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Background Frontotemporal dementia (FTD) is a neurodegenerative disease, resulting in progressive problems in language and/or behaviour and is often diagnosed before 65 years of age. Ubiquitin positive protein aggregates in the brain are among the key pathologic hallmarks of frontotemporal lobar degeneration (FTLD) postmortem. The TANK-binding kinase 1 gene (TBK1) is on the list of genes that can contribute to the development of FTD as well as the related neurodegenerative disease amyotrophic lateral sclerosis (ALS). Methods In this study, using an array of clinical and neuropathological data combined with biochemical and proteomics assays, we analyze the TBK1 splice-mutation (c.1340 + 1G > A) in a Swedish family with a history of FTD and ALS. We also explore the K63 ubiquitination landscape in post-mortem brain tissue and fibroblast cultures. Results The intronic (c.1340 + 1G > A) mutation in TBK1 results in haploinsufficiency and affects the activity of the protein in symptomatic and pre-symptomatic mutation carriers. Conclusion Our results suggest that the mutation leads to a significant reduction of TBK1 activity and induce alterations in K63 ubiquitination profile of the cell already in the presymptomatic stages.

Background and Objective PSEN1‐H163Y carriers, at the presymptomatic stage, have reduced 18FDG‐PET binding in the cerebrum of the brain (Scholl et al., Neurobiol Aging 32:1388–1399, 2011). This could imply dysfunctional energy metabolism in the brain. In this study, plasma of presymptomatic PSEN1 mutation carriers was analyzed to understand associated metabolic changes. Methods We analyzed plasma from noncarriers (NC, n = 8) and presymptomatic PSEN1‐H163Y mutation carriers (MC, n = 6) via untargeted metabolomics using gas and liquid chromatography coupled with mass spectrometry, which identified 1199 metabolites. All the metabolites were compared between MC and NC using univariate analysis, as well as correlated with the ratio of Aβ 1–42/A β 1–40, using Spearman’s correlation. Altered metabolites were subjected to Ingenuity Pathway Analysis (IPA). Results Based on principal component analysis the plasma metabolite profiles were divided into dataset A and dataset B. In dataset A, when comparing between presymptomatic MC and NC, the levels of 79 different metabolites were altered. Out of 79, only 14 were annotated metabolites. In dataset B, 37 metabolites were significantly altered between presymptomatic MC and NC and nine metabolites were annotated. In both datasets, annotated metabolites represent amino acids, fatty acyls, bile acids, hexoses, purine nucleosides, carboxylic acids, and glycerophosphatidylcholine species. 1‐docosapentaenoyl‐GPC was positively correlated, uric acid and glucose were negatively correlated with the ratio of plasma Aβ 1–42/Aβ 1–40 (P

We identified an autosomal dominant progranulin mutation carrier without symptoms of dementia in her lifetime (Reduced Penetrance Mutation Carrier, RedPenMC). This resistance to develop expected pathology presents a unique opportunity to interrogate neurodegenerative mechanisms. We performed multimodal single-nuclei analyses of post-mortem frontal cortex from RedPenMC, including transcriptomics and global levels of chromatin marks. RedPenMC had an increased ratio of GRN-expressing microglia, higher levels of activating histone mark H3k4me3 in microglia and lower levels of the repressive chromatin marks H3k9me1 and H3k9me3 in the frontal cortex than her affected mutation carrier son and evidence of higher protein levels of progranulin in both plasma and brain homogenates. Although the study is limited to one case, the results support that restoring brain progranulin levels may be sufficient to escape neurodegeneration and FTD. In addition to previously identified modifier genes, it is possible that epigenetic marks may contribute to the increased progranulin expression in cases of reduced penetrance. These findings may stimulate similar follow-up studies and new therapeutic approaches.

Summary We identified an individual with reduced penetrance (RedPenMC) associated with an autosomal dominant progranulin (GRN) pathogenic variant (p.Tyr294*) causing frontotemporal dementia. The RedPenMC carrier had no signs or symptoms of frontotemporal lobar degeneration in life or at autopsy. This resistance to develop expected pathology gives a unique opportunity to interrogate neurodegenerative mechanisms, identify protective disease modifiers, and gain new therapeutic insights. We performed multimodal droplet-based single nuclei analyses of the frontal cortex from the RedPenMC post-mortem, including unbiased transcriptomics and profiling of global levels of twelve chromatin marks. Further, we analyzed neurons directly reprogrammed from skin fibroblasts from RedPenMC. Single nuclei analyses revealed that the RedPenMC carrier showed a higher expression of GRN in microglia than in any other cell types as well as compared to an affected mutation carrier and a non-carrier. Global levels of heterochromatin marks H3k9me1 and H3k9me3 were significantly lower in the RedPenMC carrier, whereas global levels of H2A2 were significantly upregulated in the RedPenMC carrier compared to an affected mutation carrier. Analyses of directly reprogrammed neurons from the RedPenMC carrier suggested a dendritic loss of GRN and spillage of TAR DNA-binding protein 43 (TDP-43) from the nucleus into the cytoplasm which was not observed in directly reprogrammed neurons from non-carriers. Taken together, our data suggest that higher expression of GRN in microglia and reduced levels of repressive marks may provide endogenous protection against the disease process/neurodegeneration in the RedPenMC carrier. Our study uses unique patient material and provides novel insights into disease mechanisms that can be explored for designing new therapeutic approaches for GRN associated frontotemporal dementia. Graphical abstract

