Anne-Marie Childs

Loss-of-function mutations in MICU1 cause a brain and muscle disorder linked to primary alterations in mitochondrial calcium signaling

Mitochondrial Ca2+ uptake has key roles in cell life and death. Physiological Ca2+ signaling regulates aerobic metabolism, whereas pathological Ca2+ overload triggers cell death. Mitochondrial Ca2+ uptake is mediated by the Ca2+ uniporter complex in the inner mitochondrial membrane, which comprises MCU, a Ca2+-selective ion channel, and its regulator, MICU1. Here we report mutations of MICU1 in individuals with a disease phenotype characterized by proximal myopathy, learning difficulties and a progressive extrapyramidal movement disorder. In fibroblasts from subjects with MICU1 mutations, agonist-induced mitochondrial Ca2+ uptake at low cytosolic Ca2+ concentrations was increased, and cytosolic Ca2+ signals were reduced. Although resting mitochondrial membrane potential was unchanged in MICU1-deficient cells, the mitochondrial network was severely fragmented. Whereas the pathophysiology of muscular dystrophy and the core myopathies involves abnormal mitochondrial Ca2+ handling, the phenotype associated with MICU1 deficiency is caused by a primary defect in mitochondrial Ca2+ signaling, demonstrating the crucial role of mitochondrial Ca2+ uptake in humans.

Genotype-phenotype correlation in a large population of muscular dystrophy patients with LAMA2 mutations.

Merosin deficient congenital muscular dystrophy 1A (MDC1A) results from mutations in the LAMA2 gene. We report 51 patients with MDC1A and examine the relationship between degree of merosin expression, genotype and clinical features. Thirty-three patients had absence of merosin and 13 showed some residual merosin. Compared to the residual merosin group, patients with absent merosin had an earlier presentation (<7days) (P=0.0073), were more likely to lack independent ambulation (P=0.0215), or require enteral feeding (P=0.0099) and ventilatory support (P=0.0354). We identified 33 novel LAMA2 mutations; these were distributed throughout the gene in patients with absent merosin, with minor clusters in exon 27, 14, 25 and 26 (55% of mutations). Patients with residual merosin often carried at least one splice site mutation and less frequently frameshift mutations. This large study identified novel LAMA2 mutations and highlights the role of immunohistochemical studies for merosin status in predicting clinical severity of MDC1A.

Nemaline myopathy caused by absence of α‐skeletal muscle actin

To investigate seven congenital myopathy patients from six families: one French Gypsy, one Spanish Gypsy, four British Pakistanis, and one British Indian. Three patients required mechanical ventilation from birth, five died before 22 months, one is ventilator‐dependent, but one, at 30 months, is sitting with minimal support. All parents were unaffected.

SEPN1-related myopathies: clinical course in a large cohort of patients.

Objective: To assess the clinical course and genotype–phenotype correlations in patients with selenoprotein-related myopathy (SEPN1-RM) due to selenoprotein N1 gene (SEPN1) mutations for a retrospective cross-sectional study. Methods: Forty-one patients aged 1–60 years were included. Clinical data including scoliosis, respiratory function, and growth measurements were collected by case note review. Results: Mean age at onset was 2.7 years, ranging from birth to the second decade of life. All but 2 remained independently ambulant: one lost ambulation at age 5 years and another in his late 50s. The mean age of starting nocturnal noninvasive ventilation (NIV) was 13.9 years. One child required full-time NIV at the age of 1 year while in 2 cases NIV was started at 33 years. Two patients died from respiratory failure at the age of 10 and 22 years, respectively. The mean age at scoliosis onset was 10 years, in most cases preceded by rigidity of the spine. Fourteen patients had successful spinal surgery (mean age 13.9 years). Twenty-one were underweight; however, overt feeding difficulties were not a feature. Conclusions: This study describes the largest population affected by SEPN1-RM reported so far. Our findings show that the spectrum of severity is wider than previously reported. Respiratory insufficiency generally develops by 14 years but may occur as early as in infancy or not until the fourth decade. Motor abilities remain essentially static over time even in patients with early presentation. Most adult patients remain ambulant and fully employed.

Homozygous deletion in MICU1 presenting with fatigue and lethargy in childhood

Objective: To define the mechanism responsible for fatigue, lethargy, and weakness in 2 cousins who had a normal muscle biopsy. Methods: Exome sequencing, long-range PCR, and Sanger sequencing to identify the pathogenic mutation. Functional analysis in the patient fibroblasts included oxygen consumption measurements, extracellular acidification studies, Western blotting, and calcium imaging, followed by overexpression of the wild-type protein. Results: Analysis of the exome sequencing depth revealed a homozygous deletion of exon 1 of MICU1 within a 2,755-base pair deletion. No MICU1 protein was detected in patient fibroblasts, which had impaired mitochondrial calcium uptake that was rescued through the overexpression of the wild-type allele. Conclusions: MICU1 mutations cause fatigue and lethargy in patients with normal mitochondrial enzyme activities in muscle. The fluctuating clinical course is likely mediated through the mitochondrial calcium uniporter, which is regulated by MICU1.

A cohort study of children and young people with progressive neuromuscular disorders: clinical and demographic profiles and changing patterns of referral for palliative care.

