Serum CCL24 as a Biomarker of Fibrotic and Vascular Disease Severity in Systemic Sclerosis

BACKGROUND

Systemic sclerosis (SSc) is a heterogeneous disease, characterized by variable tissue and vascular fibrosis in the context of autoimmune activation. CCL24 (or Eotaxin2) has been shown to promote microangiopathic, proinflammatory, and profibrotic processes in preclinical models of SSc. Here, we study serum CCL24 levels in a real-life cohort of patients with SSc, to determine its distribution across disease features and its value in predicting disease progression and related mortality.

METHODS

Serum CCL24 was assessed in an observational cohort of consecutively enrolled patients with SSc. A high CCL24 cutoff was defined based on its distribution in a matched cohort of healthy controls. Disease progression and mortality were analyzed from the date of serum assessment.

RESULTS

Two-hundred thirteen consecutively enrolled patients with SSc were included in this analysis. Median disease duration was six years (interquartile range 3-14), 28.6% of patients presented with interstitial lung disease (ILD), 46.9% had digital ulcers, and 25.3% showed high CCL24 serum concentration. High-CCL24 patients were more frequently male and positive for anti-scl-70, with a diagnosis of ILD and synovitis (P < 0.05 for all). Notably, high-CCL24 patients had lower diffusion of carbon monoxide and higher prevalence of digital ulcers, telangiectasias, and calcinosis (P < 0.05 for all). In a longitudinal setting, high CCL24 was associated with greater lung function decline and with higher disease-related mortality.

CONCLUSION

Serum CCL24 is a biomarker of disease severity across fibrotic and vascular disease manifestations. These data support the development of therapies targeting CCL24 as a novel comprehensive therapeutic target in SSc.

Power Doppler signal at the enthesis and bone erosions are the most discriminative OMERACT ultrasound lesions for SpA: results from the DEUS (Defining Enthesitis on Ultrasound in Spondyloarthritis) multicentre study

OBJECTIVES

To assess, in spondyloarthritis (SpA), the discriminative value of the Outcome Measures in Rheumatology (OMERACT) ultrasound lesions of enthesitis and their associations with clinical features in this population.

METHODS

In this multicentre study involving 20 rheumatology centres, clinical and ultrasound examinations of the lower limb large entheses were performed in 413 patients with SpA (axial SpA and psoriatic arthritis) and 282 disease controls (osteoarthritis and fibromyalgia). 'Active enthesitis' was defined as (1) power Doppler (PD) at the enthesis grade ≥1 plus entheseal thickening and/or hypoechoic areas, or (2) PD grade >1 (independent of the presence of entheseal thickening and/or hypoechoic areas).

RESULTS

In the univariate analysis, all OMERACT lesions except enthesophytes/calcifications showed a significant association with SpA. PD (OR=8.77, 95% CI 4.40 to 19.20, p<0.001) and bone erosions (OR=4.75, 95% CI 2.43 to 10.10, p<0.001) retained this association in the multivariate analysis. Among the lower limb entheses, only the Achilles tendon was significantly associated with SpA (OR=1.93, 95% CI 1.30 to 2.88, p<0.001) in the multivariate analyses. Active enthesitis showed a significant association with SpA (OR=9.20, 95% CI 4.21 to 23.20, p<0.001), and unlike the individual OMERACT ultrasound lesions it was consistently associated with most clinical measures of SpA disease activity and severity in the regression analyses.

CONCLUSIONS

This large multicentre study assessed the value of different ultrasound findings of enthesitis in SpA, identifying the most discriminative ultrasound lesions and entheseal sites for SpA. Ultrasound could differentiate between SpA-related enthesitis and other forms of entheseal pathology (ie, mechanical enthesitis), thus improving the assessment of entheseal involvement in SpA.

Clinical trajectories of hand function impairment in systemic sclerosis: an unmet clinical need across disease subsets

BACKGROUND

Hand involvement is an early manifestation of systemic sclerosis (SSc), culprit of diagnosis and classification, and recognised major driver of disability. Impairment of hand function burdens both limited and diffuse cutaneous subsets and therefore could be targeted as 'basket' endpoint in SSc. Nevertheless, its natural history in current standard of care is not well characterised, limiting the design of targeted trials. The aim of this study is to describe prevalence, natural history and clinical factors associated with hand function deterioration in a longitudinal, multicentre, observational SSc cohort.

METHODS

Hand function was captured through the validated Cochin Hand Function Scale in patients consecutively enrolled in a multicentre observational study and observed over 24 months. Minimal clinically important differences and patient acceptable symptom state were analysed as previously described.

RESULTS

Three hundred and ninety-six consecutive patients were enrolled from 10 centres; 201 with complete follow-up data were included in the analysis. Median (IQR) disease duration was 5 (2-11) years. One hundred and five (52.2%) patients reported clinically significant worsening. Accordingly, the proportion of patients reporting unacceptable hand function increased over 2 years from 27.8% to 35.8% (p<0.001). Least absolute shrinkage and selection operator analysis identified male gender, disease subset, Raynaud's Condition Score, tenosynovitis and pain, as some of the key factors associated with worsening hand involvement.

CONCLUSIONS

Hand function deteriorates over time in more than 50% of SSc patients despite available therapies. The analysis of factors associated with hand function worsening supports the involvement of both inflammation, vascular and fibrotic processes in hand involvement, making it a hallmark clinical manifestation of SSc. Our data are poised to inform the design of intervention studies to target this major driver of disability in SSc.

The assessment of atlantoaxial joint involvement in patients with rheumatoid arthritis, results from an observational "real-life" study

Atlantoaxial joint is a possible affected site during rheumatoid arthritis (RA) and, in this work, we evaluated its occurrence and associated characteristics in a "real-life" cohort. By a medical records review study of RA patients longitudinally followed-up, the occurrence of severe atlantoaxial joint involvement was estimated (incidence proportion and incidence rate per 1000 person-years at risk). Regression analyses were also exploited to evaluate possible associated factors. Based on these findings, a prospective recruitment was performed to build a descriptive cross-sectional study in evaluating a subclinical atlantoaxial joint involvement in patients with the same clinical characteristics. Retrospectively, 717 patients (female 56.6%, age 64.7 ± 12.3 years) were studied. The incidence proportion of severe atlantoaxial joint involvement was 2.1% [1.5-2.5], occurring in 15 out of 717 patients, and identified by both MRI and CT scan. Considering over 3091 person-years, an incidence rate of 5.2 × 1000 [2.9-8.3] person-years was estimated. Regression analyses suggested that male gender, a longer disease duration, ACPA positivity and extra-articular manifestations resulted to be significantly associated with a severe atlantoaxial joint involvement. Given these findings, 30 asymptomatic patients were selected according to these clinical characteristics and underwent MRI of cervical spine. To date, almost 50% of these asymptomatic patients showed a subclinical atlantoaxial joint involvement. The occurrence of the severe atlantoaxial joint involvement in RA patients was estimated in a "real-life" setting. Male gender, ACPA positivity, long disease duration, and extra-articular manifestations could be associated with the severe atlantoaxial joint involvement in RA. MRI could provide a useful clinical tool to early evaluate the atlantoaxial joint involvement in RA, also in asymptomatic patients.

