- Email: [email protected]
Follow-up study of variants of the GIGYF2 gene in Chinese patients with Parkinson’s disease
Journal of Clinical Neuroscience 18 (2011) 1699–1701
Contents lists available at SciVerse ScienceDirect
Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Laboratory Study
Follow-up study of variants of the GIGYF2 gene in Chinese patients with Parkinson’s disease Lei Wang a, Ji-Feng Guo a,b, Wen-Wen Zhang a, Qian Xu a, Xing Zuo a, Chang-He Shi a, Lin-Zi Luo a, Jia Liu a, Liang Hu a, Ya-Cen Hu a, Xin-Xiang Yan a,b, Bei-Sha Tang a,b,c,⇑ a b c
Department of Neurology, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008, China Neurodegenerative Disorders Research Center, Central South University, Changsha, Hunan, China State Key Laboratory of Medical Genetics of China, Changsha, Hunan, China
a r t i c l e
i n f o
Article history: Received 6 October 2010 Accepted 29 May 2011 Keywords: GIGYF2 gene Parkinson’s disease Variants
a b s t r a c t 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. Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction Parkinson’s disease (PD; Online Mendelian Inheritance in Man database #168600) is the second most common neurodegenerative disease, with major clinical features of bradykinesia, rigidity, resting tremor and postural instability. Genetic factors are known to play an important role in the development of this disease.1 To date, 11 factors associated with autosomal-dominant inherited PD have been cloned, including SCNA and LRRK2.2,3 In contrast, the factors Parkin, PINK1, DJ-1, ATP13A2, PLA2G6 and FBXO7 are observed more frequently in recessive PD, while UCH-L1 and Htra2 have shown little or no correlation with PD.4–11 PARK11/Grb10-interacting GYF protein-2 gene (GIGYF2) reportedly has a causal role in familial PD in populations from Italy and France.12 Since the GIGYF2 gene was first identified, studies in Portuguese, US, Australian, Norwegian, Belgian, Spanish, French, Italian, Japanese, Singaporean and Chinese populations have provided conflicting data on the causal role of this gene.13–30 However, around half of these studies only analyzed some or all of the reported pathogenic mutations, rather than comprehensively sequencing the GIGYF2 gene. In our previous study, we directly sequenced the GIGYF2 gene and identified nine missense variants and 14
⇑ Corresponding author. Tel.: +86 731 84327398; fax: +86 731 84327332. E-mail address: [email protected] (B-S Tang). 0967-5868/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jocn.2011.05.014
polymorphisms.28 Of these 14 polymorphisms, six (c.1378C>A, c.1554G>A, c.2940A>G, c.-4A>C, c.713-47A>G and c.1480-68T>G) were found in the dbSNP database, while the others (c.297T>C, c.2610G>A, c.171+2T>A, c.267+21C>A, c.491+24T>A, c.2370+3A>G, c.2530-14T>C and c.2766+46T>A) were novel (Table 1). In the present study, for these 14 polymorphisms, we performed a casecontrol analysis for 300 PD patients and 200 healthy controls from mainland China.
2. Patients and methods 2.1. Patients and controls A total of 300 patients were diagnosed with sporadic PD based on the United Kingdom PD Brain Bank Criteria.31 The majority of these patients were from central China, and all were ethnically Han Chinese. There were 174 male and 126 female patients (mean age at onset: 60.9 ± 6.4 years, range 50–81 years; mean course: 3.2 ± 2.8 years, range 1–18 years). Control subjects comprised 200 healthy volunteers with no history of neurodegenerative disease. There were 100 males and 100 females from the same population as the patients (mean age at the time of the study: 61.4 ± 8.5 years, range 50–96 years). Blood samples were obtained from the patients and the controls. Informed consent was obtained from all study subjects. The institutional ethics committee approved this study.
