Novel GIGYF2 gene variants in patients with Parkinson's disease in Chinese population

Association study of DNAJC13, UCHL1, HTRA2, GIGYF2, and EIF4G1 with Parkinson's disease

Rare mutations in genes originally discovered in multigenerational families have been associated with increased risk of Parkinson's disease (PD). The involvement of rare variants in DNAJC13, UCHL1, HTRA2, GIGYF2, and EIF4G1 loci has been poorly studied or has produced conflicting results across cohorts. However, they are still being often referred to as "PD genes" and used in different models. To further elucidate the role of these 5 genes in PD, we fully sequenced them using molecular inversion probes in 2408 patients with PD and 3444 controls from 3 different cohorts. A total of 788 rare variants were identified across the 5 genes and 3 cohorts. Burden analyses and optimized sequence Kernel association tests revealed no significant association between any of the genes and PD after correction for multiple comparisons. Our results do not support an association of the 5 tested genes with PD. Combined with previous studies, it is unlikely that any of these genes plays an important role in PD. Their designation as "PARK" genes should be reconsidered.

Regulation of plant immune receptor accumulation through translational repression by a glycine-tyrosine-phenylalanine (GYF) domain protein

Plant immunity is tightly regulated to ensure proper defense against surrounding microbial pathogens without triggering autoimmunity, which negatively impacts plant growth and development. Immune receptor levels are intricately controlled by RNA processing and post-translational modification events, such as ubiquitination. It remains unknown whether, and if yes, how, plant immune receptor homeostasis is regulated at the translational level. From a mutant, snc1-enhancing (muse) forward genetic screen, we identified MUSE11/EXA1, which negatively regulates nucleotide-binding leucine-rich repeat (NLR) receptor mediated defence. EXA1 contains an evolutionarily conserved glycine-tyrosine-phenylalanine (GYF) domain that binds proline-rich sequences. Genetic and biochemical analysis revealed that loss of EXA1 leads to heightened NLR accumulation and enhanced resistance against virulent pathogens. EXA1 also associates with eIF4E initiation factors and the ribosome complex, likely contributing to the proper translation of target proteins. In summary, our study reveals a previously unknown mechanism of regulating NLR homeostasis through translational repression by a GYF protein.

Meta-analyses of seven GIGYF2 polymorphisms with Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder that affects ~2% of the global population aged ≥65 years. Grb10-interacting GYF protein-2 (GIGYF2) can influence the development of PD through the regulation of insulin-like growth factor-1. The aim of the present meta-analysis study was to establish the contribution of GIGYF2 polymorphisms to PD. The study was conducted based on nine eligible studies consisting of 7,246 PD patients and 7,544 healthy controls. The results indicated that the GIGYF2 C.3630A>G polymorphism increased the risk of PD by 37% [P=0.008; odds ratio (OR), 1.37; 95% confidence interval (CI), 1.08-1.73] and that the GIGYF2 C.167G>A polymorphism was significantly associated with PD (P=0.003; OR, 3.67; 95% CI, 1.56-8.68). The meta-analyses of the other five GIGYF2 polymorphisms (C.1378C>A, C.1554G>A, C.2940A>G, C.1370C>A and C.3651G>A) did not reveal any significant associations. The present meta-analyses of the GIGYF2 genetic polymorphisms may provide a comprehensive overview of this PD candidate gene for future studies.

Parkinson's disease: from genetics to treatments

Parkinson's disease (PD) is a common neurodegenerative disease and typically presents with tremor, rigidity, bradykinesia, and postural instability. The hallmark pathological features of PD are loss of dopaminergic neurons in the substantia nigra (SN) and the presence of neuronal intracellular Lewy body (LB) inclusions. In general, PD is sporadic; however, familial PD, while uncommon, can be inherited in an autosomal dominant (AD) or autosomal recessive (AR) manner. The molecular investigations of proteins encoded by PD-linked genes have clarified that ADPD is associated with α-synuclein and LRRK2, while ARPD is linked to Parkin, PINK1, DJ1, and ATP13A2. Understanding these genes can bring insights into this disease and create possible genetic tests for early diagnosis. Long-term pharmacological treatment is so far disappointing, probably due to unwanted complications and decreasing drug efficacy. Several strategies have been proposed and tested as alternatives for PD. Cellular transplantation of dopamine-secreting stem cells opens the door to new therapeutic avenues for restoration of the functions of degenerative and/or damaged neurons in PD.