Spinocerebellar ataxia type 19 (SCA19), allelic with spinocerebellar ataxia type 22 (SCA22), is a rare syndrome caused by mutations in the KCND3 gene which encodes the potassium channel Kv4.3. Only 18 SCA19/22 families and sporadic cases of different ethnic backgrounds have been previously reported. As in other SCAs, the SCA19/22 phenotype is variable and usually consists of adult-onset slowly progressive ataxia and cognitive impairment; myoclonus and seizures; mild Parkinsonism occurs in some cases. Here we describe a Swedish SCA19/22 family spanning five generations and harboring the T377M mutation in KCND3. For the first time for this disease, 18F-fluorodeoxyglucose PET was assessed revealing widespread brain hypometabolism. In addition, we identified white matter abnormalities and found unusual features for SCA19/22 including early age of onset and fast rate of progression in the late course of disease in the oldest patient of this family. Electronic supplementary material The online version of this article (10.1007/s12311-018-0927-4) contains supplementary material, which is available to authorized users.

BACKGROUND Polyneuropathy (pnp) is recognized as a clinical feature of Parkinson's disease (PD). Whether pnp is a result of the alpha-synucleinopathy or related to treatment is debated. Previous studies support underlying disturbances in the methionine cycle mediated by L-dopa. OBJECTIVE Describe possible relationships between methionine cycle metabolism and the development of pnp in L-dopa treated PD. Furthermore, we aim to investigate possible genetic risk factors by genotyping specific SNPs in enzymes involved in the abovementioned pathways. METHODS In a cross-sectional study design, L-dopa treated PD patients (n = 33) and controls (n = 16) were evaluated with biochemical and genetic analyses. Subjects were assessed clinically and with regards to signs of pnp using established clinical neuropathy rating scales. RESULTS 16/33 patients fulfilled a study diagnosis of pnp compared to 0 age-matched controls. Levels of homocysteine (Hcy) were significantly higher in patients with pnp (n = 16) compared to controls. A significant correlation between neuropathy scores and Hcy was seen in the whole patient group (n = 33). A significant difference in the genotype distribution of the COMT A158G polymorphism was demonstrated, favoring the low activity genotype in patients with pnp compared to both controls and patients without pnp. CONCLUSIONS Pnp is a prevalent condition in L-dopa treated PD and an association may exist with elevated levels of Hcy, possibly reflecting an underlying impaired cellular methylation capacity. Furthermore, an association may exist between the low activity COMT genotype and pnp. These preliminary findings and the suggested pathophysiological mechanisms should be confirmed in future large-scale studies.

Spinocerebellar ataxia type 2 (SCA2) is part of a group of at least nine dominantly inherited disorders characterized by progressive degeneration of specific neuronal populations and a shared mutational mechanism involving the expansion of a CAG repeat tract in coding regions of novel genes. Efforts have been made to identify biomarkers of disease progression, which would allow timely preventive therapeutic interventions. In the present study was assessed the influence of several genome instability biomarkers on SCA2 clinical severity. A case-control design was applied on exfoliated epithelial buccal cells to determine micronuclei frequency and others nuclear anomalies, using 5% Giemsa stains. The slides were analyzed under 1000X magnification and nuclei morphological anomalies were identified according to Tolbert PE, et al. (1992) and Bolognesi C, et al. (2013) criteria. It was found a highly significant increase in micronuclei frequency in cases related to age and sex-matched healthy controls (p0.001). There was a trend for karyolytic, pyknotic and condensed chromatin cells to be increased in SCA2 cases, and a significant association was found between binucleated cells and disease duration (r = 0.46; p = 0.027). Nor the CAG repeat length neither the age at onset correlated significantly with any of the studied markers (p0.05). Our results are consistent with report previous in similar neurodegenerative diseases, and suggest that micronuclei and binucleated cells constitute potential peripheral biomarkers for SCA2. These results should be validated by other studies.

Biallelic mutations in the elaC ribonuclease Z 2 ( ELAC2 ) gene cause a rare mitochondrial disease, the main features of which are hypertrophic cardiomyopathy, delayed psychomotor development, and usually death during childhood.1 Only 20 families have been reported with this syndrome.1–3 Neither movement disorders nor psychotic features have been described as part of the spectrum of ELAC2 mutations. We describe a patient with a complex hyperkinetic syndrome and acanthocytosis, harboring biallelic ELAC2 mutations.

