Congenital Dystrophy Research Articles

Clinical exome sequencing identifies novel compound heterozygous mutations of the POMT2 gene in patients with limb-girdle muscular dystrophy.

Mutations in protein O-mannosyltransferase 2 (POMT2) (MIM#607439) have been identified in severe congenital muscular dystrophy such as Walker-Warburg syndrome (WWS) and milder limb-girdle muscular dystrophy type 2N (LGMD2N). The aim of this study is to investigate the genetic causes in patients with LGMD2N. Three patients diagnosed with mild limb-girdle muscular dystrophy were recruited. The genetically pathogenic variant was identified by clinical exome sequencing, and healthy controls were verified by Sanger sequencing. Novel compound heterozygous mutations c.800A > G and c.1074_1075delinsAT of POMT2 were revealed in one affected individual by clinical exome sequencing. There was no report of these two variants and predicted to be highly damaging to the function of the POMT2. The novel variants extend the spectrum of POMT2 mutations, which promotes the prognostic value of testing for POMT2 mutations in patients with LGMD2N.

Establishment of a PBMC-derived induced pluripotent stem cell (NJUCMi001-A) from a patient with LAMA2-related congenital muscular dystrophy (MDC1A) carrying frameshift deletion c.3367delA in LAMA2 gene

LAMA2-related congenital muscular dystrophy (MDC1A), the most commonly recognized type of congenital muscular dystrophies, is a severe neonatal onset muscle disease caused by recessive mutations in the LAMA2 gene. Here, we established an induced pluripotent stem cell line from a MDC1A patient carrying a frameshift deletion c.3367delA in LAMA2 gene. The iPSC line expressed pluripotency markers, retained normal karyotype, showed capability of differentiating into three germ layers. The iPSC line will help to further elucidate the pathogenic mechanisms of LAMA2 mutation, and benefit treatment for congenital muscular dystrophies in the future.

An ecological approach to self-reflections on the inaccessibility of arts and cultural activities to wheelchair users

First, as a fan of live music and a power wheelchair user living with congenital muscular dystrophy, I use critical storytelling to describe my personal experiences of negotiating for accessibility during participation in arts and cultural activities. Second, I reflect broadly on the ableist ideologies that contribute to the inaccessibility of arts and cultural activities, focusing on the narrow scope of target participants, the ableist rationale for accessibility service provision, the inaccessibility of promotional materials and ticketing, segregated seating arrangements, venue inaccessibility, and single-modal performance. Third, I highlight the detrimental impact of the inaccessibility of arts and cultural activities at the organizational, social, intergroup, interpersonal, and individual levels. Finally, I propose future research directions and suggestions for inclusive practice in arts and cultural activities. This paper aims to promote self-empowerment, unravel the manifestations of ableism in arts and cultural activities, and stimulate readers’ critical reflection on in/accessibility of arts and cultural activities.

P.20 Experiences of and perspectives on bullying in youth with myopathies

Bullying is intentional behaviour designed to harm victims. 1 in 10 Canadian youth are bullied 2 or more times a month. Youth with physical disabilities are more likely to be bullied, especially those with mobility restrictions. A gap exists in bullying research about populations with progressive mobility restrictions. Myopathies are a group of muscle diseases (i.e., muscular dystrophy, congenital myopathy) with a progressive course and can result in a dependence on assistive devices and assistance with activities of daily living. This study explored bullying experiences of youth with myopathies, and the barriers and facilitators when dealing with bullying. Youth with myopathies (10-19 years) were approached at 2 pediatric neuromuscular clinics to participate in a larger study that included a survey exploring the frequency and types of bullying experienced. Participants were approached to complete a semi-structured interview. Qualitative analysis was conducted phenomenologically using NVivo. Deductive coding by 2 independent investigators focused on bullying type, time of incidents, and barriers and facilitators to address bullying. Field notes and documentations of coding changes ensured validity of coding. 6 participants were interviewed (4 male, 2 female; mean age=15.8±3.4 years) with diagnoses of Duchenne muscular dystrophy (n=4), congenital muscular dystrophy (n=1) and congenital myopathy (n=1). Participants experienced verbal (n=6), social (n=1) and physical (n=1) bullying. Five participants were bullied in primary school. Successful prevention strategies noted by participants were educating their class at the start of the school year, healthcare institution resiliency programs, and school initiatives to minimize bullying. Youth with myopathies experience unique circumstances when encountering bullying. Earlier screening in clinical visits should be considered. Further research on coping strategies, bullying education and prevention strategies are needed.

