Generation of three isogenic gene-edited Huntington's disease human embryonic stem cell lines with DOX-inducible NGN2 expression cassette in the AAVS1 safe locus.

Neurogenin 2 (NGN2), a neuronal transcription factor, can expedite differentiation of stem cells into mature glutamatergic neurons. We have utilized an allelic series of previously published and characterized isogenic Huntington's disease (IsoHD) human embryonic stem cell lines (Ooi et al., 2019), carrying different CAG repeat lengths in the first exon of the huntingtin gene. These IsoHDs were modified using CRISPR/Cas9 to insert NGN2 under the TET-ON doxycycline inducible promoter. The resulting IsoHD-NGN2 cell lines retained pluripotency in the absence of doxycycline (DOX), and via addition of DOX to the culturing media differentiation to neurons was achieved within 14 days.

The significance of mitochondrial haplogroups in preeclampsia risk.

OBJECTIVE: To determine whether mitochondrial haplogroups function as disease-modifiers or as susceptibility factors in preeclampsia using a traditional haplogroup association model. METHODS: This retrospective study haplotyped 235 control and 78 preeclamptic pregnancies from Denmark using either real-time PCR or Sanger sequencing depending on the rarity of the haplogroup. RESULTS: No significant association between haplogroups and the risk of preeclampsia was found, nor was any role for haplogroups in disease severity uncovered. CONCLUSION: Mitochondrial haplogroups are not associated with preeclampsia or the severity of preeclampsia in the Danish population. However, this study cannot exclude a role for less common mtDNA variation. Models that can examine these should be applied in preeclamptic patients.

Progressive Mitochondrial Dysfunction of Striatal Synapses in R6/2 Mouse Model of Huntington's Disease.

BACKGROUND: Huntington's disease (HD) is a neurodegenerative disorder characterized by synaptic dysfunction and loss of white matter volume especially in the striatum of the basal ganglia and to a lesser extent in the cerebral cortex. Studies investigating heterogeneity between synaptic and non-synaptic mitochondria have revealed a pronounced vulnerability of synaptic mitochondria, which may lead to synaptic dysfunction and loss. OBJECTIVE: As mitochondrial dysfunction is a hallmark of HD pathogenesis, we investigated synaptic mitochondrial function from striatum and cortex of the transgenic R6/2 mouse model of HD. METHODS: We assessed mitochondrial volume, ROS production, and antioxidant levels as well as mitochondrial respiration at different pathological stages. RESULTS: Our results reveal that striatal synaptic mitochondria are more severely affected by HD pathology than those of the cortex. Striatal synaptosomes of R6/2 mice displayed a reduction in mitochondrial mass coinciding with increased ROS production and antioxidants levels indicating prolonged oxidative stress. Furthermore, synaptosomal oxygen consumption rates were significantly increased during depolarizing conditions, which was accompanied by a marked increase in mitochondrial proton leak of the striatal synaptosomes, indicating synaptic mitochondrial stress. CONCLUSION: Overall, our study provides new insight into the gradual changes of synaptic mitochondrial function in HD and suggests compensatory mitochondrial actions to maintain energy production in the HD brain, thereby supporting that mitochondrial dysfunction do indeed play a central role in early disease progression of HD.

Nicotinamide Adenine Dinucleotide Phosphate Oxidases Are Everywhere in Brain Disease, but Not in Huntington's Disease?

