Social cognition in myotonic dystrophy type 1: Specific or secondary impairment?

Aims The cognitive profile of Myotonic Dystrophy type 1 (DM1) has been described in recent decades. Moreover, DM1 patients show lowered social engagement and difficulties in social-cognitive functions. The aim of the present study is to explore whether social cognition impairment is present in DM1 taking into account the overall cognitive condition. Method 38 patients and a control group paired in age and gender participated in the study. All the participants had an IQ within the normal range. Subjects were administered an abbreviated neuropsychological battery which comprised a facial emotion recognition test (POFA) and Faux Pas Test, as well as a self-report questionnaire on cognitive and affective empathy (TECA). Results Statistically significant differences were found only for facial emotion recognition (U = 464.0, p = .006) with a moderate effect size (.31), with the controls obtaining a higher score than the patients. Analyzing each emotion separately, DM1 patients scored significantly lower than controls on the recognition of anger and disgust items. Emotion recognition did not correlate with genetic load, but did correlate negatively with age. No differences were found between patients and controls in any of the other variables related to Theory of Mind (ToM) and empathy. Conclusion DM1 does not manifest specific impairments in ToM since difficulties in this area predominantly rely on the cognitive demand of the tasks employed. However, a more basic process such as emotion recognition appears as a core deficit. The role of this deficit as a marker of aging related decline is discussed.The present study has been supported by grants of the Instituto de Salud Carlos III co-founded by Fondo Europeo de Desarrollo Regional - FEDER (Ref: PI17/01231)

Regional brain atrophy in gray and white matter is associated with cognitive impairment in Myotonic Dystrophy type 1

Background: Myotonic Dystrophy type 1 (DM1) is a slowly progressive myopathy characterized by varying multisystemic involvement. Several cerebral features such as brain atrophy, ventricular enlargement, and white matter lesions (WMLs) have frequently been described. The aim of this study is to investigate the structural organization of the brain that defines the disease through multimodal imaging analysis, and to analyze the relation between structural cerebral changes and DM1 clinical and neuropsychological profiles. Method: 31 DM1 patients and 57 healthy controls underwent an MRI scan protocol, including T1, T2 and DTI. Global gray matter (GM), global white matter (WM), and voxel-level Voxel Based Morphometry (VBM) and voxel-level microstructural WM abnormalities through Diffusion Tensor Imaging (DTI) were assessed through group comparisons and linear regression analysis with age, degree of muscular impairment (MIRS score), CTG expansion size and neuropsychological outcomes from a comprehensive assessment. Results: Compared with healthy controls, DM1 patients showed a reduction in both global GM and WM volume; and further regional GM decrease in specific primary sensory, multi-sensory and association cortical regions. Fractional anisotropy (FA) was reduced in both total brain and regional analysis, being most marked in frontal, paralimbic, temporal cortex, and subcortical regions. Higher ratings on muscular impairment and longer CTG expansion sizes predicted a greater volume decrease in GM and lower FA values. Age predicted global GM reduction, specifically in parietal regions. At the cognitive level, the DM1 group showed significant negative correlations between IQ estimate, visuoconstructive and executive neuropsychological scores and both global and regional volume decrease, mainly distributed in the frontal, parietal and subcortical regions. Conclusions: In this study, we describe the structural brain signatures that delineate the involvement of the CNS in DM1. We show that specific sensory and multi-sensory — as well as frontal cortical areas — display potential vulnerability associated with the hypothesized neurodegenerative nature of DM1 brain abnormalities

Shedding light on motor premanifest myotonic dystrophy type 1: A molecular, muscular and central nervous system follow-up study