McLeod syndrome (MLS) is a rare adult-onset, progressive and incurable X-linked multisystemic disorder characterized by chorea, cognitive decline, seizures, polyneuropathy, myopathy and dilated cardiomyopathy with subsequent heart failure and increased risk for arrhythmia [1]. Variable psychiatric symptoms are common; the presence of acanthocytes on blood smears, elevated CK levels and striatal atrophy are other features. MLS is caused by mutation in the XK gene which encodes a membrane transport protein containing the Kx erythrocyte antigen [1]. So far, less than 200 MLS cases have been reported. In general, women harboring XK mutations rarely manifest symptoms. In addition, myoclonus has not been described in association with MLS and functional imaging studies are scarce.

Spinocerebellar ataxia type 2 (SCA2) is a neurodegenerative disease caused by a CAG repeat expansion in the ATXN2 gene. Cuba has the highest prevalence (6.57 cases/10(5) inhabitants) of SCA2 in the world. The existence of 753 affected individuals and 7173 relatives at risk prompted the development in 2001 of the first predictive testing program in the country. The medical records of over 1193 individuals, who requested the test within a 13-year period, were analyzed retrospectively. The presymptomatic and the prenatal tests had uptake rates of 43.4 and 23.9 %, respectively. Several ethical challenges resulted from this program. These include the following: (1) withdrawal due to the initial protocol's length; (2) the request to participate by 16 at-risk adolescents; (3) the decision made by ten out of 33 couples with a test-positive fetus to carry the pregnancy to term, leading to de facto predictive testing of minors; (4) the elevated frequency of the ATXN2 gene large normal alleles (≥23 to 31 repeats) in the reference population. These issues have led to major changes in the guidelines of the predictive testing protocol: (1) the protocol length was shortened; (2) the inclusion criteria were expanded to reach at-risk adolescents with an interest in prenatal diagnosis; (3) interdisciplinary follow-up was offered to families in which test-positive fetuses were not aborted; (4) prenatal testing was made available to carriers of large normal alleles with ≥27 CAG repeats. The profiles of the participants were similar to those reported for other predictive testing programs for conditions like Huntington disease and familial adenomatous polyposis. The genetic counseling practices at the community level, the ample health education provided to the at-risk population, together with multidisciplinary and specialized attention to the affected families, are lessons from the Cuban experience that can be relevant for other international teams conducting predictive testing for other late-onset neurodegenerative disorders.

Epigenetics is the group of changes in the phenotype which are related with the process independently of the primary DNA sequence. These changes are intimately related with changes in the gene expression level and its profile across the body. These are mediated by histone tail modifications, DNA methylation, micro-RNAs, with chromatin remodeling remaining as the foundation of epigenetic changes. DNA methylation involves the covalent addition of methyl group to cytosine of the DNA, which is mediated by methyltransferases enzymes. DNA methylation regulates gene expression by repressing transcription, while de-methylation activates gene transcription. Several human diseases are related with the epigenetic process: cancer, Alzheimer disease, stroke, Parkinson disease, and diabetes. We present here the basis of epigenetic inheritance and show the pathogenic mechanisms relating epigenetics in human diseases, specifically with regard to neurodegeneration. We discuss current concepts aimed at understanding the contribution of epigenetics to human neurodegenerative diseases. We also discuss recent findings obtained in our and other centers regarding the ATXN2 gene that causes spinocerebellar ataxia 2 and amyotrophic lateral sclerosis. Epigenetics play a pivotal role in the pathogenesis of human diseases and in several neurodegenerative disorders, and this knowledge will illuminate the pathways in the diagnostic and therapeutic field, which ultimately will be translated into the clinic context of neurodegenerative diseases.

The prodromal phase of spinocerebellar ataxias (SCAs) has not been systematically studied. Main findings come from a homogeneous SCA type 2 (SCA2) population living in Cuba. The aim of this study was to characterize extensively the prodromal phase of SCA2 by several approaches. Thirty-seven non-ataxic SCA2 mutation carriers and its age- and sex-matched controls underwent clinical assessments, including standardized neurological exam, structured interviews and clinical scales, and looking for somatic and autonomic features, as well as a neuropsychological battery, antisaccadic recordings, and MRI scans. Main clinical somatic features of non-ataxic mutation carriers were cramps, sensory symptoms, sleep disorders, and hyperreflexia, whereas predominating autonomic symptoms were pollakiuria/nocturia, constipation, and frequent throat clearing. Cognitive impairments included early deficits of executive functions and visual memory, suggesting the involvement of cerebro-cerebellar-cerebral loops and/or reduced cholinergic basal forebrain input to the cortex. Antisaccadic task revealed impaired oculomotor inhibitory control but preserved ability for error correction. Cognitive and antisaccadic deficits were higher as carriers were closer to the estimated onset of ataxia, whereas higher Scale for the Assessment and Rating of Ataxia (SARA) scores were associated most notably to vermis atrophy. The recognition of early features of SCA2 offers novel insights into the prodromal phase and physiopathological base of the disease, allowing the assessment of its progression and the efficacy of treatments, in particular at early phases when therapeutical options should be most effective.