Huntington's disease (HD) is an inherited neurodegenerative disorder characterized by neuronal loss and tissue atrophy mainly in the striatum and cortex. In the early stages of the disease, impairment of neuronal function, synaptic dysfunction and white matter loss precedes neuronal death itself. Relative to other neurodegenerative diseases such as Alzheimer's and Parkinson's disease and Amyotrophic Lateral Sclerosis, where the effects of either microglia or NADPH oxidases (NOXs) are recognized as important contributors to disease pathogenesis and progression, there is a pronounced lack of information in HD. This information void contrasts with evidence from human HD patients where blood monocytes and microglia are activated well before HD clinical symptoms (PET scans), and the clear signs of oxidative stress and inflammation in post mortem HD brain. Habitually, NOX activity and oxidative stress in the central nervous system (CNS) are equated with microglia, but research of the last two decades has carved out important roles for NOX enzyme function in neurons. Here, we will convey recent information about the function of NOX enzymes in neurons, and contemplate on putative roles of neuronal NOX in HD. We will focus on NOX-produced reactive oxygen species (ROS) as redox signaling molecules in/among neurons, and the specific roles of NOXs in important processes such as neurogenesis and lineage specification, neurite outgrowth and growth cone dynamics, and synaptic plasticity where NMDAR-dependent signaling, and long-term depression/potentiation are redox-regulated phenomena. HD animal models and induced pluripotent stem cell (iPSC) studies have made it clear that the very same physiological processes are also affected in HD, and we will speculate on possible roles for NOX in the pathogenesis and development of disease. Finally, we also take into account the limited information on microglia in HD and relate this to any contribution of NOX enzymes.

Paroxysmal Cranial Dyskinesia and Nail-Patella Syndrome Caused by a Novel Variant in the LMX1B Gene.

BACKGROUND: In a Danish family, multiple individuals in five generations present with early-onset paroxysmal cranial dyskinesia, musculoskeletal abnormalities, and kidney dysfunction. OBJECTIVE: To demonstrate linkage and to identify the underlying genetic cause of disease. METHODS: Genome-wide single-nucleotide polymorphisms analysis, Sequence-Tagged-Site marker analyses, exome sequencing, and Sanger sequencing were performed. RESULTS: Linkage analyses identified a candidate locus on chromosome 9. Exome sequencing revealed a novel variant in LMX1B present in all affected individuals, logarithm of the odds (LOD) score of z = 6.54, predicted to be damaging. Nail-patella syndrome (NPS) is caused by pathogenic variants in LMX1B encoding a transcription factor essential to cytoskeletal and kidney growth and dopaminergic and serotonergic network development. NPS is characterized by abnormal musculoskeletal features and kidney dysfunction. Movement disorders have not previously been associated with NPS. CONCLUSIONS: Paroxysmal dyskinesia is a heretofore unrecognized feature of the NPS spectrum. The pathogenic mechanism might relate to aberrant dopaminergic circuits. © 2020 International Parkinson and Movement Disorder Society.

Compromised IGF signaling causes caspase-6 activation in Huntington disease.

Huntington disease (HD) is an autosomal dominant neurodegenerative disorder caused by an expansion of a polyglutamine repeat in the huntingtin (HTT) protein. Aberrant activation of caspase-6 and cleavage of mutant HTT generating the toxic N-terminal 586 HTT fragment are important steps in the pathogenesis of HD. Similarly, alterations in the insulin-like growth factor 1 (IGF-1) signaling pathway have been implicated in the disease as a result of decreased plasma IGF-1 levels in HD patients. In addition, two recent studies have demonstrated therapeutic benefit of IGF-1 treatment in mouse models of HD. Since IGF-1 promotes pro-survival pathways, we examined the relationship between IGF-1 signaling and aberrant caspase-6 activation in HD. Using immortalized mouse striatal cells expressing wild-type (STHdhQ7) or mutant HTT (STHdhQ111), we show that reduced levels of IGF-1 are associated with enhanced activation of caspase-6, increased cell death, and mutant HTT cleavage in a cellular stress paradigm. We demonstrate that IGF-1 supplementation reverses these effects and lowers the level of the toxic 586 HTT fragment. In addition, transcriptional analysis in the R6/2 HD transgenic mouse model demonstrated that the IGF-1 signaling system is dysregulated at multiple levels in several tissues including liver, muscle, and brain. Among these changes, we found increased expression of IGF-1 binding protein 3 (IGFBP-3), which may further reduce the bioavailability of IGF-1 as a consequence of increased IGF-1 binding. Our findings thus suggest that the therapeutic benefit of IGF-1 supplementation in HD may be significantly improved if other defects in the IGF-1 signaling pathway are corrected concurrently.

Serotonin transporter gene (SLC6A4) variation and sensory processing sensitivity-Comparison with other anxiety-related temperamental dimensions.