Background: Progressive neuromuscular disease in children is life limiting and these children and young people would benefit from palliative care services, but data are limited on the number and demography of these children. Aim: To describe the clinical and demographic profile of children referred to a Children’s hospice in the UK with progressive neuromuscular disease. Setting/participants: All children and young people with progressive neuromuscular disorders referred to Martin House Children’s Hospice between 1987 and 2010. Design: Retrospective cohort study Results: 300 children with progressive neuromuscular disease were referred to the hospice. Seventy percent (210) of these children had Duchenne Muscular Dystrophy, 22% (67) had Spinal Muscular Atrophy (34 with Type I) and 8% had other neuromuscular diseases. Numbers of referrals have not significantly increased over the last 15 years, although an increasing number come from a South Asian background (from 4% to 32%) and a higher number of children have conditions other than Duchenne Muscular Dystrophy. A total of 55.3% (166) of all referrals came from areas of the highest deprivation. Survival patterns varied by diagnostic group, but ethnicity and deprivation were not associated with survival in these children. Conclusions: The profile of children with progressive neuromuscular conditions who were referred for palliative care has changed over the last 20 years, with a different spectrum of underlying diagnoses and a greater number from a South Asian background. The higher than expected proportion of children living in areas of high deprivation has been consistent over time.

Developing standardized corticosteroid treatment for Duchenne muscular dystrophy

Despite corticosteroids being the only treatment documented to improve strength and function in boys with Duchenne muscular dystrophy (DMD) corticosteroid prescription is inconsistent and in some countries, corticosteroids are not prescribed. We are conducting a clinical trial that (1) compares the 3 most frequently prescribed corticosteroid regimes; (2) standardizes treatment of DMD complications; and (3) standardizes prevention of corticosteroid side effects. Investigators at 38 sites in 5 countries plan to recruit 300 boys aged 4-7 who are randomly assigned to one of three regimens: daily prednisone; daily deflazacort; or intermittent prednisone (10days on/10days off). Boys are followed for a minimum of 3years to assess the relative effectiveness and adverse event profiles of the different regimens. The primary outcome is a 3-dimensional variable consisting of log-transformed time to rise from the floor, forced vital capacity, and subject/parent satisfaction with treatment, each averaged over all post-baseline visits. The study protocol includes evidence- and consensus-based treatment of DMD complications and of corticosteroid side effects. This study seeks to establish a standard corticosteroid regimen for DMD. Since all new interventions for DMD are being developed as add-on therapies to corticosteroids, defining the optimum regimen is of importance for all new treatments.

The clinical, biochemical and genetic features associated with RMND1-related mitochondrial disease

Background Mutations in the RMND1 (Required for Meiotic Nuclear Division protein 1) gene have recently been linked to infantile onset mitochondrial disease characterised by multiple mitochondrial respiratory chain defects. Methods We summarised the clinical, biochemical and molecular genetic investigation of an international cohort of affected individuals with RMND1 mutations. In addition, we reviewed all the previously published cases to determine the genotype–phenotype correlates and performed survival analysis to identify prognostic factors. Results We identified 14 new cases from 11 pedigrees that harbour recessive RMND1 mutations, including 6 novel variants: c.533C>A, p.(Thr178Lys); c.565C>T, p.(Gln189*); c.631G>A, p.(Val211Met); c.1303C>T, p.(Leu435Phe); c.830+1G>A and c.1317+1G>T. Together with all previously published cases (n=32), we show that congenital sensorineural deafness, hypotonia, developmental delay and lactic acidaemia are common clinical manifestations with disease onset under 2 years. Renal involvement is more prevalent than seizures (66% vs 44%). In addition, median survival time was longer in patients with renal involvement compared with those without renal disease (6 years vs 8 months, p=0.009). The neurological phenotype also appears milder in patients with renal involvement. Conclusions The clinical phenotypes and prognosis associated with RMND1 mutations are more heterogeneous than that were initially described. Regular monitoring of kidney function is imperative in the clinical practice in light of nephropathy being present in over 60% of cases. Furthermore, renal replacement therapy should be considered particularly in those patients with mild neurological manifestation as shown in our study that four recipients of kidney transplant demonstrate good clinical outcome to date.

Mri Features of Developing Periventricular (Pv) White Matter in Preterm Infants: Evidence of Glial Cell Migration. 41

Mri Features of Developing Periventricular (Pv) White Matter in Preterm Infants: Evidence of Glial Cell Migration. 41

Bradycardia without associated hypertension: a common sign of ventriculo-peritoneal shunt malfunction

IntroductionDelayed diagnosis of ventriculo-peritoneal (VP) shunt malfunction results in avoidable morbidity and mortality. One reason is that most of the signs of shunt malfunction have low specificity.ObjectiveThe objective of this study was to evaluate the presence of bradycardia as a sign of VP shunt malfunction in children with treated hydrocephalus.MethodsChildren presenting with clinical features suggestive of possible VP shunt malfunction were retrospectively identified. Children with confirmed shunt malfunction formed the study group. Those who did not have shunt malfunction formed the control group, and the symptoms and signs were compared between the two groups. In particular, the presence of bradycardia (a heart rate less than the second centile of age-related norms) was sought. The positive predictive value (PPV) of bradycardia was compared with other common features of shunt malfunction.ResultsData were obtained for 52 patients: 34 in the study group (data from 40 admissions) and 18 controls. Bradycardia was present in 18 of 40 (45%) of the study group and 2 of 18(11%) controls (p = 0.011). Only two of the patients with bradycardia had associated hypertension. The PPV for bradycardia was 90% compared with 92% for reduced conscious level and 65% for both headache and vomiting (the four commonest presenting features).ConclusionsBradycardia without hypertension is common in children with VP shunt malfunction. The significance of bradycardia is often not recognised; the value of this sign should be emphasised.