Juvenile Huntington's disease in northern Brazil: a case series report / Doença de Huntington juvenil no norte do Brasil: relato de uma série de casos

Introduction: Huntington's disease (HD) is a neurodegenerative disorder caused by CAG expansion repeats in the HTT gene. Usually, the symptoms start to manifest in mid-adulthood. In about 5% of cases, however, the signs begin before the age of 20 years. These cases are known as juvenile HD (JHD). Objective: here we report a case series of JHD from Amazonas, a state where data are scarce due to the restricted access to specialized medical assistance for diagnosis and care. Case series: the patients were attended by neurologists specialized in movement disorders at Manaus. Two cases manifested the disease in childhood (6 and 7 years old) and two cases, in adolescence (12 and 16 years old). All cases showed dystonia and parkinsonism as predominant motor disorders. Moreover, signs of cognitive decline, depression, and psychosis were observed in all patients. Conversely, cerebellar signs, gait disturbances, seizures, and some psychiatric symptoms were variable among the cases. Expansion size varied from 66 to 84 to CAG repeats and the difference in age at onset between parent and child varied from 23 to 43 years. Conclusion: to our knowledge, these are the first clinical reports of JHD in northern Brazil. These cases illustrate the variability in clinical phenotypes and genetic features of JHD cases. Furthermore, they can contribute to the awareness of HD here, both by professionals and the public in general.

Introdução: a doença de Huntington (DH) é um distúrbio neurodegenerativo causado pela expansão de repetições CAG no gene HTT. Geralmente, os sintomas começam a se manifestar na vida adulta tardia. Em cerca de 5% dos casos, no entanto, os sinais começam antes da idade de 20 anos. Esses casos são conhecidos como DH juvenil (DHJ). Objetivo: neste estudo, nós reportamos uma série de casos de DHJ do Amazonas, um estado onde os dados ainda são escassos devido ao acesso restrito à assistência médica especializada para o diagnóstico e cuidado. Série de casos: os pacientes foram atendidos por neurologistas especializados em transtornos do movimento em Manaus. Dois casos manifestaram a doença na infância (6 e 7 anos) e dois casos, na adolescência (12 e 16 anos). Todos os casos apresentaram distonia e parkinsonismo como sintomas motores predominantes. Sinais de declínio cognitivo, depressão e psicose também foram observados em todos os pacientes. Por outro lado, sinais cerebelares, distúrbios da marcha, convulsões e alguns sintomas psiquiátricos foram variáveis entre os casos. O tamanho da expansão CAG variou de 66 a 84 repetições e a diferença na idade de início dos sintomas entre pais e filhos variou de 23 a 43 anos. Conclusão: ao nosso conhecimento, estes são os primeiros relatos clínicos da DHJ na região Norte. Esses casos ilustram a variabilidade nos fenótipos clínicos e nas características genéticas dos casos de DHJ. Além disso, eles podem contribuir para a conscientização da DH na região, tanto pelos profissionais quanto pelo público geral.

Genetic anticipation of breast cancer among BRCA1/BRCA2 mutation carriers: A retrospective study.

OBJECTIVE: To study the anticipation phenomenon among hereditary breast cancer patients, by evaluating trends in age at diagnosis and phenotype of breast cancer across two successive generation pairs of BRCA1/2 mutation carriers/non-carriers with breast cancer after reports of an earlier age of diagnosis in successive generations among BRCA1/2 mutation carrier families. METHOD: A retrospective cohort study. Patient characteristics, pathologic data and survival were compared between mothers and daughters and between carriers and non-carriers. RESULTS: Overall, 126 patients were found, who formed 67 pairs of mothers and daughters diagnosed with breast cancer and genetically tested for BRCA mutations. Age at diagnosis was significantly younger in the daughter versus mother generation, in both groups of BRCA carriers/non-carriers. Tumor characteristics were not different between mothers and daughters. Survival analysis revealed a not significant better outcome for the daughter generation versus the mother generation. CONCLUSIONS: Breast cancer appeared to be diagnosed at an earlier age in successive generations among BRCA mutation carriers and non-carriers. The fact that we also observed a downshift at age of diagnosis in non-carrier pairs emphasizes that other factors (environmental, lifestyle, or social) may influence the age at diagnosis.

