Endoplasmic reticulum proteins impact penetrance in a pink1-mutant Drosophila model

Parkinson’s disease (PD) is a neurodegenerative disorder with a high variability of age at onset, disease severity, and progression. This suggests that other factors, including genetic, environ-mental, or biological factors, are at play in PD. Loss of PINK1 causes a recessive form of PD and is typically fully penetrant; however, it features a wide range in disease onset, further supporting the existence of protective factors, endogenous or exogenous, to play a role. Loss of Pink1 in Drosophila melanogaster results in locomotion deficits, also observed in PINK1-related PD in humans. In flies, Pink1 deficiency induces defects in the ability to fly; none-theless, around ten percent of the mutant flies are still capable of flying, indicating that advanta-geous factors affecting penetrance also exist in flies. Here, we aimed to identify the mechanisms underlying this reduced penetrance in Pink1-deficient flies. We performed genetic screening in pink1-mutant flies to identify RNA expression alterations affecting the flying ability. The most important biological processes involved were transcription-al and translational activities, endoplasmic reticulum (ER) regulation, and flagellated movement and microtubule organization. We validated 2 ER-related proteins, zonda, and windbeutel, to positively affect the flying ability of Pink1-deficient flies. Thus, our data suggest that these pro-cesses are involved in the reduced penetrance and that influencing them may be beneficial for Pink1 deficiency. w pink1B9 null mutants and controls (w pink1RV) were kindly provided by Jeehye Park and Jongkyeong Chung (Korea Advanced Institute of Science and Technology). y[1] w[*]; M{RFP[3xP3.PB] w[+mC]=UAS-KDELR-RFP}ZH-22A (UASKdelR) were generously shared by the Katanaev laboratory (Department of Pharmacology and Toxicology, University of Lausanne) . Two independent lines of Zda (w1118; PBac{IT.GAL4}zda0818-G4 (Zda1) and y1 w67c23; P{EPgy2}zdaEY08359 (Zda2)), and daughterless Gal4 (DaGal4) were purchased from the Bloomington Stock Center (Indianapolis, United States of America). M[UAS-Torsin.ORF.3xHA.GW]ZH-86Fb (UASTor-sin) and M[UAS-Wbl.ORF.3xHA.GW] (UASWbl) were purchased from the FlyORF stock center (Zurich, Switzerland). One-day-old male flies were collected and tested for their flying ability. Flies were placed in an empty vial that was gently tapped. Flies able or unable to fly were scored one and zero, respectively. For the sequencing analyses, the offspring of each parent pair that was able to fly (group 4) was separately collected from those that were not able to fly (group 3). RNA sequencing was performed on four different groups. Group 1 are control flies (pink1RV), group 2 are pink1B9-mutant flies of which none of the offspring was able to fly, groups 3 and 4 are pink1B9-mutant flies that are offspring from the same parent, but in group 3, none of the flies were able to fly, while in group 4 all the flies were able to fly.