Background and purpose Myotonic dystrophy type 1 (DM1) is a hereditary and multisystemic disease that is characterized by heterogeneous manifestations. Although muscular impairment is central to DM1, a premanifest DM1 form has been proposed for those characterized by the absence of muscle signs in precursory phases. Nevertheless, subtle signs and/or symptoms related to other systems, such as the central nervous system (CNS), may emerge and progress gradually. This study aimed to validate the premanifest DM1 concept and to characterize and track affected individuals from a CNS centred perspective. Methods Retrospective data of 120 participants (23 premanifest DM1, 25 manifest DM1 and 72 healthy controls) were analysed transversally and longitudinally (over 11.17 years). Compiled data included clinical, neuropsychological and neuroradiological (brain volume and white matter lesion, WML) measures taken at two time points. Results Manifest DM1 showed significantly more molecular affectation, worse performance on neuropsychological domains, lower grey and white matter volumes and a different pattern of WMLs than premanifest DM1. The latter was slightly different from healthy controls regarding brain volume and WMLs. Additionally, daytime sleepiness and molecular expansion size explained 50% of the variance of the muscular deterioration at follow-up in premanifest individuals. Conclusions Premanifest DM1 individuals showed subtle neuroradiological alterations, which suggests CNS involvement early in the disease. Based on follow-up data, a debate emerges around the existence of a ‘non-muscular DM1’ subtype and/or a premanifest phase, as a precursory stage to other DM1 manifestations.This work was supported by the Centro de Investigación Biomédica en Red de Enfermedades Neurodegenerativas (Ref: 609), from the Institute of Health Carlos III co-founded by Fondo Europeo de Desarrollo Regional (PI17/01231 to A.S.; PI17/01841 to A.L.); Basque Government (S-PE13UN030 to A.S.); and University of the Basque Country (UPV/EHU) (PIF 20/238 to J.G.; GU 20/057 to J.G., G.L. and A.S.)

Neurodegeneration trajectory in pediatric and adult/late DM1: A follow‐up MRI study across a decade

Objective: To characterize the progression of brain structural abnormalities in adults with pediatric and adult/late onset DM1, as well as to examine the potential predictive markers of such progression. Methods: 21 DM1 patients (pediatric onset: N = 9; adult/late onset: N = 12) and 18 healthy controls (HC) were assessed longitudinally over 9.17 years through brain MRI. Additionally, patients underwent neuropsychological, genetic, and muscular impairment assessment. Inter-group comparisons of total and voxel-level regional brain volume were conducted through Voxel Based Morphometry (VBM); cross-sectionally and longitudinally, analyzing the associations between brain changes and demographic, clinical, and cognitive outcomes. Results: The percentage of GM loss did not significantly differ in any of the groups compared with HC and when assessed independently, adult/late DM1 patients and their HC group suffered a significant loss in WM volume. Regional VBM analyses revealed subcortical GM damage in both DM1 groups, evolving to frontal regions in the pediatric onset patients. Muscular impairment and the outcomes of certain neuropsychological tests were significantly associated with follow-up GM damage, while visuoconstruction, attention, and executive function tests showed sensitivity to WM degeneration over time. Interpretation: Distinct patterns of brain atrophy and its progression over time in pediatric and adult/late onset DM1 patients are suggested. Results indicate a possible neurodevelopmental origin of the brain abnormalities in DM1, along with the possible existence of an additional neurodegenerative process. Fronto-subcortical networks appear to be involved in the disease progression at young adulthood in pediatric onset DM1 patients. The involvement of a multimodal integration network in DM1 is discussed.CIBERNED609 Eusko JaurlaritzaPRE_ 2016_1_0187PRE_2019_1_0070SAIO08- PE08BF01 Institute of Health Carlos III cofounded by Fondo Europeo de Desarrollo Regional-FEDERPI17/01231 PI17/0184

Phenotypic correlations in a large single center cohort of patients with BSCL2 nerve disorders: a clinical, neurophysiological and muscle MRI study

Background: BSCL2 heterozygote mutations are a common cause of distal hereditary motor neuropathies (dHMN). We present a series of BSCL2 patients and correlate clinical, neurophysiological and muscle-MRI findings. Methods: 26 patients from 5 families carrying the p.N88S mutation were ascertained. Age of onset, clinical phenotype (dHMN, Charcot-Marie-Tooth/CMT, spastic paraplegia), physical examination, disability measured as modified Rankin score (mRS) and neurophysiological findings were collected. A whole body muscle-MRI had been performed in 18 patients. We analyzed the pattern of muscle involvement on T1-weighted and STIR sequences. Hierarchical analysis using heatmaps and a MRI Composite Score (MRI CS) were generated. Statistical analysis was carried out with STATA SE v.15. Results Mean age was 51.54+/-19.94 years and 14 patients were males. dHMN was the most common phenotype (50%) and 5 patients (19.23%) showed no findings on examination. Disease onset was commonly in childhood and disability was low (mRS=1.34+/-1.13) although median time since onset of disease was 32 years (range=10-47). CMT-like patients were more disabled and disability correlated with age. On muscle-MRI, thenar eminence, soleus and tibialis anterior were most frequently involved, irrespective of clinical phenotype. MRI CS was strongly correlated with disability. Conclusion: Patients with the p.N88S BSCL2 gene mutation are phenotypically variable, although dHMN is most frequent and generally slowly progressive. Muscle-MRI pattern is consistent regardless of phenotype and correlates with disease severity, probably serving as a reliable outcome measure for future clinical trials