Does genetic anticipation occur in familial Alexander disease?

Alexander Disease (AxD) is a rare leukodystrophy caused by missense mutations of glial fibrillary acidic protein (GFAP). Primarily seen in infants and juveniles, it can present in adulthood. We report a family with inherited AxD in which the mother presented with symptoms many years after her daughter. We reviewed the age of onset in all published cases of familial AxD and found that 32 of 34 instances of parent-offspring pairs demonstrated an earlier age of onset in offspring compared to the parent. We suggest that genetic anticipation occurs in familial AxD and speculate that genetic mosaicism could explain this phenomenon.

30 years of repeat expansion disorders: What have we learned and what are the remaining challenges?

Tandem repeats represent one of the most abundant class of variations in human genomes, which are polymorphic by nature and become highly unstable in a length-dependent manner. The expansion of repeat length across generations is a well-established process that results in human disorders mainly affecting the central nervous system. At least 50 disorders associated with expansion loci have been described to date, with half recognized only in the last ten years, as prior methodological difficulties limited their identification. These limitations still apply to the current widely used molecular diagnostic methods (exome or gene panels) and thus result in missed diagnosis detrimental to affected individuals and their families, especially for disorders that are very rare and/or clinically not recognizable. Most of these disorders have been identified through family-driven approaches and many others likely remain to be identified. The recent development of long-read technologies provides a unique opportunity to systematically investigate the contribution of tandem repeats and repeat expansions to the genetic architecture of human disorders. In this review, we summarize the current and most recent knowledge about the genetics of repeat expansion disorders and the diversity of their pathophysiological mechanisms and outline the perspectives of developing personalized treatments in the future.

The Contribution of Somatic Expansion of the CAG Repeat to Symptomatic Development in Huntington's Disease: A Historical Perspective.

The discovery in the early 1990s of the expansion of unstable simple sequence repeats as the causative mutation for a number of inherited human disorders, including Huntington's disease (HD), opened up a new era of human genetics and provided explanations for some old problems. In particular, an inverse association between the number of repeats inherited and age at onset, and unprecedented levels of germline instability, biased toward further expansion, provided an explanation for the wide symptomatic variability and anticipation observed in HD and many of these disorders. The repeats were also revealed to be somatically unstable in a process that is expansion-biased, age-dependent and tissue-specific, features that are now increasingly recognised as contributory to the age-dependence, progressive nature and tissue specificity of the symptoms of HD, and at least some related disorders. With much of the data deriving from affected individuals, and model systems, somatic expansions have been revealed to arise in a cell division-independent manner in critical target tissues via a mechanism involving key components of the DNA mismatch repair pathway. These insights have opened new approaches to thinking about how the disease could be treated by suppressing somatic expansion and revealed novel protein targets for intervention. Exciting times lie ahead in turning these insights into novel therapies for HD and related disorders.

Factors Associated with Intergenerational Instability of ATXN3 CAG Repeat and Genetic Anticipation in Chinese Patients with Spinocerebellar Ataxia Type 3.

Spinocerebellar ataxia type 3 (SCA3) is caused by unstable expanded CAG repeats (expCAGs) in ATXN3. Factors associated with intergenerational instability (delta-expCAG) and genetic anticipation in SCA3 have never been reported in Chinese mainland. Here, we demonstrated that unstable transmissions occurred more often in sons than in daughters (91% vs 72%, Fisher's exact test, p = 0.012). The extended delta-expCAG of father-son transmissions was greater than that of mother-son transmissions (3.8 ± 2.3 repeats vs 1.6 ± 1.0 repeats, Mann-Whitney U, p = 0.001). Genetic anticipation was frequently observed between generations but not affected by the delta-expCAG.

Clues For Genetic Anticipation In Multiple Endocrine Neoplasia Type 1.

