Disease Models & Mechanisms

Danon disease is a rare disorder caused by mutations in the LAMP2 gene, which encodes a lysosomal membrane protein key to the endolysosomal pathway and autophagy. Affected individuals show multisystemic alterations that include cardiomyopathy, skeletal muscle weakness, visual deficits and cognitive impairment. Here we establish a knockout LAMP2 line in Xenopus tropicalis that reproduces the characteristic cardiac activity, mobility impairments and vision deficits present in the disease. Damaged mitochondria were abundantly found in skeletal muscle fibers. LAMP2 mutant X. tropicalis detected light with a reduced preference for green wavelengths. Visual deficits were consistent with the finding of damaged mitochondria in the inner segment of rods but not in cones. Differences in autophagic flux were found in presynaptic terminals from photoreceptors and olfactory sensory neurons (OSNs), which establish the first synapse processing vision and olfaction, respectively. In wild-type animals autophagic shapes were observed in OSN terminals but were absent from photoreceptor ribbon synapses. In knockout LAMP2 tadpoles, autophagic organelles covered 7% of the OSN presynaptic terminal surface, a three-fold increase compared to photoreceptor terminals. These differences suggest that LAMP2 plays synapse-specific roles that could be an important determinant of the psychiatric manifestations present in Danon disease and support the use of LAMP2 X. tropicalis to shed new light on the pathological bases of this lysosomal storage disorder.

Colorectal cancer across sub-Saharan Africa presents a growing global health burden, with increasing cases and mortality linked to late diagnosis, limited healthcare access and lack of effective treatments. African patients typically present with aggressive disease marked by distinct genomic signatures, indicating the need for targeted treatment approaches. We integrated genetic modelling, phenotypic scoring, imaging and biochemical analysis to explore how mutations found in individual Nigerian colorectal cancer patients influence drug responsiveness. We used the data from Cancer Genome Atlas to identify mutation profiles specific to Nigerian patients. We then generated ten stable Drosophila melanogaster personalised patient avatar lines designed to model patient genomic profiles. This study focused on three lines; each line included oncogenic RAS plus targeting patient-specific variants. These models exhibited various phenotypes including altered larval size, gut size and reduced survival. Two of the three avatar lines showed improved survival, reduced hindgut proliferation zone expansion and restored redox balance after treatment with regorafenib and trametinib. Mirroring clinical patient responses, we found that response to therapy is dependent on the specific genetic profile of the tumour. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=111 SRC="FIGDIR/small/714433v1_ufig1.gif" ALT="Figure 1"> View larger version (31K): org.highwire.dtl.DTLVardef@110518aorg.highwire.dtl.DTLVardef@5965a0org.highwire.dtl.DTLVardef@11f16a3org.highwire.dtl.DTLVardef@744a1_HPS_FORMAT_FIGEXP M_FIG C_FIG O_LIAfrican colorectal cancer showed distinct mutation patterns that contribute to tumour heterogeneity. C_LIO_LIPatient-derived Drosophila avatars were engineered using tumour-specific genetic mutations with key features of human colorectal cancer. C_LIO_LITreatment with targeted therapies showed responses patterned by tumour genotype. C_LIO_LIResponse patterns indicated the need for personalised for colorectal cancer therapies among diverse populations. C_LI

