A study in a Polish ataxia cohort indicates genetic heterogeneity and points to MTCL1 as a novel candidate gene.

Inherited ataxias are a group of highly heterogeneous, complex neurological disorders representing a significant diagnostic challenge in clinical practice. We performed a next-generation sequencing (NGS) analysis in 10 index cases with unexplained progressive cerebellar ataxia of suspected autosomal recessive inheritance. A definite molecular diagnosis was obtained in 5/10 families and included the following diseases: autosomal recessive spastic ataxia of Charlevoix-Saguenay, POLR3B-related hypomyelinating leukodystrophy, primary coenzyme Q10 deficiency type 4, Niemann-Pick disease type C1 and SYNE1-related ataxia. In addition, we found a novel homozygous MTCL1 loss of function variant p.(Lys407fs) in a 23-year-old patient with slowly progressive cerebellar ataxia, mild intellectual disability, seizures in childhood and episodic pain in the lower limbs. The identified variant is predicted to truncate the protein after first 444 of 1586 amino acids. MTCL1 encodes a microtubule-associated protein highly expressed in cerebellar Purkinje cells; its knockout in a mouse model causes ataxia. We propose MTCL1 as a candidate gene for autosomal recessive cerebellar ataxia in humans. In addition, our study confirms the high diagnostic yield of NGS in early-onset cerebellar ataxias, with at least 50% detection rate in our ataxia cohort.

An association between genetic variation in the glutamatergic system and suicide attempts in alcohol-dependent individuals.

BACKGROUND AND OBJECTIVES: Pathological alterations of glutamatergic systems were observed in neurodegenerative and psychiatric disorders. There is some evidence that this system may be involved in the genetic vulnerability to suicide. The aim of the present study was to analyze possible relationship between the GRIN2B polymorphism and suicidal behavior. We hypothesized that this genetic factor may be associated with suicide attempts in alcohol-dependent patients and with death by suicide. METHODS: To analyze the relationship between GRIN2B and suicide attempts, the selected rs2268115 polymorphism was genotyped in a sample of 345 alcohol-dependent individuals stratified by the history of suicide attempts. The second part of the study concerning suicide was based on a sample of 510 suicide victims and 450 controls. RESULTS: The frequency of rs2268115 G allele among alcohol-dependent patients with the history of suicide attempts was significantly higher than among non-suicidal alcohol-dependent individuals (OR = 1.45, p = .033). This association was more significant when analyzing alcohol-dependent patients only without co-occurring drug dependence (OR = 1.62, p = .021). The analyzed GRIN2B polymorphism was associated with a twofold increase in odds of a suicide attempt (OR = 2.01, p = .004). No relationships between rs2268115 and death by suicide were identified. DISCUSSION AND CONCLUSIONS: Our results suggest that glutamatergic system influence susceptibility to suicide attempts in alcohol-dependent individuals. Suicidal behavior and alcohol dependence may share a common etiology related to the glutamatergic system. SCIENTIFIC SIGNIFICANCE: The major contribution of the present study is a novel finding of the possible association between GRIN2B rs2268115 polymorphism and suicide attempts in alcohol-dependent individuals. (Am J Addict 2017;26:595-601).

Association between FKBP5 Functional Polymorphisms and Completed Suicide.

OBJECTIVES: Dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis leads to impaired stress response. FK506-binding protein 51 (FKBP5), which influences HPA axis activity via glucocorticoid receptors, is supposed to play an important role in the regulation of negative feedback and glucocorticoid resistance. Since ineffective stress response mechanisms are considered as a biological background of suicide behavior, we aimed to analyze a possible association between FKBP5 functional polymorphisms and completed suicide. METHODS: The selected FKBP5 polymorphisms rs1360780 and rs3800373 were genotyped in a sample of 563 suicide victims and 475 controls. RESULTS: A significant association between the high-induction rs3800373 C allele and completed suicide was detected (OR = 1.36, p = 0.007). In this polymorphism, genotype distribution supported a codominant model of inheritance. The analyzed SNPs were in strong linkage disequilibrium (D' = 0.916 and r2 = 0.826) with the rs1360780 (T)-rs3800373 (C) haplotype apparently responsible for the observed association (OR = 1.34, p = 0.010). CONCLUSION: The results of the present study indicate that genetic alterations in FKBP5 may influence vulnerability to suicide.

Exome sequencing reveals mutations in MFN2 and GDAP1 in severe Charcot-Marie-Tooth disease.

The aim of our study was to characterize electrophysiologically and explain the genetic cause of severe Charcot-Marie-Tooth (CMT) in a 3.5-year-old with asymptomatic parents and a maternal grandfather with a history of mild adult-onset axonal neuropathy. Severity of neuropathy was assessed by Charcot-Marie-Tooth neuropathy score (CMTNS). Whole-exome sequencing was performed using an Illumina TruSeq Exome Enrichment Kit on the HiSeq 1500 with results followed up by Sanger sequencing on an ABI Prism 3500XL (Applied Biosystems, Foster City, CA, USA). Paternity was confirmed using a panel of 15 hypervariable markers. Electrophysiological studies demonstrated severe axonal sensory-motor neuropathy in the proband, mild motor neuropathy in his mother, and mild sensory-motor neuropathy in his grandfather. CMTNS in the proband, his mother, and grandfather was 21, 1, and 12, respectively. On genetic analysis, the boy was found to carry a heterozygous dominant MFN2 T236M mutation transmitted via the maternal line and a de novo GDAP1 H123R mutation. Our findings emphasize the need to search for more than one causative mutation when significant intrafamilial variability of CMT phenotype occurs and underline the role of whole-exome sequencing in the diagnosis of compound forms of CMT disease.

