’s bio­chem­i­cal activ­i­ties to deter­mine the ways in which expe­ri­ences acti­vate genes within brain cells to form last­ing mem­o­ries. The researchers have dis­cov­ered that the Arc gene and its pro­tein prod­uct, also called Arc, play an essen­tial role in the mem­ory for­ma­tion process.
Such as cytoskele­ton. Cytoskele­ton is unique to eukary­otic cells. It is a dynamic three-​dimensional struc­ture that fills the cyto­plasm. This struc­ture acts as both mus­cle and skele­ton, for move­ment and sta­bil­ity. The long fibers of the cytoskele­ton are poly­mers of sub­units. The pri­mary types of fibers com­pris­ing the cytoskele­ton are micro­fil­a­ments, micro­tubules, and inter­me­di­ate filaments.

Micro­fil­a­ments

Micro­fil­a­ments are fine, thread-​like pro­tein fibers, 36 nm in diam­e­ter. They are com­posed pre­dom­i­nantly of a con­trac­tile pro­tein called actin, which is the most abun­dant cel­lu­lar pro­tein. Micro­fil­a­ments’ asso­ci­a­tion with the pro­tein myosin is respon­si­ble for mus­cle con­trac­tion. Micro­fil­a­ments can also carry out cel­lu­lar move­ments includ­ing glid­ing, con­trac­tion, and cytoki­ne­sis. (Cytoki­ne­sis is the part of the cell divi­sion process)

Micro­tubules

Micro­tubules are cylin­dri­cal tubes, 2025 nm in diam­e­ter. They are com­posed of sub­units of the pro­tein tubu­lin – these sub­units are termed alpha and beta. Micro­tubules act as a scaf­fold to deter­mine cell shape, and pro­vide a set of “tracks” for cell organelles and vesi­cles to move on. Micro­tubules also form the spin­dle fibers for sep­a­rat­ing chro­mo­somes dur­ing mito­sis. When arranged in geo­met­ric pat­terns inside fla­gella and cilia, they are used for locomotion.

Inter­me­di­ate Filaments

Inter­me­di­ate fil­a­ments are about 10 nm diam­e­ter and pro­vide ten­sile strength for the cell.

Mem­ory gene acts like a virus: Two inde­pen­dent teams of NIH-​funded researchers dis­cov­ered that the Arc gene can pack­age its genetic mate­r­ial in a virus-​like shell for deliv­ery to nearby cells


Arc is found in the brain’s hip­pocam­pus region (the area involved in many forms of learn­ing), and acti­vates as mem­o­ries form. “We’ve shown that to form new mem­o­ries the hip­pocam­pus must pro­duce Arc and that block­ing Arc pro­duc­tion, blocks mem­ory for­ma­tion and recall,” explains Otto.

Edi­tors note: Could lead to mem­ory research for eli­ma­nat­ing mem­o­ries (Dark City)

The Arc pro­tein (dark spots) gets expressed by the Arc gene when a mem­ory forms in the hip­pocam­pus. To zero in on Arc activ­ity in the brains of rats, Otto and his team inject a sub­stance that binds to the Arc gene which are flu­o­resces and lights up when the hip­pocam­pus pro­duces Arc pro­tein. As the genes and pro­teins light up, they cre­ate a map of the cells involved in mem­ory for­ma­tion. “With the map we can see how a healthy brain works and the brain regions involved in mak­ing new and dif­fer­ent types of mem­ory,” says Otto.
Know­ing how a healthy brain forms mem­o­ries is an impor­tant step to under­stand­ing what goes wrong in a range of mem­ory dis­or­ders includ­ing Alzheimer’s dis­ease and stroke. Con­sid­er­ing the pub­lic health aspects of his work, Otto notes that “fig­ur­ing out how to fix these dis­or­ders is cru­cial since the num­ber of brain-​related dis­or­ders will likely sky­rocket as the pop­u­la­tion increas­ingly ages.”
So where does the idea of a bug come in?
Elissa D. Pas­tuzyn, who authored one of the stud­ies, said: “Evo­lu­tion­ary analy­sis indi­cates that Arc is derived from a ver­te­brate lin­eage of Ty3/​gypsy retro­trans­posons, which are also ances­tors to retro­viruses.” It’s believed that between 40 per cent and 80 per cent of the human genome was devel­oped thanks to ancient viruses.
Unlike bac­te­ria, which sim­ply live in the body, viruses make active changes to your cells, inject­ing their own genetic code.

This can often be entirely use­less – and some­times causes harm, includ­ing through the repro­duc­tion of more viruses – but occa­sion­ally we end up with use­ful mod­i­fi­ca­tions. And it seems an ancient virus may have given rise to all human thought – thanks to the Arc gene.

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