Human mutations that truncate the massive sarcomere protein titin (TTNtv) are the most common genetic cause for dilated cardiomyopathy (DCM), a major cause of heart failure and premature death. Here we show that cardiac microtissues engineered from human induced pluripotent stem (iPS) cells are a powerful system for evaluating the pathogenicity of titin gene variants. We found that certain missense mutations, like TTNtv, diminish contractile performance and are pathogenic. By combining functional analyses with RNAseq, we explain why truncations in the A-band domain of TTN cause DCM while truncations in the I-band are better tolerated. Finally, we demonstrate that mutant titin protein in iPS-cardiomyocytes results in sarcomere insufficiency, impaired responses to mechanical and β-adrenergic stress, and attenuated growth factor and cell signaling activation. Our findings indicate that titin mutations cause DCM by disrupting critical linkages between sarcomerogenesis and adaptive remodelling.

BackgroundSengers syndrome is an autosomal recessive condition characterized by congenital cataract, hypertrophic cardiomyopathy, skeletal myopathy and lactic acidosis. Mutations in the acylglycerol kinase (AGK) gene have been recently described as the cause of Sengers syndrome in nine families.MethodsWe investigated the clinical and molecular features of Sengers syndrome in seven new families; five families with the severe and two with the milder form.ResultsSequence analysis of AGK revealed compound heterozygous or homozygous predicted loss-of-function mutations in all affected individuals. A total of eight different disease alleles were identified, of which six were novel, homozygous c.523_524delAT (p.Ile175Tyrfs*2), c.424-1G > A (splice site), c.409C > T (p.Arg137*) and c.877 + 3G > T (splice site), and compound heterozygous c.871C > T (p.Gln291*) and c.1035dup (p.Ile346Tyrfs*39). All patients displayed perinatal or early-onset cardiomyopathy and cataract, clinical features pathognomonic for Sengers syndrome. Other common findings included blood lactic acidosis and tachydyspnoea while nystagmus, eosinophilia and cervical meningocele were documented in only either one or two cases. Deficiency of the adenine nucleotide translocator was found in heart and skeletal muscle biopsies from two patients associated with respiratory chain complex I deficiency. In contrast to previous findings, mitochondrial DNA content was normal in both tissues.ConclusionWe compare our findings to those in 21 previously reported AGK mutation-positive Sengers patients, confirming that Sengers syndrome is a clinically recognisable disorder of mitochondrial energy metabolism.

Prigogine I, Lefever R, Goldbeter A et al. (1969) Symmetry breaking instabilities in biological systems. Nature 223:913-6 Savill NJ, Sherratt JA (2003) Control of epidermal stem cell clusters by Notch-mediated lateral induction. Dev Biol 258:141-53 Serra R, Villani M, Graudenzi A et al. (2007) Why a simple model of genetic regulatory networks describes the distribution of avalanches in gene expression data. J Theor Biol 246:449-60 Turing AM (1952) The chemical basis of morphogenesis. Phil Trans Roy Soc B Biol Sci 237:37-72 Varela FG, Maturana HR, Uribe R (1974) Autopoiesis: the organization of living systems, its characterization and a model.

BackgroundMutations 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.MethodsWe 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.ResultsWe 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.ConclusionsThe 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.

