Tokyo: Often dubbed 'junk DNA',
retrotransposons - short sequences of DNA that autonomously amplify and move
around the genome - may play a key role in developing schizophrenia.
A team of researchers in Japan
found that a class of retrotransposons named Long Interspersed Nuclear Elements
(LINE-1) in the schizophrenia brain modify the expression of genes related to
schizophrenia during brain development and may be one of the causes of the
disease.
The team led by Kazuya Iwamoto
from the University of Tokyo and Tadafumi Kato from the RIKEN Brain Science
Institute demonstrated that the number of LINE-1 copies is elevated in the
post-mortem brains of patients with schizophrenia.
The results showed that
exposure to environmental risk factors during development, as well as the
presence of genetic risk factors for schizophrenia, can lead to increased
levels of LINE-1 in neurons, said the study published in the journal Neuron.
“Our findings strongly suggest
that abnormal, enhanced retrotransposition of LINE-1 in neurons, triggered by
environmental factors and/or combined with a genetic risk factor, plays a
defining role in schizophrenia," concluded the authors.
"Previously, schizophrenia
was regarded as a disease caused by gene-environment interactions, but our
study shows that the environment can alter the genome and may contribute to the
disease," explained Kato.
LINE-1 have been shown to be
more abundant in brain cells than in other cells in the body in adults,
providing evidence for enhanced activity of LINE-1 in the human brain. However,
the role played by LINE-1 in mental disorders, and in particular schizophrenia,
has remained unclear till date.
LINE-1 retrotransposons make up
a large part of the eukaryotic genome and it is believed that they may
contribute to a number of disorders and diseases such as cancer.
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