Reduced astrocytic reactivity in human brains and midbrain organoids with PRKN mutations

Masayoshi Kano,Makiko Nagai,Asako Yoritaka,Kazuko Hasegawa,Kei-Ichi Ishikawa,Kazutoshi Nishiyama,Kahori Shiba-Fukushima,Taku Hatano,Genko Oyama,Tsuyoshi Inoshita,Nobutaka Hattori,Yuzuru Imai,Wado Akamatsu,Silvia Bolognin,Jens Christian Schwamborn,Masashi Takanashi

doi:10.1038/s41531-020-00137-8

Abstract

Parkin (encoded by PRKN) is a ubiquitin ligase that plays an important role in cellular mitochondrial quality control. Mutations in PRKN cause selective dopaminergic cell loss in the substantia nigra and are presumed to induce a decrease in mitochondrial function caused by the defective clearance of mitochondria. Several studies have demonstrated that parkin dysfunction causes mitochondrial injury and astrocytic dysfunction. Using immunohistochemical methods, we analyzed astrocytic changes in human brains from individuals with PRKN mutations. Few glial fibrillary acidic protein- and vimentin-positive astrocytes were observed in the substantia nigra in PRKN-mutated subjects compared with subjects with idiopathic Parkinson’s disease. We also differentiated patient-specific induced pluripotent stem cells into midbrain organoids and confirmed decreased numbers of glial fibrillary acidic protein-positive astrocytes in PRKN-mutated organoids compared with age- and sex-matched controls. Our study reveals PRKN-mutation-induced astrocytic alteration and suggests the possibility of an astrocyte-related non-autonomous cell death mechanism for dopaminergic neurons in brains of PRKN-mutated patients.

Highlights

Parkin RBR E3 ubiquitin-protein ligase (PRKN) is a causative gene for young-onset Parkinson’s disease (PD), and mutations in this gene are most frequent among young-onset PD patients[1]
When astrocytes respond to central nervous system (CNS) damage and change to reactive forms, the intermediate filaments (IFs) proteins glial fibrillary acidic protein (GFAP) and vimentin are upregulated[16]
The band intensities of each protein varied among the cases, there were no statistically significant differences in GFAP, vimentin, or ALDH1L1 expression in the frontal cortex. These results suggest that astrocytes are not markedly altered in the PRKN-mutated frontal cortex, in which neurodegeneration was not detected in the PRKN-mutated brains

Summary

Introduction

Parkin RBR E3 ubiquitin-protein ligase (PRKN) is a causative gene for young-onset Parkinson’s disease (PD), and mutations in this gene are most frequent among young-onset PD patients[1]. To confirm whether GFAP and vimentin were decreased in the SN and in other brain regions, we performed immunohistochemistry using astrocytic markers in the frontal cortex, which usually shows no neurodegenerative changes in patients with PRKN mutations. GFAP (Fig. 4a, e, i, m, q, u, y), vimentin (Fig. 4b, f, j, n, r, v, z), and ALDH1L1 (Fig. 4d, h, l, p, t, x, β) positivity were observed in the astrocytes of the three PRKN-mutated patients.

Results

Conclusion