A deep intronic splice variant advises reexamination of presumably dominant SPG7 Cases

Objective: to identify causative mutations in a patient affected by ataxia and spastic paraplegia. Methods: whole-exome sequencing (WES) and whole-genome sequencing (WGS) were performed using patient's DNA sample. RT-PCR and cDNA Sanger sequencing were performed on RNA extracted from patient's fibroblasts, as well as western blot. Results: a novel missense variant in SPG7 (c.2195T> C; p.Leu732Pro) was first found by whole-exome sequencing (WES), while the second, also unreported, deep intronic variant (c.286 + 853A>G) was identified by whole-genome sequencing (WGS). RT-PCR confirmed the in silico predictions showing that this variant activated a cryptic splice site, inducing the inclusion of a pseudoexon into the mRNA sequence, which encoded a premature stop codon. Western blot showed decreased SPG7 levels in patient's fibroblasts. Interpretation: identification of a deep intronic variant in SPG7, which could only have been detected by performing WGS, led to a diagnosis in this HSP patient. This case challenges the notion of an autosomal dominant inheritance for SPG7, and illustrates the importance of performing WGS subsequently or alternatively to WES to find additional mutations, especially in patients carrying one variant in a gene causing a predominantly autosomal recessive disease

White matter integrity changes and neurocognitive functioning in adult-late onset DM1: a follow-up DTI study

[EN] Myotonic Dystrophy Type 1 (DM1) is a multisystemic disease that affects gray and white matter (WM) tissues. WM changes in DM1 include increased hyperintensities and altered tract integrity distributed in a widespread manner. However, the precise temporal and spatial progression of the changes are yet undetermined. MRI data were acquired from 8 adult- and late-onset DM1 patients and 10 healthy controls (HC) at two different timepoints over 9.06 years. Fractional anisotropy (FA) and mean diffusivity (MD) variations were assessed with Tract-Based Spatial Statistics. Transversal and longitudinal intra- and intergroup analyses were conducted, along with correlation analyses with clinical and neuropsychological data. At baseline, reduced FA and increased MD values were found in patients in the uncinate, anterior-thalamic, fronto-occipital, and longitudinal tracts. At follow-up, the WM disconnection was shown to have spread from the frontal part to the rest of the tracts in the brain. Furthermore, WM lesion burden was negatively correlated with FA values, while visuo-construction and intellectual functioning were positively correlated with global and regional FA values at follow-up. DM1 patients showed a pronounced WM integrity loss over time compared to HC, with a neurodegeneration pattern that suggests a progressive anterior–posterior disconnection. The visuo-construction domain stands out as the most sensitive neuropsychological measure for WM microstructural impairment.The present study has been supported by funding from the Institute of Health Carlos III co-founded by Fondo Europeo de Desarrollo Regional-FEDER [Grant Numbers PI17/01231 and PI17/01841], CIBERNED (Grant Number: 609), the Basque Government [SAIO08-PE08BF01] and the University of the Basque Country (Neurosciences group: GIU20-057). BC was supported by a predoctoral grant from the Basque Government [PRE-2020-1-0187]. AJM was supported by a predoctoral grant from the Basque Government [PRE-2019-1-0070]. JG was supported by a predoctoral grant from the University of the Basque Country [PIF20/238]

Senescence plays a role in myotonic dystrophy type 1 br

Myotonic dystrophy type 1 (DM1; MIM #160900) is an autosomal dominant disorder, clinically characterized by progressive muscular weakness and multisystem degeneration. The broad phenotypes observed in patients with DM1 resemble the appearance of an accelerated aging process. However, the molecular mechanisms underlying these phenotypes remain largely unknown. Transcriptomic analysis of fibroblasts derived from patients with DM1 and healthy individuals revealed a decrease in cell cycle activity, cell division, and DNA damage response in DM1, all of which related to the accumulation of cellular senescence. The data from transcriptome analyses were corroborated in human myoblasts and blood samples, as well as in mouse and Drosophila models of the disease. Serial passage studies in vitro confirmed the accelerated increase in senescence and the acquisition of a senescence-associated secretory phenotype in DM1 fibroblasts, whereas the DM1 Drosophila model showed reduced longevity and impaired locomotor activity. Moreover, functional studies highlighted the impact of BMI1 and downstream p16INK4A/ RB and ARF/p53/p21CIP pathways in DM1-associated cellular phenotypes. Importantly, treatment with the senolytic compounds Quercetin, Dasatinib, or Navitoclax reversed the accelerated aging phenotypes in both DM1 fibroblasts in vitro and in Drosophila in vivo. Our results identify the accumulation of senescence as part of DM1 pathophysiology and, therefore, demonstrate the efficacy of senolytic compounds in the preclinical setting.MGP and ASA are recipient of predoctoral fellowships from the University of the Basque Country (PIF 15/245) and Carlos III Institute (FI17/00250), respectively. We thank the methodological support service of Biodonostia Institute for help with statistical analysis. This work is supported by grants from the Instituto Salud Carlos III and FEDER funds (PI16/01580, PI17/01841, DTS18/00181, PI19/01355, CPII19/00021, and DTS20/00179), La Caixa, and Health department from Basque Country (2017222021, 2018222021, and 2020333008)

