Age-dependent alpha-synuclein accumulation and aggregation in the colon of a transgenic mouse model of Parkinson’s disease

Background:Parkinson’s disease(PD)is one of the most common neurodegenerative diseases,neuropathologically characterized by misfolded protein aggregation,called Lewy bodies and Lewy neurites.PD is a slow-progressive disease with colonic dysfunction appearing in the prodromal stage and lasting throughout the course of the disease.Methods:In order to study PD pathology in the colon,we examined the age-dependent morphological and pathological changes in the colon of a PD mouse model expressing human wildtype α-synuclein(α-syn)fused with the green fluorescent protein(GFP),under the endogenous mouse α-syn promoter.Results:We observed an age-dependent progressive expression and accumulation of α-syn-GFP in the enteric neurons of Meissner’s(submucosal)and Auerbach’s(myenteric)plexuses of the colon.Additionally,the phosphorylation of α-syn at serine 129 also increased with age and the aggregation ofα-syn-GFP coincided with the appearance of motor deficits at 9 months of age.Furthermore,α-syn(-GFP)distinctly co-localized with different subtypes of neurons,as identified by immunohistochemical labeling of vasoactive intestinal peptide(VIP),neuronal nitric oxide synthase(nNOS),and calretinin.Conclusions:Our results show the development of α-syn pathology in the enteric neurons of the colon in a PD mouse model,which coincide with the appearance of motor deficits.Our mouse model possesses the potential and uniqueness for studying PD gastrointestinal dysfunction.