Huntington disease is the most frequent polyglutamine disorder with variable worldwide prevalence. Although some Latin American populations have been studied, HD prevalence in Cuban population remains unknown. In order to characterize the disease in Cuba, the relative frequency of HD was determined by studying 130 patients with chorea and 63 unrelated healthy controls, emphasizing in the molecular epidemiology of the disease. Sixty-two patients with chorea belonging to 16 unrelated families carried a pathological CAG expansion in the HTT gene, ranging from 39 to 67 repeats. Eighty-three percent of them come from the eastern region of the country. A significant inverse correlation between age at onset and expanded CAG repeats was seen. Intermediate alleles in affected individuals and controls represented 4.8% and 3.97% respectively, which have been a putative source of de novo mutation. This study represents the largest molecular characterization of Huntington disease in the Cuban population. These results may have significant implications for an understanding of the disease, its diagnosis and prognosis in Cuban patients, giving health professionals the tools to implement confirmatory genetic testing, pre-symptomatic testing and clinical trials in this population.

Cuba reports the highest worldwide prevalence of spinocerebellar ataxia type 2 (SCA2) and the greatest number of descendants at risk. A protocol for genetic counseling, presymptomatic testing, and prenatal diagnosis of hereditary ataxias has been under development since 2001. Considering that the revision of the experience with prenatal diagnosis for SCA2 in Cuba would enable comparison of ours with international findings, we designed a descriptive study, based on the retrospective revision of the medical records belonging to the 58 couples that requested their inclusion in the program, during an 11-year period (2001-2011). Most of the participants in the prenatal diagnosis program were known presymptomatic carriers, diagnosed through the presymptomatic testing in the same period of study, for an uptake among them of 22.87 % (51 out of 223). In 28 cases, the fetuses were carriers, 20 of these couples (71.43 %) decided to terminate the pregnancy; the rest continued the pregnancy to term, this resulting in a predictive test for their unborn children. A predominance of females as the at-risk progenitor was observed. Except for a slightly lower average age, the results attained in the Cuban SCA2 prenatal diagnosis program resulted similar to the ones reported for Huntington disease in other countries. It is necessary to have easy access to the Cuban program through its expansion to other genetic centers along the island. Future research is needed to evaluate the long-term impact of both the predictive testing in unborn children and the selection of other reproductive options by the at-risk couples.

The characterization of prodromal stages in neurodegenerative disorders is becoming increasingly important because of the need for early neuroprotective therapies. Research during the past 3 decades in spinocerebellar ataxia type 2 has revealed a large body of evidence suggesting that many disease features precede the manifest cerebellar syndrome, which delineates the prodromal stage of this disorder. This stage is defined by clinical, imaging, and functional criteria, which are supported by early molecular events demonstrated in animal models. Knowledge regarding prodromal spinocerebellar ataxia type 2 provides insight into the mechanisms underlying neurodegeneration from the early stages, which enables the design of promising disease-modifying clinical trials through the identification of the optimum moment to begin the therapies, the appropriate selection of individuals, and the identification of sensitive outcome measures. The management of patients in prodromal spinocerebellar ataxia type 2 may raise ethical dilemmas related to predictive diagnosis and early interventions, which impose new challenges to clinical and therapeutic research. © 2017 International Parkinson and Movement Disorder Society.

Background Spinocerebellar ataxia type 2 is a neurodegenerative disorder caused by a CAG repeat expansion in ATXN2 gene. There is high clinical variability among affected patients suggesting the occurring of modifier genes influencing the clinical phenotype. Objective The objective is to assess the association of GSTO1 rs4925 and GSTO2 rs2297235 SNPs on the clinical phenotype in SCA2 patients. Methods A case-control study was performed in a sample of 120 SCA2 Cuban patients and 100 healthy subjects. Age at onset, 60° Maximal Saccade Velocity and SARA score were used as clinical markers. GSTO1 rs4925 and GSTO2 rs2297235 SNPs were determined by PCR/RFLP. Results Distribution of the GSTO1 alleles and genotypes was nearly equal between the control group and SCA2 patients. GSTO1 genotypes were not associated to clinical markers in SCA2 patients. Distribution of the GSTO2 "G" allele and "AG" genotype differed significantly between SCA2 patients and controls. Symptomatic SCA2 individuals had a 2.29-fold higher chance of carrying at least one "G" allele at GSTO2 rs2297235 than controls (OR=2.29, 95% CI: 1.29–4.04). GSTO2 genotypes were significantly associated to age at onset (p=0.037) but not to 60° Maximal Saccade Velocity or SARA score in SCA2 patients. Conclusion The GSTO1 rs4925 polymorphism is not associated to SCA2. Meanwhile, the GSTO2 rs2297235 "AG" genotype is associated to SCA2 but failed to show any association with clinical markers, with the exception of a potential association with the age at disease onset.