BACKGROUND: The short (s) allele of the 5-HTTLPR polymorphism in the promoter region of the human serotonin transporter (5-HTT) gene SLC6A4 has previously been associated with anxiety-related personality dimensions. However, this relationship has not been confirmed in all studies and may be modified by environmental circumstances and/or psychiatric illness. This study examined whether the temperamental trait sensory processing sensitivity (SPS), characterized by increased responsivity to environmental stimuli, is related to 5-HTTLPR/rs25531 genotype. METHODS: 5-HTTLPR and rs25531 genotypes, level of SPS, self-reported Revised NEO Personality Inventory (NEO-PI-R) and Temperament and Character Inventory (TCI) personality profiles, and symptoms of psychological distress (SCL-90R Global Severity Index) were determined for 405 healthy volunteers. RESULTS: Sensory processing sensitivity was highly correlated with the anxiety-related dimensions of the NEO-PI-R and the TCI models of personality, Neuroticism, and Harm Avoidance, respectively. However, the level of SPS was not associated with the combined 5-HTTLPR and rs25531 s'/s' genotype. Neuroticism and Harm Avoidance were also not associated with 5-HTTLPR/rs25531 s'/s' genotype. Correcting for symptoms of psychological distress had no effect on the relationships between personality and genotype. CONCLUSION: The level of SPS was not associated with serotonin transporter gene variation. Further, combined 5-HTTLPR and rs25531 genotype was not associated with other anxiety-related dimensions.

Haploinsufficiency of ARHGAP42 is associated with hypertension.

Family studies have established that the heritability of blood pressure is significant and genome-wide association studies (GWAS) have identified numerous susceptibility loci, including one within the non-coding part of Rho GTPase-activating protein 42 gene (ARHGAP42) on chromosome 11q22.1. Arhgap42-deficient mice have significantly elevated blood pressure, but the phenotypic effects of human variants in the coding part of the gene are unknown. In a Danish cohort of carriers with apparently balanced chromosomal rearrangements, we identified a family where a reciprocal translocation t(11;18)(q22.1;q12.2) segregated with hypertension and obesity. Clinical re-examination revealed that four carriers (age 50-77 years) have had hypertension for several years along with an increased body mass index (34-43 kg/m2). A younger carrier (age 23 years) had normal blood pressure and body mass index. Mapping of the chromosomal breakpoints with mate-pair and Sanger sequencing revealed truncation of ARHGAP42. A decreased expression level of ARHGAP42 mRNA in the blood was found in the translocation carriers relative to controls and allele-specific expression analysis showed monoallelic expression in the translocation carriers, confirming that the truncated allele of ARHGAP42 was not expressed. These findings support that haploinsufficiency of ARHGAP42 leads to an age-dependent hypertension. The other breakpoint truncated a regulatory domain of the CUGBP Elav-like family member 4 (CELF4) gene on chromosome 18q12.2 that harbours several GWAS signals for obesity. We thereby provide additional support for an obesity locus in the CELF4 domain.

Enhanced cerebral branched-chain amino acid metabolism in R6/2 mouse model of Huntington's disease.