Follow-up study of variants of the GIGYF2 gene in Chinese patients with Parkinson’s disease

The Grb10-interacting GYF protein-2 gene (GIGYF2) is a PARK11 gene that reportedly has a causal role in familial Parkinson’s disease (PD) among populations from Italy and France. However, no comprehensive study of the GIGYF2 gene has been conducted among PD patients from mainland China. In our previous study, the GIGYF2 gene was directly sequenced, and nine missense variants and 14 polymorphisms were identified. For these 14 polymorphisms, in the present study we performed a case–control analysis for 300 PD patients and 200 healthy controls from mainland China. The c.297T>C p.Ala99Ala polymorphism was associated with increased risk with respect to the pathogenesis of sporadic PD. In conclusion, within the Chinese population, the c.297T>C p.Ala99Ala polymorphism of the GIGYF2 gene may be associated with an increased risk of developing PD.

Association study of SCARB2 rs6812193 polymorphism with Parkinson's disease in Han Chinese

Recently, a nucleotide polymorphism rs6812193 near SCARB2 was found to be significantly associated with Parkinson's disease (PD) in populations of European ancestry. Herein, we conducted a case-control study with attempt to further evaluate the association between SNP rs6812193 and PD in a Chinese population from mainland China. rs6812193 was genotyped by PCR-RFLP technique in 449 PD patients and 452 controls in a Chinese population. In our study, we did not detect statistically significant differences between cases and controls in terms of both allele and genotype distribution of the rs6812193 polymorphism (P=0.97 and P=0.77, respectively), even after stratification by age at onset. Our data do not support the association of SNP rs6812193 with PD in Han Chinese of mainland China.

Mutation analysis of LRRK2, SCNA, UCHL1, HtrA2 and GIGYF2 genes in Chinese patients with autosomal dorminant Parkinson's disease

Autosomal dorminant Parkinson's disease (ADPD) has been associated with mutations in the SCNA, LRRK2, UCHL1, HtrA2 and GIGYF2 genes. We studied the prevalence of variants in all five genes in 12 Chinese unrelated families with ADPD and 4 families with both essential tremor (ET) and Parkinson's disease (PD) phenotypes using direct sequencing analysis. We found 27 variants in the LRRK2 gene, eight in GIGYF2 gene, three in the SCNA and UCHL1 gene respectively, in which five variants were novel. However, no pathogenic mutations in the five genes were found in these families. Our result indicated that SCNA, LRRK2, UCHL1, HtrA2 and GIGYF2 genes' mutations might not be a main reason for Chinese ADPD.

What genetics tells us about the causes and mechanisms of Parkinson's disease

Parkinson's disease (PD) is a common motor disorder of mysterious etiology. It is due to the progressive degeneration of the dopaminergic neurons of the substantia nigra and is accompanied by the appearance of intraneuronal inclusions enriched in α-synuclein, the Lewy bodies. It is becoming increasingly clear that genetic factors contribute to its complex pathogenesis. Over the past decade, the genetic basis of rare PD forms with Mendelian inheritance, representing no more than 10% of the cases, has been investigated. More than 16 loci and 11 associated genes have been identified so far; genome-wide association studies have provided convincing evidence that polymorphic variants in these genes contribute to sporadic PD. The knowledge acquired of the functions of their protein products has revealed pathways of neurodegeneration that may be shared between inherited and sporadic PD. An impressive set of data in different model systems strongly suggest that mitochondrial dysfunction plays a central role in clinically similar, early-onset autosomal recessive PD forms caused by parkin and PINK1, and possibly DJ-1 gene mutations. In contrast, α-synuclein accumulation in Lewy bodies defines a spectrum of disorders ranging from typical late-onset PD to PD dementia and including sporadic and autosomal dominant PD forms due to mutations in SCNA and LRRK2. However, the pathological role of Lewy bodies remains uncertain, as they may or may not be present in PD forms with one and the same LRRK2 mutation. Impairment of autophagy-based protein/organelle degradation pathways is emerging as a possible unifying but still fragile pathogenic scenario in PD. Strengthening these discoveries and finding other convergence points by identifying new genes responsible for Mendelian forms of PD and exploring their functions and relationships are the main challenges of the next decade. It is also the way to follow to open new promising avenues of neuroprotective treatment for this devastating disorder.