Previous studies have investigated the close association that exists between CAG repeat number and the age at onset in SCA2 = spinocerebellar ataxia type 2. These studies have focused on affected individuals. To further characterize this association and estimate the risk of a carrier developing SCA2 at a particular age as a function of a specific CAG repeat size, we have analyzed a large group of 924 individuals, including 394 presymptomatic and 530 affected individuals with a CAG repeat length of 32-79 units. Using a Kaplan-Meier survival analysis, we obtained cumulative probability curves for disease manifestation at a particular age for each CAG repeat length in the 34-45 range. These curves were significantly different (p < 0.001) and showed small overlap. All these information may be very valuable in predictive-testing programs, in the planning of studies for the identification of other genetic and environmental factors as modifiers of age at onset, and in the design of clinical trials for people at enlarged risk for SCA2.

Background Spinocerebellar Ataxia Type 3/Machado-Joseph Disease (SCA3/MJD) is a hereditary neurodegenerative disorder resulting from the expansion of CAG repeats in the ATXN3 gene. It is the most common autosomal dominant ataxia in the world, but its frequency prevalence in Cuba remains uncertain. We undertook a national study in order to characterize the ATXN3 gene and to determine the prevalence of SCA3/MJD in Cuba. Results Twenty-two individuals belonging to 8 non-related families were identified as carriers of an expanded ATXN3 allele. The affected families come from the central and western region of the country. Ataxia of gait was the initial symptom in all of the cases. The normal alleles ranged between 14 and 33 CAG repeats while the expanded ones ranged from 63 to 77 repeats. The mean age at onset was 40 ± 9 years and significantly correlated with the number of CAG repeats in the expanded alleles. Conclusions This disorder was identified as the second most common form of spinocerebellar ataxia (SCA) in Cuba based on molecular testing, and showing a different geographical distribution from that of SCA2. This research constitutes the first clinical and molecular characterization of Cuban SCA3 families, opening the way for the implementation of predictive diagnosis for at risk family members.

The effects of ATXN2 expansion on the nervous system arise before the cerebellar syndrome can be diagnosed; however, progression of the underlying early clinical manifestations is unknown. We aimed to assess progression of the main clinical features in early stages of the spinocerebellar ataxia type 2 (SCA2).We did this longitudinal study between Aug 12, 1986, and Sept 3, 2013, in carriers and non-carriers of the SCA2 mutation. We enrolled participants aged 6-60 years who were asymptomatic offspring or siblings of patients with SCA2. Participants were repeatedly assessed (two to seven times) until they presented definite cerebellar syndrome. All participants underwent standardised neurological examinations and electrophysiological (nerve conduction tests and somatosensory evoked potentials) and genetic assessments.We enrolled 40 (73%) of 55 eligible participants to the baseline assessment, of whom 21 (13 women and eight men) were carriers of the SCA2 mutation, and 19 (14 women and five men) were non-carriers. Muscle cramps and sensory abnormalities were the most common clinical features in carriers (n=17 [81%] for both features) compared with controls (n=3 [16%] and n=4 [21%], respectively; χ(2)=84·58; p0.0001, and χ(2)=72·03; p0·0001, respectively) Both features showed a notable worsening over time and, in 17 (81%) carriers, age at onset was inversely correlated to CAG repeats (cramps: r -0·76, p=0·0004; sensory abnormalities: r -0·77, p=0·0004). Hyper-reflexia was associated with long time to ataxia onset (mean 5·71 years [SD 5·03]), whereas hyporeflexia was associated with short time (median 1·29 years [range 1-3]). Electrophysiological recordings obtained between 5 and 8 years before ataxia in 11 (52%) carriers showed reduced sensory amplitudes for median nerve (10·34 uV [SD 5·07]) and prolonged mean P40 latency (39·31 ms [2·40]) compared with age-matched and sex-matched controls (20·72 uV [9·08 uV]; p=0·0085, and 35·60 ms [2·05]; p=0·0023, respectively).Early features of SCA2 are detectable before the onset of the cerebellar syndrome, and are associated with expanded CAG repeats and the time to onset of cerebellar syndrome. These findings could aid early diagnosis and genetic counselling, and also offer physiopathological insights that could help in the implementation of clinical trials in early stages of the disease.Cuban Ministry of Public Health.