CONTEXT: Multiple endocrine neoplasia type 1 (MEN1) is a rare autosomal dominant hereditary disease caused by the loss of function of the MEN1 gene, a tumor-suppressor gene that encodes the protein menin. It is characterized by the occurrence of primary hyperparathyroidism (pHPT), duodenopancreatic neuroendocrine tumors (dpNET), pituitary tumors (PIT), adrenal adenomas, and bronchopulmonary (bp-NET), thymic, and gastric neuroendocrine tumors. More insight into factors influencing the age-related penetrance of MEN1 manifestations could provide clues for more personalized screening programs. OBJECTIVE: To investigate whether genetic anticipation plays a role in the largest known MEN1 families in the Netherlands. METHODS: All Dutch MEN1 families with ≥ 10 affected members in ≥ 2 successive generations were identified. Age at detection of the different MEN1-related manifestations were compared among generations using regression analyses adjusted for competing risks. To correct for the beneficial effect of being under surveillance, manifestations occurring during surveillance were also separately compared. RESULTS: A total of 152 MEN1 patients from 10 families were included. A significantly decreased age at detection of pHPT, dpNET, PIT, and bp-NET was found in successive generations (P < 0.0001). Adjusted analyses led to the same results. CONCLUSIONS: These results suggest the presence of genetic anticipation. However, due to a risk of residual bias, the results must be interpreted with caution. After independent validation in other cohorts and further translational research investigating the molecular mechanisms explaining this phenomenon in MEN1, the results might add to future, more personalized, screening protocols and earlier screening for future generations of MEN1 patients.

Microbial evolutionary strategies in a dynamic ocean.

Marine microbes form the base of ocean food webs and drive ocean biogeochemical cycling. Yet little is known about the ability of microbial populations to adapt as they are advected through changing conditions. Here, we investigated the interplay between physical and biological timescales using a model of adaptation and an eddy-resolving ocean circulation climate model. Two criteria were identified that relate the timing and nature of adaptation to the ratio of physical to biological timescales. Genetic adaptation was impeded in highly variable regimes by nongenetic modifications but was promoted in more stable environments. An evolutionary trade-off emerged where greater short-term nongenetic transgenerational effects (low-γ strategy) enabled rapid responses to environmental fluctuations but delayed genetic adaptation, while fewer short-term transgenerational effects (high-γ strategy) allowed faster genetic adaptation but inhibited short-term responses. Our results demonstrate that the selective pressures for organisms within a single water mass vary based on differences in generation timescales resulting in different evolutionary strategies being favored. Organisms that experience more variable environments should favor a low-γ strategy. Furthermore, faster cell division rates should be a key factor in genetic adaptation in a changing ocean. Understanding and quantifying the relationship between evolutionary and physical timescales is critical for robust predictions of future microbial dynamics.

Li-Fraumeni syndrome heterogeneity.

Clinical variability is commonly seen in Li-Fraumeni syndrome. Phenotypic heterogeneity is present among different families affected by the same pathogenic variant in TP53 gene and among members of the same family. However, causes of this huge clinical spectrum have not been studied in depth. TP53 type mutation, polymorphic variants in TP53 gene or in TP53-related genes, copy number variations in particular regions, and/or epigenetic deregulation of TP53 expression might be responsible for clinical heterogeneity. In this review, recent advances in the understanding of genetic and epigenetic aspects influencing Li-Fraumeni phenotype are discussed.

Pseudo-anticipation in Creutzfeldt-Jakob disease is due to a rhomboid-shaped artifact.

BACKGROUND AND PURPOSE: Previous studies have reported conflicting results regarding possible anticipation in familial E200K Creutzfeldt-Jakob disease (fCJD). Our objective was to use a large database to assess the age of disease onset (AODO) in CJD. METHODS: The study population included 477 CJD patients [266 with fCJD, 145 with sporadic CJD (sCJD) and 66 patients of Libyan origin but negative family history] from the Israeli registry of CJD conducted since 1954. In all patients, AODO in relatives and family trees was documented. Comparison of AODO was done using a paired t test and regression using Pearson correlation for birth and year of onset. RESULTS: The initial analysis in 52/73 families in which more than one generation was affected revealed an AODO of 63.30 ± 9.44 in the first generation compared to 56.96 ± 8.99 in the second generation (P < 0.001). However, inspection of individual AODO values plotted by year of birth showed a clear rhomboid methodological artifact generated by missing data of many young onset CJD patients who died before the database began to function in 1954 and of many late onset CJD patients missing at the present time since they will only develop the disease in the future. The 'generation' effect completely disappears if analysis is performed by year of disease onset or for the periods in which complete data are available. CONCLUSIONS: In this very large dataset, true anticipation in fCJD patients was not detected. It is plausible that previous reports supporting the presence of anticipation are biased by a rhomboid-shaped data availability artifact.

