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TARS2 encodes human mitochondrial threonyl tRNA-synthetase that is responsible for generating mitochondrial Thr-tRNAThr and clearing mischarged Ser-tRNAThr during mitochondrial translation. Pathogenic variants in TARS2 have hitherto been reported in a pair of siblings and an unrelated patient with an early onset mitochondrial encephalomyopathy and a combined respiratory chain enzyme deficiency in muscle. We here report five additional unrelated patients with TARS2-related mitochondrial diseases, expanding the clinical phenotype to also include epilepsy, dystonia, hyperhidrosis and severe hearing impairment. In addition, we document seven novel TARS2 variants—one nonsense variant and six missense variants—that we demonstrate are pathogenic and causal of the disease presentation based on population frequency, homology modeling and functional studies that show the effects of the pathogenic variants on TARS2 stability and/or function.

Background In 2009, we identified TACO1 as a novel mitochondrial disease gene in a single family, however no second family has been described to confirm the role of TACO1 in mitochondrial disease. Objective In this report, we describe two independent consanguineous families carrying pathogenic variants in TACO1, confirming the phenotype. Methods Detailed clinical investigations and whole exome sequencing with haplotype analysis have been performed in several members of the two reported families. Results Clinical phenotype of the patients confirms the originally reported phenotype of a childhood-onset progressive cerebellar and pyramidal syndrome with optic atrophy and learning difficulties. Brain MRI showed periventricular white matter lesions with multiple cystic defects, suggesting leukoencephalopathy in both patients. One patient carried the previously described homozygous TACO1 variant (p.His158ProfsTer8) and haplotype analysis suggested that this variant is a rare founder mutation. The second patient from another family carried a homozygous novel frame shift variant (p.Cys85PhefsTer15). Conclusions The identification of two Turkish families with similar characteristic clinical presentation and an additional homozygous nonsense mutation confirms that TACO1 is a human mitochondrial disease gene. Although most patients with this clinical presentation undergo next generation sequencing analysis, screening for selected founder mutations in the Turkish population based on the precise clinical presentation may reduce time and cost of finding the genetic diagnosis even in the era of massively parallel sequencing.

Reversible infantile respiratory chain deficiency (RIRCD) is a rare mitochondrial myopathy leading to severe metabolic disturbances in infants, which recover spontaneously after 6‐months of age. RIRCD is associated with the homoplasmic m.14674T>C mitochondrial DNA mutation; however, only ~ 1/100 carriers develop the disease. We studied 27 affected and 15 unaffected individuals from 19 families and found additional heterozygous mutations in nuclear genes interacting with mt‐tRNAGlu including EARS2 and TRMU in the majority of affected individuals, but not in healthy carriers of m.14674T>C, supporting a digenic inheritance. Our transcriptomic and proteomic analysis of patient muscle suggests a stepwise mechanism where first, the integrated stress response associated with increased FGF21 and GDF15 expression enhances the metabolism modulated by serine biosynthesis, one carbon metabolism, TCA lipid oxidation and amino acid availability, while in the second step mTOR activation leads to increased mitochondrial biogenesis. Our data suggest that the spontaneous recovery in infants with digenic mutations may be modulated by the above described changes. Similar mechanisms may explain the variable penetrance and tissue specificity of other mtDNA mutations and highlight the potential role of amino acids in improving mitochondrial disease., Heterozygous mutations in nuclear genes interacting with mt‐tRNAGlu induce the integrated stress response and metabolic rearrangements, reducing penetrance and promoting spontaneous recovery in a rare mitochondrial myopathy.

The work highlights the link between dysfunction of the RNA exosome, ribosome biogenesis, p53-dependent signalling, and apoptosis. Pontocerebellar hypoplasia caused by mutations of the exosome subunits could be classified as a ribosomopathy., The RNA exosome is a ubiquitously expressed complex of nine core proteins (EXOSC1-9) and associated nucleases responsible for RNA processing and degradation. Mutations in EXOSC3, EXOSC8, EXOSC9, and the exosome cofactor RBM7 cause pontocerebellar hypoplasia and motor neuronopathy. We investigated the consequences of exosome mutations on RNA metabolism and cellular survival in zebrafish and human cell models. We observed that levels of mRNAs encoding p53 and ribosome biogenesis factors are increased in zebrafish lines with homozygous mutations of exosc8 or exosc9, respectively. Consistent with higher p53 levels, mutant zebrafish have a reduced head size, smaller brain, and cerebellum caused by an increased number of apoptotic cells during development. Down-regulation of EXOSC8 and EXOSC9 in human cells leads to p53 protein stabilisation and G2/M cell cycle arrest. Increased p53 transcript levels were also observed in muscle samples from patients with EXOSC9 mutations. Our work provides explanation for the pathogenesis of exosome-related disorders and highlights the link between exosome function, ribosome biogenesis, and p53-dependent signalling. We suggest that exosome-related disorders could be classified as ribosomopathies.

