Arthrogryposis, Renal dysfunction and Cholestasis (ARC) syndrome is a rare inherited disorder caused by defects in the VPS33B trafficking protein, leading to impaired bile flow, progressive liver disease and early death. No effective treatments are currently available. Gene therapy offers a potential approach by restoring the missing VPS33B protein in liver cells. Here, we show that liver-targeted lentiviral gene therapy safely and effectively rescues key features of ARC syndrome in a mouse model following in vivo administration by intravenous injection, combined with transient liver macrophage depletion. To assess the treatment efficacy, disease severity is exacerbated by 0.25% cholic acid diet feeds. A liver-specific vector shows a favourable safety profile over a ubiquitous vector. Mice receiving the safe liver-specific vector display improved survival, growth and liver function, reduced fibrosis and bile canaliculi restoration. These findings support targeted gene therapy as a promising treatment for ARC syndrome and related early-onset liver diseases.

Trisomy of chromosome 21, the cause of Down syndrome (DS), is the most commonly occurring genetic cause of Alzheimer’s disease (AD). Here, we compare the frontal cortex proteome of people with Down syndrome–Alzheimer’s disease (DSAD) to demographically matched cases of early onset AD and healthy ageing controls. We find dysregulation of the proteome, beyond proteins encoded by chromosome 21, including an increase in the abundance of the key AD-associated protein, APOE, in people with DSAD compared to matched cases of AD. To understand the cell types that may contribute to changes in protein abundance, we undertook a matched single-nuclei RNA-sequencing study, which demonstrated that APOE expression was elevated in subtypes of astrocytes, endothelial cells, and pericytes in DSAD. We further investigate how trisomy 21 may cause increased APOE. Increased abundance of APOE may impact the development of, or response to, AD pathology in the brain of people with DSAD, altering disease mechanisms with clinical implications. Overall, these data highlight that trisomy 21 alters both the transcriptome and proteome of people with DS in the context of AD, and that these differences should be considered when selecting therapeutic strategies for this vulnerable group of individuals who have high risk of early onset dementia.

Children infected with SARS-CoV-2 rarely progress to respiratory failure. However, the risk of mortality in infected people over 85 years of age remains high. Here we investigate differences in the cellular landscape and function of paediatric (<12 years), adult (30-50 years) and older adult (>70 years) ex vivo cultured nasal epithelial cells in response to infection with SARS-CoV-2. We show that cell tropism of SARS-CoV-2, and expression of ACE2 and TMPRSS2 in nasal epithelial cell subtypes, differ between age groups. While ciliated cells are viral replication centres across all age groups, a distinct goblet inflammatory subtype emerges in infected paediatric cultures and shows high expression of interferon-stimulated genes and incomplete viral replication. In contrast, older adult cultures infected with SARS-CoV-2 show a proportional increase in basaloid-like cells, which facilitate viral spread and are associated with altered epithelial repair pathways. We confirm age-specific induction of these cell types by integrating data from in vivo COVID-19 studies and validate that our in vitro model recapitulates early epithelial responses to SARS-CoV-2 infection.

Parkinson's disease is increasingly prevalent. It progresses from the pre-motor stage (characterised by non-motor symptoms like REM sleep behaviour disorder), to the disabling motor stage. We need objective biomarkers for early/pre-motor disease stages to be able to intervene and slow the underlying neurodegenerative process. Here, we validate a targeted multiplexed mass spectrometry assay for blood samples from recently diagnosed motor Parkinson's patients (n = 99), pre-motor individuals with isolated REM sleep behaviour disorder (two cohorts: n = 18 and n = 54 longitudinally), and healthy controls (n = 36). Our machine-learning model accurately identifies all Parkinson patients and classifies 79% of the pre-motor individuals up to 7 years before motor onset by analysing the expression of eight proteins-Granulin precursor, Mannan-binding-lectin-serine-peptidase-2, Endoplasmatic-reticulum-chaperone-BiP, Prostaglaindin-H2-D-isomaerase, Interceullular-adhesion-molecule-1, Complement C3, Dickkopf-WNT-signalling pathway-inhibitor-3, and Plasma-protease-C1-inhibitor. Many of these biomarkers correlate with symptom severity. This specific blood panel indicates molecular events in early stages and could help identify at-risk participants for clinical trials aimed at slowing/preventing motor Parkinson's disease. Parkinson's disease is lacking easily accessible biomarkers. Here the authors show, that targeted blood proteomics is feasible to identify the patients and to predict the phenoconvertion in prodromal subjects up to 7 years before symptom onset.