P.175 Global FKRP registry - the research database for limb girdle muscular dystrophy R9 (2I)

The Global FKRP Registry is an international registry for individuals with conditions caused by mutation of the Fukutin-Related Protein gene (<i>FKRP</i>): limb girdle muscular dystrophy R9 (LGMDR9, formerly LGMD2I) and the congenital muscular dystrophies (MD) MDC1C, Muscle-Eye-Brain Disease and Walker-Warburg Syndrome. The registry seeks to further understanding of the natural history and prevalence of FKRP-related MD and to aid the rapid identification of eligible patients for clinical studies. It disseminates FKRP-relevant information; provides a source of information to academics, industry and healthcare professionals; and supports the FKRP community. Registration is patient-initiated through a secure online portal (www.fkrp-registry.org). Participants give their consent and are invited to complete a questionnaire about their condition. Data is reported by both patients and their healthcare professionals and includes gene mutation, age of onset, presenting symptoms, motor function and muscle strength, respiratory and cardiac function, and medication. In addition, participants are invited to complete validated questionnaires on quality of life (INQoL) and pain (McGill). In recent years, the registry has assisted recruitment to natural history studies and clinical trials in LGMDR9. It has facilitated research by responding to data enquiries and circulating surveys, demonstrating its effectiveness as a repository of patient data, a tool for data collection and assembly of a trial-ready patient cohort. This year, the registry will implement the newly developed TREAT-NMD LGMD Core Dataset. Collection of a shared dataset by individual LGMD patient registries from around the world will enable a larger and potentially more powerful body of data to be collected on this diverse patient cohort. As knowledge of rare neuromuscular conditions increases and advances in the development of potential therapies are made, the registry is centrally placed to help support the accumulation of natural history and post-marketing surveillance data and facilitate recruitment to clinical trials.

P.147 Deflazacort treatment in LMNA-related congenital muscular dystrophy: an ongoing Italian cohort pilot study

<i>LMNA</i>-related congenital muscular dystrophy (L-CMD) and <i>LMNA</i>-linked Emery-Dreifuss muscular dystrophy (EDMD2) with early onset (<5 years) may be considered a continuum phenotype. There is no cure for patients with these neuromuscular diseases. Literature data and ongoing clinical approaches suggest the use of steroids. Starting from the collaborative approach and the multidisciplinary effort of the Italian network for laminopathies, we are planning an open-label prospective cohort pilot study aimed to: <i>1)</i> evaluate the effect of the treatment with deflazacort in a cohort of 20 L-CMD or EDMD2 patients with infantile onset, aged 3-30 years; <i>2)</i> analyze the secretome profile at basal condition and during steroid treatment, to evaluate variations and establish a correlation between steroid treatment and clinical outcome; <i>3)</i> validate selected cytokines as biomarkers for L-CMD and EDMD2. Study protocol: Patients will be monitored for a period of six months. Then, they will start therapy with Deflazacort for 12 months. After 12 months, the treatment will be stopped and the patients will continue to be clinically followed every 3 months until the end of the study. Overall, we expect to evaluate whether a 12-month-treatment with deflazacort is effective in improving clinical outcome measures in L-CMD patients. We also expect to identify a panel of cytokines altered in L-CMD that can be considered as biomarkers of disease.