1700
L. Wang et al. / Journal of Clinical Neuroscience 18 (2011) 1699–1701
Table 1 Analysis of 14 polymorphisms of the GIGYF2 gene in Chinese patients with Parkinson’s disease and control subjects Position
Ex1 Ivs2 Ivs3 Ex4 Ivs5 Ivs8 Ex11 Ex12 Ivs12 Ivs18 Ivs20 Ivs20 Ex20 Ex22
Nucleotide change
c.-4A>C c.171+2T>A c.267+21C>A c.297T>C c.491+24T>A c.713-47A>G c.1378C>A c.1554G>A c.1480-68T>G c.2370+3A>G c.2530-14T>C c.2766+46T>A c.2610G>A c.2940A>G
Amino acid change
None None None p.Ala99Ala None None p.Pro460Thr p.Glu518Glu None None None None p.Glu870Glu p.Gln980Gln
SNP
rs11555646 None None None None rs2289913 rs2289912 rs2305138 rs2305139 None None None None rs3816334
Major allele
A T C T T A C G T A T T G A
Allele frequency PD 600 chr
Control 400 chr
v2
p-value
OR
95% CI
0.7200 0.9983 0.9833 0.9867 0.9967 0.8067 0.7483 0.8233 0.8900 0.9983 0.9933 0.9950 0.9933 0.3683
0.6100 1.0000 0.9725 0.9500 0.9975 0.8275 0.8025 0.8175 0.9215 1.0000 1.0000 1.0000 1.0000 0.3550
3.245 – 1.370 11.856 0.056 0.691 3.976 0.056 1.338 – – – – 0.185
0.072 – 0.242 0.001 0.813 0.406 0.046 0.814 0.247 – – – – 0.668
1.282 – 1.668 3.895 0.749 0.870 1.366 1.040 0.776 – – – – 1.059
0.978–1.680 – 0.702–3.966 1.698–8.932 0.068–8.292 0.626–1.209 1.005–1.859 0.749–1.446 0.504–1.194 – – – – 0.814–1.379
300 PD patients and 200 healthy controls. Chr = chromosome, CI = confidence interval, OD = odds ratio, PD = Parkinson’s disease, SNP = single nucleotide polymorphism. P < 0.0056 was considered significant.
2.2. Genotypic analysis DNA extraction from venous blood was performed using standard protocols. The 14 polymorphisms were amplified using the polymerase chain reaction (PCR) and sequenced (ABI 3100 automated sequencer; Applied Biosystems, Foster City, CA, USA). The primers used for PCR amplification have been described previously.28 For sequence analysis, exons were amplified under the following conditions: denaturation at 95 °C for 15 minutes, followed by 30–35 cycles of denaturation at 95 °C, annealing at 58–63 °C and elongation at 72 °C for 30 seconds, and a final elongation step of 10 minutes at 72 °C. The PCR reaction was performed in a volume of 10 lL with 2.5 mM MgCl2, 0.2 mM deoxynucleotide triphosphates (dNTPs), 0.5 lM forward and reverse primers, 1 U Taq polymerase, and 50 ng of DNA. The PCR products were separated on 6% polyacrylamide gels. Alignment and analysis was performed using DNAStar software (DNAStar Inc., Madison, WI, USA). 2.3. Statistical analysis Data are presented as the mean ± standard deviation. The allele and genotype frequencies in the PD and control groups were analyzed using a v2 test (Statistical Package for the Social Sciences 13.0; SPSS, Chicago, IL, USA). A p-value of <0.05 was considered statistically significant. We calculated the p-values for nine separate comparisons between the PD and control groups (Table 1). A Bonferroni correction was used to take into account multiple testing. For this test, a value of 0.0056 (0.05/9) was considered statistically significant.
Portuguese population,13 but no significant effect in Italian, French, Belgian, US or Chinese populations.12,13,18,19,26,27,29 There has been only one prior study of the effect of c.297T>C, which identified no significant difference among 52 patients with familial PD and 56 healthy controls from mainland China.26 However, there remains much uncertainty as to the effects of these variants on the pathogenesis of PD, which only further study will elucidate. There are several potential explanations for the discrepancies in the results discussed above. One major cause may be differences in genetic background. Another possible cause is bias caused by a range of confounding variables. Issues such as selection bias, genetic admixture, misclassification of cases or controls, sizes of groups and differences in statistical analysis are all possible sources of inconsistency between studies.32 Another factor that may impact on study results is whether these polymorphisms are in linkage disequilibrium with other functional variants, which remains unknown. Finally, possible complex gene–environment and gene–gene interactions (or a combination of both) may also contribute to differences in the risks attributable to genetic polymorphisms.33 In this case–control study, we aimed to avoid potential bias by matching controls to cases according to age, sex, area of residence and ethnic background. After analysis of 14 polymorphisms of the GIGYF2 gene, we concluded that c.297T>C p.Ala99Ala is significantly associated with sporadic PD. This study suggests that, in the Chinese population, the c.297T>C p.Ala99Ala polymorphism of the GIGYF2 gene may be associated with an increased risk of developing sporadic PD. Acknowledgments
3. Results Our analysis of 14 polymorphisms in 300 Chinese patients with sporadic PD and 200 Chinese controls suggested that the c.1378C>A p.Pro460Thr polymorphism has a protective effect with respect to the pathogenesis of sporadic PD (p = 0.046, v2 = 3.976), while the c.297T>C p.Ala99Ala polymorphism is a risk factor (p = 0.001, v2 = 11.856; Table 1). However, after Bonferroni correction, c.297T>C p.Ala99Ala remained significantly associated with PD, whereas c.1378C>A p.Pro460Thr did not.
