Gut Transit Defects in Drosophila Models of Monogenic Parkinson's Disease Using a Constipation Assay

Parkinson's disease (PD) is a common neurodegenerative motor disorder and is frequently accompanied by several non-motor symptoms. Among the latter, gastrointestinal problems, including constipation, often emerge years before the manifestation of locomotion difficulties and before a diagnosis of PD is established. A recent study proposed a method to measure constipation in a PD fly model that expresses wild-type human alpha-synuclein. In this study, we examined the feasibility of this method and tested whether other genetic fly PD models equally result in constipation. Available fly lines were used to measure the constipation level in autosomal dominant and recessive PD models, including three different mutant human alpha-synuclein-expressing Drosophila lines and Pink1- and Parkin-deficient flies. These flies and their corresponding controls were placed on blue-colored food one day before the experiment to induce blue fecal spots. On the day of the experiment, these flies were transferred to standard cornmeal. The percentage of blue fecal spots to total fecal spots was recorded and calculated every 90 min. The different fly PD models show slower or incomplete expulsion of blue-colored food compared to their respective control flies. Hence, a previously proposed method to measure constipation was validated and applied to various fly models of different forms of genetic PD.