An add-on Ayurvedic approach in the management of lissencephaly- A case report

Abstract Lissencephaly is a rare genetic brain developmental disease characterized by brain malformations, eye anomalies, and congenital muscular dystrophy. The present case is of a 2-year-old child previously diagnosed with lissencephaly, which was well managed with Ayurvedic treatment protocol, in addition to conventional antiepileptic medicines. The patient presented with delayed milestones and recurrent episodes of seizures. Sarvangavata, Kapha Avrita Vyana Vata, and Vyadhija Phakka were the probable Ayurvedic diagnoses considered. Agnideepana (stimulation of digestive/metabolic factors), Srotoshodhana (bio-cleansing of structural and functional channels), Balya (promoting strength), and Vata Shamaka (pacification of Vata Dosha) were the treatment principles adopted in this case. Indukanta Ghrita, Rajanyadi Churna, Gopichandanadi Vati, and Sahacharadi Kashaya were administered internally. Procedures such as Abhyanga (oil massage), Dhanyamla Dhara (therapeutic streaming of sour rice gruel over the body), Pratimarsha Nasya (medication through nasal route), and Jihvalepa (tongue anointment) were performed externally. The child achieved some important milestones within 37 days of inpatient (IP) and 2 months of outpatient treatment; no single episode of seizure was reported during the period. This case report advocates the institution of Ayurvedic treatment protocol in improving the quality of life of lissencephaly patient as an add-on therapy.

FP.38 Linker protein-mediated gene therapy ameliorates muscle and nerve pathology in mouse models for LAMA2-related congenital muscular dystrophy

<i>LAMA2</i>-related muscular dystrophy (LAMA2 MD or MDC1A) is the most frequent form of congenital muscular dystrophies. It is caused by mutations in <i>LAMA2</i>, the gene encoding laminin-α2, one chain of the heterotrimeric extracellular matrix protein laminin-211 (α2β1γ1). The large size of the cDNA encoding laminin-α2 and the heterotrimeric structure of laminin-211 present a challenge for gene replacement or gene editing strategies. Here, we describe the development of an AAV-based gene therapy to functionally replace laminin-211 by two small linker proteins. The two linker proteins, mini-agrin (mag) and αLNNd, are assembled from selected domains of agrin, nidogen-1 and laminin-α1. Previous work from our lab in transgenic mice has demonstrated that this Simultaneous Expression of Artificial Linkers (SEAL) in skeletal muscle of LAMA2 MD mice has a tremendous ameliorative effect on muscle pathology and survival. However, muscle-specific treatment makes the peripheral neuropathy phenotype in aged LAMA2 MD mice very apparent, as they develop a severe hindlimb paralysis. Here, we show in novel transgenic models that ubiquitous expression of linker proteins additionally overcomes this LAMA2-related peripheral neuropathy. We also show that the linker proteins are efficiently expressed upon systemic delivery by AAV9. Expression by a muscle-specific promoter significantly ameliorates the muscle disease phenotype in LAMA2 MD mice, as shown on the level of body- and muscle mass, fiber size, inflammation and muscle function (grip strength and locomotion). These experiments show that AAV-mediated expression of the two linker proteins is possible and they suggest that this functional replacement strategy by the design of small proteins assembled from protein domains present in patients may overcome some of the current challenges of gene therapy trials. Additionally, the linker proteins are secreted and are deposited in the extracellular matrix, which allows their accumulation upon expression by AAV. In summary, this study serves as a proof-of-concept in mice and establishes systemic delivery of AAVs that express the two linkers (SEAL technology) as a promising gene therapy for treating LAMA2 MD. Our current efforts focus on the use of next-generation AAVs with increased tropisms to skeletal muscle but low infection of liver (AAVMYO) and the use of ubiquitous promoters to evaluate the possibility of ameliorating the peripheral neuropathy.

VP.76 Natural history of a novel mouse model for LAMA2-related congenital muscular dystrophy

VP.76 Natural history of a novel mouse model for LAMA2-related congenital muscular dystrophy

P.190 Congenital muscular dystrophy associated to conserved oligomeric Golgi complex subunit 1 homozygous mutation

P.190 Congenital muscular dystrophy associated to conserved oligomeric Golgi complex subunit 1 homozygous mutation

VP.77 Muscle transcriptomic study of a novel LAMA2-related congenital muscular dystrophy mouse model

VP.77 Muscle transcriptomic study of a novel LAMA2-related congenital muscular dystrophy mouse model

VP.73 Characteristics of cardiac dysfunction in patients with Fukuyama congenital muscular dystrophy

VP.73 Characteristics of cardiac dysfunction in patients with Fukuyama congenital muscular dystrophy

Editorial introductions.