Spinocerebellar ataxia type 2 (SCA2) is a neurodegenerative and incurable hereditary disorder caused by a CAG repeat expansion mutation on ATXN2 gene. The identification of reliable biochemical markers of disease severity is of paramount significance for the development and assessment of clinical trials. In order to evaluate the potential use of glutathione-S-transferase (GST) activity as a biomarker for SCA2, a case-control study in 38 affected, presymptomatic individuals or healthy controls was conducted. An enlarged sample of 121 affected individuals was set to assess the impact of GST activity on SCA2 clinical expression. There was a significant increase in GST activity in affected individuals relative to controls, although sensibility and specificity were not high. GST activity was not significantly influenced by sex, age, disease duration or CAG repeat size and did not significantly influence disease severity markers. These findings show a disruption of in vivo GST activity in SCA2, suggesting a role for oxidative stress in the neurodegenerative process.

Epigenetics is the group of changes in the phenotype which are related with the process independently of the primary DNA sequence. These changes are intimately related with changes in the gene expression level and its profile across the body. These are mediated by histone tail modifications, DNA methylation, micro-RNAs, with chromatin remodeling remaining as the foundation of epigenetic changes. DNA methylation involves the covalent addition of methyl group to cytosine of the DNA, which is mediated by methyltransferases enzymes. DNA methylation regulates gene expression by repressing transcription, while de-methylation activates gene transcription. Several human diseases are related with the epigenetic process: cancer, Alzheimer disease, stroke, Parkinson disease, and diabetes. We present here the basis of epigenetic inheritance and show the pathogenic mechanisms relating epigenetics in human diseases, specifically with regard to neurodegeneration. We discuss current concepts aimed at understanding the contribution of epigenetics to human neurodegenerative diseases. We also discuss recent findings obtained in our and other centers regarding the ATXN2 gene that causes spinocerebellar ataxia 2 and amyotrophic lateral sclerosis. Epigenetics play a pivotal role in the pathogenesis of human diseases and in several neurodegenerative disorders, and this knowledge will illuminate the pathways in the diagnostic and therapeutic field, which ultimately will be translated into the clinic context of neurodegenerative diseases.

Since 2001 a program for the presymptomatic testing of families affected with SCA2 has been under development in Cuba. According to the initial protocol, access would be given to nonsymptomatic individuals at 50% risk, over 18 years; nevertheless, eleven minors requested their inclusion in the program. A retrospective and descriptive study based on the analysis of the medical records belonging to these individuals was designed. Being aware of how challenging clinical settings of predictive genetic testing for minors are, this paper reviews their profile, the outcome of the carried out studies, as well as the reproductive option chosen by the gene positive consultands. The mean age at the time of testing was 16.2 years. Nine adolescents completed the protocol (three had positive test results) and two withdrew. They had a distinctive profile; all were females, pregnant, motivated by the risk assessment for their descendants, and interested in PND with termination of the gestation were the fetus a carrier. Nevertheless, once the result of the test is known, the gene positive consultands chose discordant reproductive options. Further research is necessary to assess the long-term psychological impact in both gene positive and gene negative participants, as well as in their parents and at-risk relatives.

Pathogenic CAG repeat expansion in the ataxin-2 gene (ATXN2) is the genetic cause of spinocerebellar ataxia type 2 (SCA2). Recently, it has been associated with Parkinsonism and increased genetic risk for amyotrophic lateral sclerosis (ALS). Here we report the association of de novo mutations in ATXN2 with autosomal dominant ALS. These findings support our previous conjectures based on population studies on the role of large normal ATXN2 alleles as the source for new mutations being involved in neurodegenerative pathologies associated with CAG expansions. The de novo mutations expanded from ALS/SCA2 non-risk alleles as proven by meta-analysis method. The ALS risk was associated with SCA2 alleles as well as with intermediate CAG lengths in the ATXN2. Higher risk for ALS was associated with pathogenic CAG repeat as revealed by meta-analysis.

In 2001 a program for predictive testing of Spinocerebellar Ataxia type 2 was developed in Cuba, based on the detection of an abnormal CAG trinucleotide repeat expansion in the ATXN2 gene. A descriptive study was designed to assess the implications of ATXN2 large normal and intermediate alleles in the context of the SCA2 Prenatal Diagnosis Program. Four clinical scenarios were selected based upon the behaviour of large normal and intermediate alleles when passing from one generation to the next, showing expansions, contractions, or stability in the CAG repeat size. In some populations, traditional Mendelian risk figures of 0 % or 50 % may not be applicable due to the high frequency of unstable large normal alleles. Couples with no family history of SCA2 may have a >0 % risk of having an affected offspring. Similarly, couples in which there is both an expanded and a large normal allele may have a recurrence risk >50 %. It is imperative that these issues be addressed with these couples during genetic counseling. These recurrence risks have to be carefully estimated in the presence of such alleles (particularly alleles ≥27 CAG repeats), carriers need to be aware of the potential risk for their descendants, and programs for prenatal diagnosis must be available for them.

