Mitochondrial UQCRC1 mutations cause autosomal dominant parkinsonism with polyneuropathy

Abstract

Parkinson’s disease is a neurodegenerative disorder with a multifactorial aetiology. Nevertheless, the genetic predisposition in many families with multi-incidence disease remains unknown. This study aimed to identify novel genes that cause familial Parkinson’s disease. Whole exome sequencing was performed in three affected members of the index family with a late-onset autosomal-dominant parkinsonism and polyneuropathy. We identified a novel heterozygous substitution c.941A>C (p.Tyr314Ser) in the mitochondrial ubiquinol-cytochrome c reductase core protein 1 (UQCRC1) gene, which co-segregates with disease within the family. Additional analysis of 699 unrelated Parkinson’s disease probands with autosomal-dominant Parkinson’s disease and 1934 patients with sporadic Parkinson’s disease revealed another two variants in UQCRC1 in the probands with familial Parkinson’s disease, c. 931A>C (p.Ile311Leu) and an allele with concomitant splicing mutation (c.70-1G>A) and a frameshift insertion (c.73_74insG, p.Ala25Glyfs*27). All substitutions were absent in 1077 controls and the Taiwan Biobank exome database from healthy participants (n = 1517 exomes). We then assayed the pathogenicity of the identified rare variants using CRISPR/Cas9-based knock-in human dopaminergic SH-SY5Y cell lines, Drosophila and mouse models. Mutant UQCRC1 expression leads to neurite degeneration and mitochondrial respiratory chain dysfunction in SH-SY5Y cells. UQCRC1 p.Tyr314Ser knock-in Drosophila and mouse models exhibit age-dependent locomotor defects, dopaminergic neuronal loss, peripheral neuropathy, impaired respiratory chain complex III activity and aberrant mitochondrial ultrastructures in nigral neurons. Furthermore, intraperitoneal injection of levodopa could significantly improve the motor dysfunction in UQCRC1 p.Tyr314Ser mutant knock-in mice. Taken together, our in vitro and in vivo studies support the functional pathogenicity of rare UQCRC1 variants in familial parkinsonism. Our findings expand an additional link of mitochondrial complex III dysfunction in Parkinson’s disease.

Glial Nrf2 signaling mediates the neuroprotection exerted by Gastrodia elata Blume in Lrrk2-G2019S Parkinson’s disease

“…Frozen nigrostriatal brain tissues were homogenized and mixed with lysis buffer to determine protein content and for immunoblotting, as described previously [35]. The membrane was incubated overnight at 4°C with the following primary antibodies: anti-LRRK2 (Abcam, ab133474, 1:5000); anti-phospho-LRRK2 (Ser 935 , Abcam, ab133450, 1:1000); anti-phospho-LRRK2 (Ser 1292 , Abcam, ab203181, 1:1000); anti-Smad2 (Cell Signaling, 5339T, 1:1000); anti-phospho-Smad2 (Ser465/467, Cell Signaling, 3108T, 1:1000); anti-Smad3 (Cell Signaling, 9523T, 1:1000); anti-phospho-Smad3 (Ser423/425, Abcam, ab52903, 1:1000); and anti-beta actin (Sigma-Aldrich, A5441, 1:5000).…”

“…We employed two behavioral tests to assay mouse motor function, i.e., an open field assay to assess spontaneous locomotor activity and CatWalk XT gait analysis to assay coordination. Behavioral experiments were conducted blind to genotype, as described previously (Lin et al, 2020).…”

“…The substantia nigra and striatum were dissected out. The substantia nigra was subjected to immunostaining, as described previously (Lin et al, 2020). Anti-tyrosine hydroxylase (TH) (Millipore, AB152, 1:200) and anti-ionized calcium-binding adapter molecule 1 (Iba-1) (GeneTex, GTX100042, 1:200) were used as primary antibodies for 24 h at 4°C.…”

UQCRC1 engages cytochrome c for neuronal apoptotic cell death

“…UQCRC1 knockout mice confer embryonic lethality, whereas UQCRC1's heterozygotes show increased volume of infarction in the brain and impaired learning and memory after ischemic brain injury (Shan et al, 2019). We found that the mouse model of the PD-associated UQCRC1 Y314S knockin allele (hereafter called Y314S) exhibits age-dependent locomotor decline and loss of DA neurons (Lin et al, 2020). However, the endogenous function and pathogenic mechanism of UQCRC1 in neurons remain unclear.…”

“…Recently, we identified a missense mutation of human ubiquinol-cytochrome c reductase core protein 1 (UQCRC1) that is associated with patients of familial parkinsonism using whole-exome sequencing analyses (Lin et al, 2019). UQCRC1 is a core component of mitochondrial respiratory chain (RC) complex III (cIII), with enriched expression in the mammalian brain and in particular in the substantia nigra (Lin et al, 2020;Shan et al, 2019). UQCRC1 knockout mice confer embryonic lethality, whereas UQCRC1's heterozygotes show increased volume of infarction in the brain and impaired learning and memory after ischemic brain injury (Shan et al, 2019).…”