Saul-Wilson syndrome (SWS) is a skeletal dysplasia characterized by primordial dwarfism and progeroid features caused by a recurrent dominant COG4 variant (p.G516R). We previously showed that this mutation accelerates Golgi retrograde trafficking and disrupts glycosylation of the proteoglycan decorin, while zebrafish models revealed defects in chondrocyte elongation and intercalation. We have also shown that the SW1353 chondrosarcoma cells carrying the SWS variant exhibit reduced secretion of extracellular matrix (ECM) components. While these results indicate a critical function of COG4 in Golgi processing, the developmental process leading to skeletal dysplasia in SWS patients remains unknown. Here, we generated patient-derived iPSC cartilage organoids (SWS organoids), modeling early human chondrogenesis. SWS organoids failed to produce cartilage structures and displayed poor expression of chondrogenic markers. Time-course RNA-seq analysis of the chondrogenic process revealed reduced activation of gene networks involved in skeletal development, ECM organization, ossification, and glycosaminoglycan metabolism. Spatial multiomic analysis of protein and glycosylation by CODEX and GLYPH imaging revealed an altered chondrogenic trajectory, persistence of mesenchymal states, global glycosylation changes, and reduced deposition of chondroitin sulfate proteoglycans. These results indicate that the COG4 mutation disrupts ECM glycosylation and chondrogenic commitment, and that SWS organoids model early defects in cartilage formation underlies impaired skeletal growth in SWS. HighlightsO_LIPatient iPSC-derived cartilage organoids model development defects in Saul-Wilson syndrome C_LIO_LISWS organoids show defective extracellular matrix deposition and attenuated chondrogenic gene expression C_LIO_LIGlycan profiling reveals global glycosylation defects and deficient proteoglycan GAG chains C_LIO_LIAn early developmental impairment in chondrogenesis alters skeletal formation in Saul-Wilson syndrome C_LI

Metastatic breast cancer is responsible for around 11,500 deaths a year in the UK. The primary tumour likely plays a major role in priming the distant site for metastasis and crosstalk between primary and metastatic sites may be essential for secondary tumour growth. We have developed a novel in vitro model in which we can further study these interactions; evaluating niche priming and cancer cell conditioning as well as assessing their influence on cell homing and colonisation. In this paper we describe a model that we believe adds to the array of in vitro tools available to study various stages of the metastatic cascade, offering a unique opportunity to assess bidirectional, primary to niche interactions in vitro. We show that proliferation, migration and chemotaxis, and stem cell activity are altered in both cancer cell lines and in lung epithelial cells following linked, fluidic culture. Changes in cell homing and colonisation can be modelled in cell lines and within viable lung tissue explants taken from mice, with breast cancer cells settling and growing within the lung epithelial cells and tissue explants over 7 days. The colonisation/growth of cells injected into the system closely represents that seen following tail vein injection and cancer cells can be seen to settle and grow within the lung epithelial cells.

TBCK Syndrome is a rare Mendelian disorder caused by variants in the TBCK gene. Although symptoms affect multiple organ systems, hallmark features include intellectual and developmental disability, craniofacial differences, hypotonia, and premature death. At the cellular level, TBCK has been implicated in mTOR signaling, autophagy, mitophagy, and mRNA trafficking; however, the mechanisms underlying disease onset and progression remain unclear. To address this gap, we characterized a mouse model of TBCK Syndrome. These mice lack exon 5 of the TBCK gene, resulting in a whole-body knockout of Tbck, modeling the most severe known variant. We performed a comprehensive battery of developmental assays, along with microcomputed tomography and histological analyses, which revealed systemic alterations consistent with those observed in affected individuals. Notably, phenotypic changes arising from Tbck loss emerge early and are detectable in the brain, indicating a primary neurodevelopmental origin of disease pathology. Rigorous characterization of this Tbck-deficient mouse establishes the first in vivo platform to investigate disease mechanisms and provides a foundation for preclinical evaluation of gene and targeted pharmacological therapy strategies. Summary StatementThis study establishes a rigorously validated animal model recapitulating systemic features of TBCK Syndrome, enabling targeted investigation of disease biology and preclinical assessment of candidate therapies.