MRI Digital Artery Volume Index (DAVIX) as a surrogate outcome measure of digital ulcer disease in patients with systemic sclerosis: a prospective cohort study

BACKGROUND

Vascular fibrosis is a key manifestation of systemic sclerosis that leads to the narrowing of small and medium arteries, causing vascular clinical manifestations including digital ulcers and pulmonary arterial hypertension. We investigated the potential of the MRI-based Digital Artery Volume Index (DAVIX) as a surrogate outcome measure of vascular fibrosis by using it to quantify and predict the burden of digital ulcer disease in patients with systemic sclerosis.

METHODS

Two independent cohorts of patients participating in the prospective observational study STRIKE were consecutively enrolled from the Scleroderma Clinic of the Leeds Teaching Hospitals Trust, Leeds, UK. Eligible patients were aged 18 years or older and fulfilled the very early diagnosis of systemic sclerosis (VEDOSS) or the 2013 American College of Rheumatology (ACR)-European Alliance of Associations for Rheumatology (EULAR) systemic sclerosis classification criteria. DAVIX was calculated as the percentage mean of the ratio of digital artery volume to finger volume in the four fingers of the dominant hand. Data were collected at baseline and 12-month follow-up, and the primary outcome was the presence of digital ulcers at 12-month follow-up.

FINDINGS

Between Feb 7, 2018, and April 11, 2022, we included 85 patients in the exploratory cohort and 150 in the validation cohort. In the exploratory cohort, the mean age was 54·5 years (SD 11·6), 75 (88%) of 85 patients were women, ten (12%) were men, and 69 (82%) were White. In the validation cohort, the mean age was 53·5 years (SD 13·8), 136 (91%) of 150 patients were women, 14 (9%) were men, and 127 (85%) were White. In the exploratory cohort, DAVIX was significantly lower in patients with previous or active digital ulcers (0·34% [IQR 0·16-0·69]) than in those without digital ulcer disease (0·65% [0·42-0·88]; p=0·015); this finding was substantiated in the validation cohort (0·43% [0·20-0·73] vs 0·73% [0·53-0·97]; p<0·0001). Patients who developed new digital ulcers during 12-month follow-up had a lower DAVIX (0·23% [0·10-0·66]) than those who did not (0·65% [0·45-0·91]; p=0·0039). DAVIX was negatively correlated with disease duration (r=-0·415; p<0·0001), the ratio of forced vital capacity to the diffusing capacity of the lungs for carbon monoxide (r=-0·334; p=0·0091), nailfold capillaroscopy pattern (r=-0·447; p<0·0001), and baseline modified Rodnan skin score (r=-0·305; p=0·014) and was positively correlated with the diffusing capacity of carbon monoxide (r=0·368; p=0·0041). DAVIX was negatively correlated with change in score on the Scleroderma Health Assessment Questionnaire-Disability Index (r=-0·308; p=0·024), Visual Analogue Scale (VAS) Raynaud's (r=-0·271; p=0·044), and VAS digital ulcers (r=-0·291; p=0·044).

INTERPRETATION

DAVIX is a promising surrogate outcome measure of digital ulcer disease in patients with systemic sclerosis. The ability of DAVIX to non-invasively predict future digital ulcers and worsening of patient-reported outcomes could aid patient enrichment and stratification in clinical trials. Clinically, DAVIX could offer insights into the assessment of vascular activity. The sensitivity of DAVIX to change over time and with treatment will establish its value as an imaging outcome measure of vascular disease.

FUNDING

National Institute for Health Research Biomedical Research Centre and University of Leeds Industry Engagement Accelerator Fund.

The negative impact of pain catastrophising on disease activity: analyses of data derived from patient-reported outcomes in psoriatic arthritis and axial spondyloarthritis

OBJECTIVES

Psychosocial factors are recognised as important determinants of pain experience in patients with inflammatory arthritides. Among them, pain catastrophising, a maladaptive cognitive style, observed in patients with anxiety and depressive disorders, garnered specific attention. Here, we evaluated pain catastrophising (PC) and its related domains (Rumination, Magnification, and Helplessness), in psoriatic arthritis (PsA) and axial spondyloarhtiritis (axSpA) participants, to assess its impact on disease activity. Furthermore, we analysed possible correlations of PC-Scale (PCS) with those psychometric domains which have been already related to catastrophisation in patients with chronic pain. Lastly, we aimed to define the relationship between PCS and the different variables included in the composite indices of disease activity.

METHODS

A multi-centre, cross-sectional, observational study has been conducted on 135 PsA (age 56 (47-64) years, males/females 40.74/59.26%; Disease Activity in Psoriasic Arthritis (DAPSA) 13.34 (5.21-22.22)) and 71 axSpA (age 49 (37-58) years, males/females 56.34/43.66%; Bath Ankylosing Spondylitis Arthritis Activity (BASDAI) 4.17 (2.1-6.3)) participants. Multivariable regressions and correlations were performed to evaluate the relationship between pain catastrophising and both disease activity and patient-reported outcomes.

RESULTS

The adjusted linear regression model showed a positive association between PCS and DAPSA as well as between PCS and BASDAI; PCS negative impacts on the subjective domains of disease activity scores.

CONCLUSIONS

This study suggests the role of PC, independently of inflammation, in disease perception and achievement of remission or low disease activity in chronic arthritides.

Circulating extracellular vesicles in the context of interstitial lung disease related to systemic sclerosis: A scoping literature review

BACKGROUND

Interstitial lung disease (ILD) is a significant cause of disability and mortality in systemic sclerosis (SSc), where lung fibrosis stems from the interaction of cells within the epithelial, endothelial, interstitial, and immune cell compartments. Extracellular vesicles (EVs) are particles released by cells capable of transferring functionally active molecules, playing a crucial role in intercellular communication. This scoping review aims to identify and map existing evidence about the role of EVs as biomarkers or pathophysiological actors in SSc-ILD. It also retrospectively assesses the compliance of published articles with the current reporting guidelines established by the International Society of Extracellular Vesicles (ISEV).

METHODS

This scoping review was conducted based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) checklist. The searches were conducted up until 31 May 2023, with no restrictions on the starting year.

RESULTS

Out of 778 publications identified and screened, 9 references were selected. The eligible studies collectively involved a total of 539 SSc patients, with 220 patients presenting with ILD, as demonstrated by high-resolution computed tomography. The studies largely focused on the quantitative assessment of EVs through flow cytometry, primarily concerning larger EVs. The studies primarily focused on the association of EV features with vascular complications, with fibrotic pulmonary involvement typically explored as a secondary finding. The evaluated patients' clinical characteristics were significantly heterogeneous across the studies as well as the association of EV features with the evidence of ILD but none of them longitudinally investigated the relationships with SSc-ILD prognosis. Adherence of these exploratory studies to ISEV reporting guidelines in terms of EV nomenclature, reporting of pre-analytic variables, and qualitative verification of EV separation products was incomplete.

CONCLUSIONS

The evidence concerning the clinical association of EV features is limited and conflicting. The interpretation of available data is substantially biased due to patient selection tailored for vascular complications, heterogeneity of separation methodology, and a lack of validation procedures.

