Background: Why some individuals experience severe neuropathy following infection is unknown. Nucleocytoplasmic trafficking (NCT) is an essential process in nucleated cells, and its disruption has been implicated in many neurodegenerative conditions including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia. Methods: We performed genomic and clinical studies in 24 individuals from 12 families with acute onset axonal neuropathy. Genetic variants were characterized by thermal stability and enzymatic assays using recombinantly expressed protein. Protein localization was determined in patient fibroblasts using immunofluorescence following heat or oxidative stress. A humanized Drosophila model was generated to determine the effect of stress on in vivo function. Results: We identified deleterious biallelic variants in human RCC1, encoding a GTP exchange factor essential in maintaining Ran GTPase-dependent NCT function. Clinical presentations ranged from a rapidly progressive, fatal axonal neuropathy with encephalopathy to a mild motor neuropathy resulting in impaired walking. In most patients (n=22/24), neurological presentation was secondary to infection, resulting in prior diagnosis of Guillain-Barre syndrome (GBS) in 13. The efficiency of cellular Ran GDP-GTP exchange and the thermal stability of Rcc1 protein was reduced by disease-associated variants. Heat shock or oxidative stress revealed defects in Ran nuclear localization, impaired NCT, and TDP-43 mislocalization in patient fibroblasts. Disease associated variants were unable to rescue the thermosensitive phenotype of a rcc1 deficient hamster cell line. RCC1 Drosophila models revealed a fatal intolerance to oxidative stress. Conclusion: We describe a novel autosomal recessive acute onset axonal neuropathy triggered by infection caused by biallelic RCC1 variants, which mimics GBS and has important mechanistic overlap with ALS. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement We acknowledge grant support from: the Wellcome Trust ; the Manchester NIHR BRC (NIHR203308); LifeArc Pathfinder award; and NIHR Doctoral Fellow, 301748). This research was made possible through access to data in the National Genomic Research Library, which is managed by Genomics England Limited (a wholly owned company of the Department of Health and Social Care). The National Genomic Research Library holds data provided by patients and collected by the NHS as part of their care and data collected as part of their participation in research. The National Genomic Research Library is funded by the National Institute for Health Research and NHS England. The Wellcome Trust, Cancer Research UK and the Medical Research Council have also funded research infrastructure. Further acknowledgements of funding are provided in the supplementary appendix. A.B. is supported by a Wellcome PhD Training Fellowship for Clinicians and the 4Ward North PhD Programme for Health Professionals (223521/Z/21/Z). P.L. is supported by Ministry of Health of the Czech Republic, grant. no: NW24-04-00349. R.H. is supported by the Wellcome Discovery Award (226653/Z/22/Z), the Medical Research Council (UK) (MR/V009346/1), the Addenbrookes Charitable Trust (G100142), the Hereditary Neuropathy Foundation, the Stoneygate Trust, the Lily Foundation, Ataxia UK, Action for AT, the Muscular Dystrophy UK, the LifeArc Centre to Treat Mitochondrial Diseases (LAC-TreatMito) and the UKRI/Horizon Europe Guarantee MSCA Doctoral Network Programme (Project 101120256: MMM). This research was supported by the NIHR Cambridge Biomedical Research Centre (BRC-1215-20014). The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care. H.L. receives support from the Canadian Institutes of Health Research (CIHR) for Foundation Grant FDN-167281 (Precision Health for Neuromuscular Diseases), Transnational Team Grant ERT-174211 (ProDGNE) and Network Grant OR2-189333 (NMD4C), from the Canada Foundation for Innovation (CFI-JELF 38412), the Canada Research Chairs program (Canada Research Chair in Neuromuscular Genomics and Health, 950-232279), the European Commission (Grant # 101080249) and the Canada Research Coordinating