Spinocerebellar ataxia type 1 (SCA1) is a progressive neurodegenerative disorder caused by polyglutamine expansion in ATXN1, yet the normal physiological roles of ATXN1 and its paralog ATXN1L remain incompletely understood. To define these roles, we generated the first zebrafish knockouts (KOs) of the three ataxin-1 family genes, atxn1a, atxn1b, and atxn1l, using CRISPR/Cas9. These mutants reveal distinct and shared developmental, behavioral, and transcriptomic alterations. All KOs showed reduced early survival and mild larval growth deficits, indicating essential developmental functions. Behavioral assays revealed distinct paralog-specific effects: atxn1a KO larvae exhibited a unique light-dependent locomotor deficit, whereas atxn1b and atxn1l KOs displayed global hypoactivity. Adult behavioral assessment revealed a gradient of phenotypic severity: atxn1a KOs displayed the earliest and most pronounced alterations in vertical tank exploration and the greatest impairment in swim-tunnel performance, followed by atxn1b and then atxn1l mutants. To define molecular mechanisms underlying these phenotypes, we performed RNA-seq at 5 days post-fertilization and identified unique and shared differentially expressed genes across the three KO lines. Shared transcriptomic signatures highlighted suppression of leukotriene-biosynthetic pathways and diminished innate-immune pathways; suggesting that ATXN1-family genes influence neuroimmune signaling during early development. Weighted gene co-expression network analysis identified distinct KO-associated gene modules, including a phototransduction-enriched module strongly correlated with atxn1a KO status, offering a mechanistic link to its light-dependent locomotor phenotype. Together, these findings establish a comprehensive assessment of zebrafish models that reveal both shared core functions and specialized roles of ATXN1-family genes in development, neuroimmune regulation, sensorimotor behavior, and retinal signaling.

Adolescents with Down syndrome face unique menstrual health challenges, yet their experiences remain under-researched. This study aimed to describe the menstruation experiences of adolescents with Down syndrome and their caregivers, in the UK, to inform the development of tailored, evidence-based interventions for this population. Guided by an advisory group of caregivers and young people with Down syndrome, this mixed-methods study (September 2024 -July 2025) involved a national online survey of primary caregivers (N=143) and participatory interviews with adolescents (n=6), mothers (n=11) and healthcare and education professionals (n=8). Quantitative data were analysed descriptively according to support needs (high vs low), and qualitative data were analysed thematically. The median age of menarche (12 years) aligned with the general population. While adolescents generally coped better with menarche than caregivers anticipated, 91% of 120 caregivers of adolescents who had reached menarche had ongoing menstruation concerns. While products like period underwear ("magic pants") improved independence and simplified care, key remaining concerns include: heavy periods (48%); personal care (45%); menstrual pain (45%); and the communication of pain (26%). The impact on adolescent wellbeing was greater for those with greater support needs. Additionally, 33% of caregivers felt "overwhelmed" by menstrual-related care. Decision-making for hormonal intervention was a source of heavy responsibility for caregivers. There is substantial demand for accessible educational and practical resources to support menstruation. Menstrual health is a highly individualised experience for adolescents with Down syndrome. Significant unmet needs persist, particularly for those with higher support needs. Successful outcomes require supporting caregivers through provision of accurate information that dispels pre-menarche anxiety alongside accessible and appropriate guidance to foster young peoples independence, choice and autonomy. Future interventions must be co-developed with the Down syndrome community to ensure safe, dignified menstruation. FundingDowns Syndrome Research Foundation UK

Plasma Membrane Calcium ATPase (PMCA) is essential for maintaining intracellular calcium homeostasis. Previously, we used constitutive PMCA downregulation in Drosophila melanogaster dopaminergic neurons as a model to increase intracellular calcium and mimic early neuronal alterations associated with Parkinsons disease. Here, we examined the mechanisms underlying the effects mediated by the conditional, adult-specific downregulation of PMCA in dopaminergic neurons in Drosophila melanogaster, both in vivo and in primary neuronal cultures. Adult-specific conditional silencing of PMCA in dopaminergic neurons reduced lifespan but to a lesser extent than the constitutive model and impaired locomotor performance. At the cellular level, PMCA-downregulated dopaminergic neurons exhibited elevated basal calcium, indicating disrupted calcium regulation. This was associated with a progressive increase in presynaptic vesicles and extracellular dopamine levels, suggesting enhanced neurotransmitter release. Notably, the synaptic active zone structure was preserved, indicating primarily functional rather than structural alterations. In primary neuronal cultures, PMCA downregulation reduced dopaminergic neuron survival and induced transient increases in neurite branching. Together, these findings show that PMCA downregulation leads to calcium dysregulation and presynaptic dysfunction without overt neurodegeneration in vivo, while promoting premature neuronal death in culture, indicating increased vulnerability and supporting a pre-degenerative state in which synaptic alterations precede neuronal loss.

