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Homozygous SMN2 deletion is a protective factor in the Swedish ALS population.

ABSTRACT: Abnormal survival motor neuron 1 (SMN1)-copy number has been associated with an increased risk of amyotrophic lateral sclerosis (ALS) in French and Dutch population studies. The aim of this study was to determine whether SMN gene copy number increases the risk of ALS or modulates its phenotype in a cohort of Swedish sporadic ALS (SALS) patients. In all, 502 Swedes with SALS and 502 Swedish controls matched for gender and age were enrolled. SMN1 and SMN2 gene copy numbers were studied by a semi-quantitative PCR method. A genotype-phenotype comparison was performed in order to determine whether SMN genes modulate the phenotype of ALS. The results were also compared with our previously reported French cohort of ALS patients. There was no difference between Swedish patients and controls in the frequency of SMN1 and SMN2 copy numbers. The frequency of SMN1 gene copies differed significantly between the French and Swedish ALS populations. The duration of the disease was significantly longer in the Swedish cohort with homozygous deletions of SMN2 when compared with the French cohort. Abnormal SMN1 gene copy number cannot be considered as a universal genetic susceptibility factor for SALS and this result underlines the importance of reproducing association gene studies in groups from different origins. We also suggest that SMN2 gene copy number might have different effects on ALS progression in disparate human populations.

SUBMITTER: Corcia P

PROVIDER: S-EPMC3330228 | biostudies-other | 2012 May

REPOSITORIES: biostudies-other

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Project description:BACKGROUND:The 2016 World Health Organization (WHO) classification of central nervous system tumors stratifies isocitrate dehydrogenase (IDH)-mutant gliomas into 2 major groups depending on the presence or absence of 1p/19q codeletion. However, the grading system remains unchanged and it is now controversial whether it can be still applied to this updated molecular classification. METHODS:In a large cohort of 911 high-grade IDH-mutant gliomas from the French national POLA network (including 428 IDH-mutant gliomas without 1p/19q codeletion and 483 anaplastic oligodendrogliomas, IDH-mutant and 1p/19q codeleted), we investigated the prognostic value of the cyclin-dependent kinase inhibitor 2A (CDKN2A) gene homozygous deletion as well as WHO grading criteria (mitoses, microvascular proliferation, and necrosis). In addition, we searched for other retinoblastoma pathway gene alterations (CDK4 amplification and RB1 homozygous deletion) in a subset of patients. CDKN2A homozygous deletion was also searched in an independent series of 40 grade II IDH-mutant gliomas. RESULTS:CDKN2A homozygous deletion was associated with dismal outcome among IDH-mutant gliomas lacking 1p/19q codeletion (P < 0.0001 for progression-free survival and P = 0.004 for overall survival) as well as among anaplastic oligodendrogliomas, IDH-mutant + 1p/19q codeleted (P = 0.002 for progression-free survival and P < 0.0001 for overall survival) in univariate and multivariate analysis including age, extent of surgery, adjuvant treatment, microvascular proliferation, and necrosis. In both groups, the presence of microvascular proliferation and/or necrosis remained of prognostic value only in cases lacking CDKN2A homozygous deletion. CDKN2A homozygous deletion was not recorded in grade II gliomas. CONCLUSIONS:Our study pointed out the utmost relevance of CDKN2A homozygous deletion as an adverse prognostic factor in the 2 broad categories of IDH-mutant gliomas stratified on 1p/19q codeletion and suggests that the grading of these tumors should be refined.

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Homozygous SMN2 deletion is a protective factor in the Swedish ALS population.

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