Committee New Frontiers in Research Fund (NFRFG-2022-00033) for SIMPATHIC, and from the Government of Canada Canada First Research Excellence Fund (CFREF) for the Brain-Heart Interconnectome (CFREF-2022-00007). RWT is funded by the Wellcome Centre for Mitochondrial Research (203105/Z/16/Z), the Mitochondrial Disease Patient Cohort (UK) (G0800674), the Medical Research Council (MR/W019027/1), the Lily Foundation, the Pathological Society, the UK NIHR Biomedical Research Centre for Ageing and Age-related disease award to the Newcastle upon Tyne Foundation Hospitals NHS Trust, LifeArc and the UK NHS Highly Specialised Service for Rare Mitochondrial Disorders of Adults and Children. R.D.S.P. is funded by The Lily Foundation, Muscular Dystrophy UK (MDUK), and a seedcorn award from the Rosetrees Trust and Stoneygate Foundation. R.D.S.P. is supported by a Medical Research Council (UK) Transition Support award (MR/X02363X/1), Medical Research Council (UK) award MC\_PC\_21046 to establish a National Mouse Genetics Network Mitochondria Cluster (MitoCluster), and the LifeArc Centre to Treat Mitochondrial Diseases (LAC-TreatMito). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Written informed consent was obtained from all persons in the study (or from their parents or guardians) in accordance with the Declaration of Helsinki protocols, and our experimental protocols were approved by the NHS institutional review board (IRAS 64321). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors

Background: Biallelic variants in polyribonucleotide-nucleotidyltransferase-1 (PNPT1) have been associated with a range of phenotypes from syndromic hearing loss to Leigh's syndrome. More recently, heterozygous variants in PNPT1, have been reported in three families with cerebellar ataxia and prominent sensory neuropathy. Methods: Whole genome sequencing was performed in two families with autosomal dominant sensory ataxic neuropathy (SAN). Results: Segregating heterozygous splice site (c.2014-3C>G) and nonsense (p.Arg715Ter) variants were detected in both families. All patients initially presented with an isolated SAN clinically and neurophysiologically with subsequent variable cerebellar involvement. Conclusion: We report two heterozygous PNPT1 variants in two families with a predominant SAN, including the novel p.Arg715Ter. This strengthens the argument of PNPT1 causing dominant disease and highlights a new cause for dominantly inherited SAN.

BACKGROUND:Lower limb muscle magnetic resonance imaging (MRI) obtained fat fraction (FF) can detect disease progression in patients with Charcot-Marie-Tooth disease 1A (CMT1A). However, analysis is time-consuming and requires manual segmentation of lower limb muscles. We aimed to assess the responsiveness, efficiency and accuracy of acquiring FF MRI using an artificial intelligence-enabled automated segmentation technique. METHODS:We recruited 20 CMT1A patients and 7 controls for assessment at baseline and 12 months. The three-point-Dixon fat water separation technique was used to determine thigh-level and calf-level muscle FF at a single slice using regions of interest defined using Musclesense, a trained artificial neural network for lower limb muscle image segmentation. A quality control (QC) check and correction of the automated segmentations was undertaken by a trained observer. RESULTS:The QC check took on average 30 seconds per slice to complete. Using QC checked segmentations, the mean calf-level FF increased significantly in CMT1A patients from baseline over an average follow-up of 12.5 months (1.15%±1.77%, paired t-test p=0.016). Standardised response mean (SRM) in patients was 0.65. Without QC checks, the mean FF change between baseline and follow-up, at 1.15%±1.68% (paired t-test p=0.01), was almost identical to that seen in the corrected data, with a similar overall SRM at 0.69. CONCLUSIONS:Using automated image segmentation for the first time in a longitudinal study in CMT, we have demonstrated that calf FF has similar responsiveness to previously published data, is efficient with minimal time needed for QC checks and is accurate with minimal corrections needed.