Well- and dedifferentiated liposarcomas (WDLPS and DDLPS) are characterized by extensive copy- number alterations rather than recurrent gene-inactivating mutations, obscuring the molecular mechanisms that drive disease progression and, critically, the transition from well-differentiated to the more aggressive dedifferentiated tumor states. Despite marked differences in clinical behavior and prognosis, the regulatory events underlying adipocytic lineage destabilization in DDLPS remain poorly understood. Here, we establish an in vivo model of retroperitoneal liposarcoma in Xenopus tropicalis through early embryonic mosaic perturbation of p53 and Rb pathway components. Combined disruption reproducibly induced retroperitoneal WDLPS development, demonstrating that pathway-level deregulation of the MDM2-p53 and CDK4-Rb axes is sufficient to initiate liposarcoma development in vivo. Strikingly, additional perturbation of transcriptional co-activator ep300 in this context resulted in increased tumor dedifferentiation, yielding lesions composed of spatially coexisting well- and dedifferentiated adipocytic states. In contrast, direct targeted disruption of downstream adipogenic regulators recurrently lost in human DDLPS, including cebpa, g0s2, and dgat2, failed to induce dedifferentiation in the same genetic context in vivo. These findings indicate that dedifferentiation cannot be explained by loss of downstream adipocytic effectors alone but instead reflects destabilization of higher-order regulatory programs governing adipocytic identity. Together, these results establish an in vivo model that closely reflects the clinical situation on a pathway level and provides initial mechanistic insight into how adipocytic differentiation may become destabilized during disease progression. This framework offers a foundation for future studies leveraging higher-order and multi-omic approaches to dissect the molecular processes underlying the WDLPS-to-DDLPS transition.

