Scientists have identified a rare genetic variant that may have a fundamental role in the development of schizophrenia -- a chronic and severe mental disorder that affects over 21 millon people worldwide.

It is known that more than 80 per cent of schizophrenia cases have a hereditary cause, but the new study identified RTN4R gene variant that leads to the complicated disorder, which often appears in early adulthood."Schizophrenia is a disease caused by disturbances in neural circuits. Myelin-related genes are associated with the disease," said Toshihide Yamashita, professor at Osaka University in Japan.Myelin, which acts as a conductor of signals for the neural circuits, could contribute to the pathology of schizophrenia.

RTN4R is a subunit of RTN4, which regulates crucial functions for neural circuits, namely, axon regeneration and structural plasticity.Moreover, "RTN4 is a promising candidate gene for schizophrenia because it is located at chromosome 22q11.2 -- a hotspot for schizophrenia", Yamashita said.In the study, published in Translational Psychiatry, the team searched for rare variants of RTN4 by screening the DNA of 370 schizophrenia patients. They found a single missense mutation -- R292H -- that changed the amino acid of this protein from arginine to histidine, proving that rare variants could act as risk factors for schizophrenia."There is growing evidence that rare variants contribute to neurodevelopment diseases. Our findings strengthen the evidence that rare variants could contribute to schizophrenia," Yamashita said.