Whole-genome sequencing (WGS) has recently become the first-line genetic investigation for many suspected genetic neurological disorders. While its diagnostic capabilities are innumerable, as with any test, it has its limitations. Clinicians should be aware of where WGS is extremely reliable (detecting single-nucleotide variants), where its reliability is much improved (detecting copy number variants and small repeat expansions) and where it may miss/misinterpret a variant (large repeat expansions, balanced structural variants or low heteroplasmy mitochondrial DNA variants). Bioinformatic technology and virtual gene panels are constantly evolving, and it is important to know what genes and what types of variant are being tested; the current National Health Service Genomic Medicine Service WGS offers more than early iterations of the 100 000 Genomes Project analysis. Close communication between clinician and laboratory, ideally through a multidisciplinary team meeting, is encouraged where there is diagnostic uncertainty.

Charcot-Marie-Tooth disease (CMT) is one of the most common and genetically heterogeneous inherited neurological diseases, with more than 130 disease-causing genes. Whole genome sequencing (WGS) has improved diagnosis across genetic diseases, but the diagnostic impact in CMT is yet to be fully reported. We present the diagnostic results from a single specialist inherited neuropathy centre, including the impact of WGS diagnostic testing.Patients were assessed at our specialist inherited neuropathy centre from 2009 to 2023. Genetic testing was performed using single gene testing, next-generation sequencing targeted panels, research whole exome sequencing and WGS and, latterly, WGS through the UK National Health Service. Variants were assessed using the American College of Medical Genetics and Genomics and Association for Clinical Genomic Science criteria.Excluding patients with hereditary ATTR amyloidosis, 1515 patients with a clinical diagnosis of CMT and related disorders were recruited. In summary, 621 patients had CMT1 (41.0%), 294 CMT2 (19.4%), 205 intermediate CMT (CMTi, 13.5%), 139 hereditary motor neuropathy (HMN, 9.2%), 93 hereditary sensory neuropathy (HSN, 6.1%), 38 sensory ataxic neuropathy (2.5%), 72 hereditary neuropathy with liability to pressure palsies (HNPP, 4.8%) and 53 'complex' neuropathy (3.5%). Overall, a genetic diagnosis was reached in 76.9% (1165/1515). A diagnosis was most likely in CMT1 (96.8%, 601/621), followed by CMTi (81.0%, 166/205) and then HSN (69.9%, 65/93). Diagnostic rates remained less than 50% in CMT2, HMN and complex neuropathies. The most common genetic diagnosis was PMP22 duplication (CMT1A; 505/1165, 43.3%), then GJB1 (CMTX1; 151/1165, 13.0%), PMP22 deletion (HNPP; 72/1165, 6.2%) and MFN2 (CMT2A; 46/1165, 3.9%). We recruited 233 cases to the UK 100 000 Genomes Project (100KGP), of which 74 (31.8%) achieved a diagnosis; 28 had been otherwise diagnosed since recruitment, leaving a true diagnostic rate of WGS through the 100KGP of 19.7% (46/233). However, almost half of the solved cases (35/74) received a negative report from the study, and the diagnosis was made through our research access to the WGS data. The overall diagnostic uplift of WGS for the entire cohort was 3.5%.Our diagnostic rate is the highest reported from a single centre and has benefitted from the use of WGS, particularly access to the raw data. However, almost one-quarter of all cases remain unsolved, and a new reference genome and novel technologies will be important to narrow the 'diagnostic gap'. Record et al. present the genetic breakdown for 1515 patients with Charcot-Marie-Tooth disease assessed at a single specialist inherited neuropathy centre. Whole genome sequencing contributed to a 'solved' rate of 76.9%, enhancing a diagnostic strategy based on phenotype-driven analysis and a multidisciplinary team approach.