STUDY QUESTIONAre pathogenic variants in Homeodomain-interacting protein kinase (HIPK4) associated with sperm head abnormalities causing male infertility? SUMMARY ANSWERHIPK4 is a novel candidate gene associated with sperm head defects and human male infertility. WHAT IS KNOWN ALREADYNumerous genes causing male infertility due to Multiple Morphological Abnormalities of the sperm flagella (MMAF) have been described but the genetic basis of sperm head defects is less well understood. STUDY DESIGN, SIZE, DURATIONFour infertile brothers displaying varying degrees of quantitatively and/or qualitatively impaired spermatogenesis, their parents, and their fertile brother were included in the study. Further, the Male Reproductive Genomics (MERGE) cohort comprising exome/genome sequencing data of >3,300 men was queried. PARTICIPANTS/MATERIALS, SETTING, METHODSWe performed exome sequencing in all five brothers and their parents. To characterise the sperm phenotype, standard semen analysis, immunofluorescence staining, and transmission-electron microscopy (TEM) were carried out. Further, we evaluated the impact of the HIPK4 variant in cell culture experiments using HEK293T cells. MAIN RESULTS AND THE ROLE OF CHANCEAnalysing the exome data, we could not identify a common genetic cause in all four affected brothers. However, one of the affected brothers was compound heterozygous for two loss-of-function variants in DNAH17 (c.1076_1077dup p.(Lys360*) and c.7752+2T>A p.?) associated with markedly reduced sperm motility and MMAF. The variants pathogenicity was further validated by TEM of flagellar cross-sections revealing an outer dynein arm defect and axonemal disruption. On the contrary, his three infertile brothers were homozygous for the start-loss variant c.1A>G in HIPK4. This gene is expressed during spermiogenesis and is reportedly involved in sperm head shaping in mice. Heterologous expression of (partial) HIPK4 variant cDNA elucidated the alternative use of an in frame start codon located 35 amino acids downstream, resulting in an N-terminally truncated protein p.(Met1_Glu35del). The truncated HIPK4 protein lacks parts of its kinase domain and shows reduced protein stability. In line with published mouse models, all three brothers displayed 100% abnormal sperm head morphology with variable defects. Importantly, one brother affected by HIPK4 variants fathered a child after successful intracytoplasmic sperm injection demonstrating that it is a treatment option for HIPK4-related teratozoospermia. No further men from the MERGE cohort were affected by biallelic HIPK4 variants. Taken together, HIPK4 is an autosomal-recessive candidate gene associated with sperm head defects and male infertility. LARGE SCALE DATAThe reported variants in DNAH17 and HIPK4 were submitted to ClinVar. LIMITATIONS, REASONS FOR CAUTIONIndependent replication is required to assess the phenotypic spectrum and the reproductive outcome associated with biallelic HIPK4 variants and to formally establish the gene-disease relationship for male infertility. WIDER IMPLICATIONS OF THE FINDINGSThis study raises awareness of the significant genetic heterogeneity of male infertility. The described family highlights that distinct genetic causes may underlie a seemingly similar phenotype. Exome sequencing of families is helpful to efficiently disentangle individual causes among affected family members. STUDY FUNDING/COMPETING INTEREST(S)N.N., J.R., H.O., S.L., C.F., and F.T. were supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) within the Clinical Research Unit Male Germ Cells (CRU326, project number 329621271). R.T.W., N.N., J.R., H.O., and F.T. were supported by the Federal Ministry of Research, Technology and Space (BMFTR) as part of the project ReproTrack.MS (grant 01GR2303). S.A.K. was supported by the DFG Clinician Scientist programme CareerS Munster (project number 493624047). A.S.G. was supported by the Medical Faculty Munster via an Innovative Medical Research (IMF) grant (GA-122104).

Rett syndrome is a severe neurodevelopmental disorder caused predominantly by loss-of-function mutations in the X-linked gene MECP2. Besides a vast array of neurological and physiological impairments, patients also frequently develop severe osteopenia with increased fracture risk, however, the mechanisms underlying these skeletal defects are not completely understood. Previous work in Mecp2-null mouse models has suggested that osteopenia is mainly due to impaired osteoblast function and reduced bone formation. Here, we examined bone mass, microarchitecture, and remodeling parameters in a Mecp2-null mouse model during postnatal development, with a particular focus on osteoclast involvement. Micro-computed tomography and histomorphometric analyses showed reduced bone mineral density and trabecular bone volume, associated with increased trabecular separation and cortical thinning. These structural alterations were accompanied by increased osteoclast number per bone surface, elevated urinary deoxypyridinoline, and higher expression of osteoclast-associated genes, including Cathepsin K. Furthermore, gene expression analysis revealed an age-dependent shift in bone remodeling. At postnatal day 35, mutant mice showed reduced expression of Dlx5 and Dlx6, consistent with low bone turnover. By postnatal day 55, Rankl and Cathepsin K were markedly upregulated, suggesting an increase in osteoclast resorptive activity, while key osteoblast markers and the RANKL/OPG ratio did not change significantly. A potential cell-autonomous contribution of Mecp2 to osteoclast maturation is also suggested by the analysis of public transcriptomic datasets on human osteoclast differentiation. Together, our findings identify increased osteoclast activity as a significant contributor to Rett-associated osteopenia and suggest that skeletal pathology in Mecp2 deficiency progresses from an early low-turnover state to a later phase of increased osteoclast resorption. HIGHLIGHTSO_LIWhat are the main findings. O_LIMecp2-null mice display reduced bone mass and altered bone microarchitecture during postnatal development, associated not only with reduced osteoblast activity, but also with increased osteoclast number, elevated urinary deoxypyridinoline, and increased expression of osteoclast-associated genes. C_LIO_LIBone remodelling shows an age-dependent shift in Mecp2 deficiency, from an early low-turnover state at postnatal day 35 to increased osteoclast resorptive activity at postnatal day 55. C_LI C_LIO_LIWhat are the implications of the main findings? O_LIRett-associated osteopenia is not explained solely by impaired osteoblast function, but also involves a significant osteoclast contribution to skeletal deterioration. C_LIO_LIThese findings refine the pathophysiological model of bone involvement in Rett syndrome and support the idea that skeletal alterations evolve dynamically during disease progression. C_LI C_LI