Current Opinion in Neurology was launched in 1988. It is one of a successful series of review journals whose unique format is designed to provide a systematic and critical assessment of the literature as presented in the many primary journals. The field of neurology is divided into 14 sections that are reviewed once a year. Each section is assigned a Section Editor, a leading authority in the area, who identifies the most important topics at that time. Here we are pleased to introduce the Journal's Section Editors for this issue. SECTION EDITORS Luis QuerolLuis QuerolLuis Querol (Valencia, 1980) graduated in Medicine at the University of Oviedo, Spain, and completed his residency in Neurology at the Santa Creu i Sant Pau Hospital in Barcelona. In 2009, he joined the group of Prof. Isabel Illa where he developed his doctoral thesis on the role of autoantibodies in immune-mediated neuropathies. In 2012, he worked as an associate researcher in the group of Dr Kevin O’Connor, Department of Neurology, Yale University (USA), where he developed projects related to autoantibodies in multiple sclerosis and myasthenia gravis. He completed his PhD in Medicine at the Universidad Autónoma de Barcelona, Spain, in 2013 thanks to studies that identified anti-contactin antibodies in a specific subgroup of patients with CIDP, in what is the first clinically useful marker detected in CIDP. Since then, he has led the auoimmune neurology clinics at Hospital Sant Pau in Barcelona and has continued a fruitful scientific production in the field of autoantibodies and biomarkers in autoimmune neurological disorders. Ichizo NishinoIchizo NishinoDr Ichizo Nishino, FAAN, FANA, is Director of Department of Neuromuscular Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry (NCNP). He obtained his M.D. in 1989 and Ph.D. in 1998 from Kyoto University, Japan. After five years of training in clinical neurology and six years of research fellowship, including two years at Columbia University, he was appointed to his current position in 2001. By now, he has published more than 600 PubMed-listed papers in the field, including the reports of gene discoveries for MNGIE and Danon disease, and the report of a new muscle disease – megaconial congenital muscular dystrophy (OMIM: 602541) whose causative was also later identified by his own group. His laboratory functions as a nationwide referral center for muscle disease, providing diagnostic analyses for muscle pathology and genetic diagnosis. His lab receives around 80% of muscle biopsies performed in Japan (1103 cases in 2021) and he signs out all cases. As a result, more than 22,000 frozen muscle biopsy samples have been accumulated in his muscle repository, which is one of the largest collections of the patient's muscles. Currently, Dr Nishino is a Visiting Professor at six universities: University of Yamanashi (Japan), Shinshu University (Japan), Kaohsiung Medical University (Taiwan), Fu Jen Catholic University (Taiwan), Peking University First Hospital (China), and Siriraj Hospital Mahidol University (Thailand). He is also serving as President of Asian-Oceanian Myology Center and Executive Board member in several societies including World Muscle Society. Albert LudolphAlbert LudolphAlbert Ludolph is currently Professor of Neurology, Chair and Director of the Department of Neurology, University of Ulm, Ulm, Germany and Speaker of the Site Ulm of the German Center for Neurodegenerative diseses (DZNE, Helmholtz Society). He obtained his M.D. from the University of Mainz, Germany, in 1981 and is a boarded neurologist and psychiatrist (education from University of Münster, Germany). His research focusses on translational work in neurodegenerative diseases; his work is mirrored by more than 600 PubMed-listed papers. His specific focus of interests are motor neuron diseases, Huntington's disease and frontotemporal dementias. The Department of Neurology in Ulm is an international referral center in particular for patients with ALS/MND. In the past his research focused on neurotoxicological and neuropharmacological research in humans, but also non-human primates. He was involved and initiated studies of neurogenetics of ALS, of the epidemiology of the disease (established registers in Southern Germany, Egypt and Mongolia), of the definition of the neuroanatomical sequence of events describing ALS and FTD, the development of biomarkers in ALS and FTD and beyond, and several drug trials, including investigator-initiated interventions. In recent years he tried to define the preclinical period of ALS including the role of the hypothalamus and its metabolic consequences.