This work was supported by grant 2006cb500700 from the Major State Basic Research Development Program of China (973 Program) to Bei-Sha Tang; Grant 2006AA02A408 from the National High-Tech Research and Development Program of China to Bei-Sha Tang; Grants 30570638, 30770735 and 30971035 from the National Natural Science Foundation of China to Bei-Sha Tang; and Grant 30900469 from the National Natural Science Foundation of China to Ji-Feng Guo. References
4. Discussion In previous studies of polymorphisms of the GIGYF2 gene, c.1378C>A was found to have a protective effect for PD in a
1. Toulouse A, Sullivan AM. Progress in Parkinson’s disease-where do we stand? Prog Neurobiol 2008;85:376–92. 2. Polymeropoulos MH, Lavedan C, Leroy E, et al. Mutation in the alpha-synuclein gene identified in families with Parkinson’s disease. Science 1997;276:2045–7.
L. Wang et al. / Journal of Clinical Neuroscience 18 (2011) 1699–1701 3. Paisan-Ruiz C, Jain S, Evans EW, et al. Cloning of the gene containing mutations that cause PARK8-linked Parkinson’s disease. Neuron 2004;44:575–7. 4. Kitada T, Asakawa S, Hattori N, et al. Mutations in the parkin gene cause autosomal recessive juvenile parkinsonism. Nature 1998;392:605–8. 5. Valente EM, Abou-Sleiman PM, Caputo V, et al. Hereditary early-onset Parkinson’s disease caused by mutations in PINK1. Science 2004;304:1158–60. 6. Bonifati V, Rizzu P, van Baren MJ, et al. Mutations in the DJ-1 gene associated with autosomal recessive early-onset parkinsonism. Science 2003;299:256–9. 7. Ramirez A, Heimbach A, Gründemann J, et al. Hereditary parkinsonism with dementia is caused by mutations in ATP13A2, encoding a lysosomal type 5 Ptype ATPase. Nat Genet 2006;38:1184–91. 8. Paisan-Ruiz C, Bhatia KP, Li A, et al. Characterization of PLA2G6 as a locus for dystonia-parkinsonism. Ann Neurol 2009;65:19–23. 9. Di Fonzo A, Dekker MC, Montagna P, et al. FBXO7 mutations cause autosomal recessive, early-onset parkinsonian-pyramidal syndrome. Neurology 2009;72: 240–5. 10. Healy DG, Abou-Sleiman PM, Casas JP, et al. UCHL-1 is not a Parkinson’s disease susceptibility gene. Ann Neurol 2006;59:627–33. 11. Simón-Sánchez J, Singleton AB. Sequencing analysis of OMI/HTRA2 shows previously reported pathogenic mutations in neurologically normal controls. Hum Mol Genet 2008;17:1988–93. 12. Lautier C, Goldwurm S, Durr A, et al. Mutations in the GIGYF2 (TNRC15) gene at the PARK11 locus in familial Parkinson disease. Am J Hum Genet 2008;82:822–33. 13. Bras J, Simon-Sanchez J, Federoff M, et al. Lack of replication of association between GIGYF2 variants and Parkinson disease. Hum Mol Genet 2009;18:341–6. 14. Sutherland GT, Siebert GA, Newman JR, et al. Haplotype analysis of the PARK 11 gene, GIGYF2, in sporadic Parkinson’s disease. Mov Disord 2009;24:449–52. 15. Vilarino-Guell C, Ross OA, Soto AI, et al. Reported mutations in GIGYF2 are not a common cause of Parkinson’s disease. Mov Disord 2009;24:619–22. 16. Zimprich A, Schulte C, Reinthaler E, et al. PARK11 gene (GIGYF2) variants Asn56Ser and Asn457Thr are not pathogenic for Parkinson’s disease. Parkinsonism Relat Disord 2009;15:532–4. 17. Nichols WC, Kissell DK, Pankratz N, et al. Variation in GIGYF2 is not associated with Parkinson disease. Neurology 2009;72:1886–92. 18. Meeus B, Nuytemans K, Crosiers D, et al. GIGYF2 has no major role in parkinson genetic etiology in a Belgian population. Neurobiol Aging 2011;32:308–12.