BackgroundMarfan syndrome (MFS) is a life-threatening heritable connective tissue disorder caused by pathogenic variants in fibrillin-1, characterized by progressive cardiovascular disease. Current medical therapies slow disease progression but do not prevent major complications, underscoring the need for new treatment strategies and unbiased discovery approaches. MethodsWe used a zebrafish model of MFS lacking fibrillin-3 (fbn3-/-), which recapitulates key cardiovascular phenotypes including cardiac stress, valvular defects, arrhythmia, and aortic dilation. To enable sensitive, quantitative assessment of cardiac stress, we generated a novel transgenic zebrafish reporter expressing secreted nanoluciferase under control of the stress-responsive nppb promoter. This reporter was combined with morphological phenotyping and bulbus arteriosus (BA) imaging. We evaluated standard MFS therapies, targeted modulators of TGF-{beta} signaling, and performed an unbiased high-throughput drug screen of over 1 500 clinically approved compounds across multiple developmental treatment windows. Resultsfbn3-/- larvae exhibited markedly elevated nppb activity that correlated with phenotypic severity and peaked during stages of highest mortality. The nanoluciferase reporter provided a [~]1 000-fold dynamic range, substantially outperforming Firefly luciferase-based assays. Pharmacological inhibition of TGF-{beta} signaling produced transient or deleterious effects, while {beta}-blockers, losartan, and allopurinol failed to consistently improve cardiac stress, pericardial edema, or BA dilation. The unbiased high-throughput drug screen identified a small number of primary and secondary hits; however, none demonstrated reproducible phenotypic rescue upon rigorous multi-dose, multi-time window validation. ConclusionsThis study establishes a sensitive zebrafish-based platform for early, quantitative assessment of cardiovascular stress in MFS. Our findings highlight the limited efficacy of current therapies, the context-dependent nature of TGF-{beta} modulation, and the biological complexity underlying MFS pathogenesis. Although no definitive therapeutic candidates were identified, this work lays a robust foundation for expanded unbiased discovery efforts aimed at identifying disease-modifying interventions for MFS.

Wolfram syndrome is a rare autosomal recessive disorder characterized by antibody-negative early-onset diabetes mellitus, optic atrophy, sensorineural hearing loss, arginine-vasopressin deficiency, and progressive neurodegeneration of the brainstem and cerebellum. It is caused primarily by pathogenic variants in the WFS1 gene, which encodes a transmembrane endoplasmic reticulum-resident protein involved in the unfolded protein response and cellular calcium homeostasis. Although multiple rodent models of Wolfram syndrome have been developed and shown to exhibit visual defects, some studies have reported significant vision loss prior to any detectable axonal degeneration or myelin abnormalities, and the mechanisms underlying these early visual deficits remain poorly understood. Recent in vitro studies have demonstrated altered synaptic contacts and aberrant neurite morphology in WFS1-deficient cerebral organoids and human iPSC-derived neurons, respectively. These findings prompted us to investigate, for the first time in vivo, whether synaptic and dendritic abnormalities occur in the retina of Wfs1 knockout mice. Using confocal microscopy, we examined retinal and optic nerve histology in Wfs1 knockout mice at 4 and 7 months of age. Our analysis reveals progressive synaptic alterations in the inner plexiform layer, driven by early presynaptic compartment failure. These changes represent the earliest detectable phenotype associated with vision loss in this model and precede overt axonal degeneration.