Heterozygous RTN2 variants have been previously identified in a limited cohort of families affected by autosomal dominant spastic paraplegia (SPG12-OMIM:604805) with a variable age of onset. Nevertheless, the definitive validity of SPG12 remains to be confidently confirmed due to the scarcity of supporting evidence.In this study, we identified and validated seven novel or ultra-rare homozygous loss-of-function RTN2 variants in 14 individuals from seven consanguineous families with distal hereditary motor neuropathy (dHMN) using exome, genome and Sanger sequencing coupled with deep-phenotyping.All affected individuals (seven males and seven females, aged 9-50 years) exhibited weakness in the distal upper and lower limbs, lower limb spasticity and hyperreflexia, with onset in the first decade of life. Nerve conduction studies revealed axonal motor neuropathy with neurogenic changes in the electromyography. Despite a slowly progressive disease course, all patients remained ambulatory over a mean disease duration of 19.71 +/- 13.70 years. Characterization of Caenorhabditis elegans RTN2 homologous loss-of-function variants demonstrated morphological and behavioural differences compared with the parental strain. Treatment of the mutant with an endoplasmic/sarcoplasmic reticulum Ca2+ reuptake inhibitor (2,5-di-tert-butylhydroquinone) rescued key phenotypic differences, suggesting a potential therapeutic benefit for RTN2-disorder. Despite RTN2 being an endoplasmic reticulum (ER)-resident membrane shaping protein, our analysis of patient fibroblast cells did not find significant alterations in ER structure or the response to ER stress.Our findings delineate a distinct form of autosomal recessive dHMN with pyramidal features associated with RTN2 deficiency. This phenotype shares similarities with SIGMAR1-related dHMN and Silver-like syndromes, providing valuable insights into the clinical spectrum and potential therapeutic strategies for RTN2-related dHMN. Maroofian et al. delineate a new form of autosomal recessive distal hereditary motor neuropathy (dHMN) with pyramidal features associated with RTN2 deficiency, and conclude that the disorder shares similarities with SIGMAR1-related dHMN and Silver-like syndromes.

Neuromuscular disorders affect almost 20 million people worldwide. Advances in molecular diagnosis have provided valuable insights into neuromuscular disorders, allowing for improved standards of care and targeted therapeutic approaches. Despite this progress, access to genomic diagnosis remains scarce and inconsistent in middle-income countries such as Brazil. The lack of public health policies to enable feasible genetic diagnosis and the shortage of neuromuscular disorders specialists are the main reasons in this process. We report our experience in a transcontinental genomic consortium for neuromuscular disorders highlighting how collaborative efforts have helped overcome various obstacles in diagnosing our patients. We describe several challenging cases categorized into three major themes, underlining significant gaps in genetic diagnosis: (i) reverse phenotyping and variant validation, (ii) deep phenotyping and identifying a bespoke molecular approach, and (iii) exploring the use of genomic tests beyond whole exome sequencing. We applied a qualitative case-based approach to exemplify common pitfalls in genomic diagnosis in a middle-income country. Our experience has shown that establishing a virtual transcontinental partnership is viable, offering effective exchange of scientific experiences, providing both guidance for rational decision-making and specialized training on a local level and access to diverse molecular diagnosis strategies and functional analyses. Collaborative efforts such as these have the potential to overcome local obstacles, strengthen scientific capabilities, foster diverse multi-ethnic cohorts, and ultimately provide improved care for patients.

Aim: X-linked variants in Filamin A (FLNA) are associated with the Ehlers-Danlos-syndrome-variant form of periventricular heterotopia, and autosomal dominant variants in ubiquitin C-terminal hydrolase L1 (UCHL1) are associated with a late-onset spastic ataxia, peripheral neuropathy and optic atrophy. Here we present a rare case involving both a novel heterozygous whole-gene deletion of UCHL1 and a heterozygous frameshift variant in the FLNA gene resulting in a complex phenotype.Methods: A 67-year-old female with a confirmed pathogenic variant in the FLNA gene, resulting in an enlarged aorta and joint pains, presented with a 4-year history of severe sensory ataxia, upper motor neuron signs, eye movement abnormalities and severe sensory loss.Results: Neurophysiology including Somatosensory-evoked potentials confirmed the sensory loss as predominantly preganglionic with denervation. Genetic testing revealed a digenic cause of her complex presentation, confirming a pathogenic frameshift variant in the FLNA gene and a heterozygous loss of function deletion in the UCHL1 gene.Conclusions: To the best of our knowledge, this is the first case with concomitant pathogenic variants in the FLNA and UCHL1 genes which explain the complex phenotype. The severe preganglionic sensory loss is also a rare finding and expands the phenotype of UCHL1 variants.