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19. Guo Y, Jankovic J, Zhu S, et al. GIGYF2 Asn56Ser and Asn457Thr mutations in Parkinson disease patients. Neurosci Lett 2009;454:209–11. 20. Tan EK, Lin CH, Tai CH, et al. Non-synonymous GIGYF2 variants in Parkinson’s disease from two Asian populations. Hum Genet 2009;126:425–30. 21. Di Fonzo A, Fabrizio E, Thomas A, et al. GIGYF2 mutations are not a frequent cause of familial Parkinson’s disease. Parkinsonism Relat Disord 2009;15:703–5. 22. Bonetti M, Ferraris A, Petracca M, et al. GIGYF2 variants are not associated with Parkinson’s disease in Italy. Mov Disord 2009;24:1867–8. 23. Zhang Y, Zheng L, Zhang T, et al. GIGYF2 Asn56Ser mutation is rare in Chinese Parkinson’s disease patients. Neurosci Lett 2009;463:172–5. 24. Samaranch L, Lorenzo E, Pastor MA, et al. Analysis of the GIGYF2 gene in familial and sporadic Parkinson disease in the Spanish population. Eur J Neurol 2010;17:321–5. 25. Lesage S, Condroyer C, Lohman E, et al. Follow-up study of the GIGYF2 gene in French families with Parkinson’s disease. Neurobiol Aging 2010;31:1069–71. 26. Cao L, Zhang T, Zheng L, et al. The GIGYF2 variants are not associated with Parkinson’s disease in the mainland Chinese population. Parkinsonism Relat Disord 2010;16:294–7. 27. Guella I, Pistocchi A, Asselta R, et al. Mutational screening and zebrafish functional analysis of GIGYF2 as a Parkinson-disease gene. Neurobiol Aging 2011;32:1994–2005. 28. Wang L, Guo JF, Zhang WW, et al. Novel GIGYF2 gene variants in patients with Parkinson’s disease in Chinese population. Neurosci Lett 2010;473:131–5. 29. Li L, Funayama M, Tomiyama H, et al. No evidence for pathogenic role of GIGYF2 mutation in Parkinson disease in Japanese patients. Neurosci Lett 2010;479:245–8. 30. Dos Santos AV, Pestana CP, Diniz KR, et al. Mutational analysis of GIGYF2; ATP13A2 and GBA genes in Brazilian patients with early-onset Parkinson’s disease. Neurosci Lett 2010;485:121–4. 31. Hughes AJ, Daniel SE, Kilford L, et al. Accuracy of clinical diagnosis of idiopathic Parkinson’s disease: a clinico-pathological study of 100 cases. J Neurol Neurosurg Psychiatry 1992;55:181–4. 32. Nicholl DJ, Bennett P, Hiller L, et al. A study of five candidate genes in Parkinson’s disease and related neurodegenerative disorders. European Study Group on Atypical Parkinsonism. Neurology 1999;53:1415–21. 33. Chan DK, Mellick GD, Hung WT, et al. Genetic and environmental risk factors and their interactions for Parkinson’s disease in a Chinese population. J Clin Neurosci 2003;10:313–5.