Tumor cells commonly exhibit aerobic glycolysis and produce lactate despite oxygen availability. Lactate dehydrogenase (LDH) catalyzes pyruvate-lactate interconversion and regulates intracellular lactate levels. Endothelial cells also depend on glycolysis for ATP production, which prompted us to investigate LDH in canine hemangiosarcoma (HSA), a malignant endothelial tumor. We inhibited LDH with (R)-GNE-140 or sodium oxamate in two canine HSA cell lines (HU-HSA-2 and HU-HSA-3) and generated HU-HSA-3 clones with knockout of LDHA or LDHB to evaluate the effects of LDH perturbation. (R)-GNE-140 and sodium oxamate suppressed proliferation and reduced global histone lactylation levels in both cell lines. mRNA-sequencing (mRNA-seq) of (R)-GNE-140-treated HU-HSA-2 cells identified cholesterol/lipid metabolism-related gene sets among the top negatively enriched pathways. Representative cholesterol/lipid metabolism genes responded differently depending on cell lines and inhibitors. (R)-GNE-140 decreased these genes in HU-HSA-2 but not HU-HSA-3, whereas sodium oxamate decreased them in HU-HSA-3 with limited effects in HU-HSA-2. In HU-HSA-3, LDHA and LDHB knockout clones decreased SREBP2 expression and reduced the number of lipid droplets. Fluvastatin, a cholesterol metabolism inhibitor, inhibited HSA cell growth in vitro but did not significantly suppress tumor growth in two HSA patient-derived xenograft (PDX) models. In contrast, combined fluvastatin and dipyridamole treatment inhibited proliferation in vitro and tumor growth in PDX models. Collectively, these results suggest a context-dependent association between LDH and cholesterol/lipid metabolism in canine HSA cell lines and provide a rationale for further evaluation of combined cholesterol pathway inhibition.

Dietary restriction (DR) extends lifespan in many animal species. In C. elegans, Eat mutants with pharyngeal defects that impair feeding exhibit reduced growth rate and fertility and are typically long-lived, suggesting a DR effect. We report that Eat mutant longevity is largely or wholly a consequence of suppression of feeding activity-dependent infection of the pharynx by their E. coli food source. eat-2 mutants, widely used as a DR model, were among only 2/8 Eat mutants tested whose longevity were to any degree independent of bacterial infection. Moreover, among Eat mutants, phenotypic indicators of reduced nutrition correlated with one another, yet not with longevity. Thus, eat-2 longevity is partially due to infection resistance rather than DR, and residual, infection-independent longevity could equally reflect DR or some other consequence of their cholinergic signaling defect. We therefore conclude that eat-2 mutants are not at present a trustworthy model for studies of DR.

Mutations in the spliceosomal gene PRPF8 are associated with a range of human diseases. Studies in mouse and zebrafish suggest that Prpf8 also has a developmental function. Here, using a Prpf8 mutant mouse line isolated from a chemical induced mutagenesis screen, we uncover a previously unrecognised and essential role for Prpf8 in heart development, consistent with the embryonic lethality observed in Prpf8N1531S homozygous mutants. Prpf8N1531S mutant embryos display severe defects in ventricular trabeculation and compact zone formation, accompanied by increased cardiomyocyte proliferation specifically in the compact zone. Mutant embryonic hearts also exhibit disrupted cellular organisation, altered cytoskeletal architecture and changes in extracellular matrix protein expression. Notably, these cardiac abnormalities were exacerbated in embryos exhibiting cardiac looping defects. Transcriptomic analysis identified multiple aberrantly spliced transcripts in Prpf8N1531S mutant embryos, among which the cardiac transcription factor Tead1 was selected as a key functional candidate due to it known role in cardiac ventricle wall developemnt. Tead1 mis-splicing generated an in-frame, lower molecular weight protein isoform, associated with reduced overall TEAD1 expression. The Tead1 mis-spliced isoform showed altered nuclear localisation and dysregulation of TEAD1-dependent gene network important for heart development, including known cardiac sarcomeric genes. In addition, we observed reduced levels of the intracellular domain of the NOTCH1 receptor (NICD1), indicating impaired Notch signalling.. These findings suggest that impaired TEAD1-dependent transcription and Notch signalling contribute to abnormal cardiac trabeculation and compact zone development, highlighting a critical role for Prpf8 in maintaining proper heart development through the regulation of cardiac transcription factor expression and associated signalling networks. This study offers new mechanistic insights into congenital heart diseases linked to spliceosomal gene mutations.