P.146 Characterising the molecular consequences of LMNA-related congenital muscular dystrophy in patient myoblasts

P.146 Characterising the molecular consequences of LMNA-related congenital muscular dystrophy in patient myoblasts

P.184 Defining the pathological natural history of LAMA2 muscular dystrophy

LAMA2 muscular dystrophy (LAMA2-MD), is an autosomal recessive condition due to pathogenic variants in the <i>LAMA2</i> gene. The <i>LAMA2</i> gene encodes for the alpha 2 subunit of laminin proteins, which act as an important component of the extracellular matrix. Specifically, laminin-211 (Lm-211; merosin) is the major laminin of mature skeletal muscle, acts as an anchor for myofibers in the basement membrane; its laminin subunit composition is alpha2beta1gamma1. Variants in the <i>LAMA2</i> gene and subsequent alterations in laminin-211 protein expression or composition result in a spectrum of clinical manifestations that range from severe, early onset congenital muscular dystrophy (a.k.a. MDC1A) to a milder, later-onset muscular dystrophy (a.k.a. LGMD R23). The pathology of LAMA2-MD in skeletal muscle biopsies includes dystrophic changes (active and chronic degeneration and regeneration), with a decrease in or loss of laminin alpha 2 (merosin) immunostaining. However, the pathological natural history of LAMA2-MD has not been systematically studied and it is unclear what spectrum of altered expression may be seen in other extracellular matrix proteins. In this study, we assessed the histologic and immunofluorescent findings of a cohort of 57 muscle biopsy samples obtained from 50 different LAMA2-MD patients and in comparison, to 9 age-matched patients with normal skeletal muscle histology. The severity of dystrophic disease was established using H&E, Masson trichrome, and developmental myosin stains. Expression of laminins in muscle was assessed through immunostaining for laminin-211, laminin-111, laminin-411, and laminin-511. While analysis is still in progress, the severity of dystrophic pathology will be evaluated in the context of patient age, type of <i>LAMA2</i> mutation, and expression patterns of laminin proteins. Our findings will clarify the pathological spectrum of LAMA2-MD in a manner that will allow the identification of useful pathological endpoints for future human studies.

FP.39 An international retrospective early natural history study of LAMA2-related dystrophies

<i>LAMA2</i>-related dystrophies (LAMA2-RDs), caused by recessively inherited mutations in the <i>LAMA2</i> gene, represent one of the most common forms of congenital muscular dystrophy and are characterized by a complete or partial deficiency of laminin-211 (merosin). Patients with LAMA2-RDs presenting congenitally typically have a phenotype of severe weakness, delayed motor milestones, failure to thrive and progressive respiratory insufficiency. While a comprehensive prospective natural history study has been performed in LAMA2-RD patients >5 years, the early natural history of patients with LAMA2-RD 5 years and younger has not been comprehensively characterized. Extracting data from the CMD international registry, we describe a cohort of 62 patients with LAMA2-RD from 10 countries. Data for ages birth-5 years was retrospectively collected from the medical records. Inclusion criteria required that the patients had either two causative <i>LAMA2</i> variants or one confirmed causative <i>LAMA2</i> variant and a supporting clinical phenotype. Initial analyses reveal key findings including significant elevations of creatine kinase during the neonatal period which declined rapidly within the first few months of life. The mean age of first recognition of abnormal brain white matter appearance on MRI was 12.0 months. The first report of failure to thrive was at a mean age of 23.4 months. Noninvasive ventilation was initiated in half the patients by 24 months of age. This data represents the largest multinational retrospective early natural history study of LAMA2-RD which provides data essential for understanding early clinical history, especially as international, prospective early natural history data collection is in progress. Promising therapies in preclinical development for LAMA2-RD may ameliorate the phenotype of LAMA2-RD, particularly when initiated early in the course of the disease, making the comprehensive understanding of early natural history of LAMA2-RD timely and of great importance.

