Modification of Huntington's disease by short tandem repeats.

Expansions of glutamine-coding CAG trinucleotide repeats cause a number of neurodegenerative diseases, including Huntington's disease and several of spinocerebellar ataxias. In general, age-at-onset of the polyglutamine diseases is inversely correlated with the size of the respective inherited expanded CAG repeat. Expanded CAG repeats are also somatically unstable in certain tissues, and age-at-onset of Huntington's disease corrected for individual HTT CAG repeat length (i.e. residual age-at-onset), is modified by repeat instability-related DNA maintenance/repair genes as demonstrated by recent genome-wide association studies. Modification of one polyglutamine disease (e.g. Huntington's disease) by the repeat length of another (e.g. ATXN3, CAG expansions in which cause spinocerebellar ataxia 3) has also been hypothesized. Consequently, we determined whether age-at-onset in Huntington's disease is modified by the CAG repeats of other polyglutamine disease genes. We found that the CAG measured repeat sizes of other polyglutamine disease genes that were polymorphic in Huntington's disease participants but did not influence Huntington's disease age-at-onset. Additional analysis focusing specifically on ATXN3 in a larger sample set (n = 1388) confirmed the lack of association between Huntington's disease residual age-at-onset and ATXN3 CAG repeat length. Additionally, neither our Huntington's disease onset modifier genome-wide association studies single nucleotide polymorphism data nor imputed short tandem repeat data supported the involvement of other polyglutamine disease genes in modifying Huntington's disease. By contrast, our genome-wide association studies based on imputed short tandem repeats revealed significant modification signals for other genomic regions. Together, our short tandem repeat genome-wide association studies show that modification of Huntington's disease is associated with short tandem repeats that do not involve other polyglutamine disease-causing genes, refining the landscape of Huntington's disease modification and highlighting the importance of rigorous data analysis, especially in genetic studies testing candidate modifiers.

Disclosure of genetic risk to family members: A qualitative study on healthcare professionals' perceived roles and responsibilities.

This paper presents the perspectives of healthcare professionals regarding their roles and responsibilities in supporting patients with the disclosure of genetic risk to their families. The study involved eight focus groups and two individual interviews with 34 healthcare professionals working in medical genetics services across Portugal. The data were analyzed thematically, resulting in three primary themes: i) informing patients about the risk to relatives; ii) ensuring patient confidentiality; and iii) encouraging family communication. Participants believed it is their responsibility to inform patients about the genetic risk to their relatives, with patients bearing a moral responsibility to convey this information. They explained that the principles of medical confidentiality of the patient take precedence over any direct responsibility to patients' relatives. Treating personal and familial genetic information separately was perceived as challenging to implement and potentially problematic. While most participants reported encouraging patients to inform their relatives, the extent to which they facilitate this communication varies and is also constrained by lack of resources and concerns about complying with legal requirements. Some participants called for clearer national guidelines. These results contribute for ongoing discussions regarding the scope of practice and the roles and responsibilities of healthcare professionals in appropriately cascading pertinent information to at-risk relatives.

Machado-Joseph disease in a Sudanese family links East Africa to Portuguese families and allows reestimation of ancestral age of the Machado lineage.

Machado-Joseph disease (MJD/SCA3) is the most frequent dominant ataxia worldwide. It is caused by a (CAG)n expansion. MJD has two major ancestral backgrounds: the Machado lineage, found mainly in Portuguese families; and the Joseph lineage, present in all five continents, probably originating in Asia. MJD has been described in a few African and African-American families, but here we report the first diagnosed in Sudan to our knowledge. The proband presented with gait ataxia at age 24; followed by muscle cramps and spasticity, and dysarthria, by age 26; he was wheel-chair bound at 29 years of age. His brother had gait problems from age 20 years and, by age 21, lost the ability to run, showed dysarthria and muscle cramps. To assess the mutational origin of this family, we genotyped 30 SNPs and 7 STRs flanking the ATXN3_CAG repeat in three siblings and the non-transmitting father. We compared the MJD haplotype segregating in the family with our cohort of MJD families from diverse populations. Unlike all other known families of African origin, the Machado lineage was observed in Sudan, being shared with 86 Portuguese, 2 Spanish and 2 North-American families. The STR-based haplotype of Sudanese patients, however, was distinct, being four steps (2 STR mutations and 2 recombinations) away from the founder haplotype shared by 47 families, all of Portuguese extraction. Based on the phylogenetic network constructed with all MJD families of the Machado lineage, we estimated a common ancestry at 3211 ± 693 years ago.

