Schizophrenia, major depressive disorder and bipolar disorder can be referred to as chronic mental illnesses because of their lifelong and recurrent nature. They are amongst the most disabling diseases in Europe and globally. Existing methods of diagnosing and treating chronic mental illnesses are psychotherapy, as well as treatment with antipsychotics and antidepressants. Modern research projects concerning mental illnesses are attempting to improve these methods by trying to identify the biological pathways involved in these illnesses. These findings would focus treatment on the biological factors rather than only on symptoms. One rising factor being investigated is protein aggregation. Recent discoveries have found that a few proteins form aggregates in brain samples taken from patients suffering from chronic mental illnesses. These findings imply that protein aggregation could be one of the mechanisms contributing to the development of mental disorders. To expand these studies, novel proteins are being identified in brain samples from patients with mental illnesses. In this study, we investigated 12 proteins which were identified in the purified insoluble fractions from brain samples from the patients. The proteins and their quantity were identified with mass spectroscopy. These proteins may represent new aggregating proteins, and so we aimed to confirm if they have the ability to aggregate. To be able to express the genes in the mammalian cells they were transferred using the Gateway cloning system into the expression vector. When expressed they were analyzed by Western blot and fluorescent microscopy. Out of 12 investigated proteins, 6 were proven by Western blot and fluorescent microscopy, of which one was clearly seen to form aggregates, with the strong indication that another would as well. Further study of these two proteins should, therefore, be a priority for future research. Key words: mental illness, protein aggregation, novel protein.