Parkinson’s disease (PD) is a neurodegenerative disorder. But not just. And it may not start that way. There is increasing evidence that a-synuclein, the protein whose aggregates eventually destroy midbrain dopaminergic neurons in PD (and that are the cause of other diseases collectively known as the synucleinopathies), first aggregates “in enteric neurons, the neurons that control gastrointestinal function,” Collin Challis told BioWorld.