The role of short, large or intermediate normal alleles (ANs) of the ataxin-2 gene in generating expanded alleles (EAs) causing spinocerebellar ataxia type 2 (SCA2) is poorly understood. It has been postulated that SCA2 prevalence is related to the frequency of large ANs. SCA2 shows the highest worldwide prevalence in Cuban population, which is therefore a unique source for studying the relationship between the frequency of large and intermediate alleles and the frequency of SCA2 mutation. Through genetic polymorphism analyses in a comprehensive sample (∼3000 chromosomes), we show that the frequency of large ANs in the ataxin-2 gene is the highest worldwide, although short ANs are also frequent. This highly polymorphic population displayed also high variability in the CAG sequence, featured by loss of the anchor CAA interruption(s). In addition, large ANs showed germinal and somatic instability. Our study also includes related genotypic, genealogical and haplotypic data and provides substantial evidence with regard to the role of large and intermediate alleles in the generation of pathological EAs.

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant cerebellar ataxia characterized by a progressive cerebellar syndrome associated to saccadic slowing, peripheral neuropathy, cognitive disorders, and other multisystem features. SCA2 is caused by the abnormal expansion of cytosine–adenine–guanine triplet repeats in the encoding region of the ATXN2 gene and therefore the expression of toxic polyglutamine expansions in the ataxin 2 protein, which cause progressive neuronal death of Purkinje cells in the cerebellum and several pontine, mesencephalic, and thalamic neurons among other cells. Worldwide, SCA2 is the second most frequent type of spinocerebellar ataxia, only surpassed by SCA3. Nevertheless, in Holguin, Cuba, the disease reaches the highest prevalence, resulting from a putative foundational effect. This review discusses the most important advances in the genotypical and phenotypical studies of SCA2, highlighting the comprehensive characterization reached in Cuba through clinical, neuroepidemiological, neurochemical, and neurophysiological evaluation of SCA2 patients and pre-symptomatic subjects, which has allowed the identification of new disease biomarkers and therapeutical opportunities. These findings provide guidelines, from a Cuban viewpoint, for the clinical management of the disease, its diagnosis, genetic counseling, and therapeutical options through rehabilitative therapy and/or pharmacological options.

Rapid eye movement (REM) sleep disorders are commonly associated to patients with spinocerebellar ataxia type 2 (SCA2); however, these abnormalities have not been studied in presymptomatic gene carriers. To determine whether the REM sleep pathology is detectable before clinical manifestation of SCA2 and evaluate it as a preclinical biomarker, we studied 36 presymptomatic SCA2 individuals and 36 controls by video-polysomnography (VPSG) and sleep questionnaires. Presymptomatic subjects showed significant decrease of REM sleep percentage, REMs density, total sleep time, and sleep efficiency. Aging effect on REM sleep percentage was significant in both groups. There was no correlation between cytosine-adenine-guanine (CAG) repeat length and REM sleep. Our findings identified the REM sleep pathology as a prominent herald sign of SCA2, conferring a special importance to VPSG as a sensitive neurophysiological tool to detect early changes associated with SCA2, which contributes to the understanding of disease pathophysiology and the development of therapeutic trials focused on the preclinical disease stage.

This report describes two families who presented with autosomal recessive ataxia. By means of Polymerase Chain Reaction (PCR) molecular testing we identified expansions in the gene encoding Frataxin (FTX) that is diagnostic of Friedreich ataxia. A history of reproductive loss in the two families, prominent scoliosis deformity preceding the onset of ataxic gait, the presence of a sensitive axonal neuropathy, as well as the common origin of ancestors are unusual features of these families. These cases illustrate the importance of molecular diagnosis in patients with a recessive ataxia. The origin of the expanded gene and the GAA repeat size in the normal population are issues to be further investigated. The molecular diagnosis of Friedreich ataxia is now established in Cuba.

Las enfermedades poliglutamínicas constituyen un grupo creciente de enfermedades neurodegenerativas humanas, causadas por la expansión de secuencias repetitivas de CAG que son traducidas para dar lugar a proteínas con dominios poliglutamínicos expandidos. La edad de inicio es un marcador fenotípico para estas enfermedades, y muestra una gran variación en las familias afectadas. El número de repeticiones de CAG contenido en los genes causales, explica entre el 47 y 80% de la variabilidad observada en la edad de inicio. Para explicar la varianza restante ha sido propuesta la hipótesis de la existencia de genes modificadores. Aquí realizamos una revisión actualizada acerca de esta temática, abordando las estrategias más usadas para su identificación, los principales hallazgos obtenidos y sus implicaciones. La identificación de estos genes contribuye al esclarecimiento de los mecanismo patológicos involucrados en estas enfermedades, y puede conducir a la proposición y diseño de estrategias terapéuticas potenciales.