Background: Peripartum cardiomyopathy (PPCM) occurs in approximately 1:2000 deliveries in the US and worldwide. The genetic underpinnings of PPCM remain poorly defined. Approximately 10% of women with PPCM harbor truncating variants in TTN (TTNtvs). Whether mutations in other genes can predispose to PPCM is not known. It is also not known if the presence of TTNtvs predicts clinical presentation or outcomes. Nor is it known if the prevalence of TTNtvs differs in women with PPCM and preeclampsia, the strongest risk factor for PPCM. Methods: Women with PPCM were retrospectively identified from several US and international academic centers, and clinical information and DNA samples were acquired. Next-generation sequencing was performed on 67 genes, including TTN , and evaluated for burden of truncating and missense variants. The impact of TTNtvs on severity of clinical presentation, and on clinical outcomes, was evaluated. Results: 469 women met inclusion criteria. 10.4% of women with PPCM bore TTNtvs (Odds ration [OR]=9.4 compared with 1.2% in reference population; Bonferroni-corrected P [P*] =1.2x10 -46 ). We additionally identified overrepresentation of truncating variants in FLNC (OR=24.8, P*=7.0x10 -8 ), DSP (OR=14.9, P*=1.0x10-8), and BAG3 (OR=53.1, P*=0.02), genes not previously associated with PPCM. This profile is highly similar to that found in non-ischemic dilated cardiomyopathy (DCM). Women with TTNtvs had lower left ventricular ejection fraction (LVEF) on presentation than did women without TTNtvs (23.5% vs 29%, P=2.5x10 -4 ), but did not differ significantly in timing of presentation after delivery, in prevalence of preeclampsia, or in rates of clinical recovery. Conclusions: This study provides the first extensive genetic and phenotypic landscape of PPCM, and demonstrates that predisposition to heart failure is an important risk factor for PPCM. The work reveals a degree of genetic similarity between PPCM and DCM, suggesting that gene-specific therapeutic approaches being developed for DCM may also apply to PPCM, and that approaches to genetic testing in PPCM should mirror those taken in DCM. Finally, the clarification of genotype/phenotype associations has important implications for genetic counseling.

BackgroundJuvenile pulmonary alveolar proteinosis (PAP) due to CSF2RA mutations is a rare disorder with only a few cases described worldwide.MethodsWe identified nine children with severe diffuse interstitial lung disease due to CSF2RA mutations. Clinical course, diagnostic findings and treatment were evaluated and correlated to the genotype. Functional impairment of the intracellular JAK/pStat5 signaling pathway was assessed using flow-cytometry of peripheral mononuclear cells (PBMC) and granulocytes.ResultsWe identified six individuals with homozygous missense/nonsense/frameshift mutations and three individuals homozygous for a deletion of the complete CSF2RA gene locus. Overall, four novel mutations (c.1125 + 1G > A, duplication exon 8, deletion exons 2–13, Xp22.3/Yp11.3) were found. Reduced STAT5 phosphorylation in PBMC and granulocytes was seen in all cases examined (n = 6). Pulmonary symptoms varied from respiratory distress to clinically silent. Early disease onset was associated with a more severe clinical phenotype (p = 0.0092). No association was seen between severity of phenotype at presentation and future clinical course or extent of genetic damage. The clinical course was favorable in all subjects undergoing whole lung lavage (WLL) treatment.ConclusionsOur cohort broadens the spectrum of knowledge about the clinical variability and genotype-phenotype correlations of juvenile PAP, and illustrates the favorable outcome of WLL treatment in severely affected patients.Electronic supplementary materialThe online version of this article (doi:10.1186/s13023-014-0171-z) contains supplementary material, which is available to authorized users.

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There are some uncontrolled studies about the efficacy and safety of both aripiprazole and risperidone for treating tic disorder. Moreover, the efficacy of these medications has never been compared. This is the first double blind randomized clinical trial comparing the safety and efficacy of aripiprazole and risperidone for treating patients with tic disorder. Sixty children and adolescents with tic disorder were randomly allocated into one of the two groups to receive either aripiprazole or risperidone for 2 months. The primary outcome measure was the score of Yale Global Tic Severity Scale. In addition, health related quality of life and adverse events were assessed. Both aripiprazole and risperidone decreased the Yale Global Tic Severity Scale score during this trial. Moreover, both medications increased the health related quality of life score. Both aripiprazole and risperidone were tolerated well. Aripiprazole [3.22 (1.9) mg/day] decreased tic score as much as risperidone [0.6 (0.2) mg/day]. Their adverse effects and their effects on health related quality of life were comparable. However, risperidone increased the patients' social functioning more than aripiprazole in short term.