Biallelic variants in PPP1R13L cause paediatric dilated cardiomyopathy.

Childhood dilated cardiomyopathy (DCM) is a leading cause of heart failure requiring cardiac transplantation and approximately 5% of cases result in sudden death. Knowledge of the underlying genetic cause can aid prognostication and clinical management and enables accurate recurrence risk counselling for the family. Here we used genomic sequencing to identify the causative genetic variant(s) in families with children affected by severe DCM. In an international collaborative effort facilitated by GeneMatcher, biallelic variants in PPP1R13L were identified in seven children with severe DCM from five unrelated families following exome or genome sequencing and inheritance-based variant filtering. PPP1R13L encodes inhibitor of apoptosis-stimulating protein of p53 protein (iASPP). In addition to roles in apoptosis, iASPP acts as a regulator of desmosomes and has been implicated in inflammatory pathways. DCM presented early (mean: 2 years 10 months; range: 3 months-9 years) and was progressive, resulting in death (n = 3) or transplant (n = 3), with one child currently awaiting transplant. Genomic sequencing technologies are valuable for the identification of novel and emerging candidate genes. Biallelic variants in PPP1R13L were previously reported in a single consanguineous family with paediatric DCM. The identification here of a further five families now provides sufficient evidence to support a robust gene-disease association between PPP1R13L and severe paediatric DCM. The PPP1R13L gene should be included in panel-based genetic testing for paediatric DCM.

Blunt cervical spine trauma as a cause of spinal cord injury and delayed cortical blindness.

STUDY DESIGN: Case report. OBJECTIVE: To present and discuss the case of a patient who sustained a significant flexion compression injury of the cervical spine with resulting tetraplegia and development of cortical blindness. SETTING: National Spinal Injuries Unit and Institute of Neurological Sciences, Southern General Hospital, Glasgow, Scotland, UK. METHODS: Clinical and radiological follow-up of the patient. RESULTS: Cortical blindness resulted from vertebral artery dissection associated with blunt cervical spine trauma. The patient is registered blind and is ventilator dependent. CONCLUSION: The potential complications of blunt vertebral artery injury remain poorly recognised. Screening is routinely not performed. Advances in noninvasive radiological techniques may result in recognition of asymptomatic disease and the potential for therapeutic intervention.

The metabolism of the carcinogen dibenz[a,j]acridine in isolated rat hepatocytes and in vivo in rats.

1. 3H-Dibenz[a,j]acridine (DBAJAC) metabolism occurred readily in vitro in incubations with hepatocytes from phenobarbital-pretreated, 3-methylcholanthrene-pretreated and untreated rats, with the formation of water-soluble conjugates and unconjugated metabolites. 2. For incubations of 3H-DBAJAC with hepatocytes the major organic solvent-soluble metabolites found with and without beta-glucuronidase/arylsulphatase hydrolysis were the phenols, 3-hydroxy-DBAJAC, and 4-hydroxy-DBAJAC, and the proposed proximate carcinogen, trans-3,4-dihydroxy-3,4-dihydro-DBAJAC. The latter comprised 34-66% of the total organic solvent-soluble metabolites. 3. In contrast to results previously reported for rat hepatic microsomes, the K-region 5,6-oxide, and its dihydrodiol were minor metabolites detected after hepatocyte incubations. 4. Faecal excretion accounted for the bulk of radioactivity after i.p. doses of 3H-DBAJAC (0.5 mg/kg), and i.v. doses (0.5 mg/kg) were rapidly excreted into the 6 h bile. The organic solvent-soluble fraction obtained after enzymic hydrolysis of bile (approximately 25% of excreted radioactivity) was subjected to h.p.l.c. It contained polar secondary oxidation products and virtually no 3,4-dihydrodiol. 5. Experiments conducted with greater hepatocyte densities (10(7) cells/ml) and longer incubation times showed increased extents of metabolism, DNA and protein binding of radioactivity which paralleled the extent of metabolism. Very considerable metabolism of the 3,4-dihydrodiol occurred by the end of the incubation period.