Pseudodominance in Friedreich Ataxia-Impact of High Prevalence of Carriers and Intrafamilial Clinical Variation.

Background: Friedreich ataxia (FA) is the most common form of autosomal recessive (AR) ataxia. It is a rare disease, but carriers are frequent (1/100). Pseudodominance in FA has seldomly been reported; it may pose additional challenges for diagnosis. Cases: A family with two consecutive generations affected by FA is described. The proband and two younger siblings had typical FA, characterized by infantile-onset ataxia, hyporeflexia, Babinski sign, cardiomyopathy, and loss of ambulation in the second decade of life. Another female sibling had delayed-onset (>25 years old), with mild cerebellar and sensitive ataxia since her mid-30s. Their father presented very late-onset FA (>40 years old), with sensitive axonal neuropathy. All five patients had biallelic (GAA)n expansion in FXN. The first three had larger expansions (>800 repeats), while the latter two had one shorter expanded allele (~90 repeats). Literature Review: Pseudodominant inheritance has been described in 13 neurological disorders. Seven are movement disorders, of which three were associated with high frequency of carriers (FA, Wilson's disease and PRKN-related parkinsonism). Conclusions: Clinicians should be aware of the possibility of pseudodominance when facing an apparent autosomal dominant pedigree, particularly in disorders with high frequency of carriers and variable expression. Otherwise, genetic diagnoses may be delayed.

Short Communication: Restrictions in care following the COVID-19 pandemic severely impacted Machado-Joseph disease patients: a study in the Azores Islands, Portugal.

This qualitative study describes how the restrictions imposed by the COVID-19 pandemic impacted on Machado-Joseph disease (MJD) patients and their care, in the island of São Miguel (the Azores, Portugal). In-person semi-structured interviews were conducted with 11 participants, including patients, family members, healthcare professionals, and care providers. Main findings highlighted the key role played by the local association in psychosocial and healthcare for MJD patients and families, and the adverse effects on their care following the onset of the COVID-19 pandemic. In particular, hindered access to the day-care centre increased isolation and had a negative impact on mental health and disease progression. For persons with a progressive and severe neurological disease, there is no "back to normal." Future restrictive measures ensuing need to be accompanied by a careful definition of daily care routines for patients.

Short Communication: Restrictions in care following the COVID-19 pandemic severely impacted Machado-Joseph disease patients: a study in the Azores Islands, Portugal.

This qualitative study describes how the restrictions imposed by the COVID-19 pandemic impacted on Machado-Joseph disease (MJD) patients and their care, in the island of São Miguel (the Azores, Portugal). In-person semi-structured interviews were conducted with 11 participants, including patients, family members, healthcare professionals, and care providers. Main findings highlighted the key role played by the local association in psychosocial and healthcare for MJD patients and families, and the adverse effects on their care following the onset of the COVID-19 pandemic. In particular, hindered access to the day-care centre increased isolation and had a negative impact on mental health and disease progression. For persons with a progressive and severe neurological disease, there is no "back to normal." Future restrictive measures ensuing need to be accompanied by a careful definition of daily care routines for patients.

From older to younger generations: Intergenerational transmission of health-related roles in families with Huntington's disease.