SARS-CoV-2 initially infects cells in the nasopharynx and oral cavity. The immune system at these mucosal sites plays a crucial role in minimizing viral transmission and infection. To develop new strategies for preventing SARS-CoV-2 infection, this study aimed to identify proteins that protect against viral infection in saliva. We collected 551 saliva samples from 290 healthcare workers who had tested positive for COVID-19, before vaccination, between June and December 2020. The samples were categorized based on their ability to block or enhance infection using in vitro assays. Mass spectrometry and enzyme-linked immunosorbent assay experiments were used to identify and measure the abundance of proteins that specifically bind to SARS-CoV-2 antigens. Immunoglobulin (Ig)A specific to SARS-CoV-2 antigens was detectable in over 83% of the convalescent saliva samples. We found that concentrations of anti-receptor-binding domain IgA >500 pg/µg total protein in saliva correlate with reduced viral infectivity in vitro. However, there is a dissociation between the salivary IgA response to SARS-CoV-2, and systemic IgG titers in convalescent COVID-19 patients. Then, using an innovative technique known as spike-baited mass spectrometry, we identified novel spike-binding proteins in saliva, most notably vimentin, which correlated with increased viral infectivity in vitro and could serve as a therapeutic target against COVID-19.

During the COVID-19 pandemic, development of diagnostic tests was vital to chart the course and to reduce the impact of the infection. Continued testing and surveillance of vaccine escape will continue for years to come which presents an opportunity to integrate such testing into clinical biochemistry laboratories that form part of integrated healthcare testing. Here we describe a protocol for a targeted mass spectrometry based proteomic assay (COVIDCAP) developed to detect SARS-CoV-2 peptides from oro-nasopharyngeal swabs (ONP) and saliva. This uses novel SISCAPA antibodies bound to magnetic beads and subsequent analysis of captured and purified SARS-CoV-2 nucleocapsid (NCAP) peptides. The method involves immediate deactivation of the sample using an ethanolic solution. This simultaneously inactivates the virus and denatures viral proteins at sampling in contrast to the approach for RT-PCR testing, with benefits for the assay as well as for downstream processing. A plate-based preparation of the samples involving acetone precipitation followed by a short tryptic digestion and subsequent immunocapture allows LC-MS detection and quantification of peptides from the NCAP protein, in a 3-minute inject-to-inject assay with an LOD of 20 attomoles from starting sample. For 576 ONP swab samples taken as exemplars here, the sensitivity and specificity of this analysis is shown to be 97.0% and 96.6% respectively.

Parkinson’s Disease (PD) is an increasingly prevalent condition within the aging population. PD can be attributed to rare genetic mutations, but most cases are sporadic where the gene-environment interactions are unknown/likely contributory. Age related dysregulation of the glycosphingolipid degradation pathway has been implicated in the development of PD, however, our understanding of how brain lipids vary across different regions of the brain, with age and in disease stages, remains limited. In this study we profiled several phospho- and sphingolipid classes in eight distinct regions of the human brain and investigated the association of lipids with a spatio-temporal pathology gradient, utilising PD samples from early, mid, and late stages of the disease. We performed high-precision tissue sampling in conjunction with targeted LC-MS/MS and applied this to post-mortem samples from PD and control subjects. The lipids were analysed for correlations with untargeted proteomics and mitochondrial activity data, in a multi-omics approach. We concluded that the different brain regions demonstrated their own distinct profiles and also found that several lipids were correlated with age. The strongest differences between PD and controls were identified in ganglioside, sphingomyelin and n-hexosylceramides. Sphingomyelin was also found to correlate with several proteins implicated in Parkinson’s disease pathways. Mitochondrial activity was correlated with the levels of several lipids in the putamen region. Finally, we identified a gradient corresponding to Braak’s disease spread across the brain regions, where the areas closer to the brainstem/substantia nigra showed alterations in PC, LPC and glycosphingolipids, while the cortical regions showed changes in glycosphingolipids, specifically gangliosides, HexCer and Hex2Cer. ![Figure][1] ### Competing Interest Statement The authors have declared no competing interest. [1]: pending:yes