Charcot-Marie-Tooth (CMT) disease is a neuromuscular disorder affecting the peripheral nervous system. The diagnostic yield in demyelinating CMT (CMT1) is typically ∼80-95%, of which at least 60% is due to the PMP22 gene duplication. The remainder of CMT1 is more genetically heterogeneous. We used whole exome and whole genome sequencing data included in the GENESIS database to investigate novel causal genes and mutations in a cohort of ∼2,670 individuals with CMT neuropathy. A recurrent heterozygous missense variant p.Thr1424Met in the recently described CMT gene ITPR3, encoding IP3R3 (inositol 1,4,5-trisphosphate receptor 3) was identified. This previously reported p.Thr1424Met change was present in 33 affected individuals from nine unrelated families from multiple populations, representing an unusual recurrence rate at a mutational hotspot, strengthening the gene-disease relationship (GnomADv4 allele frequency 1.76e-6). Sanger sequencing confirmed the co-segregation of the CMT phenotype with the presence of the mutation in autosomal dominant and de novo inheritance patterns, including a four-generation family with multiple affected second-degree cousins. Probands from all families presented with slow nerve conduction velocities, matching the diagnostic category of CMT1. Remarkably, we observed a uniquely variable clinical phenotype for age at onset and phenotype severity in p.Thr1424Met carrying patients, even within families. Finally, we present data supportive of a dominant-negative effect of the p.Thr1424Met mutation with associated changes in protein expression in patient-derived cells.

Myelination is essential for neuronal function and health. In peripheral nerves, >100 causative mutations have been identified that cause Charcot-Marie-Tooth disease, a disorder that can affect myelin sheaths. Among these, a number of mutations are related to essential targets of the posttranslational modification neddylation, although how these lead to myelin defects is unclear. Here, we demonstrate that inhibiting neddylation leads to a notable absence of peripheral myelin and axonal loss both in developing and regenerating mouse nerves. Our data indicate that neddylation exerts a global influence on the complex transcriptional and posttranscriptional program by simultaneously regulating the expression and function of multiple essential myelination signals, including the master transcription factor EGR2 and the negative regulators c-Jun and Sox2, and inducing global secondary changes in downstream pathways, including the mTOR and YAP/TAZ signaling pathways. This places neddylation as a critical regulator of myelination and delineates the potential pathogenic mechanisms involved in CMT mutations related to neddylation.