Huntington's disease (HD) is a hereditary and fatal disease causing profound neurodegeneration. Deficits in cerebral energy and neurotransmitter metabolism have been suggested to play a central role in the neuronal dysfunction and death associated with HD. The branched-chain amino acids (BCAAs), leucine, isoleucine and valine, are important for cerebral nitrogen homeostasis, neurotransmitter recycling and can be utilized as energy substrates in the tricarboxylic acid (TCA) cycle. Reduced levels of BCAAs in HD have been validated by several reports. However, it is still unknown how cerebral BCAA metabolism is regulated in HD. Here we investigate the metabolism of leucine and isoleucine in the R6/2 mouse model of HD. Acutely isolated cerebral cortical and striatal slices of control and R6/2 mice were incubated in media containing 15N- or 13C-labeled leucine or isoleucine and slice extracts were analyzed by gas chromatography-mass spectrometry (GC-MS) to determine isotopic enrichment of derived metabolites. Elevated BCAA transamination was found from incubations with [15N]leucine and [15N]isoleucine, in both cerebral cortical and striatal slices of R6/2 mice compared to controls. Metabolism of [U-13C]leucine and [U-13C]isoleucine, entering oxidative metabolism as acetyl CoA, was maintained in R6/2 mice. However, metabolism of [U-13C]isoleucine, entering the TCA cycle as succinyl CoA, was elevated in both cerebral cortical and striatal slices of R6/2 mice, suggesting enhanced metabolic flux via this anaplerotic pathway. To support the metabolic studies, expression of enzymes in the BCAA metabolic pathway was assessed from a proteomic resource. Several enzymes related to BCAA metabolism were found to exhibit augmented expression in the R6/2 brain, particularly related to isoleucine metabolism, suggesting an increase in the BCAA metabolic machinery. Our results show that the capacity for cerebral BCAA metabolism, predominantly of isoleucine, is amplified in the R6/2 brain and indicates that perturbations in cerebral BCAA homeostasis could have functional consequences for HD pathology.

Functional Differences between Synaptic Mitochondria from the Striatum and the Cerebral Cortex.

Mitochondrial dysfunction has been shown to play a major role in neurodegenerative disorders such as Huntington's disease, Alzheimer's disease and Parkinson's disease. In these and other neurodegenerative disorders, disruption of synaptic connectivity and impaired neuronal signaling are among the early signs. When looking for potential causes of neurodegeneration, specific attention is drawn to the function of synaptic mitochondria, as the energy supply from mitochondria is crucial for normal synaptic function. Mitochondrial heterogeneity between synaptic and non-synaptic mitochondria has been described, but very little is known about possible differences between synaptic mitochondria from different brain regions. The striatum and the cerebral cortex are often affected in neurodegenerative disorders. In this study we therefore used isolated nerve terminals (synaptosomes) from female mice, striatum and cerebral cortex, to investigate differences in synaptic mitochondrial function between these two brain regions. We analyzed mitochondrial mass, citrate synthase activity, general metabolic activity and mitochondrial respiration in resting as well as veratridine-activated synaptosomes using glucose and/or pyruvate as substrate. We found higher mitochondrial oxygen consumption rate in both resting and activated cortical synaptosomes compared to striatal synaptosomes, especially when using pyruvate as a substrate. The higher oxygen consumption rate was not caused by differences in mitochondrial content, but instead corresponded with a higher proton leak in the cortical synaptic mitochondria compared to the striatal synaptic mitochondria. Our results show that the synaptic mitochondria of the striatum and cortex differently regulate respiration both in response to activation and variations in substrate conditions.

Ghrelin-mediated improvements in the metabolic phenotype in the R6/2 mouse model of Huntington's disease.

Huntington's disease (HD) is a heritable neurodegenerative disorder, characterised by metabolic disturbances, along with cognitive and psychiatric impairments. Targeting metabolic HD dysfunction via the maintenance of body weight and fat mass and restoration of peripheral energy metabolism can improve the progression of neurological symptoms. In this respect, we focused on the therapeutic potential of the orexigenic peptide hormone ghrelin, which plays an important role in promoting a positive energy balance. In the present study, we found a significant disruption of circadian metabolic regulation in a R6/2 mouse HD model in the late stage of disease. Daily circadian rhythms of activity, energy expenditure, respiratory exchange ratio and feeding were strongly attenuated in R6/2 mice. During the rest phase, R6/2 mice had a higher total activity, elevated energy expenditure and excessive water consumption compared to control mice. We also found that, in the late stage of disease, R6/2 mice had ghrelin axis deficiency as a result of low circulating ghrelin levels, in addition to down-regulation of the ghrelin receptor and several key signalling molecules in the hypothalamus, as well as a reduced responsiveness to exogenous peripheral ghrelin. We demonstrated that, in pre-symptomatic mice, responsiveness to ghrelin is preserved. Chronic ghrelin treatment efficiently increased lean body mass and decreased the energy expenditure and fat utilisation of R6/2 mice in the early stage of disease. In addition, ghrelin treatment was also effective in the normalisation of drinking behaviour and the rest activity of these mice. Ghrelin treatment could provide a novel therapeutic possibility for delaying disease progression; however, deficiency in ghrelin receptor expression could limit its therapeutic potential in the late stage of disease.