BACKGROUND AND OBJECTIVES: Older generations play relevant roles in the well-being of younger generations, namely by influencing their health management. Literature regarding the influence in families affected by highly incapacitating hereditary diseases, such as Huntington's disease (HD), however, is scarce. This study addresses the intergenerational flow of health-related roles, from older to younger generations in families with HD, that is, who plays what roles towards whom while considering age, gender, kinship and genetic status in both generations. RESEARCH DESIGN AND METHODS: This qualitative exploratory study adopted the critical incidents technique, applied through semi-structured interviews. Ten participants reported 189 critical incidents. Thematic analysis was applied to transcript data from the interviews to glean common themes. RESULTS: The main findings suggested two main roles performed by older generations: "shaping awareness" and "influencing management". The intergenerational flow involved mainly women, in contiguous generations (usually mother-to-daughter); it was more frequent from either older non-biological or affected relatives aged ≥60 years towards younger members aged 20-29 years, who were still at-risk or non-carriers. DISCUSSION AND IMPLICATIONS: Older generations are relevant influencers in the health management of their younger relatives and they create illness-related legacies. The results are relevant for healthcare services and professionals, as they bring further insight into how older relatives may be involved in genetic counselling, as well as insight into the provision of psychological support to affected families.

Molecular Characterization of Portuguese Patients with Hereditary Cerebellar Ataxia.

Hereditary cerebellar ataxia (HCA) comprises a clinical and genetic heterogeneous group of neurodegenerative disorders characterized by incoordination of movement, speech, and unsteady gait. In this study, we performed whole-exome sequencing (WES) in 19 families with HCA and presumed autosomal recessive (AR) inheritance, to identify the causal genes. A phenotypic classification was performed, considering the main clinical syndromes: spastic ataxia, ataxia and neuropathy, ataxia and oculomotor apraxia (AOA), ataxia and dystonia, and ataxia with cognitive impairment. The most frequent causal genes were associated with spastic ataxia (SACS and KIF1C) and with ataxia and neuropathy or AOA (PNKP). We also identified three families with autosomal dominant (AD) forms arising from de novo variants in KIF1A, CACNA1A, or ATP1A3, reinforcing the importance of differential diagnosis (AR vs. AD forms) in families with only one affected member. Moreover, 10 novel causal-variants were identified, and the detrimental effect of two splice-site variants confirmed through functional assays. Finally, by reviewing the molecular mechanisms, we speculated that regulation of cytoskeleton function might be impaired in spastic ataxia, whereas DNA repair is clearly associated with AOA. In conclusion, our study provided a genetic diagnosis for HCA families and proposed common molecular pathways underlying cerebellar neurodegeneration.

Novel Machado-Joseph disease-modifying genes and pathways identified by whole-exome sequencing.

Machado-Joseph disease (MJD/SCA3) is a neurodegenerative polyglutamine disorder exhibiting a wide spectrum of phenotypes. The abnormal size of the (CAG)n at ATXN3 explains ~55% of the age at onset variance, suggesting the involvement of other factors, namely genetic modifiers, whose identification remains limited. Our aim was to find novel genetic modifiers, analyse their epistatic effects and identify disease-modifying pathways contributing to MJD variable expressivity. We performed whole-exome sequencing in a discovery sample of four age at onset concordant and four discordant first-degree relative pairs of Azorean patients, to identify candidate variants which genotypes differed for each discordant pair but were shared in each concordant pair. Variants identified by this approach were then tested in an independent multi-origin cohort of 282 MJD patients. Whole-exome sequencing identified 233 candidate variants, from which 82 variants in 53 genes were prioritized for downstream analysis. Eighteen disease-modifying pathways were identified; two of the most enriched pathways were relevant for the nervous system, namely the neuregulin signaling and the agrin interactions at neuromuscular junction. Variants at PARD3, NFKB1, CHD5, ACTG1, CFAP57, DLGAP2, ITGB1, DIDO1 and CERS4 modulate age at onset in MJD, with those identified in CFAP57, ACTG1 and DIDO1 showing consistent effects across cohorts of different geographical origins. Network analyses of the nine novel MJD modifiers highlighted several important molecular interactions, including genes/proteins previously related with MJD pathogenesis, namely between ACTG1/APOE and VCP/ITGB1. We describe novel pathways, modifiers, and their interaction partners, providing a broad molecular portrait of age at onset modulation to be further exploited as new disease-modifying targets for MJD and related diseases.