Metabolism of the carcinogen 7-methylbenz[c]-acridine in the rat.

The biliary excretion of radioactivity by adult Wistar rats given i.v. 7-methyl-[7-14C]benz[c]acridine(14C-7-MBAC) and [methyl-3H]-7-methylbenz[c]acridine (3H-7-MBAC) (2 mg/kg) was 61% and 48%, respectively, in males in six hours. Females excreted 33% of a 2 mg/kg dose of 3H-7-MBAC in the same time-period. For male rats, the urinary and faecal excretions were about 10% and 61% of the dose of 14C-7-MBAC, respectively, in seven days. No enterohepatic circulation could be demonstrated in control male rats. The biliary excretion of radioactivity by phenobarbital- and 3-methylcholanthrene-induced male rats given 14C-7-MBAC was similar to or greater than that of control male rats. The organo-soluble biliary metabolites after beta-glucuronidase/arylsulphatase hydrolysis were separated by h.p.l.c., and quantitative metabolite distributions were obtained for induced and control rats by comparison with metabolite standards. The mutagenicity of bile from carcinogen-dosed control rats was greater than that of equivalent bile from carcinogen-dosed 3-methylcholanthrene-pretreated animals.

A new systematic strategy for the isolation of proteins, illustrated by the purification of a mammalian exo-beta-N-acetyl-D-glucosaminidase.

The ;B' form of the exo-beta-N-acetyl-d-glucosaminidase from pig epididymis was purified by a new systematic strategy to yield a preparation with a specific activity at least equal to that obtainable by an existing empirically derived procedure. The new strategy is essentially a sequence of three carefully chosen steps consisting of an initial fractionation of the constituent proteins according to molecular size, followed by an ion-exchange step designed to select out proteins with closely similar electric-charge properties to those of the protein of interest, and a final high-resolution step dependent on the isoelectric points of the residual proteins. Gel isoelectric focusing itself, or as an element in the technique described by Leaback & Robinson (1974) for the separate display of the molecular size and electric-charge characteristics of proteins, played an important part in the choice of the experimental conditions used in the new strategy, and also in monitoring the progress of the purification.

The preparation of ribosomal ribonucleic acid from whole bacteria.

1. A simple method for the preparation of ribonuclease-free ribosomal RNA is described in which ribonuclease-deficient bacteria are treated with acetone and the RNA is extracted with phenol and purified by precipitating it with potassium acetate. The treatment with acetone appears to render the cell wall permeable to RNA but not to DNA during the extraction with phenol. The method thus avoids the need to disrupt the bacteria and greatly simplifies the subsequent purification. 2. The method has been used successfully with ribonuclease-deficient strains of Escherichia coli, Pseudomonas fluorescens and Staphylococcus epidermidis. The recovered purified RNA accounts for about 70% of the total ribosomal RNA and shows the normal sedimentation pattern of the 16s and 23s components in the analytical centrifuge.

Magnesium ion-independent ribonucleic acid depolymerases in bacteria.

The distribution of ribonucleases among bacteria has been determined from the examination of a wide variety of species. Bacteria that had been growing rapidly on a solid medium were harvested, treated with acetone and incubated in the presence of EDTA between pH4 and pH9. The ribonuclease activity was determined from the rate at which acid-soluble nucleotides were released. Out of nearly 200 strains examined, about 30 did not contain a detectable ribonuclease. The pH optima of ribonucleases in the remainder were sufficiently distinctive to suggest a use in taxonomy. Escherichia coli B was examined in more detail to determine the factors responsible for variations in the ribonuclease content of this bacterium. Growth rate had little influence on ribonuclease content when a complex medium containing no readily assimilable carbohydrate was used; the addition of glucose resulted in a marked increase in ribonuclease and a dependence of enzyme content on growth rate. An increase in the concentration of sodium chloride in the medium decreased the ribonuclease content of bacteria growing on it.