Pittsburgh: An in-depth computational analysis of genetic variants implicated in both schizophrenia and rheumatoid arthritis by researchers at the University of Pittsburgh points to eight genes that may explain why susceptibility to one of the disorders could place individuals at lower risk for the other, according to the results of a study published today in the journal npj Schizophrenia. “There is a wealth of genomic data on both schizophrenia and rheumatoid arthritis. Analyzing it jointly with known protein interaction information could provide invaluable clues to the relationship between the diseases and also shed light on their shared roots,” said Madhavi Ganapathiraju Ph.D., associate professor of biomedical informatics at the University of Pittsburgh School of Medicine and senior author of the study.
While schizophrenia is a psychiatric disorder of unknown
origin and rheumatoid arthritis is an autoimmune disease of the joints
that occurs as a result of the body’s immune system attacking its own
cells, both disorders are thought to be influenced by multiple genetic
risk factors modified by the environment.
research studies have hinted at a potential inverse relationship in the
prevalence and risk for the two disorders, so we wondered if individual
genetic variants may exist that could have opposing effects on the risk
of schizophrenia and rheumatoid arthritis,” said co-senior author
Vishwajit Nimgaonkar M.D., Ph.D., professor of psychiatry at Pitt’s
School of Medicine and human genetics at Pitt’s Graduate School of
The researchers first analyzed two large databases
of genetic variants significantly associated with either schizophrenia
or rheumatoid arthritis. They identified 18 unique variants, also known
as single nucleotide polymorphisms (SNPs) that were located in the HLA
region of the genome that harbors genes associated with immune function.
The variants appeared to confer different risk for schizophrenia or
rheumatoid arthritis. As the SNPs were located near eight known genes in
this region, the authors suggested those genes might lead to
dysfunction in both schizophrenia and rheumatoid arthritis. Proteins
encoded by two of these eight genes, HLA-B and HLA-C, are present in
both brain and immune cells.
Analysis of proteins that interact with these eight genes using a computational model developed last year by Ganapathiraju’s team called High-Precision Protein Interaction Prediction
found more than 25 signaling pathways with proteins common to both
rheumatoid arthritis and schizophrenia signaling. Moreover, several of
these pathways were associated with immune system function and
The findings are encouraging because they support
associations of the HLA gene region and immune function with
schizophrenia and rheumatoid arthritis that were known over four decades
ago, said Ganapathiraju.
Increasing evidence also suggests that a dysfunctional immune system could play a role in the development of schizophrenia.
“We believe that the research community studying these two disorders will find our results extremely helpful,” Nimgaonkar said.
authors note that the study only focused on SNPs in known gene regions,
and other mechanisms apart from the ones they described may also
contribute to the diseases. However, the study has significantly
narrowed the list of potential genes for examining the
schizophrenia/rheumatoid arthritis relationship. Studying the functional
relevance of the gene candidates in cells and tissues will provide
insights into the two disorders, according to the researchers.
study authors included Tulsi A. Malavia, Srilakshmi Chaparala, Joel
Wood, Kodavalli Chowdari, Ph.D., Konasale M. Prasad, M.D., and Lora
McClain, Ph.D., all of Pitt; and Anil G. Jegga, D.V.M., of Cincinnati
The research was funded by National Institutes of Health grants MH93480, MH093246, MH084053 and MH094564.