A study in Cell Genomics has found a link between somatic genetic mutations and schizophrenia. Researchers analyzed over 20,000 blood samples, identifying genes NRXN1 and ABCB11 as associated with schizophrenia when disrupted during fetal development. The finding highlights the role of non-inherited genetic mutations in psychiatric disorders, and the team plans to explore other potential associated mutations.
As a psychiatric disorder with onset in adulthood, schizophrenia is thought to be triggered by some combination of environmental factors and genetics, although the exact cause is still not fully understood. In a study published in the journal Cell Genomics on July 6, researchers find a correlation between schizophrenia and somatic copy-number variants, a type of mutation that occurs early in development but after genetic material is inherited. This study is one of the first to rigorously describe the relationship between somatic—not inherited—genetic mutations and schizophrenia risk.
“We originally thought of genetics as the study of inheritance. But now we know that genetic mechanisms go way beyond that,” says senior author Chris Walsh, an investigator at the Howard Hughes Medical Institute and chief of genetics and genomics at Boston Children’s Hospital. “We’re looking at mutations that are not inherited from the parents.”
The researchers analyzed genotype-marker data from over 20,000 blood samples of people with or without schizophrenia from the Psychiatric Genomics Consortium. They ultimately identified two genes—NRXN1 and ABCB11—that correlated with schizophrenia cases when disrupted in utero. NRXN1, a gene that helps transmit signals throughout the brain, has been associated with schizophrenia before. However, this is the first study to associate somatic, not inherited, NRXN1 mutations with schizophrenia.
Unlike inherited mutations, which are present in all the cells of the body, somatic mutations are only present in a fraction of cells based on when and where a mutation occurred. If a mutation occurs early in development, it is expected that the variant is present throughout the body in a mosaic pattern. On the basis of this principle, researchers can identify somatic mutations that occurred early in development and are present not only in the brain but also in a fraction of cells in the blood.
“If a mutation occurs after fertilization when there are only two cells, the mutation will be present in half of the cells of the body,” says Walsh. “If it occurs in one of the first four cells, it will be present in about a quarter of the cells of the body, and so on.”
The second gene the researchers identified, ABCB11, is most known to encode a liver protein. “That one came out of nowhere for us,” says Eduardo Maury, a student in Harvard-DOI: 10.1016/j.xgen.2023.100356
This work was supported by the Harvard/MIT MD-PhD program, the Biomedical Informatics and Data Science Training Program, the Ruth L. Kirschstein NRSA F31 Fellowship, the