Reversible infantile respiratory chain deficiency (RIRCD) is a rare mitochondrial myopathy leading to severe metabolic disturbances in infants, which recover spontaneously after 6 months of age. RIRCD is associated with the homoplasmic m.14674T>C mitochondrial DNA mutation, however only ∼1/100 carriers develop the disease. We studied 27 affected and 15 unaffected individuals from 19 families and found additional heterozygous mutations in nuclear genes interacting with mt-tRNAGluincludingEARS2andTRMUin the majority of affected individuals, but not in healthy carriers of m.14674T>C, supporting a digenic inheritance. The spontaneous recovery in infants with digenic mutations is modulated by changes in amino acid availability in a multi-step process. First, the integrated stress-response associated with increasedFGF21andGDF15expression enhances catabolism via β-oxidation and the TCA cycle increasing the availability of amino acids. In the second phase mitochondrial biogenesis increases via mTOR activation, leading to improved mitochondrial translation and recovery. Similar mechanisms may explain the variable penetrance and tissue specificity of other mtDNA mutations and highlight the potential role of amino acids in improving mitochondrial disease.

Deoxyguanosine kinase (dGK) is an essential rate-limiting component of the mitochondrial purine nucleotide salvage pathway, encoded by the nuclear gene encoding deoxyguanosine kinase (DGUOK). Mutations in DGUOK lead to mitochondrial DNA (mtDNA) depletion typically in the liver and brain, causing a hepatocerebral phenotype. Previous work has shown that in cultured DGUOK patient cells it is possible to rescue mtDNA depletion by increasing substrate amounts for dGK. In this study we developed a mutant dguok zebrafish (Danio rerio) line using CRISPR/Cas9 mediated mutagenesis; dguok−/− fish have significantly reduced mtDNA levels compared with wild-type (wt) fish. When supplemented with only one purine nucleoside (dGuo), mtDNA copy number in both mutant and wt juvenile animals was significantly reduced, contrasting with previous cell culture studies, possibly because of nucleotide pool imbalance. However, in adult dguok−/− fish we detected a significant increase in liver mtDNA copy number when supplemented with both purine nucleosides. This study further supports the idea that nucleoside supplementation has a potential therapeutic benefit in mtDNA depletion syndromes by substrate enhancement of the purine nucleoside salvage pathway and might improve the liver pathology in patients.

The subject of this study concerns a method of manufacture of porous media for which the solid matrix is capable of experiencing deformation under the influence of the flow field. Conventionally, the matrix design parameters, elasticity and pore geometry, cannot be precisely controlled and the choice of parameters is limited to existing available media. Here a solution is provided that uses an indirect solid-free form fabrication process that combines 3D Printing with an infused Polydimethylsiloxane elastomer to provide a highly deformable matrix with controlled pore architecture. The manufacturing method is presented in detail. Local microscopy analysis of the manufactured matrix shows that the method has a high capability to accurately create pore structures at length scales as low as 0.75 mm. Experimental flow measurements further validate that the intended pore geometry is able to be reproduced in highly deformable matrices. The experimentally determined permeability of the deformable matrix is determined to agree with the intended within 95 %.

We propose a high level network architecture for an economic system that integrates money, governance and reputation. We introduce a method for issuing, and redeeming a digital coin using a mechanism to create a sustainable global economy and a free market. To maintain a currency's value over time, and therefore be money proper, we claim it must be issued by the buyer and backed for value by the seller, exchanging the products of labour, in a free market. We also claim that a free market and sustainable economy cannot be maintained using economically arbitrary creation and allocation of money. Nakamoto, with Bitcoin, introduced a new technology called the cryptographic blockchain to operate a decentralised and distributed accounts ledger without the need for an untrusted third party. This blockchain technology creates and allocates new digital currency as a reward for "proof-of-work", to secure the network. However, no currency, digital or otherwise, has solved how to create and allocate money in an economically non-arbitrary way, or how to govern and trust a world-scale free enterprise money system. We propose an "Ontologically Networked Exchange" (ONE), with purpose as its highest order domain. Each purpose is defined in a contract, and the entire economy of contracts is structured in a unified ontology. We claim to secure the ONE network using economically non-arbitrary methodologies and economically incented human behaviour. Decisions influenced by reputation help to secure the network without an untrusted third party. The stack of contracts, organised in a unified ontology, functions as a super recursive algorithm, with individual use programming the algorithm, acting as the "oracle". The state of the algorithm becomes the "memory" of a scalable and trustable artificial intelligence (AI). This AI offers a new platform for what we call the "Autonomy-of-Things" (AoT)., 55 pages, 9 figures