Contents lists available at SciVerse ScienceDirect
Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Laboratory Study
Follow-up study of variants of the GIGYF2 gene in Chinese patients with Parkinson’s disease Lei Wang a, Ji-Feng Guo a,b, Wen-Wen Zhang a, Qian Xu a, Xing Zuo a, Chang-He Shi a, Lin-Zi Luo a, Jia Liu a, Liang Hu a, Ya-Cen Hu a, Xin-Xiang Yan a,b, Bei-Sha Tang a,b,c,⇑ a b c
Department of Neurology, Xiangya Hospital, Central South University, 87 Xiangya Road, Changsha, Hunan 410008, China Neurodegenerative Disorders Research Center, Central South University, Changsha, Hunan, China State Key Laboratory of Medical Genetics of China, Changsha, Hunan, China
a r t i c l e
i n f o
Article history: Received 6 October 2010 Accepted 29 May 2011 Keywords: GIGYF2 gene Parkinson’s disease Variants
a b s t r a c t 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. Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction Parkinson’s disease (PD; Online Mendelian Inheritance in Man database #168600) is the second most common neurodegenerative disease, with major clinical features of bradykinesia, rigidity, resting tremor and postural instability. Genetic factors are known to play an important role in the development of this disease.1 To date, 11 factors associated with autosomal-dominant inherited PD have been cloned, including SCNA and LRRK2.2,3 In contrast, the factors Parkin, PINK1, DJ-1, ATP13A2, PLA2G6 and FBXO7 are observed more frequently in recessive PD, while UCH-L1 and Htra2 have shown little or no correlation with PD.4–11 PARK11/Grb10-interacting GYF protein-2 gene (GIGYF2) reportedly has a causal role in familial PD in populations from Italy and France.12 Since the GIGYF2 gene was first identified, studies in Portuguese, US, Australian, Norwegian, Belgian, Spanish, French, Italian, Japanese, Singaporean and Chinese populations have provided conflicting data on the causal role of this gene.13–30 However, around half of these studies only analyzed some or all of the reported pathogenic mutations, rather than comprehensively sequencing the GIGYF2 gene. In our previous study, we directly sequenced the GIGYF2 gene and identified nine missense variants and 14
⇑ Corresponding author. Tel.: +86 731 84327398; fax: +86 731 84327332. E-mail address: [email protected] (B-S Tang). 0967-5868/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.jocn.2011.05.014
polymorphisms.28 Of these 14 polymorphisms, six (c.1378C>A, c.1554G>A, c.2940A>G, c.-4A>C, c.713-47A>G and c.1480-68T>G) were found in the dbSNP database, while the others (c.297T>C, c.2610G>A, c.171+2T>A, c.267+21C>A, c.491+24T>A, c.2370+3A>G, c.2530-14T>C and c.2766+46T>A) were novel (Table 1). In the present study, for these 14 polymorphisms, we performed a casecontrol analysis for 300 PD patients and 200 healthy controls from mainland China.
2. Patients and methods 2.1. Patients and controls A total of 300 patients were diagnosed with sporadic PD based on the United Kingdom PD Brain Bank Criteria.31 The majority of these patients were from central China, and all were ethnically Han Chinese. There were 174 male and 126 female patients (mean age at onset: 60.9 ± 6.4 years, range 50–81 years; mean course: 3.2 ± 2.8 years, range 1–18 years). Control subjects comprised 200 healthy volunteers with no history of neurodegenerative disease. There were 100 males and 100 females from the same population as the patients (mean age at the time of the study: 61.4 ± 8.5 years, range 50–96 years). Blood samples were obtained from the patients and the controls. Informed consent was obtained from all study subjects. The institutional ethics committee approved this study.
1700
L. Wang et al. / Journal of Clinical Neuroscience 18 (2011) 1699–1701
Table 1 Analysis of 14 polymorphisms of the GIGYF2 gene in Chinese patients with Parkinson’s disease and control subjects Position
Ex1 Ivs2 Ivs3 Ex4 Ivs5 Ivs8 Ex11 Ex12 Ivs12 Ivs18 Ivs20 Ivs20 Ex20 Ex22
Nucleotide change
c.-4A>C c.171+2T>A c.267+21C>A c.297T>C c.491+24T>A c.713-47A>G c.1378C>A c.1554G>A c.1480-68T>G c.2370+3A>G c.2530-14T>C c.2766+46T>A c.2610G>A c.2940A>G
Amino acid change
None None None p.Ala99Ala None None p.Pro460Thr p.Glu518Glu None None None None p.Glu870Glu p.Gln980Gln
SNP
rs11555646 None None None None rs2289913 rs2289912 rs2305138 rs2305139 None None None None rs3816334
Major allele
A T C T T A C G T A T T G A
Allele frequency PD 600 chr
Control 400 chr
v2
p-value
OR
95% CI
0.7200 0.9983 0.9833 0.9867 0.9967 0.8067 0.7483 0.8233 0.8900 0.9983 0.9933 0.9950 0.9933 0.3683
0.6100 1.0000 0.9725 0.9500 0.9975 0.8275 0.8025 0.8175 0.9215 1.0000 1.0000 1.0000 1.0000 0.3550
3.245 – 1.370 11.856 0.056 0.691 3.976 0.056 1.338 – – – – 0.185
0.072 – 0.242 0.001 0.813 0.406 0.046 0.814 0.247 – – – – 0.668
1.282 – 1.668 3.895 0.749 0.870 1.366 1.040 0.776 – – – – 1.059
0.978–1.680 – 0.702–3.966 1.698–8.932 0.068–8.292 0.626–1.209 1.005–1.859 0.749–1.446 0.504–1.194 – – – – 0.814–1.379
300 PD patients and 200 healthy controls. Chr = chromosome, CI = confidence interval, OD = odds ratio, PD = Parkinson’s disease, SNP = single nucleotide polymorphism. P < 0.0056 was considered significant.