VP.78 Clinical and genetic study of LAMA2-related muscular dystrophy patients with seizures

<i>LAMA2</i>-related muscular dystrophy (LAMA2-MD) is an autosomal recessive muscular dystrophy caused by pathogenic variants in <i>LAMA2</i> gene, including two subgroups: severe, early-onset <i>LAMA2</i>-related congenital muscular dystrophy (LAMA2-CMD) and mild, late-onset autosomal recessive limb-girdle muscular dystrophy-23 (LGMD R23). Seizures frequently occurred in LAMA2-MD, however, the relationship between seizures and genotype in LAMA2-MD is not fully known. The clinical information of seizures including seizure type, frequency, treament, EEG changes, brain MRI and genetic data of LAMA2-MD patients from Peking University First Hospital between January 2003 and March 2022 were collected and analyzed. Among 141 LAMA2-MD patients, seizures were observed in 10.5% (13/124) of LAMA2-CMD patients and 29.4% (5/17) of LGMD R23 patients, including 14 patients with epilepsy and 4 patients with febrile seizures. The median (range) age of first seizure episode was 5 (0.1-20) years in LAMA2-CMD and 14 (1-24) years in LGMD R23. Eight patients with epilepsy showed focal seizures. Abnormal results of electroencephalography were found in 8/10 patients, manifesting as temporal, occipital or temporo-occipital epileptiform abnormalities. Brain magnetic resonance imaging (MRI) was performed in 16 patients with seizures, showing occipital pachygyria in 4 patients, cerebellum and brain stem dysplasia in 2 patients. Brain MRI of 41 LAMA2-MD patients without seizures were reassessed, showing occipital lobe pachygyria in 6 patients. Therefore, there was no significant association between seizures and occipital pachygyria in our cohort (P=0.18). Nine patients received antiepileptic drugs, while patients with occipital lobe pachygyria showed poor seizure control. The pathogenic variants included splice mutation (n=8), nonsense mutation (n=6) and frameshift mutation(n=6) in LAMA2-CMD patients, while missense mutation (n=5), frameshift mutation(n=4) in LGMD R23 patients. Compared with LAMA2-CMD, seizures were more frequently occurred in LGMD R23 patients and mainly manifested as focal seizures. No correlation between genotype and seizures was observed. In this study, we found that seizures occurred in 10.5% of LAMA2-CMD and 29.4% of LGMD R23 patients, and described the features of seizures in LAMA2-MD patients.

VP.75 Jab1 deletion in muscle lineage causes a muscular dystrophy that resembles LAMA2 disease

Merosin deficient congenital muscular dystrophy (LAMA2 disease) is an autosomal recessive disorder characterized by progressive wasting muscular dystrophy, dysmyelinating neuropathy and brain abnormalities. This disorder is caused by mutations in the <i>LAMA2</i> gene, which encodes for the laminin211, the primary component of the Schwann cell and muscle basal lamina. We recently identified Jab1 as a nuclear molecule downstream the laminin211 pathway and showed that Jab1 regulates Schwann cell behavior through the modulation of p27Kip1 levels. Interestingly, loss of Jab1 in Schwann cells results in a dysmyelinating neuropathy that phenocopies the neuropathy of LAMA2 disease. To evaluate whether Jab1 also plays a role in the pathogenesis of LAMA2 muscular dystrophy, we generated mice with conditional inactivation of <i>Jab1</i> in the muscle lineage through the MyoDi-cre transgene. Mice with deletion of <i>Jab1</i> in skeletal muscle (named Jab1-MscKO) showed progressive motor deficits, reduced lifespan and overt muscular dystrophy phenotype. Muscles appeared smaller in size and presented myopathic features such as reduced fiber diameter, presence of necrotic fibers, inflammatory cells, and fibrosis. The evaluation of satellite cell number showed a reduction of proliferating satellite cells, suggesting a defect of cell cycle progression. Muscle regeneration, induced by cardiotoxin injection, was significantly impaired in Jab1-MscKO mice. Jab1-MscKO muscles showed increased of p27Kip1 expression. Genetic deletion of <i>p27Kip1</i> in muscles of Jab1-MscKO mice revealed a mild, but not significant, amelioration of motor performances and muscle pathology, while reduced inflammatory infiltrates and ameliorated satellite cells cycling. Our results suggest that Jab1 in involved in the pathogenesis of LAMA2 muscular dystrophy, while p27Kip1 might influence the correct cell cycle progression of satellite cells.