Postzygotic mutations and where to find them - Recent advances and future implications in the field of non-neoplastic somatic mosaicism.

The technological progress of massively parallel sequencing (MPS) has triggered a remarkable development in the research on postzygotic mutations. Although the overwhelming majority of studies in the field focus on oncogenesis, non-neoplastic diseases are attracting more and more attention. The aim of this review was to summarize some of the most recent findings in the field of somatic mosaicism in diseases other than neoplastic events. We discuss the abundance and role of postzygotic mutations, with a special emphasis on disorders which occur only in a mosaic form (obligatory mosaic diseases; OMDs). Based on the list of OMDs compiled from the published literature and three databases (OMIM, Orphanet and MosaicBase), we demonstrate the prevalence of cancer-related genes across OMDs and suggest other sources to further explore OMDs and OMD-related genes. Additionally, we comment on some practical aspects related to mosaic diseases, such as approaches to tissue sampling, the MPS coverage required to detect variants at a very low frequency, as well as on bioinformatic and molecular tools dedicated to detect somatic mutations in MPS data.

Aicardi-Goutières Syndrome due to a SAMHD1 Mutation Presenting with Deep White Matter Cysts.

We report on the first Polish patient diagnosed with the Aicardi-Goutières syndrome 5 (AGS5). AGS is caused by mutations in one of 9 genes (TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR, IFIH, LSM11, RNU7-1) which stimulate the type I interferon response. The diagnosis was confirmed by identifying a compound heterozygous mutation p.(Phe165Ser)/p.(Gln235*) in the SAMHD1 gene using whole-exome sequencing. The cystic lesions in the temporal lobes are an uncommon finding in the presented patient carrying a SAMHD1 mutation. Reporting new cases expands the range of phenotypes and plays the crucial role in understanding the AGS pathogenesis and creates new therapy approaches.

OXTR polymorphism in depression and completed suicide-A study on a large population sample.

In the light of contradictory results concerning OXTR polymorphism rs53576 and depression, we decided to verify the potential association between the two on 1) a large, ethnically homogenous sample of 1185 individuals who completed the Beck Depression Inventory (BDI), as well as on 2) a sample of 763 suicide victims. In the population sample, AA males showed significantly lower BDI scores (p=0.005, pcor=0.030). Exploratory analyses suggested that this effect was limited to a subgroup within 0-9 BDI score range (p=0.0007, U-Mann Whitney test), whereas no main effect on depressive symptoms (BDI>9) was found. In the suicide sample no association with rs53576 genotype was present. Exploratory analyses in suicides revealed higher blood alcohol concentration (BAC) among AA than GG/GA males (p=0.014, U-Mann Whitney test). Our results show that the OXTR rs53576 variant modulates the mood in male individuals and may positively correlate with alcohol intake among male suicides, but is not associated with suicide or depression. The study adds to the growing knowledge on rs53576 genotype characteristics.

DISC1 as a Possible Genetic Contribution to Opioid Dependence in a Polish Sample.

OBJECTIVE: Disrupted-in-schizophrenia 1 (DISC1) has been linked to vulnerability to a variety of psychiatric disorders and neuropsychiatric phenotypes. However, DISC1 has not been frequently examined as a potential risk factor for substance dependence. An association between opioid dependence and DISC1 rs2738888 polymorphism has been recently reported. In addition, opioid dependence was associated with rs6419156 located close to the protein phosphatase 3 catalytic subunit alpha isoform (PPP3CA) gene. The aim of the present study was to examine the associations between opioid dependence with rs2738888 and rs6419156 in an independent sample. METHOD: The selected polymorphisms were genotyped in a sample of 392 individuals (69.9% male) diagnosed as alcohol- and/or opioid-dependent. A control group (n = 257; 67.7% male) was derived from the Polish National Health Survey (N = 14,350). RESULTS: The frequency of rs2738888 C allele was higher in controls than in opioid-dependent cases (OR = 0.65, p = .045). Phenotypic-oriented analyses performed within opioid-dependent individuals revealed the association between lifetime suicide attempt and rs2738888. The C allele of rs2738888 had a protective effect on lifetime suicide attempt in opioid-dependent patients (OR = 0.25, p = .003). Rs6419156 was not associated with substance dependence in the examined sample. CONCLUSIONS: The DISC1 may play an important role in vulnerability to opioid dependence. In addition, DISC1 may also be a genetic risk factor for suicide attempt in opioid-dependent individuals.

Inverse association between obesity predisposing FTO genotype and completed suicide.

The A allele of rs9939609 in the FTO gene predisposes to increased body mass index (BMI) and obesity. Recently we showed an inverse association between the obesity related A allele of rs9939609 and alcohol dependence which was replicated by others. Since this finding raises a possibility that FTO may be associated with other psychiatric phenotypes, we aimed to examine association of rs9939609 with completed suicide. We genotyped rs9939609 in 912 suicide victims and 733 controls using TaqMan approach. We observed an inverse association between suicide and the rs9939609 A allele (OR = 0.80, P = 0.002, Pcor = 0.006) with genotype distribution suggesting a co-dominant effect. Given the link between alcoholism and suicide under influence of alcohol reported in Polish population, confounding by alcohol addiction was unlikely due to apparently similar effect size among cases who were under influence of ethanol at the time of death (OR = 0.76, P = 0.003, N = 361) and those who were not (OR = 0.80, P = 0.007, N = 469). The search for genotype-phenotype correlations did not show significant results. In conclusion, our study proves that there is an inverse association between rs9939609 polymorphism in FTO gene and completed suicide which is independent from association between FTO and alcohol addiction.