Objective: A characteristic feature of spinocerebellar ataxia type 2 (SCA2) is saccadic slowing at early disease stages. We sought to determine whether this sign is detectable before clinical manifestation and quantifies the disease progression throughout life in linear fashion. Methods: In a specialized ataxia clinic, 54 presymptomatic carriers of SCA2 polyglutamine expansions and 56 relatives without mutation were documented with regard to their maximal saccade velocity (MSV). Results: Among the control individuals, a significant effect of aging on MSV was observed. After elimination of this age influence through a matched-pair approach, a presymptomatic decrease of MSV could be shown. The MSV reduction was stronger in carriers of large expansions. In the years before calculated disease manifestation, the MSV impairment advanced insidiously. Conclusion: Saccade velocity is a sensitive SCA2 endophenotype that reflects early pontine degeneration and may be a useful diagnostic parameter before the onset of ataxia. Significance: Future neuroprotective therapies of polyglutamine neurodegeneration may be assessed by MSV from earliest to prefinal disease stages.

Introducción: la Ataxia Espinocerebelosa tipo 2 (SCA2) es una enfermedad neurodegenerativa severa que representa un serio problema de salud en Cuba, debido a las altas tasas de prevalencia e incidencia y a la ausencia de tratamientos curativos. Objetivos: evaluar el efecto y la seguridad del tratamiento con altas dosis de vitaminas del complejo B (Compvit-B) sobre la neuropatía periférica en pacientes con SCA2. Métodos: se realizó una investigación prospectiva de intervención clínica en 20 enfermos en estadio ligero los que se sometieron a un protocolo terapéutico mediante la administración intramuscular del COMPVIT B por 12 semanas. Durante las primeras 4 semanas los individuos recibieron dos bulbos semanales y a partir de la 5ta semana un solo bulbo. Inmediatamente antes y después del tratamiento los pacientes fueron evaluados mediantes exámenes clínicos y electrofisiológicos. Resultados: una vez concluido el tratamiento, los pacientes mostraron un aumento significativo de las amplitudes de los potenciales de acción sensitivos de nervios mediano y sural, y en este último nervio se observó además reducción de la latencia y aumento de la velocidad de conducción. Los parámetros de la conducción nerviosa motora no se modificaron. Los potenciales evocados somatosensoriales de nervio mediano arrojaron una reducción significativa de la latencia del potencial de Erb. De manera interesante se observó una la disminución significativa de la frecuencia de aparición de las contracturas musculares dolorosas en el 53% de los casos después del tratamiento. Durante el estudio no se registraron eventos adversos. Conclusiones: el presente estudio identifica una nueva opción terapéutica sintomática en la SCA2, brinda nuevas evidencias sobre las bases fisiopatológicas y el manejo clínico de las contracturas musculares dolorosas y justifican la realización de estudios más amplios en pacientes y portadores de la mutación, los que presentan tales manifestaciones muchos antes de debutar con la ataxia.

Introducción: la ataxia Espinocerebelosa tipo 2 (SCA2) es una enfermedad neurodegenerativa que alcanza las mayores tasas de prevalencia e incidencia en Holguín, Cuba. Una de las principales manifestaciones clínicas de estos pacientes son los trastornos cognitivos, expresados fundamentalmente como déficits frontoejecutivos y de la memoria. Objetivo: evaluar el efecto del tratamiento con vitaminas del Complejo B sobre las funciones cognitivas, en pacientes cubanos con SCA2. Métodos: se incluyeron 20 pacientes en una investigación de intervención clínica, empleando COMPVIT-B, durante 3 meses. Se evaluaron parámetros clínicos, como la escala SARA y cognitivos como el test de Stroop, el test de Fluencia verbal fonológica y el test de memoria verbal. Todos los estudios se realizaron antes y después del tratamiento. Resultados: el estudio de las funciones frontoejecutivas reveló un aumento significativo del número de palabras mencionadas en el test de fluencia verbal fonológica, al terminar el estudio. Sin embargo, el test de Stroop no mostró cambios significativos. En relación al test de memoria verbal, se obtuvo un aumento del número de palabras recordadas en el primer ensayo, así como reducción del número de ensayos requeridos para recordar todas las palabras. La puntuación de la escala SARA no cambió significativamente. Conclusiones: el presente trabajo constituye una evidencia adicional en favor del uso terapéutico y neuroprotector de las vitaminas del complejo B e identifica una nueva opción de tratamiento sintomatológico para los enfermos con SCA2, lo que incide positivamente en el mejoramiento de la calidad de vida de estos pacientes.