Alpha-synuclein, a main component of Lewy bodies in synucleinopathies and senile 
plaques in Alzheimer disease, is centrally involved in neurodegeneration. Three 
different isoforms (alpha-synuclein 112, 126, and 140) resulting from 
alternative splicing have been described so far. The present study explores 
alpha-synuclein 126 mRNA expression levels in the prefrontal cortex of six 
patients with dementia with Lewy bodies, eight patients with Lewy body variant 
of Alzheimer disease, eight patients with Alzheimer disease, and 10 controls. 
Relative alpha-synuclein 126 expression levels were determined by real-time 
polymerase chain reaction with competimer technology. Alpha-synuclein 126 mRNA 
expression was markedly decreased in the three dementias in comparison with 
controls, suggesting an important role of this alpha-synuclein isoform in the 
normal brain.