DA TSUFA, ƘWAYOYIN HALITTA SUN DAINA AMSAWA A TARE
Ɗaya daga cikin manyan ra’ayoyi a ilimin halittar tsufa shi ne cewa lalacewar ƙwayoyin zarra ta bazata — maye gurbi a cikin DNA na ƙwayoyin halittarmu da alamomin sinadarai da suka kauce — tana taruwa a tsawon rayuwa kuma a hankali tana ɓata yadda ake kunna da kashe kwayoyin gado. Masana ilimin halitta suna kiran wannan rashin tsarin rubutun kwayoyin gado (transcriptional deregulation). Abin da ke da wuyar fahimta shi ne wannan lalacewa ta bazata ce: kowace ƙwaya tana tara nata tsarin, daban. Ta yaya irin wannan lalacewa mai warwatsewa take haɗuwa ta zama raguwar da aka sani ta tsufa?
Neman alamar da ta dace
Kwayoyin gado suna ƙarƙashin sarrafa cibiyoyin wasu kwayoyin gado, waɗanda suke daidaita ayyukansu kuma suke rage tasirin rikice-rikice. Idan tsufa yana zaizaye waɗannan cibiyoyi, lalacewar da ta fara a wuri ɗaya na iya yaɗuwa. Amma auna wannan zaizayewa yana da wuya. Duba yawan bambancin kwayoyin gado ɗaiɗai daga ƙwaya zuwa ƙwaya yana ba da sakamako mabambanta: wani kwatanci mai tsari ma ya gano cewa wannan “hayaniyar rubutu” (transcriptional noise) ba ta ƙaruwa a kai a kai da shekaru. Wannan ƙungiya ɗaya ta riga ta nuna cewa haɗin kai tsakanin kwayoyin gado yana raguwa da shekaru gaba ɗaya, amma wannan ma’auni na gaba ɗaya bai iya faɗin waɗanne kwayoyin gado ko waɗanne ƙwayoyi ne suke kaucewa ba.
Yongjian He, Orr Levy da Julia Hanna Haddad Guez na Jami’ar Bar-Ilan a Isra’ila, tare da Xu-Wen Wang na Asibitin Brigham and Women’s da Makarantar Likitanci ta Harvard, sun yi wata tambaya daban. Idan cibiyoyin sarrafawa na tsofaffin ƙwayoyi suna ƙara bambanta da juna, to kashe kwayar gado ɗaya ya kamata ya haifar da tasiri mabambanta da ke ƙaruwa daga wata ƙwaya zuwa wata. Yin hakan a zahiri, a kan kwayoyin gado da yawa da dubban ƙanana da tsofaffin ƙwayoyi, ba abu ne mai yiwuwa a babban ma’auni ba.
Kashe kwayar gado a cikin kwamfuta
Don haka sun yi amfani da wani kayan aikin koyon zurfi (deep learning) da suka ƙirƙira, DKO. Ga wani nau’in ƙwayar halitta, cibiyar jijiyoyi ta wucin gadi tana koyo, daga bayanan ƙwaya ɗaiɗai na yau da kullum, yadda jerin kwayoyin gadon da ƙwaya take bayyanawa yake da alaƙa da cikakken bayanin ayyukanta. Da zarar an horar da ita, tana iya cire kwayar gado ɗaya daga ƙwaya ta kuma hasashen sabon bayanin. Bambancin da ke tsakanin kafin da bayan yana auna tasirin wannan kwayar gado a cikin wannan ƙwaya. Idan aka maimaita a kan ƙwayoyi da yawa, yana nuna yadda tasirin yake daidai.
Da farko, gwajin tabbatarwa a kan cibiyoyin kwayoyin gado na kwaikwayo da aka lalata da gangan ta bazata. Yayin da lalacewa ta ƙaru, ainihin tasirin kashe kwayoyin gado daidai ya ƙara bambanta tsakanin ƙwayoyi — kuma DKO, wanda yake ganin bayanan da suke kama da marasa lalacewa kawai, ya yi hasashen wannan ƙaruwa ɗaya.
Tsofaffin ƙwayoyi suna nisanta da juna
Sannan bayanan gaske: ƙwayayen mata na ɗan adam (mata masu shekaru 23–29 da masu shekaru 49–54), tsokar ƙashi ta ɗan adam (shekaru 15–20 da 70–75), ɓargon ƙashi da zuciyar ɓera (watanni 3 da 24), tsutsotsin C. elegans (rana ta 3 da rana ta 11) da ƙwaƙwalwar ƙudaje na ’ya’yan itace (rana ta 0 da rana ta 30).
A cikin kwatance 45 na kyallen jiki da nau’ikan ƙwayoyi, tasirin kashe kwayar gado ɗaya ya fi bambanta tsakanin tsofaffin ƙwayoyi a cikin 41, sosai a cikin 40. A cikin huɗu, ya ragu. Marubutan sun lura cewa alƙiblar ba ta bai ɗaya ba ce, amma babban tsarin a bayyane yake. Ya tabbata ko da lokacin da aka horar da cibiyar a kan ƙananan ƙwayoyi kawai, ko a kan tsofaffi kawai.
Wasu alamomi biyu na tsufa sun bi wannan hanya. A cikin ƙwayoyin saifa (pancreas) daga mutane biyar, ƙwayoyin da ke ɗauke da mafi yawan alamar maye gurbi mai alaƙa da shekaru su ne suke da amsoshi mafi bambanta, a cikin huɗu daga cikin biyar; a na biyar, matakan maye gurbi sun yi daidai sosai ba za a iya bambancewa ba. Irin wannan sakamako ya fito daga ƙwayoyin zuciyar tsofaffin ɓeraye. Kuma a cikin samfura biyu na tsufan ƙwaya (cellular senescence) — yanayin da ƙwayoyin da suka daina hayayyafa suke kaiwa — amsoshi sun ƙara warwatsewa yayin da ƙwayoyi suka tashi daga hayayyafa zuwa tsufa, kuma, a cikin rukuni ɗaya, ƙwayoyin da suka fi tsufa su ne suka fi kaucewa.
Ƙa’idojin da ke warwarewa
Marubutan suna fassara wannan a matsayin asarar ƙarfin sarrafawa (regulatory robustness) a hankali, a matakin kwayar gado ɗaya da ƙwaya ɗaya, wanda nau’ikan halittu masu nisa kamar mutane da tsutsotsi suke da shi a tare. Hoton da suka gabatar: maye gurbi suna taruwa suna kuma raba ƙwayoyi, yayin da tsufan ƙwaya zai iya zama ɗaya daga cikin sakamakon wannan asarar kwanciyar hankali.
Suna mai da hankali kan abin da wannan ba shi ba. Kashe kwayoyin gadon hasashe ne na samfuri, ba ma’auni a cikin waɗannan ƙwayoyin ba. Alaƙar da ke tsakanin maye gurbi da tsufan ƙwaya haɗuwa ce kawai; ba ta tabbatar da me ke haifar da me ba. Idan lalacewa ta bazata ce take haifar da wannan kaucewa da gaske, in ji su, magungunan da ke nufin hanya ɗaya kawai ta tsufa za su iya kasa cimma buri, kuma kiyaye ƙarfin sarrafa kwayoyin gado da kansa zai iya zama mai muhimmanci. Mataki na gaba na dakin gwaje-gwaje ne: gwadawa, kwayar gado bayan kwayar gado, ko tsofaffin ƙwayoyi suna amsawa ba tare da jituwa ba da gaske.