Cardiometabolic multimorbidity may identify a more severe subset of rheumatoid arthritis, results from a "real-life" study

This "real-life" cross-sectional study has been designed to describe disease features of rheumatoid arthritis (RA) participants affected by cardiometabolic multimorbidity than those without. Our purpose was also the identification of possible associations between these cardiometabolic diseases and RA clinical characteristics. Consecutive RA participants with and without cardiometabolic multimorbidity were assessed and their clinical characteristics were recorded. Participants were grouped and compared by the presence or not of cardiometabolic multimorbidity (defined as ≥ 2 out of 3 cardiovascular risk factors including hypertension, dyslipidemia, and type 2 diabetes). The possible influence of cardiometabolic multimorbidity on RA features of poor prognosis was assessed. The positivity of anti-citrullinated protein antibodies, presence of extra-articular manifestations, lack of clinical remission, and biologic Disease-Modifying anti-Rheumatic Drugs (bDMARDs) failure were considered as RA features of poor prognosis. In the present evaluation, 757 consecutive RA participants were evaluated. Among them, 13.5% showed cardiometabolic multimorbidity. These were older (P < .001) and characterized by a longer disease duration (P = .023). They were more often affected by extra-articular manifestations (P = .029) and frequently displayed smoking habit (P = .003). A lower percentage of these patients was in clinical remission (P = .048), and they showed a more frequent history of bDMARD failure (P < .001). Regression models showed that cardiometabolic multimorbidity was significantly correlated with RA features of disease severity. They were predictors of anti-citrullinated protein antibodies positivity, of extra-articular manifestations, and of lack of clinical remission, in both univariate and multivariate analyses. Cardiometabolic multimorbidity was significantly associated with a history of bDMARD failure. We described disease features of RA participants with cardiometabolic multimorbidity, identifying a possible more difficult to treat subset, which may need a new management approach to achieve the treatment goal.

2-Arachidonoylglycerol Reduces the Production of Interferon-Gamma in T Lymphocytes from Patients with Systemic Lupus Erythematosus

Background: the endocannabinoid 2-arachidonoylglycerol (2-AG) plays a pivotal role in immune cells regulation. The plasma levels of 2-AG are increased in patients with systemic lupus erythematosus (SLE) and correlate with disease activity. Moreover, in plasmacytoid dendritic cells from SLE patients, 2-AG is able to control the production of type 1 interferon (IFN) through CB₂ activation. The aim of this study was to evaluate the potential role of 2-AG on T lymphocytes from SLE patients. Methods: peripheral blood mononuclear cells (PBMCs) from SLE participants and age- and sex-matched healthy donors (HD) were isolated by Ficoll–Hypaque density-gradient centrifugation. The PBMCs were treated with increasing concentrations of 2-AG, and AM251 and AM630 were used to antagonize CB₁ and CB_2, respectively. Flow cytometry was used to assess the expression of CD3, CD4, CD8, CD25, IFN-ɣ, IL-4, and IL-17A. Results: 2-AG (1 μM) decreased IFN-ɣ expression (p = 0.0005) in the Th1 lymphocytes of SLE patients. 2-AG did not modulate the cytokine expression of any other T lymphocyte population from either SLE or HD. Treatment with both 2-AG and AM630 increased the IFN-ɣ expression in Th1 lymphocytes of SLE patients (p = 0.03). Discussion: 2-AG is able to modulate type 2 IFN production from CD4+ T lymphocytes from SLE patients through CB₂ activation.

Cellular and Molecular Diversity in Scleroderma

With the increasing armamentarium of high-throughput tools available at manageable cost, it is attractive and informative to determine the molecular underpinnings of patient heterogeneity in systemic sclerosis (SSc). Given the highly variable clinical outcomes of patients labelled with the same diagnosis, unravelling the cellular and molecular basis of disease heterogeneity will be crucial to predicting disease risk, stratifying management and ultimately informing a patient-centered precision medicine approach. Herein, we summarise the findings of the past several years in the fields of genomics, transcriptomics, and proteomics that contribute to unraveling the cellular and molecular heterogeneity of SSc. Expansion of these findings and their routine integration with quantitative analysis of histopathology and imaging studies into clinical care promise to inform a scientifically driven patient-centred personalized medicine approach to SSc in the near future.

Current Treatment Options for HCC: From Pharmacokinetics to Efficacy and Adverse Events in Liver Cirrhosis

BACKGROUND

Hepatocellular carcinoma (HCC) is among the world's most common cancers. For over ten years, the only medical treatment for it has been the multikinase inhibitor Sorafenib. Currently, however, other first or second-line therapeutic options have also shown efficacy against HCC, such as multikinase inhibitors (Regorafenib, Lenvatinib, and Cabozantinib), a monoclonal antibody against the vascular endothelial growth factor receptor 2 (Ramucirumab), and immune-checkpoint inhibitors (Nivolumab, Pembrolizumab, Ipilimumab).

AIM

The aim of this paper is to review the metabolic pathways of drugs that have been tested for the treatment of HCC and the potential influence of liver failure over those pathways.

METHODS

The Food and Drug Administration (FDA)'s and European Medicines Agency (EMA)'s datasheets, results from clinical trials and observational studies have been reviewed.

RESULTS

This review summarizes the current knowledge regarding targets, metabolic pathways, drug interactions, and adverse events of medical treatments for HCC in cirrhotic patients.

CONCLUSION

The new scenario of systemic HCC therapy includes more active drugs with different metabolic pathways and different liver adverse events. Clinical and pharmacological studies providing more data on the safety of these molecules are urgently needed.

Early and brain region-specific decrease of de novo cholesterol biosynthesis in Huntington's disease: A cross-validation study in Q175 knock-in mice

Cholesterol precursors and cholesterol levels are reduced in brain regions of Huntington's disease (HD) mice. Here we quantified the rate of in vivo de novo cholesterol biosynthesis in the HD brain. Samples from different brain regions and blood of the heterozygous knock-in mouse model carrying 175 CAG repeats (Q175) at different phenotypic stages were processed independently by two research units to quantify cholesterol synthesis rate by ²H₂O labeling and measure the concentrations of lathosterol, cholesterol and its brain-specific cholesterol catabolite 24-hydroxy-cholesterol (24OHC) by isotope dilution mass spectrometry. The daily synthesis rate of cholesterol and the corresponding concentration of lathosterol were significantly reduced in the striatum of heterozygous Q175 mice early in the disease course. We also report that the decrease in lathosterol was inversely correlated with CAG-size at symptomatic stage, as observed in striatal samples from an allelic series of HD mice. There was also a significant correlation between the fractional synthesis rates of total cholesterol and 24OHC in brain of wild-type (WT) and Q175 mice, supporting the evidence that plasma 24OHC may reflect cholesterol synthesis in the adult brain. This comprehensive analysis demonstrates consistent cholesterol biosynthesis defects in HD mouse models and suggests that plasma 24OHC may serve as a biomarker of brain cholesterol metabolism.

Cholesterol-loaded nanoparticles ameliorate synaptic and cognitive function in Huntington's disease mice

Brain cholesterol biosynthesis and cholesterol levels are reduced in mouse models of Huntington's disease (HD), suggesting that locally synthesized, newly formed cholesterol is less available to neurons. This may be detrimental for neuronal function, especially given that locally synthesized cholesterol is implicated in synapse integrity and remodeling. Here, we used biodegradable and biocompatible polymeric nanoparticles (NPs) modified with glycopeptides (g7) and loaded with cholesterol (g7‐NPs‐Chol), which per se is not blood–brain barrier (BBB) permeable, to obtain high‐rate cholesterol delivery into the brain after intraperitoneal injection in HD mice. We report that g7‐NPs, in contrast to unmodified NPs, efficiently crossed the BBB and localized in glial and neuronal cells in different brain regions. We also found that repeated systemic delivery of g7‐NPs‐Chol rescued synaptic and cognitive dysfunction and partially improved global activity in HD mice. These results demonstrate that cholesterol supplementation to the HD brain reverses functional alterations associated with HD and highlight the potential of this new drug‐administration route to the diseased brain.

