Premature Termination Of Translation Research Articles

An aldehyde dehydrogenase gene, GhALDH7B4_A06, positively regulates fiber strength in upland cotton (Gossypium hirsutum L.).

High fiber strength (FS) premium cotton has significant market demand. Consequently, enhancing FS is a major objective in breeding quality cotton. However, there is a notable lack of known functionally applicable genes that can be targeted for breeding. To address this issue, our study used specific length-amplified fragment sequencing combined with bulk segregant analysis to study FS trait in an F2 population. Subsequently, we integrated these results with previous quantitative trait locus mapping results regarding fiber quality, which used simple sequence repeat markers in F2, F2:3, and recombinant inbred line populations. We identified a stable quantitative trait locus qFSA06 associated with FS located on chromosome A06 (90.74-90.83 Mb). Within this interval, we cloned a gene, GhALDH7B4_A06, which harbored a critical mutation site in coding sequences that is distinct in the two parents of the tested cotton line. In the paternal parent Ji228, the gene is normal and referred to as GhALDH7B4_A06O; however, there is a nonsense mutation in the maternal parent Ji567 that results in premature termination of protein translation, and this gene is designated as truncated GhALDH7B4_A06S. Validation using recombinant inbred lines and gene expression analysis revealed that this mutation site is correlated with cotton FS. Virus-induced gene silencing of GhALDH7B4 in cotton caused significant decreases in FS and fiber micronaire. Conversely, GhALDH7B4_A06O overexpression in Arabidopsis boosted cell wall component contents in the stem. The findings of our study provide a candidate gene for improving cotton fiber quality through molecular breeding.

Mutations in the NUP93, NUP107 and NUP160 genes cause steroid-resistant nephrotic syndrome in Chinese children

BackgroundThe variants of nucleoporins are extremely rare in hereditary steroid-resistant nephrotic syndrome (SRNS). Most of the patients carrying such variants progress to end stage kidney disease (ESKD) in their childhood. More clinical and genetic data from these patients are needed to characterize their genotype–phenotype relationships and elucidate the role of nucleoporins in SRNS.MethodsFour patients of SRNS carrying biallelic variants in the NUP93, NUP107 and NUP160 genes were presented. The clinical and molecular genetic characteristics of these patients were summarized, and relevant literature was reviewed.ResultsAll four patients in this study were female and initially presented with SRNS. The median age at the onset of the disease was 5.08 years, ranging from 1 to 10.5 years. Among the four patients, three progressed to ESKD at a median age of 7 years, ranging from 1.5 to 10.5 years, while one patient reached stage 3 chronic kidney disease (CKD3). Kidney biopsies revealed focal segmental glomerulosclerosis in three patients. Biallelic variants were detected in NUP93 in one patient, NUP107 in two patients, as well as NUP160 in one patient respectively. Among these variants, five yielded single amino acid substitutions, one led to nonsense mutation causing premature termination of NUP107 translation, one caused a single nucleotide deletion resulting in frameshift and truncation of NUP107. Furthermore, one splicing donor mutation was observed in NUP160. None of these variants had been reported previously.ConclusionThis report indicates that biallelic variants in NUP93, NUP107 and NUP160 can cause severe early-onset SRNS, which rapidly progresses to ESKD. Moreover, these findings expand the spectrum of phenotypes and genotypes and highlight the importance of next-generation sequencing in elucidating the molecular basis of SRNS and allowing rational treatment for affected individuals.

A novel hemizygous CD40L mutation of X-linked hyper IgM syndromes and compound heterozygous DOCK8 mutations of hyper IgE syndromes in two Chinese families.