Targeted Next-Generation Sequencing in a Large Cohort of Genetically Undiagnosed Patients with Neuromuscular Disorders in Spain

This article belongs to the Special Issue Genetic Advances in Neuromuscular Disorders: From Gene Identification to Gene Therapy.The term neuromuscular disorder (NMD) includes many genetic and acquired diseases and differential diagnosis can be challenging. Next-generation sequencing (NGS) is especially useful in this setting given the large number of possible candidate genes, the clinical, pathological, and genetic heterogeneity, the absence of an established genotype-phenotype correlation, and the exceptionally large size of some causative genes such as TTN, NEB and RYR1. We evaluated the diagnostic value of a custom targeted next-generation sequencing gene panel to study the mutational spectrum of a subset of NMD patients in Spain. In an NMD cohort of 207 patients with congenital myopathies, distal myopathies, congenital and adult-onset muscular dystrophies, and congenital myasthenic syndromes, we detected causative mutations in 102 patients (49.3%), involving 42 NMD-related genes. The most common causative genes, TTN and RYR1, accounted for almost 30% of cases. Thirty-two of the 207 patients (15.4%) carried variants of uncertain significance or had an unidentified second mutation to explain the genetic cause of the disease. In the remaining 73 patients (35.3%), no candidate variant was identified. In combination with patients’ clinical and myopathological data, the custom gene panel designed in our lab proved to be a powerful tool to diagnose patients with myopathies, muscular dystrophies and congenital myasthenic syndromes. Targeted NGS approaches enable a rapid and cost-effective analysis of NMD- related genes, offering reliable results in a short time and relegating invasive techniques to a second tier.This study was granted by FIS PI15/01898, funded by ISCIII and FEDER, ‘Una manera de hacer Europa’ and by Fundación Mutua Madrileña in the “Convocatoria de ayudas a la Investigación en Salud 2015”. It was also funded by an ACCI grant from CIBERER. Daniel Natera-de Benito is the recipient of a grant from the Instituto de Salud Carlos III (Contrato Rio Hortega, CM17/00044)

Detection of variants in dystroglycanopathy-associated genes through the application of targeted whole-exome sequencing analysis to a large cohort of patients with unexplained limb-girdle muscle weakness

Background: Dystroglycanopathies are a clinically and genetically heterogeneous group of disorders that are typically characterised by limb-girdle muscle weakness. Mutations in 18 different genes have been associated with dystroglycanopathies, the encoded proteins of which typically modulate the binding of alpha-dystroglycan to extracellular matrix ligands by altering its glycosylation. This results in a disruption of the structural integrity of the myocyte, ultimately leading to muscle degeneration. Methods: Deep phenotypic information was gathered using the PhenoTips online software for 1001 patients with unexplained limb-girdle muscle weakness from 43 different centres across 21 European and Middle Eastern countries. Whole-exome sequencing with at least 250 ng DNA was completed using an Illumina exome capture and a 38 Mb baited target. Genes known to be associated with dystroglycanopathies were analysed for disease-causing variants. Results: Suspected pathogenic variants were detected in DPM3, ISPD, POMT1 and FKTN in one patient each, in POMK in two patients, in GMPPB in three patients, in FKRP in eight patients and in POMT2 in ten patients. This indicated a frequency of 2.7% for the disease group within the cohort of 1001 patients with unexplained limb-girdle muscle weakness. The phenotypes of the 27 patients were highly variable, yet with a fundamental presentation of proximal muscle weakness and elevated serum creatine kinase. Conclusions: Overall, we have identified 27 patients with suspected pathogenic variants in dystroglycanopathy-associated genes. We present evidence for the genetic and phenotypic diversity of the dystroglycanopathies as a disease group, while also highlighting the advantage of incorporating next-generation sequencing into the diagnostic pathway of rare diseases.Peer reviewe