Frontal cortex BOLD signal changes in premanifest Huntington disease: a possible fMRI biomarker

OBJECTIVE

To identify a possible functional imaging biomarker sensitive to the earliest neural changes in premanifest Huntington disease (preHD), allowing early therapeutic approaches aimed at preventing or delaying clinical onset.

METHODS

Sixteen preHD and 18 healthy participants were submitted to anatomical acquisitions and functional MRI (fMRI) acquisitions during the execution of the exogenous covert orienting of attention task. Due to strong a priori hypothesis, all fMRI correlation analyses were restricted to the following: (1) the frontal oculomotor cortex identified by the means of a prosaccadic task, comprising frontal eye fields and supplementary frontal eye fields; and (2) the data collected during inhibition of return, a phenomenon occurring during the executed task. In preHD, multiple regression analysis was performed between fMRI data and the probability to develop the disease in the next 5 years (p5HD). Moreover, mean blood oxygen level-dependent (BOLD) signal changes in the frontal oculomotor cortex and striatal volumes were linearly correlated with p5HD.

RESULTS

In preHD, multiple regression analysis showed that clusters of activity strongly correlated with p5HD in the right frontal oculomotor cortex. Importantly, mean BOLD signal changes of this region correlated with p5HD (r(2) = 0.52). Among the considered striatal volumes, a modest correlation (r(2) = 0.29) was observed in the right putamen and p5HD.

CONCLUSION

fMRI activations in the right-frontal oculomotor cortex during inhibition of return can be considered a possible functional imaging biomarker in preHD.

Plasma 24S-hydroxycholesterol correlation with markers of Huntington disease progression

24S-hydroxycholesterol (24OHC) is involved in the conversion of excess cholesterol in the brain, and its level in plasma is related to the number of metabolically active neuronal cells. Previous research suggests that plasma 24OHC is substantially reduced in the presence of neurodegenerative disease. Huntington disease (HD) is an inherited autosomal dominant neurodegenerative disorder caused by a cytosine-adenine-guanine (CAG) triplet repeat expansion in the coding region of the huntingtin (HTT) gene. The current study focused on the relative importance of 24OHC as a marker of HD progression. Using mass spectrometry methods, we examined plasma 24OHC levels in three groups of gene-expanded individuals (Low, Medium, High) characterized by their progression at entry into the parent PREDICT-HD study, along with a group of non-gene-expanded controls (total N=150). In addition, the correlation of 24OHC with a number of motor, cognitive, and imagining markers was examined, and effect sizes for group differences among the markers were computed for comparison with 24OHC. Results show a progression gradient as 24OHC levels decreased as the progression group increased (Low to High). The effect size of group differences for 24OHC was larger than all the other variables, except striatal volume. 24OHC was significantly correlated with many of the other key variables. The results are interpreted in terms of cholesterol synthesis and neuronal degeneration. This study provides evidence that 24OHC is a relatively important marker of HD progression.

The first reported generation of several induced pluripotent stem cell lines from homozygous and heterozygous Huntington's disease patients demonstrates mutation related enhanced lysosomal activity

Neuronal disorders, like Huntington's disease (HD), are difficult to study, due to limited cell accessibility, late onset manifestations, and low availability of material. The establishment of an in vitro model that recapitulates features of the disease may help understanding the cellular and molecular events that trigger disease manifestations. Here, we describe the generation and characterization of a series of induced pluripotent stem (iPS) cells derived from patients with HD, including two rare homozygous genotypes and one heterozygous genotype. We used lentiviral technology to transfer key genes for inducing reprogramming. To confirm pluripotency and differentiation of iPS cells, we used PCR amplification and immunocytochemistry to measure the expression of marker genes in embryoid bodies and neurons. We also analyzed teratomas that formed in iPS cell-injected mice. We found that the length of the pathological CAG repeat did not increase during reprogramming, after long term growth in vitro, and after differentiation into neurons. In addition, we observed no differences between normal and mutant genotypes in reprogramming, growth rate, caspase activation or neuronal differentiation. However, we observed a significant increase in lysosomal activity in HD-iPS cells compared to control iPS cells, both during self-renewal and in iPS-derived neurons. In conclusion, we have established stable HD-iPS cell lines that can be used for investigating disease mechanisms that underlie HD. The CAG stability and lysosomal activity represent novel observations in HD-iPS cells. In the future, these cells may provide the basis for a powerful platform for drug screening and target identification in HD.

Pitfalls in the detection of cholesterol in Huntington's disease models

Background Abnormalities in brain cholesterol homeostasis have been reported in Huntington’s disease (HD), an adult-onset neurodegenerative disorder caused by an expansion in the number of CAG repeats in the huntingtin (HTT) gene. However, the results have been contradictory with respect to whether cholesterol levels increase or decrease in HD models. Biochemical and mass spectrometry methods show reduced levels of cholesterol precursors and cholesterol in HD cells and in the brains of several HD animal models. Abnormal brain cholesterol homeostasis was also inferred from studies in HD patients. In contrast, colorimetric and enzymatic methods indicate cholesterol accumulation in HD cells and tissues. Here we used several methods to investigate cholesterol levels in cultured cells in the presence or absence of mutant HTT protein. Results Colorimetric and enzymatic methods with low sensitivity gave variable results, whereas results from a sensitive analytical method, gas chromatography-mass spectrometry, were more reliable. Sample preparation, high cell density and cell clonality also influenced the detection of intracellular cholesterol. Conclusions Detection of cholesterol in HD samples by colorimetric and enzymatic assays should be supplemented by detection using more sensitive analytical methods. Care must be taken to prepare the sample appropriately. By evaluating lathosterol levels using isotopic dilution mass spectrometry, we confirmed reduced cholesterol biosynthesis in knock-in cells expressing the polyQ mutation in a constitutive or inducible manner. *Correspondence should be addressed to Elena Cattaneo: elena.cattaneo@unimi.it

Population stratification may bias analysis of PGC-1α as a modifier of age at Huntington disease motor onset

Huntington’s disease (HD) is an inherited neurodegenerative disorder characterized by motor, cognitive and behavioral disturbances, caused by the expansion of a CAG trinucleotide repeat in the HD gene. The CAG allele size is the major determinant of age at onset (AO) of motor symptoms, although the remaining variance in AO is highly heritable. The rs7665116 SNP in PPARGC1A, encoding the mitochondrial regulator PGC-1α, has been reported to be a significant modifier of AO in three European HD cohorts, perhaps due to affected cases from Italy. We attempted to replicate these findings in a large collection of (1,727) HD patient DNA samples of European origin. In the entire cohort, rs7665116 showed a significant effect in the dominant model (p value = 0.008) and the additive model (p value = 0.009). However, when examined by origin, cases of Southern European origin had an increased rs7665116 minor allele frequency (MAF), consistent with this being an ancestry-tagging SNP. The Southern European cases, despite similar mean CAG allele size, had a significantly older mean AO (p < 0.001), suggesting population-dependent phenotype stratification. When the generalized estimating equations models were adjusted for ancestry, the effect of the rs7665116 genotype on AO decreased dramatically. Our results do not support rs7665116 as a modifier of AO of motor symptoms, as we found evidence for a dramatic effect of phenotypic (AO) and genotypic (MAF) stratification among European cohorts that was not considered in previously reported association studies. A significantly older AO in Southern Europe may reflect population differences in genetic or environmental factors that warrant further investigation.