A new scale informed by the Reciprocal-Engagement Model for quality evaluation of genetic counselling by patients: Development and initial validation.

Monitoring the quality of genetic counselling is essential to ensure appropriate provision. This study describes the development and initial psychometric validation of a novel scale for genetic counselling quality evaluation by patients. A deductive approach was taken to formulate scale items. Exploratory factor analysis with the principal axis factoring method was used to assess the scale's factor structure (n = 118). Internal consistency (Cronbach's Alpha) was also examined. Exploratory factor analysis resulted in a single overarching construct consisting of seven factors, which account for 59% of the variance explained. Items showed, in general, strong factor loadings (>0.5). Some items focused on patient satisfaction with services provision did not load onto the factors. Thus, another factor analysis was performed with these items, which resulted in one-factor. The identified factor accounted for 57% of variance explained, and communalities were strong (≥0.5) for most items. Cronbach's alpha score for the scale was 0.85, indicating high internal consistency. Factors were significantly and moderately interrelated (from r = 0.31 to r = 0.71). Further studies are needed to establish the psychometric validity of the scale.

Novel KMT2B mutation causes cerebellar ataxia: Expanding the clinical phenotype.

Hereditary cerebellar ataxias comprise a heterogeneous group of neurodegenerative disorders affecting the cerebellum and/or cerebellar pathways. Next-generation sequencing techniques have contributed substantially to the expansion of ataxia-causing genes, including genes classically described in alternative phenotypes. Herein, we describe a patient with adult-onset cerebellar ataxia, minor dystonia, neuropathy, seizure and ophthalmological pathology, who bears a novel variant in KMT2B (NM_014727.2:c.3334 + 1G > A). Bioinformatic analysis suggested this variant completely abolished the splice-site at exon 8/intron 8, which was confirmed through analysis of mRNA extracted from fibroblasts. Exon 8 skipping would ultimately translate as an in-frame deletion at the protein level, corresponding to the loss of 91 aminoacids [p.(Gly1020_Asn1111del)]. So far, KMT2B disease causing variants have been described in patients with dystonia or neurodevelopmental delay, with no reports of a cerebellar predominant phenotype. Our findings highlight the possible role of KMT2B as a gene involved in hereditary cerebellar ataxias.

Rare occurrence of severe blindness and deafness in Friedreich ataxia: a case report.

BACKGROUND: Friedreich ataxia is the most frequent hereditary ataxia worldwide. Subclinical visual and auditory involvement has been recognized in these patients, with co-occurrence of severe blindness and deafness being rare. CASE REPORT: We describe a patient, homozygous for a 873 GAA expansion in the FXN gene, whose first symptoms appeared by the age of 8. At 22 years-old he developed sensorineural deafness, and at 26 visual impairment. Deafness had a progressive course over 11 years, until a stage of extreme severity which hindered communication. Visual acuity had a catastrophic deterioration, with blindness 3 years after visual impairment was first noticed. Audiograms documented progressive sensorineural deafness, most striking for low frequencies. Visual evoked potentials disclosed bilaterally increased P100 latency. He passed away at the age of 41 years old, at a stage of extreme disability, blind and deaf, in addition to the complete phenotype of a patient with Friedreich ataxia of more than 30 years duration. DISCUSSION: Severe vision loss and extreme deafness has been described in very few patients with Friedreich ataxia. Long duration, severe disease and large expanded alleles may account for such an extreme phenotype; nonetheless, the role of factors as modifying genes warrants further investigation in this subset of patients.

A genetic interaction of NRXN2 with GABRE, SYT1 and CASK in migraine patients: a case-control study.