Integrative Characterization of the R6/2 Mouse Model of Huntington's Disease Reveals Dysfunctional Astrocyte Metabolism.

Huntington's disease is a fatal neurodegenerative disease, where dysfunction and loss of striatal and cortical neurons are central to the pathogenesis of the disease. Here, we integrated quantitative studies to investigate the underlying mechanisms behind HD pathology in a systems-wide manner. To this end, we used state-of-the-art mass spectrometry to establish a spatial brain proteome from late-stage R6/2 mice and compared this with wild-type littermates. We observed altered expression of proteins in pathways related to energy metabolism, synapse function, and neurotransmitter homeostasis. To support these findings, metabolic 13C labeling studies confirmed a compromised astrocytic metabolism and regulation of glutamate-GABA-glutamine cycling, resulting in impaired release of glutamine and GABA synthesis. In recent years, increasing attention has been focused on the role of astrocytes in HD, and our data support that therapeutic strategies to improve astrocytic glutamine homeostasis may help ameliorate symptoms in HD.

Perturbations in the p53/miR-34a/SIRT1 pathway in the R6/2 Huntington's disease model.

The three factors, p53, the microRNA-34 family and Sirtuin 1 (SIRT1), interact in a positive feedback loop involved in cell cycle progression, cellular senescence and apoptosis. Each factor in this triad has roles in metabolic regulation, maintenance of mitochondrial function, and regulation of brain-derived neurotrophic factor (BDNF). Thus, this regulatory network holds potential importance for the pathophysiology of Huntington's disease (HD), an inherited neurodegenerative disorder in which both mitochondrial dysfunction and impaired neurotrophic signalling are observed. We investigated expression of the three members of this regulatory triad in the R6/2 HD mouse model. Compared to wild-type littermates, we found decreased levels of miR-34a-5p, increased SIRT1 mRNA and protein levels, and increased levels of p53 protein in brain tissue from R6/2 mice. The upregulation of SIRT1 did not appear to lead to an increased activity of the enzyme, as based on measures of p53 acetylation. In other words, the observed changes did not reflect the known interactions between these factors, indicating a general perturbation of the p53, miR-34a and SIRT1 pathway in HD. This is the first study investigating the entire triad during disease progression in an HD model. Given the importance of these three factors alone and within the triad, our results indicate that outside factors are regulating - or dysregulating - this pathway in HD.

The D313Y variant in the GLA gene - no evidence of a pathogenic role in Fabry disease.

Fabry disease is an X- linked inherited lysosomal storage disease caused by mutations in the GLA gene encoding the lysosomal enzyme alpha-galactosidase A (α-Gal A). The possible pathological significance of the D313Y variant in the GLA gene has not been verified and it may be a Fabry variant. Our aim was to elucidate whether the presence of the D313Y variant influenced the α-Gal A activity or resulted in Fabry symptoms or Fabry organ involvement. In two Danish families the presence of the D313Y variant did not result in reduced α-Gal A activity or clinical Fabry manifestations in males, and the presence in Fabry females did not significantly enhance the phenotype of a known causative mutation in the GLA gene (G271S). Our findings indicate that the D313Y variant is not causative to nor enhancing Fabry disease phenotype. The D313Y variant in the GLA gene was not disease causative in 2 Danish families. Investigating male family members were crucial in excluding the Fabry phenotype, and thus very important for proper genetic counceling of all family members, as well as overdiagnosing a devastating genetic disease.

TMEM106B and ApoE polymorphisms in CHMP2B-mediated frontotemporal dementia (FTD-3).