X-linked hyper-immunoglobulin M (X-HIGM) syndrome and autosomal recessive hyper-immunoglobulin E syndrome (HIES) are rare inborn errors of immunity characterized by recurrent infections due to immune system impairment. In this study, we identified a novel hemizygous CD40 ligand (CD40L) mutation and compound heterozygous dedicator of cytokinesis-8 (DOCK8) mutations in two Han Chinese families with X-HIGM and HIES, respectively. We aimed to investigate the association between their genotypes and phenotypes. Genomic DNA was extracted from peripheral blood samples obtained from the families. Whole exome sequencing and Sanger sequencing were performed to identify and verify pathogenic variants in the two families. Clinical analyses of the probands were also performed. A novel hemizygous mutation of CD40L in exon 2 (c.257delA) was identified in the first proband, resulting in the substitution of glycine with glutamic acid at codon 86 of the protein. This leads to premature termination of translation at downstream codon 9 (p.E86Gfs*9). Sanger sequencing confirmed that the variant was inherited from the mother. The second proband carried two novel compound heterozygous mutations in DOCK8: one at exon 14 (c.1546C > G) inherited from the father, and the other at intron 41 (c.5355 + 6C > T; splicing) inherited from the mother. This study enhances our understanding of the pathogenetic mutation spectrum of CD40L and DOCK8 genes, facilitating the prenatal diagnosis of X-HIGM and HIES and enabling timely treatment of patients.

Identification and Transcriptome Analysis of a Novel Allelic Mutant of NAL1 in Rice.

Leaf morphology is a crucial aspect of plant architecture, yet the molecular mechanisms underlying leaf development remain incompletely understood. In this study, a narrow leaf mutant, m625, was identified in rice (Oryza sativa L.), exhibiting pleiotropic developmental defects. Pigment measurement revealed reduced levels of photochromic pigments in m625. Cytological analysis demonstrated that the m625 gene affected vascular patterns and cell division. Specifically, the narrowing of the leaf was attributed to a decrease in small vein number, shorter vein spacing, and an abnormal V-shaped arrangement of bulliform cells, while the thickening was caused by longer leaf veins, thicker mesophyll cells, and an increased number of parenchyma cell layers. The dwarf stature and thickened internode were primarily due to shortened internodes and an increase in cell layers, respectively. Positional cloning and complementation assays indicated that the m625 gene is a novel allele of NAL1. In the m625 mutant, a nucleotide deletion at position 1103 in the coding sequence of NAL1 led to premature termination of protein translation. Further RNA-Seq and qRT-PCR analyses revealed that the m625 gene significantly impacted regulatory pathways related to IAA and ABA signal transduction, photosynthesis, and lignin biosynthesis. Moreover, the m625 mutant displayed thinner sclerenchyma and cell walls in both the leaf and stem, particularly showing reduced lignified cell walls in the midrib of the leaf. In conclusion, our study suggests that NAL1, in addition to its known roles in IAA transport and leaf photosynthesis, may also participate in ABA signal transduction, as well as regulate secondary cell wall formation and sclerenchyma thickness through lignification.

Identification of novel pathogenic variants of CUBN in patients with isolated proteinuria.

Although proteinuria is long recognized as an independent risk factor for progressive chronic kidney diseases, not all forms of proteinuria are detrimental to kidney function, one of which is isolated proteinuria caused by cubilin (CUBN)-specific mutations. CUBN encodes an endocytic receptor, initially found to be responsible for the Imerslund-Gräsbeck syndrome (IGS; OMIM #261100) characterized by a combined phenotype of megaloblastic anemia and proteinuria. After analyzing their clinical and pathological characterizations, next-generation sequencing for renal disease genes or whole-exome sequencing (WES) was performed on four patients with non-progressive isolated proteinuria. CUBN biallelic pathogenic variants were identified and further analyzed by cDNA-PCR sequencing, immunohistochemistry, minigene assay, and multiple in silico prediction tools, including 3D protein modeling. Here, we present four patients with isolated proteinuria caused by CUBN C-terminal biallelic pathogenic variants, all of which showed no typical IGS symptoms, such as anemia and vitamin B12 deficiency. Their urine protein levels fluctuated between +~++ and estimated glomerular filtration rate (eGFR) were normal or slightly higher. Mild mesangial hypercellularity was found in three children's renal biopsies. A homozygous splice-site variant of CUBN (c.6821+3 (IVS44) A>G) was proven to result in the exon 44 skipping and premature translation termination by cDNA sequencing and immunohistochemistry. Compound heterozygous mutations were identified among the other three children, including another novel splice-site variant (c.10764+1 (IVS66) G>A) causing the retention of first 4 nucleotides in intron 66 by minigene assay, two unreported missense mutations (c.4907G>A (p.R1636Q); c. 9095 A>G (p.Y3032C)), and two reported missense mutations in China (c.8938G>A (p.D2980N); c. 9287T>C (p.L3096P)), locating behind the vitamin B12-binding domain, affecting CUB11, CUB16, CUB22, CUB23, and CUB27 domains, respectively. These results demonstrate that above CUBN mutations may cause non-progressive and isolated proteinuria, expanding the variant spectrum of CUBN and benefiting our understanding of proteinuria and renal function.