VP.81 In vivo modulation of novel genetic modifiers for LAMA2-RD

Merosin-deficient congenital muscular dystrophy (LAMA2-RD) is caused by mutations in the LAMA2 gene, which encodes for the α2 subunit of laminin-211. Patients with complete laminin-211 deficiency show a clinically homogeneous and severe phenotype. To date, only one atypical patient with complete laminin-211 deficiency and a remarkably mild phenotype has been reported. Strikingly, the atypical patient and its severely affected sibling carry the same <i>LAMA2</i> loss-of-function mutation, and both lack laminin-211 expression in muscle. Since laminin-211 is not present in either sibling, we hypothesize that there is a rare genetic modifier in the atypical sibling that compensates for laminin-211 absence in muscle via a novel mechanism. We performed unbiased muscle RNA-sequencing and identified genes differentially expressed in the atypical patient compared to unrelated LAMA2-RD patients and healthy controls. Transcriptome data were complemented by the analysis of whole genome sequencing data of both siblings. We identified differentially expressed genes potentially regulated by very rare DNA polymorphisms uniquely present in the atypical sibling. These genes affect pathways commonly dysregulated in LAMA2-RD, such as energy metabolism, regeneration, inflammation and fibrosis, and represent candidate modifier gene(s)/pathway(s) that could provide a novel therapeutic approach and ameliorate LAMA2-RD severity. We are currently testing the most promising candidates in vivo in a LAMA2-knockout zebrafish model that recapitulates LAMA2-RD. In particular we are assessing the potential for these protective modifier(s) to improve muscle morphology and improve the phenotype in the diseased animals. Outcomes of this project will add new knowledge about the molecular aspects of this disorder, shed light on novel mechanisms involved in attenuating LAMA2-RD severity and potentially lead to the development of new therapeutic strategies.

Megaconial congenital muscular dystrophy due to novel CHKB variants: a case report and literature review

BackgroundCholine kinase beta (CHKB) catalyzes the first step in the de novo biosynthesis of phosphatidyl choline and phosphatidylethanolamine via the Kennedy pathway. Derangement of this pathway might also influence the homeostasis of mitochondrial membranes.Autosomal recessive CHKB mutations cause a rare form of congenital muscular dystrophy known as megaconial congenital muscular dystrophy (MCMD).Case presentationWe describe a novel proband presenting MCMD due to unpublished CHKB mutations. The patient is a 6-year-old boy who came to our attention for cognitive impairment and slowly progressive muscular weakness. He was the first son of non-consanguineous healthy parents from Sri Lanka. Neurological examination showed proximal weakness at four limbs, weak osteotendinous reflexes, Gowers’ maneuver, and waddling gate. Creatine kinase levels were mildly increased. EMG and brain MRI were normal. Left quadriceps skeletal muscle biopsy showed a myopathic pattern with nuclear centralizations and connective tissue increase. Histological and histochemical staining suggested subsarcolemmal localization and dimensional increase of mitochondria. Ultrastructural analysis confirmed the presence of enlarged (“megaconial”) mitochondria. Direct sequencing of CHKB identified two novel defects: the c.1060G > C (p.Gly354Arg) substitution and the c.448-56_29del intronic deletion, segregating from father and mother, respectively. Subcloning of RT-PCR amplicons from patient’s muscle RNA showed that c.448-56_29del results in the partial retention (14 nucleotides) of intron 3, altering physiological splicing and transcript stability. Biochemical studies showed reduced levels of the mitochondrial fission factor DRP1 and the severe impairment of mitochondrial respiratory chain activity in patient’s muscle compared to controls.ConclusionsThis report expands the molecular findings associated with MCMD and confirms the importance of considering CHKB variants in the differential diagnosis of patients presenting with muscular dystrophy and mental retardation. The clinical outcome of MCMD patients seems to be influenced by CHKB molecular defects. Histological and ultrastructural examination of muscle biopsy directed molecular studies and allowed the identification and characterization of an intronic mutation, usually escaping standard molecular testing.