Single-nucleotide polymorphisms in the TMEM106B gene have been identified as a risk factor in frontotemporal dementia (FTD). The major allele of SNP rs3173615 is a risk factor in sporadic FTD, whereas the minor allele seems protective in GRN- and C9orf72-mediated FTD. The role of apolipoprotein E (ApoE) in FTD is uncertain, though an established risk factor in Alzheimer's disease. In a unique Danish family, inherited FTD is caused by a mutation in the CHMP2B gene located on chromosome 3 (FTD-3). In this family, both risk factors TMEM106B and ApoE were analyzed and correlated to age at onset (AAO) and progression in terms of age at institutionalization (AAI) and age at death (AAD). Although TMEM106B and CHMP2B share cellular function in that both localize to endolysosomes, TMEM106B genotypes appeared to have no influence on the clinical disease course. ApoE ε4 was found to be a protective factor with later AAO and AAI, whereas ε2 seemed to aggravate the disease with earlier AAO and AAD. These results indicate ApoE ε2 as a risk factor in FTD-3 and suggest a protective role of ε4.

Simulation based virtual learning environment in medical genetics counseling: an example of bridging the gap between theory and practice in medical education.

BACKGROUND: Simulation based learning environments are designed to improve the quality of medical education by allowing students to interact with patients, diagnostic laboratory procedures, and patient data in a virtual environment. However, few studies have evaluated whether simulation based learning environments increase students' knowledge, intrinsic motivation, and self-efficacy, and help them generalize from laboratory analyses to clinical practice and health decision-making. METHODS: An entire class of 300 University of Copenhagen first-year undergraduate students, most with a major in medicine, received a 2-h training session in a simulation based learning environment. The main outcomes were pre- to post- changes in knowledge, intrinsic motivation, and self-efficacy, together with post-intervention evaluation of the effect of the simulation on student understanding of everyday clinical practice were demonstrated. RESULTS: Knowledge (Cohen's d = 0.73), intrinsic motivation (d = 0.24), and self-efficacy (d = 0.46) significantly increased from the pre- to post-test. Low knowledge students showed the greatest increases in knowledge (d = 3.35) and self-efficacy (d = 0.61), but a non-significant increase in intrinsic motivation (d = 0.22). The medium and high knowledge students showed significant increases in knowledge (d = 1.45 and 0.36, respectively), motivation (d = 0.22 and 0.31), and self-efficacy (d = 0.36 and 0.52, respectively). Additionally, 90 % of students reported a greater understanding of medical genetics, 82 % thought that medical genetics was more interesting, 93 % indicated that they were more interested and motivated, and had gained confidence by having experienced working on a case story that resembled the real working situation of a doctor, and 78 % indicated that they would feel more confident counseling a patient after the simulation. CONCLUSIONS: The simulation based learning environment increased students' learning, intrinsic motivation, and self-efficacy (although the strength of these effects differed depending on their pre-test knowledge), and increased the perceived relevance of medical educational activities. The results suggest that simulations can help future generations of doctors transfer new understanding of disease mechanisms gained in virtual laboratory settings into everyday clinical practice.

Liver function in Huntington's disease assessed by blood biochemical analyses in a clinical setting.

Huntington's disease (HD) is a dominantly inherited, progressive neurological disorder caused by a CAG repeat elongation in the huntingtin gene. In addition to motor-, psychiatric- and cognitive dysfunction, peripheral disease manifestations in the form of metabolic changes and cellular dysfunction are seen. Blood levels of a wide range of hormones, metabolites and proteins have been analyzed in HD patients, identifying several changes associated with the disease. However, a comprehensive panel of liver function tests (LFT) has not been performed. We investigated a cohort of manifest and premanifest HD gene-expansion carriers and controls, using a clinically applied panel of LFTs. Here, we demonstrate that the level of alkaline phosphatase is increased in manifest HD gene-expansion carriers compared to premanifest HD gene-expansion carriers and correlate with increased disease severity indicated by the Unified Huntington's disease rating scale-Total Functional Capacity Score (UHDRS-TFC). For gamma-glutamyl transferase, elevated levels were more frequent in the manifest groups than in both the HD gene-expansion negative controls and premanifest HD gene-expansion carriers. Finally, the manifest HD gene-expansion carriers displayed moderate increases in total cholesterol and blood glucose relative to the premanifest HD gene-expansion carriers, as well as increased C-reactive protein relative to HD gene-expansion negative controls. Our results show that LFT values are elevated more frequently in manifest compared to premanifest HD gene-expansion carriers and controls. The majority of the manifest HD gene-expansion carriers receive medication, and it is possible that this can influence the liver function tests performed in this study.