Stop codon readthrough as a treatment option for epidermolysis bullosa-Where we are and where we are going.

In the context of rare genetic diseases caused by nonsense mutations, the concept of induced stop codon readthrough (SCR) represents an attractive avenue in the ongoing search for improved treatment options. Epidermolysis bullosa (EB)-exemplary for this group of diseases-describes a diverse group of rare, blistering genodermatoses. Characterized by extreme skin fragility upon minor mechanical trauma, the most severe forms often result from nonsense mutations that lead to premature translation termination and loss of function of essential proteins at the dermo-epidermal junction. Since no curative interventions are currently available, medical care is mainly limited to alleviating symptoms and preventing complications. Complementary to attempts of gene, cell and protein therapy in EB, SCR represents a promising medical alternative. While gentamicin has already been examined in several clinical trials involving EB, other potent SCR inducers, such as ataluren, may also show promise in treating the hitherto non-curative disease. In addition to the extensively studied aminoglycosides and their derivatives, several other substance classes-non-aminoglycoside antibiotics and non-aminoglycoside compounds-are currently under investigation. The extensive data gathered in numerous invitro experiments and the perspectives they reveal in the clinical setting will be discussed in this review.

A system of reporters for comparative investigation of EJC-independent and EJC-enhanced nonsense-mediated mRNA decay.

Nonsense-mediated mRNA decay (NMD) is a network of pathways that degrades transcripts that undergo premature translation termination. In mammals, NMD can be divided into the exon junction complex (EJC)-enhanced and EJC-independent branches. Fluorescence- and luminescence-based reporters have long been effective tools to investigate NMD, yet existing reporters largely focus on the EJC-enhanced pathway. Here, we present a system of reporters for comparative studies of EJC-independent and EJC-enhanced NMD. This system also enables the study of NMD-associated outcomes such as premature termination codon (PTC) readthrough and truncated protein degradation. These reporters are compatible with fluorescence or luminescence-based readouts via transient transfection or stable integration. Using this reporter system, we show that EJC-enhanced NMD RNA levels are reduced by 2- or 9-fold and protein levels are reduced by 7- or 12-fold compared to EJC-independent NMD, depending on the reporter gene used. Additionally, the extent of readthrough induced by G418 and an NMD inhibitor (SMG1i), alone and in combination, varies across NMD substrates. When combined, G418 and SMG1i increase readthrough product levels in an additive manner for EJC-independent reporters, while EJC-enhanced reporters show a synergistic effect. We present these reporters as a valuable toolkit to deepen our understanding of NMD and its associated mechanisms.

Reclassifying BRCA1 c.4358-2A > G and BRCA2 c.475 + 5G > C variants from “Uncertain Significance” to “Pathogenic” based on minigene assays and clinical evidence