Spinocerebellar ataxia type 1

Spinocerebellar ataxia type 1 (SCA1) is one out of nine polyglutamine diseases, a group of late-onset neurodegenerative diseases present only in humans. SCA1, the first autosomal dominant cerebellar ataxia (ADCA) to be genetically characterized, is caused by the expansion of a CAG triplet repeat located in the N-terminal coding region of the disease-causing gene ATX1 located on chromosome 6p23: the mutation results in the production of a mutant protein, dubbed ataxin-1, with a longer-than-normal polyglutamine stretch. The predominant effect of the mutation is thought to be a toxic gain-of-function of the aberrant protein, and longer expansions are associated with earlier onset and more severe disease in subsequent generations. The most common presentation of SCA1 is dominant ataxia 'plus', characterized by cerebellar dysfunctions variably associated with slow saccades, ophthalmoplegia, pyramidal and extrapyramidal features, mild to moderate dementia, amyotrophy, and peripheral neuropathy. Its diagnostic pathological feature is olivopontocerebellar atrophy and degeneration predominantly affects the Purkinje cells and the dentate nuclei of the cerebellum. Pathogenesis is mainly attributed to the toxic effect of mutant ataxin-1, which localizes into the nucleus and, through restricted and aberrant protein-protein interactions, causes putative dysfunctional gene transcription in target cells which leads to late-onset cell dysfunction and death.

Brain-derived neurotrophic factor in patients with Huntington's disease

Reduced Brain-Derived Neurotrophic Factor (BDNF) levels have been described in a number of patho-physiological conditions, most notably, in Huntington's disease (HD), a progressive neurodegenerative disorder. Since BDNF is also produced in blood, we have undertaken the measurement of its peripheral levels in the attempt to identify a possible link with HD prognosis and/or its progression. Here we evaluated BDNF level in 398 blood samples including 138 controls, 56 preHD, and 204 HD subjects. We found that BDNF protein levels were not reliably different between groups, whether measured in plasma (52 controls, 26 preHD, 105 HD) or serum (39 controls, 5 preHD, 29 HD). Our experience, and a re-analysis of the literature highlighted that intra-group variability and methodological aspects affect this measurement, especially in serum. We also assessed BDNF mRNA levels in blood samples from 47 controls, 25 preHD, and 70 HD subjects, and found no differences among the groups. We concluded that levels of BDNF in human blood were not informative (mRNA levels or plasma protein level) nor reliable (serum protein levels) as HD biomarkers. We also wish to warn the scientific community in interpreting the significance of changes measured in BDNF protein levels in serum from patients suffering from different conditions.

Ataxia with oculomotor apraxia type1 (AOA1): novel and recurrent aprataxin mutations, coenzyme Q10 analyses, and clinical findings in Italian patients

Ataxia with oculomotor apraxia type1 (AOA1, MIM 208920) is a rare autosomal recessive disease caused by mutations in the APTX gene. We screened a cohort of 204 patients with cerebellar ataxia and 52 patients with early-onset isolated chorea. APTX gene mutations were found in 13 ataxic patients (6%). Eleven patients were homozygous for the known p.W279X, p.W279R, and p.P206L mutations. Three novel APTX mutations were identified: c.477delC (p.I159fsX171), c.C541T (p.Q181X), and c.C916T (p.R306X). Expression of mutated proteins in lymphocytes from these patients was greatly decreased. No mutations were identified in subjects with isolated chorea. Two heterozygous APTX sequence variants (p.L248M and p.D185E) were found in six families with ataxic phenotype. Analyses of coenzyme Q10 in muscle, fibroblasts, and plasma demonstrated normal levels of coenzyme in five of six mutated subjects. The clinical phenotype was homogeneous, irrespectively of the type and location of the APTX mutation, and it was mainly characterized by early-onset cerebellar signs, sensory neuropathy, cognitive decline, and oculomotor deficits. Three cases had slightly raised alpha-fetoprotein. Our survey describes one of the largest series of AOA1 patients and contributes in defining clinical, molecular, and biochemical characteristics of this rare hereditary neurological condition.

Mutations in the mitochondrial protease gene AFG3L2 cause dominant hereditary ataxia SCA28

Autosomal dominant spinocerebellar ataxias (SCAs) are genetically heterogeneous neurological disorders characterized by cerebellar dysfunction mostly due to Purkinje cell degeneration. Here we show that AFG3L2 mutations cause SCA type 28. Along with paraplegin, which causes recessive spastic paraplegia, AFG3L2 is a component of the conserved m-AAA metalloprotease complex involved in the maintenance of the mitochondrial proteome. We identified heterozygous missense mutations in five unrelated SCA families and found that AFG3L2 is highly and selectively expressed in human cerebellar Purkinje cells. m-AAA-deficient yeast cells expressing human mutated AFG3L2 homocomplex show respiratory deficiency, proteolytic impairment and deficiency of respiratory chain complex IV. Structure homology modeling indicates that the mutations may affect AFG3L2 substrate handling. This work identifies AFG3L2 as a novel cause of dominant neurodegenerative disease and indicates a previously unknown role for this component of the mitochondrial protein quality control machinery in protecting the human cerebellum against neurodegeneration.

Expressed Alu repeats as a novel, reliable tool for normalization of real-time quantitative RT-PCR data

Expressed Alu repeats are a reliable, accurate and universal reference for use in RT-qPCR normalization of human genes

We describe a novel strategy for mRNA normalization in quantitative real-time PCR that is based on expressed Alu repeat amplification as a measure for the mRNA fraction. We show that expressed Alu repeat amplification is a fast, accurate normalization tool that can be successfully used for quantification of selected mRNA in the human transcriptome. This result is particularly important for clinical diagnosis and biomarker validation studies based on mRNA detection in human blood.

Spinocerebellar ataxia type 28: a novel autosomal dominant cerebellar ataxia characterized by slow progression and ophthalmoparesis

We have recently mapped the spinocerebellar ataxia type 28 (SCA28) locus on chromosome 18p11.22 in a four-generation Italian family. The clinical phenotype in affected individuals of this family was characterized by juvenile onset, slowly progressive gait and limb ataxia, dysarthria, hyperreflexia at lower limbs, nystagmus, and ophthalmoparesis. The mean age at onset was 19.5 years, and no evidence of anticipation between generations was observed. The disease locus on chromosome 18p11.22-q11.2 was found to span a region of 7.9 Mb of genomic DNA. Direct sequencing of candidate genes within the critical interval led to the identification of a heterozygous point mutation in one of them. The mutation was located in a highly conserved domain with proposed functional properties in the protein product of the SCA28 gene, and segregated with the disease phenotype in all affected members of this family. Thereafter we have screened 105 patients with autosomal dominant spinocerebellar ataxia who had resulted negative for mutations in known SCA genes. Genetic screening allowed the identification in a second Italian family of a distinct missense mutation located in the very same functional domain of the protein. The affected members of this second family exhibited a neurological phenotype similar to that of the original family. Both mutations, not found in more than 500 chromosomes, are associated with amino acid changes (Glu-->Lys and Ser-->Leu, respectively) in evolutionarily conserved residues of the alleged SCA28 gene. Our data point to a putative pathogenic role of these mutations, and indicate SCA28 as the sixth recognized SCA genotype caused by point mutations.