Proteomics studies often explore phenotypic differences between whole organs and systems. Within the heart, more subtle variation exists. To date, differences in the underlying proteome are only described between whole cardiac chambers. This study, using the bovine heart as a model, investigates inter-regional differences and assesses the feasibility of measuring detailed, cross-tissue variance in the cardiac proteome. Using a bovine heart, we created a two-dimensional section through a plane going through two chambers. This plane was further sectioned into 4 × 4 mm cubes and analysed using label-free proteomics. We identified three distinct proteomes. When mapped to the extracted sections, the proteomes corresponded largely to the outer wall of the right ventricle and secondly to the outer wall of the left ventricle, right atrial appendage, tricuspid and mitral valves, modulator band, and parts of the left atrium. The third separate proteome corresponded to the inner walls of the left and right ventricles, septum, and left atrial appendage. Differential protein abundancies indicated differences in energy metabolism between regions. Data analyses of the mitochondrial proteins revealed a variable pattern of abundances of complexes I–V between the proteomes, indicating differences in the bioenergetics of the different cardiac sub-proteomes. Mapping of disease-associated proteins interestingly showed desmoglein-2, for which defects in this protein are known to cause Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy, which was present predominantly in the outer wall of the left ventricle. This study highlights that organs can have variable proteomes that do not necessarily correspond to anatomical features.

The urea cycle enzyme argininosuccinate lyase (ASL) enables the clearance of neurotoxic ammonia and the biosynthesis of arginine. Patients with ASL deficiency present with argininosuccinic aciduria, an inherited metabolic disease with hyperammonemia and a systemic phenotype coinciding with neurocognitive impairment and chronic liver disease. Here, we describe the dysregulation of glutathione biosynthesis and upstream cysteine utilization in ASL-deficient patients and mice using targeted metabolomics and in vivo positron emission tomography (PET) imaging using ( S )-4-(3- 18 F-fluoropropyl)- l -glutamate ([ 18 F]FSPG). Up-regulation of cysteine metabolism contrasted with glutathione depletion and down-regulated antioxidant pathways. To assess hepatic glutathione dysregulation and liver disease, we present [ 18 F]FSPG PET as a noninvasive diagnostic tool to monitor therapeutic response in argininosuccinic aciduria. Human hASL mRNA encapsulated in lipid nanoparticles improved glutathione metabolism and chronic liver disease. In addition, hASL mRNA therapy corrected and rescued the neonatal and adult Asl-deficient mouse phenotypes, respectively, enhancing ureagenesis. These findings provide mechanistic insights in liver glutathione metabolism and support clinical translation of mRNA therapy for argininosuccinic aciduria.

Types A and B Niemann-Pick disease (NPD) are inherited multisystem lysosomal storage disorders due to mutations in the SMPD1 gene. Respiratory dysfunction is a key hallmark of NPD, yet the mechanism for this is underexplored. SMPD1 encodes acid sphingomyelinase (ASM), which hydrolyses sphingomyelin to ceramide and phosphocholine. Here, we present a Drosophila model of ASM loss-of-function, lacking the fly orthologue of SMPD1, dASM, modelling several aspects of the respiratory pathology of NPD. dASM is expressed in the late-embryonic fly respiratory network, the trachea, and is secreted into the tracheal lumen. Loss of dASM results in embryonic lethality, and the tracheal lumen fails to fill normally with gas prior to eclosion. We demonstrate that the endocytic clearance of luminal constituents prior to gas-filling is defective in dASM mutants, and is coincident with autophagic, but not lysosomal defects, in late stage embryonic trachea. Finally, we show that although bulk sphingolipids are unchanged, dietary loss of lipids in combination with genetic and pharmacological block of ceramide synthesis rescues the airway gas-filling defects. We highlight myriocin as a potential therapeutic drug for the treatment of the developmental respiratory defects associated with ASM deficiency, and present a new NPD model amenable to genetic and pharmacological screens.