Telomeropathies: Etiology, diagnosis, treatment and follow-up. Ethical and legal considerations.

Telomeropathies involve a wide variety of infrequent genetic diseases caused by mutations in the telomerase maintenance mechanism or the DNA damage response (DDR) system. They are considered a family of rare diseases that often share causes, molecular mechanisms and symptoms. Generally, these diseases are not diagnosed until the symptoms are advanced, diminishing the survival time of patients. Although several related syndromes may still be unrecognized this work describes those that are known, highlighting that because they are rare diseases, physicians should be trained in their early diagnosis. The etiology and diagnosis are discussed for each telomeropathy and the treatments when available, along with a new classification of this group of diseases. Ethical and legal issues related to this group of diseases are also considered.

The Apparent Genetic Anticipation in PMS2-Associated Lynch Syndrome Families Is Explained by Birth-cohort Effect.

BACKGROUND: PMS2-associated Lynch syndrome is characterized by a relatively low colorectal cancer penetrance compared with other Lynch syndromes. However, age at colorectal cancer diagnosis varies widely, and a strong genetic anticipation effect has been suggested for PMS2 families. In this study, we examined proposed genetic anticipation in a sample of 152 European PMS2 families. METHODS: The 152 families (637 family members) that were eligible for analysis were mainly clinically ascertained via clinical genetics centers. We used weighted Cox-type random effects model, adjusted by birth cohort and sex, to estimate the generational effect on the age of onset of colorectal cancer. Probands and young birth cohorts were excluded from the analyses. Weights represented mutation probabilities based on kinship coefficients, thus avoiding testing bias. RESULTS: Family data across three generations, including 123 colorectal cancers, were analyzed. When compared with the first generation, the crude HR for anticipation was 2.242 [95% confidence interval (CI), 1.162-4.328] for the second generation and 2.644 (95% CI, 1.082-6.464) for the third generation. However, after correction for birth cohort and sex, the effect vanished [HR = 1.302 (95% CI, 0.648-2.619) and HR = 1.074 (95% CI, 0.406-2.842) for second and third generations, respectively]. CONCLUSIONS: Our study did not confirm previous reports of genetic anticipation in PMS2-associated Lynch syndrome. Birth-cohort effect seems the most likely explanation for observed younger colorectal cancer diagnosis in subsequent generations, particularly because there is currently no commonly accepted biological mechanism that could explain genetic anticipation in Lynch syndrome. IMPACT: This new model for studying genetic anticipation provides a standard for rigorous analysis of families with dominantly inherited cancer predisposition.

Contextualizing action observation in the predictive brain: Causal contributions of prefrontal and middle temporal areas.

Context facilitates the recognition of forthcoming actions by pointing to which intention is likely to drive them. This intention is thought to be estimated in a ventral pathway linking MTG with frontal regions and to further impact on the implementation of sensory predictions within the action observation network (AON). Additionally, when conflicting intentions are estimated from context, the DLPFC may bias action selection. However, direct evidence for the contribution of these areas to context-embedded action representations in the AON is still lacking. Here, we used a perturb-and-measure TMS-approach to disrupt neural activity, separately in MTG and DLPFC and subsequently measure cortico-spinal excitability while observing actions embedded in congruent, incongruent or ambiguous contexts. Context congruency was manipulated in terms of compatibility between observed kinematics and the action goal suggested by the ensemble of objects depicted in the environment. In the control session (vertex), we found an early facilitation and later inhibition for kinematics embedded in congruent and incongruent contexts, respectively. MTG stimulation altered the differential modulation of M1 response to congruent vs. incongruent contexts, suggesting this area specifies prior representations about appropriate object graspability. Interestingly, all effects were abolished after DLPFC stimulation highlighting its critical role in broader contextual modulation of the AON activity.