A majority of Huntington's disease patients may be treatable by individualized allele-specific RNA interference

Use of RNA interference to reduce huntingtin protein (htt) expression in affected brain regions may provide an effective treatment for Huntington disease (HD), but it remains uncertain whether suppression of both wild-type and mutant alleles in a heterozygous patient will provide more benefit than harm. Previous research has shown suppression of just the mutant allele is achievable using siRNA targeted to regions of HD mRNA containing single nucleotide polymorphisms (SNPs). To determine whether more than a minority of patients may be eligible for an allele-specific therapy, we genotyped DNA from 327 unrelated European Caucasian HD patients at 26 SNP sites in the HD gene. Over 86% of the patients were found to be heterozygous for at least one SNP among those tested. Because the sites are genetically linked, one cannot use the heterozygosity rates of the individual SNPs to predict how many sites (and corresponding allele-specific siRNA) would be needed to provide at least one treatment possibility for this percentage of patients. By computing all combinations, we found that a repertoire of allele-specific siRNA corresponding to seven sites can provide at least one allele-specific siRNA treatment option for 85.6% of our sample. Moreover, we provide evidence that allele-specific siRNA targeting these sites are readily identifiable using a high throughput screening method, and that allele-specific siRNA identified using this method indeed show selective suppression of endogenous mutant htt protein in fibroblast cells from HD patients. Therefore, allele-specific siRNA are not so rare as to be impractical to find and use therapeutically.

Analysis of the repressor element-1 silencing transcription factor/neuron-restrictive silencer factor occupancy of non-neuronal genes in peripheral lymphocytes from patients with Huntington's disease

We have previously demonstrated that the transcription of neuronal repressor element-1/neuron-restrictive silencer element (RE1/NRSE)-regulated genes is reduced in the brain of subjects with Huntington's disease (HD) as a result of increased binding of the repressor element-1 silencing transcription factor/neuron-restrictive silencer factor (REST/NRSF) to its RE1/NRSE targets. As specific non-neuronal REST/NRSF-regulated genes have been identified in the human genome, we exploited the possibility that the binding of REST/NRSF to its target RE1/NRSE sites may also be altered in the peripheral tissues of HD patients. Our results show that REST/NRSF occupancy is increased in lymphocytes from HD subjects, thus indicating for the first time that the activity of the RE1/NRSE sites is dysfunctional in vivo. Chromatin immunoprecipitation (ChIP) of the RE1/NRSE sites in lymphocytes may therefore be a reproducible, sensitive and specific means of searching for candidate markers of HD onset and progression.

Plasma 24S-hydroxycholesterol and caudate MRI in pre-manifest and early Huntington's disease

Huntington's disease (HD) is a hereditary neurodegenerative disorder for which biological indicators of disease progression, or disease stage, would be especially important for therapeutic trials. 24S-hydroxycholesterol (24OHC) is a brain-generated cholesterol metabolite which has been associated with neurodegeneration, and alterations of cholesterol metabolism in murine HD models and patients' tissues have been recently identified. On these grounds, and with the aim of identifying putative biomarkers in HD, we studied cholesterol metabolism through the analysis in vivo of plasma 24OHC and cholesterol in two independent cohorts of controls and patients of Italian and British origin. We analysed a total of 62 controls, 96 HD symptomatic patients at different disease stages (stage 1-3), and 33 HD gene-positive pre-manifest subjects [pre-manifest HD (pre-HD)]. Cholesterol and 24OHC plasma levels were comparable in both the British and Italian subjects, and were not influenced by fasting or post-meal status. Cholesterol levels did not show differences between controls, pre-HD subjects and HD patients. In contrast, the plasma levels of 24OHC were significantly higher in controls than in HD patients at all disease stages (P < 0.001). Interestingly, in pre-HD subjects plasma 24OHC concentrations were similar to those of controls, and thus significantly greater than those of HD patients at any disease stage (P < 0.001). As expected, significant differences in caudate volumes between stage 1-2 HD patients and pre-HD subjects, and pre-HD subjects and controls were found. The pre-HD cohort of subjects was heterogeneous as to 24OHC levels, since subjects closer to predicted development of motor signs of disease had lower 24OHC levels than those far from onset. Our data indicate that the brain-generated cholesterol metabolite 24OHC measured in plasma was significantly depleted in HD patients at any disease stage, and it could discriminate pre-manifest subjects from patients with overt motor disease. However, 24OHC levels failed to mark further disease progression in patients with manifest HD. Overall, we demonstrate that 24OHC levels parallel the large decrease in caudate volumes observed in gene-positive subjects from pre-manifest to HD stage 1, thus reflecting a critical phase characterized by neuronal loss. We conclude that that 24OHC levels complement MRI morphometry as a valuable tool to follow neurodegenerative changes in the early stages of Huntington disease.

Progressive dysfunction of the cholesterol biosynthesis pathway in the R6/2 mouse model of Huntington's disease

We have recently reported significantly reduced levels of the mRNA of genes critical for the cholesterol biosynthesis pathway in the brains of mice and patients with Huntington's disease (HD), which are indicative of a biological dysfunction. We here show that the brains of R6/2 transgenic mice have progressively decreasing levels of the cholesterol precursors, lathosterol and lanosterol, and declining 3-hydroxy-3-methylglutaryl coenzyme A reductase activity starting from pre-symptomatic stages. We also show that, despite the progressive reduction of brain cholesterol biosynthesis, steady-state levels of total cholesterol remain constant, thus suggesting that compensatory mechanisms are in operation. These in vivo findings indicate a consistent and progressive reduction in the activity of the cholesterol biosynthesis pathway in HD brain. The defect occurs early in these mice and generates lower levels of newly synthesized cholesterol and its intermediates, which may affect different aspects of the disease.

Cholesterol biosynthesis pathway is disturbed in YAC128 mice and is modulated by huntingtin mutation

Our recent analyses of the cholesterol biosynthetic pathway in Huntington's disease (HD) cells, in the R6/2 huntingtin-fragment mouse model of HD as well as in human tissues have provided the first evidence of altered activity of this pathway in genetically identifiable HD samples. Here we report that these changes also occur in the full-length-huntingtin YAC128 (yeast artificial chromosome) mouse model, which shows a consistent reduction in the activity or levels of multiple components of the cholesterogenic pathway. We also show that this phenotype is progressive and is specific for the brain region most affected in HD. Mice over-expressing the wild-type protein with 18 CAG (YAC18 mice) show the opposite phenotype with higher activity of the cholesterol biosynthetic pathway compared with littermate mice. Finally, we report that plasma levels of cholesterol, its precursors and its brain-derived catabolite 24-S-hydroxycholesterol in YAC mice mirror brain biosynthetic levels supporting further investigation of their potential as peripheral biomarkers in HD.