BackgroundPathogenic variants in BRCA genes play a crucial role in the pathogenesis of ovarian cancer. Intronic variants of uncertain significance (VUS) may contribute to pathogenicity by affecting splicing. Currently, the significance of many intronic variants in BRCA has not been clarified, impacting patient treatment strategies and the management of familial cases.MethodA retrospective study was conducted to analyze BRCA intronic VUS in a cohort of 707 unrelated ovarian cancer patients at a single institution from 2018 to 2023. Three splicing predictors were employed to analyze detected intronic VUS. Variants predicted to have splicing alterations were selected for further validation through minigene assays. Patient and familial investigations were conducted to comprehend cancer incidence within pedigrees and the application of poly (ADP-ribose) polymerase inhibitors (PARPi) by the patients. In accordance with the guidelines of the American College of Medical Genetics and Genomics (ACMG), the intronic VUS were reclassified based on minigene assay results and clinical evidence.ResultApproximately 9.8% (69/707) of patients were identified as carriers of 67 different VUS in BRCA1/2, with four intronic variants accounting for 6% (4/67) of all VUS. Splicing predictors indicated potential splicing alterations in splicing for BRCA1 c.4358-2A>G and BRCA2 c.475+5G>C variants. Minigene assays utilizing the pSPL3 exon trapping vector revealed that these variants induced changes in splicing sites and frameshift, resulting in premature termination of translation (p. Ala1453Glyfs and p. Pro143Glyfs). According to ACMG guidelines, BRCA1 c.4358-2A>G and BRCA2 c.475+5G>C were reclassified as pathogenic variants. Pedigree investigations were conducted on patients with BRCA1 c.4358-2A>G variant, and the detailed utilization of PARPi provided valuable insights into research on PARPi resistance.ConclusionTwo intronic VUS were reclassified as pathogenic variants. A precise classification of variants is crucial for the effective treatment and management of both patients and healthy carriers.

Genetic variations at BBX24 and MYB110a loci regulated anthocyanin accumulation in pear bud sports

Genetic variation contributes to the phenotypic diversity of plants. Most red pear cultivars that accumulate anthocyanins originated from somatic variation and are termed bud sports. ‘Hongzaosu’ is a bud sport derived from the green pear ‘Zaosu’. A new genetic map was constructed from a population derived from the cross of ‘Yuluxiang’ and ‘Hongzaosu’, from which PpBBX24 was identified as a crucial gene controlling anthocyanin accumulation. Genetic and phylogenetic evidence revealed that PpBBX24 is a repressor of anthocyanin biosynthesis in pear. A 14 bp deletion was detected in the third exon of PpBBX24 in ‘Hongzaosu’, resulting in premature termination of protein translation. The truncated PpBBX24 protein was a positive regulator of anthocyanin biosynthesis by activating the transcription of PpCHS and PpUFGT. Three independent variations in the BBX24 coding region that led to premature termination of translation were detected in other pear bud sports and the progeny of a bud sport that all accumulate anthocyanins. The genome of ‘Hongzaosu’ was assembled using both long-read and short-read sequences. By combining genomic and transcriptomic data, allele-specific expression of PpMYB110a was observed in the fruit skin of ‘Hongzaosu’, which was likely caused by large variation in the promoter. This work enhances understanding of coloration in red pears and provides a novel genomic resource for further studies on ‘Hongzaosu’ pear.

Newly discovered variants in unexplained neonatal encephalopathy.

The genetic background of neonatal encephalopathy (NE) is complicated and early diagnosis is beneficial to optimizing therapeutic strategy for patients. NE Patients with unclear etiology received regular clinical tests including ammonia test, metabolic screening test, amplitude-integrated electroencephalographic (aEEG) monitoring, brain Magnetic Resonance Imaging (MRI) scanning, and genetic test. The protein structure change was predicted using Dynamut2 and RoseTTAFold. 15 out of a total of 113 NE Patients were detected with newly reported pathogenic variants. In this sub-cohort, (1) seizure was the primary initial symptoms; (2) four patients had abnormal metabolic screening results, and two of them were also diagnosed with excessive blood ammonia concentration; (3) the brain MRI results were irregular in three infants and the brain waves were of moderate-severe abnormality in about a half of the patients. The novel pathogenic variants discovered in this study belonged to 12 genes, and seven of them were predicted to introduce a premature translation termination. In-silicon predictions showed that four variants were destructive to the protein structure of KCNQ2. Our study expands the mutation spectrum of genes associated with NE and introduces new evidence for molecular diagnosis in this newborn illness.