Pulmonary Langerhans cell histiocytosis, acute myeloid leukemia, and myelofibrosis in a large family and review of the literature.

BACKGROUND: There is mounting evidence that Langerhans cell histiocytosis (LCH) and acute myeloid leukemia (AML) are hematopoietic neoplasms that arise from the same myeloid precursor cell. In addition, studies suggest a relationship between LCH and primary idiopathic myelofibrosis (MF). Furthermore familial LCH, AML, and MF have each been reported. METHODS: We examined more than 750 pedigrees of familial hematologic malignancies for evidence of familial LCH, AML, and/or MF and identified one family with all three neoplasms, which is presented here. FINDINGS: In four generations of this large family there are five cases of AML in three generations, two cases of LCH in two generations and three cases of MF in two generations. Anticipation of -18 and -6 years was present in the patients with MF, and -8 years in the patients with LCH. Anticipation was also identified between one AML patient pair in generations III and IV (-18 years) and three patients with AML in generations II, III, and IV (-5 years and -10 years). INTERPRETATION: This is the first report of familial LCH, AML, and MF in one family. The pedigree suggests a common basis for these entities, which is further suggested by the presence of anticipation in the pedigree.

Evidence for genetic anticipation in vonHippel-Lindau syndrome.

BACKGROUND: von Hippel-Lindau (vHL) syndrome is a rare autosomal-dominant disorder that confers a lifelong risk for developing both benign and malignant tumours in multiple organs. Recent evidence suggests that vHL may exhibit genetic anticipation (GA). The aim of this study was to determine if GA occurs in vHL, and if telomere shortening may be a factor in GA. METHODS: A retrospective chart review of vHL families seen at The Hospital for Sick Children between 1984 and 2016 was performed. Age of onset (AOO, defined as the age of first physician-diagnosed vHL-related manifestation) was confirmed for 96 patients from 20 unrelated families (80 clinically affected and 16 unaffected carriers). Flow-FISH(flow cytometry sorting of cells whose telomeres are labeled by Fluorescence In Situ Hybridization) was used to measure mean telomere length of six white blood cell subtypes from 14 known VHL pathogenic variant carriers. RESULTS: The median AOO for generations I, II and III were 32.5, 22.5 and 12.0 years, respectively. The differences in the AOO between generations were highly significant using a Cox proportional hazards model (P=6.00×10-12). Telomere lengths were significantly different for granulocytes and natural killer lymphocytes of patients with vHL compared with age-matched controls. For six vHL parent-child pairs, median white blood cell telomere lengths between parent and child were not significantly different. CONCLUSIONS: Our results suggest that vHL telomere abnormalities may be primarily somatic in origin rather than a cause of GA. As tumour development exhibits GA in our cohort, vHL surveillance guidelines may need to account for a patient's generational position within a vHL pedigree.

Is there a genetic anticipation in breast and/or ovarian cancer families with the germline c.3481_3491del11 mutation?