Severe deficiency of the fatty acid amide hydrolase (FAAH) activity segregates with the Huntington's disease mutation in peripheral lymphocytes

The search for peripheral markers of neurodegenerative diseases aims at identifying molecules that could help in monitoring the effects of future therapeutics in easily accessible cells. Here we focused on the involvement of the endocannabinoid system in Huntington's disease (HD). We assayed peripheral lymphocytes from HD patients and healthy controls, and found that the activity of the fatty acid amide hydrolase (FAAH), the enzyme that degrades the endocannabinoid anandamide (AEA), was dramatically decreased (down to less than 10%) in HD compared to healthy subjects. Concomitantly, the endogenous levels of AEA were approximately 6-fold higher in HD versus healthy lymphocytes, while the other elements of the endocannabinoid system were not affected by HD. Low FAAH activity in HD lymphocytes was not due to down-regulation of protein expression, but rather to blockage of enzyme activity by a cytosolic and irreversible inhibitor. Finally, pre-HD patients showed defective FAAH activity, as did the brain of HD patients compared with healthy controls. Taken together, our data indicate that FAAH activity in lymphocytes mirrors some of the metabolic changes which take place in the brain, it is a measurable non-genetic peripheral marker that segregates with the HD mutation, and it might serve as a target to test chemicals active on the widespread toxic effects of the mutant protein.

The therapeutic potential of neural stem/progenitor cells in murine globoid cell leukodystrophy is conditioned by macrophage/microglia activation

Twitcher (GALC(twi/twi)) is the murine model of globoid cell leukodystrophy (GLD or Krabbe disease), a disease caused by mutations of the lysosomal enzyme galactocerebrosidase (GALC). To verify the therapeutic potential on twitcher of neural stem/progenitor cells (NSPC), we transduced them with a GALC lentiviral vector. Brain injection of NSPC-GALC increased survival of GALC(twi/twi) from 36.1 +/- 4.1 to 52.2 +/- 5.6 days (P < 0.0001). Detection of GALC activity and flow cytometry showed that NSPC-GALC and NSPC expressing the green fluorescent protein were attracted to the posterior area of twitcher brain, where demyelination occurs first. GALC(twi/twi) microglia, also more abundant in posterior regions of the brain, released significant amounts of the cytotoxic cytokine TNF-alpha when matched with NSPC-GALC. Thus, in murine GLD, and possibly in other demyelinating diseases, NSPC are attracted to regions of active demyelination but have limited survival and therapeutic potential if attacked by activated macrophages/microglia.

Dysfunction of the cholesterol biosynthetic pathway in Huntington's disease

The expansion of a polyglutamine tract in the ubiquitously expressed huntingtin protein causes Huntington's disease (HD), a dominantly inherited neurodegenerative disease. We show that the activity of the cholesterol biosynthetic pathway is altered in HD. In particular, the transcription of key genes of the cholesterol biosynthetic pathway is severely affected in vivo in brain tissue from HD mice and in human postmortem striatal and cortical tissue; this molecular dysfunction is biologically relevant because cholesterol biosynthesis is reduced in cultured human HD cells, and total cholesterol mass is significantly decreased in the CNS of HD mice and in brain-derived ST14A cells in which the expression of mutant huntingtin has been turned on. The transcription of the genes of the cholesterol biosynthetic pathway is regulated via the activity of sterol regulatory element-binding proteins (SREBPs), and we found an approximately 50% reduction in the amount of the active nuclear form of SREBP in HD cells and mouse brain tissue. As a consequence, mutant huntingtin reduces the transactivation of an SRE-luciferase construct even under conditions of SREBP overexpression or in the presence of an exogenous N-terminal active form of SREBP. Finally, the addition of exogenous cholesterol to striatal neurons expressing mutant huntingtin prevents their death in a dose-dependent manner. We conclude that the cholesterol biosynthetic pathway is impaired in HD cells, mice, and human subjects, and that the search for HD therapies should also consider cholesterol levels as both a potential target and disease biomarker.

SCA28, a novel form of autosomal dominant cerebellar ataxia on chromosome 18p11.22-q11.2

We describe a four-generation Italian family with a novel form of juvenile-onset, slowly progressive, autosomal dominant cerebellar ataxia. Eleven affected family members have been evaluated. The mean age at onset was 19.5 years with no evidence of anticipation. The first symptoms were invariably unbalanced standing and mild gait incoordination. Gaze-evoked nystagmus was prominent at onset, while patients with longer disease duration developed slow saccades, ophthalmoparesis and, often, ptosis. Deep tendon reflexes in lower limbs were increased in 80% of the cases. Genetic analysis excluded the presence of pathological repeat expansions in spinocerebellar ataxia (SCA) types 1-3, 6-8, 10, 12 and 17, and DRPLA genes. Linkage exclusion tests showed no evidence of association with other known SCA loci. A genome-wide screen analysis identified linkage with chromosome 18 markers. A maximum two-point limit of determination score of 4.20 was found for marker D18S53. Haplotype analysis refined a critical region of 7.9 Mb between markers D18S1418 and D18S1104. This new SCA locus on 18p11.22-q11.2 has been designated SCA28. Candidate genes within the critical interval are currently screened for mutations.

An overview of the patient with ataxia

Ataxia, a neurological sign characterized by the incoordination of voluntary movements, is the most prominent manifestation of cerebellar disease. The cardinal features of cerebellar dysfunction involve disturbances of stance, gait, eye movements, muscle tone, skilled movements, and speech. Classification and differential diagnosis of ataxic syndromes have intrinsic complexity owing to the variability in phenotypic presentations and in etiologies, which include trauma, toxic and metabolic causes, neoplasms, immune mechanisms, and genetic diseases. Pure cerebellar symptoms are rarely observed, while the clinical picture of both genetic and sporadic ataxia syndromes is sometimes complicated by the presence of extracerebellar neurological or multisystem extraneural pathology. Clinical presentation and assessment of the patients together with classification, genetic aspects, and principles in differential diagnosis of ataxias are briefly reviewed.

Mitochondrial disorders

In the medical literature the term 'mitochondrial disorders' is to a large extent applied to the clinical syndromes associated with abnormalities of the common final pathway of mitochondrial energy metabolism, i.e. oxidative phosphorylation (OXPHOS). Faulty oxidative phosphorylation may be due to overall dysfunction of the respiratory chain, a heteromultimeric structure embedded in the inner mitochondrial membrane, or can be associated with single or multiple defects of the five complexes forming the respiratory chain itself. From the genetic standpoint, the respiratory chain is a unique structure of the inner mitochondrial membrane formed by means of the complementation of two separate genetic systems: the nuclear genome and the mitochondrial genome. The nuclear genome encodes the large majority of the protein subunits of the respiratory complexes and most of the mitochondrial DNA (mtDNA) replication and expression systems, whereas the mitochondrial genome encodes only 13 respiratory complex subunits, and some RNA components of the mitochondrial translational apparatus. Accordingly, mitochondrial disorders due to defects in OXPHOS include both mendelian-inherited and cytoplasmic-inherited diseases. This review describes human genetic diseases associated with mtDNA and nuclear DNA mutations leading to impaired OXPHOS.

Molecular Genetics of Hereditary Spinocerebellar Ataxia

BACKGROUND

Autosomal dominant cerebellar ataxias are a clinical and genetically heterogeneous group of progressive neurodegenerative diseases, at present associated with 22 loci (spinocerebellar ataxia [SCA] 1-SCA8, SCA10-SCA19, SCA21, SCA22, fibroblast growth factor 14 [FGF14]-SCA, and dentatorubral-pallidoluysian atrophy [DRPLA]). The relevant gene has been identified in 12 cases (SCA1-3, SCA6-8, SCA10, SCA12, FGF14, and DRPLA), and in all but the recently identified SCA14, SCA17, PRKCG and FGF14 genes, the defect consists of the expansion of a short nucleotide repeat.