Drosophila models used to simulate human ATP1A1 gene mutations that cause Charcot-Marie-Tooth type 2 disease and refractory seizures

Abstract JOURNAL/nrgr/04.03/01300535-990000000-00156/inline-graphic1/v/2023-12-22T072605Z/r/image-tiff Certain amino acids changes in the human Na+/K+-ATPase pump, ATPase Na+/K+ transporting subunit alpha 1 (ATP1A1), cause Charcot-Marie-Tooth disease type 2 (CMT2) disease and refractory seizures. To develop in vivo models to study the role of Na+/K+-ATPase in these diseases, we modified the Drosophila gene homolog, Atpα, to mimic the human ATP1A1 mutations that cause CMT2. Mutations located within the helical linker region of human ATP1A1 (I592T, A597T, P600T, and D601F) were simultaneously introduced into endogenous Drosophila Atpα by CRISPR/Cas9-mediated genome editing, generating the AtpαTTTF model. In addition, the same strategy was used to generate the corresponding single point mutations in flies (AtpαI571T, AtpαA576T, AtpαP579T, and AtpαD580F). Moreover, a deletion mutation (Atpαmut) that causes premature termination of translation was generated as a positive control. Of these alleles, we found two that could be maintained as homozygotes (AtpαI571T and AtpαP579T). Three alleles (AtpαA576T, AtpαP579 and AtpαD580F) can formed heterozygotes with the Atpαmut allele. We found that the Atpα allele carrying these CMT2-associated mutations showed differential phenotypes in Drosophila. Flies heterozygous for AtpαTTTF mutations have motor performance defects, a reduced lifespan, seizures, and an abnormal neuronal morphology. These Drosophila models will provide a new platform for studying the function and regulation of the sodium-potassium pump.

Клинические проявления и дифференциальная диагностика редкой формы наследственной дисплазии соединительной ткани - синдрома вялой кожи (сutis laxa)

Article is devoted to one of the rare forms of monogenic connective tissue disease, Cutis Laxa with an autosomal recessive type of inheritance (ARCL1C), the Urban-Rifkin-Davis syndrome. The bibliographical data on this disease and the medical records of a 6-year-old male pediatric patient who was observed at the Clinical Genetics Department of the Research and Clinical Institute of Pediatrics named after Academician Yuri Veltischev with the Pirogov Russian National Research Medical University (Moscow, Russia) are presented. In addition to skin lesions, the child had disorders of the cardiovascular, respiratory and urinary systems. The diagnosis was confirmed by the DNA diagnostics results: the two mutations in the compound heterozygous state were found in the LTBP4 gene: the variant rs397515430 p.1342C>T previously described in the scientific sources in exon 11 leading to a stop codon and premature termination of translation - p.Arg475Ter; the second variant, not previously described in the literature, was found in intron 4 - c.452-22A>C. A differential diagnosis with other phenotypically similar diseases was carried out. Further medical supervision of the patient should be carried out with the mandatory involvement of the pulmonologist, the cardiologist and the nephrologist.

[Analysis of clinical characteristics and ATP7A gene variants in a Chinese pedigree affected with Menkes disease].

To explore the clinical characteristics and variants of ATP7A gene in a child with Menkes disease. A child with Menkes disease diagnosed at the West China Second Hospital of Sichuan University and its family members in March 2022 was selected as the study subjects. Clinical manifestations and results of laboratory tests and genetic testing were summarized. The main manifestations of the child included seizures, global development delay, facial dysmorphism, sparse and curly hair, increased lactate and pyruvate, and significantly decreased cuprin. EEG showed frequent issuance of multifocal spikes, spines, polyspines (slow) and polymorphic slow waves. Multiple tortuous vascular shadows were observed on cranial MRI. Whole exome sequencing revealed that the child has harbored a hemizygous c.3076delA (p.ile1026*) variant of the ATP7A gene, which was inherited from his mother. The variant may lead to premature termination of protein translation. Based on the guidelines from the American College of Medical Genetics and Genomics (ACMG), the variant was predicted as pathogenic (PVS1+PM2+PP4). The c.3076delA (p.Ile1026*) variant of the ATP7A gene probably underlay the Menkes disease in this child. Above finding has provided evidence for clinical diagnosis. The significantly increased lactic acid and pyruvate can be used as a reference for the diagnosis and management of Menkes disease. Microscopic abnormalities in the hair of the carriers may also facilitate their diagnosis.