The aim of the current analysis is to evaluate any differences of breast or ovarian cancer age at diagnosis between mothers and daughters carrying the c.3481_3491del11 mutation in the BRCA1 gene. A study cohort of 38 women carrying the c.3481_3491del11 mutation and affected by first breast or ovarian cancer who reported a first breast or ovarian cancer in their mother carrying the c.3481_3491del11 mutation, was identified in 37 different families including members with breast and/or ovarian cancer at the Oncology Institute of Lorraine. Twelve mothers underwent genetic testing. Twenty-five pairs of the 38 mothers-daughters pairs with c.3481_3491del11 mutation were affected by breast cancer and 13 pairs by ovarian cancer. Clinical and genetic data were collected from medical files and family pedigrees. Analyses were conducted for each cancer type. We investigated an early breast cancer detection effect due to early screening programs and also an increased breast tumor aggression. Since major improvements in breast cancer clinical management and imaging techniques appeared after 1980, we compared the age at breast cancer diagnosis and the age at death in mothers and daughters before and after 1980, first, in the group of women including mothers and daughters taken together and then in mothers and daughters separately. The mean age at breast cancer diagnosis was 45.28 ± 10.27 years in mothers and 39.80 ± 7.79 years in daughters (p = 0.026). The difference of age at ovarian cancer diagnosis in mother-daughter pairs was 8.62 ± 12.76 years (p = 0.032). When considering the group of women including mothers and daughters taken together, no significant difference of age at breast cancer diagnosis was found between women affected before 1980 and those affected after 1980 (p = 0.577). However, the age at death increased in these women after 1980 (p = 0.026). Comparison of age at breast cancer diagnosis in mothers and daughters separately, showed that daughters were affected at an earlier age after 1980 (p = 0.002). Daughters had a poor prognosis and died earlier than mothers after 1980. Our results may have reflected genetic anticipation in c.3481_3491del11 mutation breast and ovarian cancer families. In order to confirm our findings, a larger cohort would provide more precision to the difference of ages at breast or ovarian cancer diagnosis between mothers and daughters and more powerful statistical analyses. Increased aggression in daughters' tumors compared to those of mothers could be also considered as a parameter of genetic anticipation. Complete information on tumor profile and proliferation would allow us to study genetic anticipation by comparing the tumor phenotypes between mothers and daughters in the future.

Spastic paraplegia type 31: A novel REEP1 splice site donor variant and expansion of the phenotype variability.

Mutations in REEP1 have been identified in three types of neurological disorders, autosomal dominant form of Hereditary Spastic Paraplegia type 31 (SPG31), autosomal dominant distal hereditary motor neuronopathy type VB (HMN5B), and autosomal recessive form of congenital axonal neuropathy and diaphragmatic palsy. Previous studies demonstrated different molecular pathogenesis in SPG31, including loss-of-function, gain-of-function and haploinsufficiency. A four-generation family from Japan, including 12 members, was investigated clinically and genetically. Seven affected members displayed pure spastic paraplegia. Impression of genetic anticipation was observed in the family, including tendency of earlier age-at-onset and increasing severity in subsequent generations. Genetic analysis revealed a heterozygous intronic variant, c.303+2T > A, in REEP1, which segregated with disease, and was also identified in one unaffected member. The variant causes exon 4 skipping leading to frame shift and a truncated transcript identified by complementary DNA sequencing of reverse transcription polymerase chain reaction products. Measurement of REEP1 transcripts in lymphocytes demonstrated a reduction through nonsense mediated mRNA decay (NMD). Our study demonstrated further evidence of allelic heterogeneity in SPG31, mutant REEP1 mRNA dosage effects through NMD and intra-familial phenotype variability.

mtDNA copy number associated with age of onset in familial amyloid polyneuropathy.

BACKGROUND: Transthyretin-related familial amyloid polyneuropathy (TTR-FAP Val30Met) shows a wide variation in age-at-onset (AO) between generations and genders, as in Portuguese families, where women display a later onset and a larger anticipation (>10 years). Mitochondrial DNA (mtDNA) copy number was assessed to clarify whether it has a modifier effect on AO variability in Portuguese patients. METHODS: The mtDNA copy number of 262 samples (175 Val30Met TTR carriers and 87 controls (proven Val30Val)) was quantified by quantitative real-time PCR. Statistical analysis was performed using IBM SPSS V.23 software. RESULTS: This study shows that Val30Met TTR carriers have a significantly higher (p<0.001) mean mtDNA copy number than controls. Furthermore, the highest mtDNA copy number mean was observed in early-onset patients (AO <40 years). Importantly, early-onset offspring showed a significant increase (p=0.002) in the mtDNA copy number, when compared with their late AO parents. CONCLUSIONS: The present findings suggest, for the first time, that mtDNA copy number may be associated with earlier events and may therefore be further explored as a potential biomarker for follow-up of TTR-FAP Val30Met carriers.