2.2. Genotypic analysis DNA extraction from venous blood was performed using standard protocols. The 14 polymorphisms were amplified using the polymerase chain reaction (PCR) and sequenced (ABI 3100 automated sequencer; Applied Biosystems, Foster City, CA, USA). The primers used for PCR amplification have been described previously.28 For sequence analysis, exons were amplified under the following conditions: denaturation at 95 °C for 15 minutes, followed by 30–35 cycles of denaturation at 95 °C, annealing at 58–63 °C and elongation at 72 °C for 30 seconds, and a final elongation step of 10 minutes at 72 °C. The PCR reaction was performed in a volume of 10 lL with 2.5 mM MgCl2, 0.2 mM deoxynucleotide triphosphates (dNTPs), 0.5 lM forward and reverse primers, 1 U Taq polymerase, and 50 ng of DNA. The PCR products were separated on 6% polyacrylamide gels. Alignment and analysis was performed using DNAStar software (DNAStar Inc., Madison, WI, USA). 2.3. Statistical analysis Data are presented as the mean ± standard deviation. The allele and genotype frequencies in the PD and control groups were analyzed using a v2 test (Statistical Package for the Social Sciences 13.0; SPSS, Chicago, IL, USA). A p-value of <0.05 was considered statistically significant. We calculated the p-values for nine separate comparisons between the PD and control groups (Table 1). A Bonferroni correction was used to take into account multiple testing. For this test, a value of 0.0056 (0.05/9) was considered statistically significant.
Portuguese population,13 but no significant effect in Italian, French, Belgian, US or Chinese populations.12,13,18,19,26,27,29 There has been only one prior study of the effect of c.297T>C, which identified no significant difference among 52 patients with familial PD and 56 healthy controls from mainland China.26 However, there remains much uncertainty as to the effects of these variants on the pathogenesis of PD, which only further study will elucidate. There are several potential explanations for the discrepancies in the results discussed above. One major cause may be differences in genetic background. Another possible cause is bias caused by a range of confounding variables. Issues such as selection bias, genetic admixture, misclassification of cases or controls, sizes of groups and differences in statistical analysis are all possible sources of inconsistency between studies.32 Another factor that may impact on study results is whether these polymorphisms are in linkage disequilibrium with other functional variants, which remains unknown. Finally, possible complex gene–environment and gene–gene interactions (or a combination of both) may also contribute to differences in the risks attributable to genetic polymorphisms.33 In this case–control study, we aimed to avoid potential bias by matching controls to cases according to age, sex, area of residence and ethnic background. After analysis of 14 polymorphisms of the GIGYF2 gene, we concluded that c.297T>C p.Ala99Ala is significantly associated with sporadic PD. This study suggests that, in the Chinese population, the c.297T>C p.Ala99Ala polymorphism of the GIGYF2 gene may be associated with an increased risk of developing sporadic PD. Acknowledgments
3. Results Our analysis of 14 polymorphisms in 300 Chinese patients with sporadic PD and 200 Chinese controls suggested that the c.1378C>A p.Pro460Thr polymorphism has a protective effect with respect to the pathogenesis of sporadic PD (p = 0.046, v2 = 3.976), while the c.297T>C p.Ala99Ala polymorphism is a risk factor (p = 0.001, v2 = 11.856; Table 1). However, after Bonferroni correction, c.297T>C p.Ala99Ala remained significantly associated with PD, whereas c.1378C>A p.Pro460Thr did not.
This work was supported by grant 2006cb500700 from the Major State Basic Research Development Program of China (973 Program) to Bei-Sha Tang; Grant 2006AA02A408 from the National High-Tech Research and Development Program of China to Bei-Sha Tang; Grants 30570638, 30770735 and 30971035 from the National Natural Science Foundation of China to Bei-Sha Tang; and Grant 30900469 from the National Natural Science Foundation of China to Ji-Feng Guo. References
4. Discussion In previous studies of polymorphisms of the GIGYF2 gene, c.1378C>A was found to have a protective effect for PD in a
1. Toulouse A, Sullivan AM. Progress in Parkinson’s disease-where do we stand? Prog Neurobiol 2008;85:376–92. 2. Polymeropoulos MH, Lavedan C, Leroy E, et al. Mutation in the alpha-synuclein gene identified in families with Parkinson’s disease. Science 1997;276:2045–7.
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