TRNA therapeutics for genetic diseases.

Transfer RNAs (tRNAs) have a crucial role in protein synthesis, and in recent years, their therapeutic potential for the treatment of genetic diseases - primarily those associated with a mutation altering mRNA translation - has gained significant attention. Engineering tRNAs to readthrough nonsense mutation-associated premature termination of mRNA translation can restore protein synthesis and function. In addition, supplementation of natural tRNAs can counteract effects of missense mutations in proteins crucial for tRNA biogenesis and function in translation. This Review will present advances in the development of tRNA therapeutics with high activity and safety in vivo and discuss different formulation approaches for single or chronic treatment modalities. The field of tRNA therapeutics is still in its early stages, and a series of challenges related to tRNA efficacy and stability in vivo, delivery systems with tissue-specific tropism, and safe and efficient manufacturing need to be addressed.

The red/far-red light photoreceptor FvePhyB regulates tissue elongation and anthocyanin accumulation in woodland strawberry.

Light is an important environmental signal that influences plant growth and development. Among the photoreceptors, phytochromes can sense red/far-red light to coordinate various biological processes. However, their functions in strawberry are not yet known. In this study, we identified an EMS mutant, named P8, in woodland strawberry (Fragaria vesca) that showed greatly increased plant height and reduced anthocyanin content. Mapping-by-sequencing revealed that the causal mutation in FvePhyB leads to premature termination of translation. The light treatment assay revealed that FvePhyB is a bona fide red/far-red light photoreceptor, as it specifically inhibits hypocotyl length under red light. Transcriptome analysis showed that the FvePhyB mutation affects the expression levels of genes involved in hormone synthesis and signaling and anthocyanin biosynthesis in petioles and fruits. The srl mutant with a longer internode is caused by a mutation in the DELLA gene FveRGA1 (Repressor of GA1) in the gibberellin pathway. We found that the P8 srl double mutant has much longer internodes than srl, suggesting a synergistic role of FvePhyB and FveRGA1 in this process. Taken together, these results demonstrate the important role of FvePhyB in regulating plant architecture and anthocyanin content in woodland strawberry.

Nucleoporin 50 proteins affect longevity and salinity stress tolerance in seeds.

Nucleoporin 50 (Nup50) is an evolutionarily conserved protein that is a constituent of the nuclear pore complex (NPC); however, its physiological role in plants is unclear. Arabidopsis has two Nup50 proteins, Nup50a and Nup50b, which are highly expressed in developing seeds. Green fluoresceent protein (GFP)-fused Nup50a and Nup50b are localized exclusively in the nucleopolasm, implying an additional function beyond the NPC in the nuclear envelope. To investigate the function of Nup50s, we employed the CRISPR/Cas9 [clustered regularly interspaced palindromic repeats (CRISPR)/CRISPR-associated protein 9] system to generate a nup50a nup50b double mutant, which exhibited premature translation termination of both Nup50 proteins. While the mutant showed no significant abnormal phenotype during vegetative growth, the nup50a nup50b seeds had an abnormal shape compared with the wild type. Comparative transcriptomics using immature seeds revealed that Nup50s regulate the expression of various genes, including cell wall-related genes. The nup50a nup50b seeds exhibited reduced seed longevity and salinity stress tolerance. Tetrazolium uptake and mucilage release assays implied that the nup50a nup50b seeds had greater water permeability than the wild type. Taken together, our results imply that Nup50s play a critical role in seed formation by regulating gene expression.

X-linked RBBP7 mutation causes maturation arrest and testicular tumors.