Charcot-Marie-Tooth Disease is a clinically and genetically heterogeneous group of hereditary neuropathies, with over 100 causative genes identified to date. Despite progress in genetic sequencing, around a quarter of patients remain unsolved. Through international collaborations, we identified 16 recessive variants in Rho GTPase activating protein 19 (ARHGAP19) causing motor-predominant neuropathy with conduction slowing in 25 individuals from 20 unrelated multi-ancestry families. ARHGAP19 is a GTPase-activating protein with activity towards RhoA. In vitro biochemical assays revealed that variants located within the GAP domain cause loss of GAP activity. iPSc-derived motor neurons exhibited 50% knockdown of ARHGAP19 protein. In vivo genetic perturbations of the Drosophila melanogaster ARHGAP19 ortholog RhoGAP54D reduced self-driven locomotor activity and startle responses to visual stimuli. Zebrafish loss-of-function models similarly exhibited movement deficits, coupled with increased motor neuron axonal branching but shorter caudal primary motor neurons. Together, these findings establish ARHGAP19 as a novel cause of early-onset neuropathy through a loss-of-function mechanism.### Competing Interest StatementThe authors have declared no competing interest.### Funding StatementWe thank the patient and relatives for consent to be part of the study as well as the clinicians for helping with patient phenotyping. The families were collected as part of the SYNaPS Study Group collaboration funded by The Wellcome Trust and strategic award (Synaptopathies) funding (WT093205 MA and WT104033AIA) and research was conducted as part of the Queen Square Genomics group at University College London, supported by the National Institute for Health Research University College London Hospitals Biomedical Research Centre. This work was partly supported by an MRC strategic award to establish an International Centre for Genomic Medicine in Neuromuscular Diseases (ICGNMD) MR/S005021/1 and ND, SE, CR, PT, MGH, MMR and HH received direct support from this award. JP is supported by Medical Research Future Fund (MRFF) Genomics Health Futures Mission (APP2007681) and by the Australian Government Research Training Program. LVdV is supported by a predoctoral fellowship of the Research Fund - Flanders (FWO) under grant agreement N11F0921N. TS is member of the European Reference Network for Rare Neuromuscular Diseases (ERN EURO-NMD). JB is supported by a Senior Clinical Researcher mandate of the Research Fund - Flanders (FWO) under grant agreement N1805021N. ANB gratefully acknowledges the support of SVIKV and the use of the services and facilities of the Koc University Research Center for Translational Medicine (KUTTAM), funded by the Presidency of Turkey, Head of Strategy and Budget. We thank collaborator Simon Bullock (University of Cambridge) for plasmids, and Florencia di Pietro for characterization of the RhoGAP54D loss of function allele. JECJ was funded by an MRC Senior Non-Clinical Fellowship (MR/V03118X/1). Work in the Bellaiche group is funded by the CNRS, the INSERM and the Institut Curie as well as by the ANR (TiMecaDiv 20CE13000801) grant. TBH was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation 418081722, 433158657), and the European Commission (Recon4IMD GAP101080997). This work was supported in part by the Fund for Scientific Research (FWO Flanders) (research grants G048220N and G0A2122N to A.J.), the Research Fund of the University of Antwerp (doctoral grant to C.A.), the Association Belge contre les Maladies Neuromusculaires (ABMM-Telethon) (research grants to A.J.), the French Muscular Dystrophy Association (AFM-Telethon, research grant 23708 to A.J.). JPark was supported by the Clinician Scientist program PRECISE.net funded by the Else Kroner-Fresenius-Stiftung. Work in the Lamarche-Vane group funded by Natural Sciences and Engineering Research Council of Canada grant RGPIN/04809 2017 and CIHR project grant PJT 180367. Leif Leclaire holds a CIHR master studentship. RH is supported by the Wellcome Discovery Award (226653/Z/22/Z), the Medical Research Council (UK) (MR/V009346/1), the Addenbrookes Charitable Trust (G100142), the Evelyn Trust, the Stoneygate Trust, the Lily Foundation, Ataxia UK, Action for AT, the Muscular Dystrophy UK. This research was supported by the NIHR Cambridge Biomedical Research Centre (BRC 1215 20014). The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care. We are also grateful to Queen Square Genomics at the Institute of Neurology University College London, supported by the National Institute for Health Research University College London Hospitals Biomedical Research Centre, for the bioinformatics support. ### Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:Individuals and/or their legal guardians recruited for this study gave informed consent for their participation. This study received approval from the Review Boards and Bioethics Committees at University College London Hospital (project 06/N076). Permission for inclusion of their anonymized medical data in this cohort, including photographs, was obtained using standard forms at each local site by the responsible referring physicians.I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).YesI have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.YesAll data produced in the present study are available upon reasonable request to the authors[https://databases.lovd.nl/shared/variants/ARHGAP19?search\_var\_status=%3D%22Marked%22%7C%3D%22Public%22][1] [1]: https://databases.lovd.nl/shared/variants/ARHGAP19?search_var_status=%3D%22Marked%22%7C%3D%22Public%22