OBJECTIVES

To investigate the relative prevalence of SCA1-3, SCA6-8, SCA10, SCA12, and SCA17 gene expansions in Italian families with hereditary ataxia, specifically to verify the occurrence of SCA10, SCA12, and SCA17 in Italy; and to analyze samples from probands with negative test results at the initial screening by means of the repeat expansion detection technique to identify CAG/CTG expansions in novel loci.Patients Two hundred twenty-five unrelated Italian index cases with hereditary ataxia, most (n = 183) of whom presented with a clear dominantly transmitted trait.

RESULTS

We found that SCA1 and SCA2 gene mutations accounted for most cases (21% and 24%, respectively). We found SCA3, SCA6, SCA7, SCA8, and SCA17 to be very rare (approximately 1% each), and no case of SCA10 or SCA12 was identified. Half of the index cases (113/225) were negative for expansions in the known SCA genes. Repeat expansion detection analysis performed on 111 of these cases showed a CAG/CTG repeat expansion of at least 50 triplets in 22 (20%). Twenty-one of 22 expansions could be attributed to length variation at 2 polymorphic loci (expanded repeat domain CAG/CTG 1 [ERDA1] or CTG repeat on chromosome 18q21.1 [CTG18.1]). In 1 patient, the expansion was assigned to the DRPLA gene.

CONCLUSIONS

The distribution of SCA1-3 and SCA6-7 gene mutations is peculiar in Italy. We found a relatively high frequency of SCA1 and SCA2 gene expansions; SCA3, SCA6, and SCA7 mutations were rare, compared with other European countries. No SCA10 or SCA12 and only a few SCA8 (2/225) and SCA17 (2/225) families were detected. In patients negative for defects in known SCA genes, repeat expansion detection data strongly suggest that, at least in our population, CAG/CTG expansions in novel genes should be considered an unlikely cause of the SCA phenotype.

The gender effect in juvenile Huntington disease patients of Italian origin

We analyzed a population of juvenile Huntington disease (HD) subjects of Italian origin (n = 57). The main aim of this study was to analyze the gender effect of the affected parent on age at onset and clinical presentation of offspring with juvenile HD. We also analyzed molecular features of the disease, including CAG mutation length and GluR6 gene polymorphism, according to the affected parent's gender. The mutation length was longer in paternally than in maternally transmitted HD juvenile patients (P = 0.025), nevertheless a similar mean early onset in the two groups (P > 0.05). This data was even enforced by that obtained from the whole cohort of patients included in the databank (n = 600) where, in the presence of increased mean parent-child CAG repeat change in paternal vs. maternal meiotic transmissions (+7.3 vs. +0.7 CAG, P = 0.0002), the mean parent-child year-of-onset change was similar in the two groups (-10.4 and -7.0 years, P > 0.05). A lower TAA-triplet in GluR6 was associated with an earlier age at onset in juvenile patients (P = 0.031, R2 = 0.10). When we added the GluR6 effect on age at onset to the CAG expanded number effect (P = 0.0001, R2 = 0.68) by multiple regression approach, the coefficient of determination R2 increased to 0.81. This effect in addition to the expanded CAG repeat number, found in juvenile and not in adult patients, was slightly enforced by paternal compared to maternal transmissions (R2=0.82). Our findings suggest the occurrence of a weaker effect of the paternal mutation on juvenile age at onset in our population, possibly amplified by other genetic factors, such as the TAA-triplet length in the GluR6 gene.

Homozygosity for CAG mutation in Huntington disease is associated with a more severe clinical course

Huntington disease is caused by a dominantly transmitted CAG repeat expansion mutation that is believed to confer a toxic gain of function on the mutant protein. Huntington disease patients with two mutant alleles are very rare. In other poly(CAG) diseases such as the dominant ataxias, inheritance of two mutant alleles causes a phenotype more severe than in heterozygotes. In this multicentre study, we sought differences in the disease features between eight homozygotes and 75 heterozygotes for the Huntington disease mutation. We identified subjects homozygous for the Huntington disease mutation by DNA testing and compared their clinical features (age at onset, symptom presentation, disease severity and disease progression) with those of a group of heterozygotes, who were assessed longitudinally. The age at onset of symptoms in the homozygote cases was within the range expected for heterozygotes with the same CAG repeat lengths, whereas homozygotes had a more severe clinical course. The observation of a more rapid decline in motor, cognitive and behavioural symptoms in homozygotes was consistent with the extent of neurodegeneration as available at imaging in three patients, and at the post-mortem neuropathological report in one case. Our analysis suggests that although homozygosity for the Huntington disease mutation does not lower the age at onset of symptoms, it affects the phenotype and the rate of disease progression. These data, once confirmed in a larger series of patients, point to the possibility that the mechanisms underlying age at onset and disease progression in Huntington disease may differ.

Phenotypic manifestations associated with CAG-repeat expansion in the androgen receptor gene in male patients and heterozygous females: a clinical and molecular study of 30 families

Spinal and bulbar muscular atrophy (Kennedy disease) is an adult form of X-linked motor neuron disease caused by the expansion of a polymorphic CAG-repeat sequence in the first exon of the androgen receptor gene. We studied clinical and molecular features of 36 patients and 19 heterozygous females. Phenotypic manifestations and disease severity broadly varied among our spinal and bulbar muscular atrophy patients. The size of CAG expansion significantly influences the age of disease onset, but neither clinical features nor disease severity. The majority of carrier women presented signs of chronic denervation at neurophysiological examination and, in three cases, low-amplitude sensory action potentials were recorded. Notably, a few women developed mild signs of bulbar motor neuron impairment later in life. The identification of a large number of patients by the use of the molecular test further supports the hypothesis that Kennedy disease had been previously underdiagnosed, probably because of the great variability of clinical presentation. Although an early diagnosis may not be crucial for treatment, given the lack of effective therapy, the molecular testing can be of great relevance for disease prognosis and genetic counseling.

Multiple abnormalities of ectoglycosyltransferases in cultured fibroblasts from patients with mucolipidosis II: Possible indication for abnormal plasma membrane glycoproteins

Ectoglycosyltransferase activities were measured in cultured normal and mucolipidosis II fibroblasts using endogenous glycoproteins and glycolipids and whole cells. Nucleotide pyrophosphatase, known to interfere with glycosyltransferases, was completely inhibited with 6 mM 5' AMP. Since preliminary experiments have shown multiple abnormalities of ectoglycosyltransferases in mucolipidosis II fibroblasts (Di Donato, unpublished results), galactosyl (Gal)-and N-acetylglucosaminyl (GluNac)-transferase were studied in further detail in confluent and nonconfluent cultures of normal and patient fibroblasts. Activities of both transferases on glycoproteins were higher in nonconfluent cultures. A 50% reduced activity of Gal-transferase was measured in confluent mucolipidosis II cultures and of GluNac-transferase in nonconfluent mucolipidosis II cultures towards incorporation of sugar precursors into glycoproteins. Substrate saturation kinetics of both transferases in mucolipidosis II fibroblasts revealed an abnormal Km for Gal incorporation into endogenous glycoproteins. Glycosylation of glycolipids in mucolipidosis fibroblasts was normal.