Summary The role of the SNCA gene locus in driving Parkinson’s disease (PD) through rare and common genetic variation is well-recognized, but the transcriptional diversity of SNCA in vulnerable cell types remains unclear. We performed SNCA long-read RNA sequencing in human dopaminergic neurons and show that annotated SNCA transcripts account for only 5% of expression. Rather, the majority of expression (75%) at the SNCA locus originates from transcripts with alternative 5’ and 3’ untranslated regions. Importantly, 10% originates from transcripts encoding open reading frames not previously annotated, which are translated and detectable in human postmortem brain. Defining the 3’ untranslated regions enabled the rational design of antisense oligonucleotides targeting the majority of SNCA transcripts, leading to the effective reversal of PD pathology, including protein aggregation, mitochondrial dysfunction, and toxicity. Resolving the complexity of the SNCA transcriptional landscape impacts RNA therapies and highlights differences in protein isoforms and their contribution to disease.

BACKGROUND:Hypertrophic cardiomyopathy (HCM) is defined clinically by pathological left ventricular hypertrophy. We have previously developed a plasma proteomics biomarker panel that correlates with clinical markers of disease severity and sudden cardiac death risk in adult patients with HCM. The aim of this study was to investigate the utility of adult biomarkers and perform new discoveries in proteomics for childhood-onset HCM.METHODS:Fifty-nine protein biomarkers were identified from an exploratory plasma proteomics screen in children with HCM and augmented into our existing multiplexed targeted liquid chromatography-tandem/mass spectrometry-based assay. The association of these biomarkers with clinical phenotypes and outcomes was prospectively tested in plasma collected from 148 children with HCM and 50 healthy controls. Machine learning techniques were used to develop novel pediatric plasma proteomic biomarker panels.RESULTS:Four previously identified adult HCM markers (aldolase fructose-bisphosphate A, complement C3a, talin-1, and thrombospondin 1) and 3 new markers (glycogen phosphorylase B, lipoprotein a and profilin 1) were elevated in pediatric HCM. Using supervised machine learning applied to training (n=137) and validation cohorts (n=61), this 7-biomarker panel differentiated HCM from healthy controls with an area under the curve of 1.0 in the training data set (sensitivity 100% [95% CI, 95-100]; specificity 100% [95% CI, 96-100]) and 0.82 in the validation data set (sensitivity 75% [95% CI, 59-86]; specificity 88% [95% CI, 75-94]). Reduced circulating levels of 4 other peptides (apolipoprotein L1, complement 5b, immunoglobulin heavy constant epsilon, and serum amyloid A4) found in children with high sudden cardiac death risk provided complete separation from the low and intermediate risk groups and predicted mortality and adverse arrhythmic outcomes (hazard ratio, 2.04 [95% CI, 1.0-4.2]; P=0.044).CONCLUSIONS:In children, a 7-biomarker proteomics panel can distinguish HCM from controls with high sensitivity and specificity, and another 4-biomarker panel identifies those at high risk of adverse arrhythmic outcomes, including sudden cardiac death.

Type A and B Niemann Pick (NPD) is an inherited multisystem lysosomal storage disorder caused by mutations in the SMPD1 gene. Respiratory dysfunction is a key hallmark of NPD, although the precise mechanisms underlying these pathologies is underexplored. Here we present a Drosophila model of Smpd1 loss-of-function that displays significant respiratory defects. Smpd1 is expressed in the late-embryonic fly respiratory network, the trachea, and is secreted into the tracheal lumen. Loss of Smpd1 results in embryonic lethality, and although tracheal morphology appears normal, trachea fail to fill with gas prior to eclosion. We demonstrate that clearance of luminal constituents through endocytosis prior to gas-filling is defective in Smpd1 mutants. This is coincident with autophagic, but not lysosomal defects. Finally, we show that although bulk sphingolipids are unchanged, dietary loss of lipids in combination with genetic and pharmacological block of ceramide synthesis is sufficient to rescue gas-filling defects. In summary, we present a novel NPD model amenable to genetic and pharmacological screens, and highlight myriocin, an inhibitor of ceramide synthesis, as a potential therapeutic drug for the treatment of NPD. ### Competing Interest Statement The authors have declared no competing interest.