Maturation arrest (MA) is a subtype of non-obstructive azoospermia, and male infertility is a known risk factor for testicular tumors. However, the genetic basis for many affected individuals remains unknown. Here, we identified a deleterious hemizygous variant of X-linked retinoblastoma-binding protein 7 (RBBP7) as a potential key cause of MA, which was also found to be associated with the development of Leydig cell tumors. This mutation resulted in premature protein translation termination, affecting the sixth WD40 domain of the RBBP7 and the interaction of the mutated RBBP7 with histone H4. Decreased BRCA1 and increased γH2AX were observed in the proband. In mouse spermatogonial and pachytene spermatocyte-derived cells, deprivation of rbbp7 led to cell cycle arrest and apoptosis. In Drosophila, knockdown of RBBP7/Caf1-55 in germ cells resulted in complete absence of germ cells and reduced testis size, whereas knockdown of RBBP7/Caf1-55 in cyst cells resulted in hyperproliferative testicular cells. Interestingly, male infertility caused by Caf1-55 deficiency was rescued by ectopic expression of wild-type human RBBP7 but not mutant variants, suggesting the importance of RBBP7 in spermatogenesis. Our study provides insights into the mechanisms underlying the co-occurrence of MA and testicular tumors and may pave the way for innovative genetic diagnostics of these 2 diseases.

Novel heterozygous VPS13A pathogenic variants in chorea-neuroacanthocytosis: a case report

BackgroundChorea-acanthocytosis (ChAc) is a rare hereditary autosomal recessive neurodegenerative disorder caused by pathogenic variants of the Vacuolar Protein Sorting 13 homolog A (VPS13A) gene. The variant spectrum of VPS13A has not been completely elucidated. This study reports two novel heterozygous VPS13A pathogenic variants in ChAc that expand the variant spectrum of VPS13A.Case presentationWe described a case of a 29-year-old man with typical clinical manifestations of ChAc, including chorea, orofacial lingual dyskinesia, vocal tics, elevated serum biochemical indicators, increased acanthocytes in peripheral blood, and caudate nucleus atrophy. Next-generation sequencing revealed two heterozygous variants of VPS13A: a nonsense variant (NM_033305.2: c.8215G > T, p. Glu2739Ter) and a deletion variant in the exons 25–31.ConclusionThe identified nonsense variant gives rise to premature translation termination, while the deletion variant is expected to cause a significant in-frame deletion of amino acid residues in the encoded protein. Both variants are considered to be pathogenic and result in loss-of-function proteins. These findings have implications for the genetic counseling of patients with VPS13A variants.

Transfer RNA-mediated restoration of potassium current and electrical correction in premature termination long-QT syndrome hERG mutants

Disease-causing premature termination codons (PTCs) individually disrupt the functional expression of hundreds of genes and represent a pernicious clinical challenge. In the heart, loss-of-function mutations in the hERG potassium channel account for approximately 30% of long-QT syndrome arrhythmia, a lethal cardiac disorder with limited treatment options. Premature termination of ribosomal translation produces a truncated and, for potassium channels, a potentially dominant-negative protein that impairs the functional assembly of the wild-type homotetrameric hERG channel complex. We used high-throughput flow cytometry and patch-clamp electrophysiology to assess the trafficking and voltage-dependent activity of hERG channels carrying patient PTC variants that have been corrected by anticodon engineered tRNA. Adenoviral-mediated expression of mutant hERG channels in cultured adult guinea pig cardiomyocytes prolonged action potential durations, and this deleterious effect was corrected upon adenoviral delivery of a human ArgUGA tRNA to restore full-length hERG protein. The results demonstrate mutation-specific, context-agnostic PTC correction and elevate the therapeutic potential of this approach for rare genetic diseases caused by stop codons.

Exclusion model of mRNA translation with collision-induced ribosome drop-off

The translation of messenger RNA transcripts to proteins is commonly modeled as a one-dimensional totally asymmetric exclusion process with extended particles. Here we focus on the effects of premature termination of translation through the irreversible detachment of ribosomes. We consider a model where the detachment is induced by the unsuccessful attempt to move to an occupied site. The model is exactly solvable in a simplified geometry consisting of the translation initiation region followed by a single slow site representing a translation bottleneck. In agreement with recent experimental and computational studies we find a non-monotonic dependence of the ribosome current on the initiation rate, but only if the leading particle in a colliding pair detaches. Simulations show that the effect persists for larger lattices and extended bottlenecks. In the homogeneous system the ribosome density decays asymptotically as the inverse square root of the distance to the initiation site.