Progressive Impairment of Lactate-based Gluconeogenesis in the Huntington's Disease Mouse Model R6/2.

Huntington's disease (HD) is a neurodegenerative illness, where selective neuronal loss in the brain caused by expression of mutant huntingtin protein leads to motor dysfunction and cognitive decline in addition to peripheral metabolic changes. In this study we confirm our previous observation of impairment of lactate-based hepatic gluconeogenesis in the transgenic HD mouse model R6/2 and determine that the defect manifests very early and progresses in severity with disease development, indicating a potential to explore this defect in a biomarker context. Moreover, R6/2 animals displayed lower blood glucose levels during prolonged fasting compared to wild type animals.

A SNP in the HTT promoter alters NF-κB binding and is a bidirectional genetic modifier of Huntington disease.

Cis-regulatory variants that alter gene expression can modify disease expressivity, but none have previously been identified in Huntington disease (HD). Here we provide in vivo evidence in HD patients that cis-regulatory variants in the HTT promoter are bidirectional modifiers of HD age of onset. HTT promoter analysis identified a NF-κB binding site that regulates HTT promoter transcriptional activity. A non-coding SNP, rs13102260:G > A, in this binding site impaired NF-κB binding and reduced HTT transcriptional activity and HTT protein expression. The presence of the rs13102260 minor (A) variant on the HD disease allele was associated with delayed age of onset in familial cases, whereas the presence of the rs13102260 (A) variant on the wild-type HTT allele was associated with earlier age of onset in HD patients in an extreme case-based cohort. Our findings suggest a previously unknown mechanism linking allele-specific effects of rs13102260 on HTT expression to HD age of onset and have implications for HTT silencing treatments that are currently in development.

A clinical classification acknowledging neuropsychiatric and cognitive impairment in Huntington's disease.

BACKGROUND: Involuntary movements, neuropsychiatric symptoms, and cognitive impairment are all part of the symptom triad in Huntington's disease (HD). Despite the fact that neuropsychiatric symptoms and cognitive decline may be early manifestations of HD, the clinical diagnosis is conventionally based on the presence of involuntary movements and a positive genetic test for the HD CAG repeat expansion. After investigating the frequencies of the triad manifestations in a large outpatient clinical cohort of HD gene-expansion carriers, we propose a new clinical classification. METHODS: In this cross-sectional study, 107 gene-expansion carriers from a Danish outpatient clinic were recruited. All participants underwent neurological examination, psychiatric evaluation and neuropsychological testing. Participants were categorised according to motor symptoms, neuropsychiatric symptoms, the use of psychotropic medication, and cognitive impairment. RESULTS: Among the motor manifest HD gene-expansion carriers, 51.8% presented with the full symptom triad, 25.0% were defined as cognitively impaired in addition to motor symptoms, and 14.3% had neuropsychiatric symptoms along with motor symptoms. Only 8.9% had isolated motor symptoms. Among gene-expansion carriers without motor symptoms, 39.2% had neuropsychiatric symptoms, were cognitively impaired, or had a combination of the two. CONCLUSION: This is the first study to report the frequencies of both motor symptoms, cognitive impairment, and neuropsychiatric symptoms in HD gene-expansion carriers in a national outpatient HD clinical cohort. We found that almost 40% of the gene-expansion carriers without motor symptoms had either neuropsychiatric symptoms, cognitive impairment or both, emphasising that these patients are not premanifest in psychiatric and cognitive terms, suggesting that the current clinical classification is neither necessarily suitable nor helpful for this patient group. Some premanifest gene-expansion carriers may have psychiatric and/or cognitive symptoms caused by reactive stress or other pathology than HD. Acknowledging this fact we, however, suggest classifying all HD gene-expansion carriers into three clinical categories: premanifest, non-motor manifest, and motor manifest.