A functional role has been ascribed to the human dihydrofolate reductase 2 ( DHFR2 ) gene based on the enzymatic activity of recombinant versions of the predicted translated protein. However, the in vivo function is still unclear. The high amino acid sequence identity (92%) between DHFR2 and its parental homolog, DHFR, makes analysis of the endogenous protein challenging. This paper describes a targeted mass spectrometry proteomics approach in several human cell lines and tissue types to identify DHFR2-specific peptides as evidence of its translation. We show definitive evidence that the DHFR2 activity in the mitochondria is in fact mediated by DHFR, and not DHFR2. Analysis of Ribo-seq data and an experimental assessment of ribosome association using a sucrose cushion showed that the two main Ensembl annotated mRNA isoforms of DHFR2, 201 and 202, are differentially associated with the ribosome. This indicates a functional role at both the RNA and protein level. However, we were unable to detect DHFR2 protein at a detectable level in most cell types examined despite various RNA isoforms of DHFR2 being relatively abundant. We did detect a DHFR2-specific peptide in embryonic heart, indicating that the protein may have a specific role during embryogenesis. We propose that the main functionality of the DHFR2 gene in adult cells is likely to arise at the RNA level.

Down syndrome (DS) is caused by trisomy of chromosome 21 (Hsa21) and is a leading genetic cause of Alzheimer’s disease (AD-DS). People with DS have a third copy of amyloid precursor protein (APP) which causes the increased risk to develop AD neuropathology and dementia, decades earlier than in the general population. However, other genes on Hsa21 have been shown to modify AD-DS development compared to the development of AD in the general population. Here, we aim to understand how AD-DS differs to EOAD at end-stage disease. Label-free mass spectrometry was performed using a SYNAPT G2-Si High-Definition machine with 2D fractionation on prefrontal cortex tissue (BA10) from individuals with AD-DS, early-onset AD (EOAD) (both Braak-stage VI), and healthy age-matched controls. Proteins identified were ranked by significance (p < 0.05) and a fold-change of difference between groups was calculated. qPCR was used to measure transcript levels of altered proteins in the same samples and to assess if transcript levels of raised proteins were altered in the Dp1Tyb (MGI:5703798) mouse model of DS which has three-copies of ∼148 Hsa21 orthologous genes. Raised abundance of Hsa21 encoded proteins, including PDXK, APP and S100B, were identified in individuals with AD-DS compared to EOAD. Importantly, non-chromosome 21 encoded proteins were also shown to be raised in individuals with AD-DS compared to EOAD, including APOE, NLRP8 and PTN. Raised APOE protein in AD-DS compared to EOAD brain tissue is Apolipoprotein E genotype independent. Apoe is not raised in the Dp1Tyb hippocampus or cortex at 6-months of age. People with AD-DS exhibit an altered proteomic profile compared to people with EOAD, likely driven by having three-copies of Hsa21 genes. Raised APOE may be driven by an interaction of trisomy 21 and AD pathogenesis, as this phenotype is not seen in the Dp1Tyb mouse model. Understanding the differences in AD pathogenesis is key for including people with DS in future AD clinical trials. Future work will validate protein expression of candidates of interest in an independent cohort of human post-mortem brain samples, as well as determine the cell types in which proteins of interest are expressed.

Children infected with SARS-CoV-2 rarely progress to respiratory failure, but the risk of mortality in infected people over 85 years of age remains high, despite vaccination and improving treatment options. Here, we take a comprehensive, multidisciplinary approach to investigate differences in the cellular landscape and function of paediatric (<11y), adult (30- 50y) and elderly (>70y) nasal epithelial cells experimentally infected with SARS-CoV-2. Our data reveal that nasal epithelial cell subtypes show different tropism to SARS-CoV-2, correlating with age, ACE2 and TMPRSS2 expression. Ciliated cells are a viral replication centre across all age groups, but a distinct goblet inflammatory subtype emerges in infected paediatric cultures, identifiable by high expression of interferon stimulated genes and truncated viral genomes. In contrast, infected elderly cultures show a proportional increase in ITGB6 hi progenitors, which facilitate viral spread and are associated with dysfunctional epithelial repair pathways. Graphical Abstract