Recent studies have shown that the genome in the human brain cells contains many brain-specific somatic variations which arise after fertilization. Insertion of retrotransposon such as Long INterspersed Element-1 (LINE-1 or L1) is one of these somatic variations which could be a driving force to diversify the brain genome. We recently reported that the copy number of long interspersed nucleotide element (LINE-1) retrotransposon was higher in the neurons of schizophrenia patients than in the neurons of healthy controls and these LINE-1 insertions in schizophrenia were enriched near the neuronal genes. However, as each cell in the brain is thought to have a different pattern of LINE-1 insertions, single cell analysis should be required to describe the complete somatic variations in the brain.
To this purpose, we have developed a novel technique for detecting LINE-1 insertions from single neuronal nuclei. We assessed novel LINE-1 insertions using postmortem brains of patients with schizophrenia as well as control subjects.
We detected about 30-40 of novel LINE-1 insertions at each single neuron. Some neuronal DNA from patients with schizophrenia had novel LINE-1 insertions within the genes associated with neuronal function.
These neuronal novel LINE-1 insertions might be one of the causes of schizophrenia.