BACKGROUND: Migraine is a multifactorial disorder that is more frequent (two to four times) in women than in men. In recent years, our research group has focused on the role of neurotransmitter release and its regulation. Neurexin (NRXN2) is one of the components of the synaptic vesicle machinery, responsible for connecting intracellular fusion proteins and synaptic vesicles. Our aim was to continue exploring the role and interaction of proteins involved in the control and promotion of neurotransmission in migraine susceptibility. METHODS: A case-control study was performed comprising 183 migraineurs (148 females and 35 males) and 265 migraine-free controls (202 females and 63 males). Tagging single nucleotide polymorphisms of NRXN2 were genotyped to assess the association between NRXN2 and migraine susceptibility. The χ2 test was used to compare allele frequencies in cases and controls and odds ratios were estimated with 95% confidence intervals. Haplotype frequencies were compared between groups. Gene-gene interactions were analysed using the Multifactor Dimensionality Reduction v2.0. RESULTS: We found a statistically significant interaction model (p = 0.009) in the female group between the genotypes CG of rs477138 (NRXN2) and CT of rs1158605 (GABRE). This interaction was validated by logistic regression, showing a significant risk effect [OR = 4.78 (95%CI: 1.76-12.97)] after a Bonferroni correction. Our data also supports a statistically significant interaction model (p = 0.011) in the female group between the GG of rs477138 in NRXN2 and, the rs2244325's GG genotype and rs2998250's CC genotype of CASK. This interaction was also validated by logistic regression, with a protective effect [OR = 0.08 (95%CI: 0.01-0.75)]. A weak interaction model was found between NRXN2-SYT1. We have not found any statistically significant allelic or haplotypic associations between NRXN2 and migraine susceptibility. CONCLUSIONS: This study unravels, for the first time, the gene-gene interactions between NRXN2, GABRE - a GABAA-receptor - and CASK, importantly it shows the synergetic effect between those genes and its relation with migraine susceptibility. These gene interactions, which may be a part of a larger network, can potentially help us in better understanding migraine aetiology and in development of new therapeutic approaches.

Between responsibility and desire: Accounts of reproductive decisions from those at risk for or affected by late-onset neurological diseases.

This paper explores ways in which genetic risk foregrounds forms of responsibility while dealing with reproduction. We analyzed individual and family semi-structured interviews (n = 35) with people at-risk for or affected by transthyretin-related familial amyloid polyneuropathy (TTR-FAP) and Machado-Joseph disease (MJD), which are late-onset neurological diseases. Although generally considered as rare diseases, some areas in Portugal present the world's highest frequency for MJD and TTR-FAP. Thematic analysis of the data revealed that participants drew on various - sometimes ambivalent and competing - understandings of their genetic risk and their wish to have children. Some participants perceived the avoidance of genetic risk to be responsible behavior, while, for others, responsibility entailed accepting risks because they prioritized values such as parenthood, family relationships and the value of life, above any question of genetic disease. Some participants shared accounts that were fraught with ambivalence, repentance and guilt, especially when children were born before participants knew of their own or their partner's risk. Participants' accounts also showed they make continued efforts to see themselves as responsible persons and to appear responsible in the eyes of others. We discuss findings in the context of participants' negotiation between genetic risk and their sense of responsibility toward themselves and others; we conclude that "genetic responsibility" is present not only in accounts of those who chose not to have children but also in those who make an informed decision to have at-risk children.

Congenital ataxia due to novel variant in ATP8A2.

Congenital ataxias are a heterogeneous group of disorders characterized by congenital or early-onset ataxia. Here, we describe two siblings with congenital ataxia, who acquired independent gait by age 4 years. After 16 years of follow-up they presented near normal cognition, cerebellar ataxia, mild pyramidal signs, and dystonia. On exome sequencing, a novel homozygous variant (c.1580-18C > G - intron 17) in ATP8A2 was identified. A new acceptor splice site was predicted by bioinformatics tools, and functionally characterized through a minigene assay. Minigene constructs were generated by PCR-amplification of genomic sequences surrounding the variant of interest and cloning into the pCMVdi vector. Altered splicing was evaluated by expressing these constructs in HEK293T cells. The construct with the c.1580-18C > G homozygous variant produced an aberrant transcript, leading to retention of 17 bp of intron 17, by the use of an alternative acceptor splice site, resulting in a premature stop codon by insertion of four amino acids. These results allowed us to establish this as a disease-causing variant and expand ATP8A2-related disorders to include less severe forms of congenital ataxia.