Lysosomal trafficking and homeostasis are biological functions that are pivotal for DRG neurons, given their metabolic demands and extremely long axons. Previous studies indicate that lysosomal signaling is altered in a mouse model of chemotherapy-induced peripheral neuropathy (CIPN) and that blocking mitogen activated protein kinase-associated kinase (MNK1/2) signaling can alleviate pain behaviors in CIPN. Here, we investigated lysosome dynamics and lysosome-associated signaling in a mouse model of CIPN induced by paclitaxel (PTX), a chemotherapeutic agent used for various types of cancer. Using spinning disk super-resolution microscope (SPINSR), we demonstrate that PTX treatment in vivo causes reduced lysosome motility observed in vitro. PTX likewise drives the accumulation of Sequestosome 1 (SQSTM1), also known as P62, in cultured mouse DRG neurons, indicating lysosomal dysfunction in DRG neurons. The transcription factor EB (TFEB), a master regulator of lysosomal biogenesis, was also upregulated in the nucleus of cultured mouse DRG neurons treated with PTX. In line with this, increased lysosomal-associated membrane protein 1 (LAMP1) expression was observed in PTX-treated mice. Given that our previous work demonstrated PTX treatment increases MNK1/2-eIF4E signaling in DRG neurons, we examined whether MNK1/2 inhibition could rescue lysosomal dysfunction. Treatment with Tomivosertib (eFT508), a potent MNK1/2 inhibitor, restored P62 levels in DRG neurons of PTX-treated mice and reduced TFEB in DRG treated in vitro. To establish translation relevance, we further show that PTX elevates phosphorylated eiF4E (p-eIF4E) in human DRG neurons, and concurrent eFT508 administration attenuates this effect. Collectively, these findings indicated that PTX disrupts lysosome trafficking and biogenesis, and that MNK inhibition with eFT508 restores lysosomal signaling and can serve as a neuroprotective strategy for CIPN.

Dominant missense mutations in ATP1A3, encoding a Na+, K+ ATPase -3 subunit, can cause Alternating Hemiplegia of Childhood (AHC), but how these mutations lead to AHC remains unclear. Here, we establish the first C. elegans AHC models by introducing AHC-causing ATP1A3 patient mutations (D801N, E815K, L839P, and G947R) into the orthologous gene, eat-6, using CRISPR/Cas9. Homozygous C. elegans AHC model animals have recessive developmental defects. Heterozygous AHC model animals have dominant defects in neuromuscular junction (NMJ) function that are inconsistent with haploinsufficiency and dominant sleep or arousal defects. Previous work in a Drosophila G755S AHC model found that loss of a K-dependent, Na/Ca{superscript 2} exchanger exacerbated neuronal defects. We introduced a loss-of-function allele of the orthologous C. elegans gene, ncx-4, into C. elegans AHC models; loss of ncx-4 function did not consistently alter C. elegans AHC model defects across alleles. Our results establish novel C. elegans models of AHC with robust phenotypes, demonstrate that AHC mutations disrupt NMJ function, and provide proof-of-concept for discovering cross-species modifiers of AHC-related phenotypes. Summary StatementWe report the first C. elegans models of Alternating Hemiplegia of Childhood. D801N, E815K, L839P, and G947R AHC model animals have recessive development defects and dominant neuromuscular defects.

Craniometaphyseal dysplasia (CMD) is a rare genetic disorder characterized by hyperostosis of craniofacial bones and flared metaphyses of long bones. Mutations in ANKH (mouse orthologue ANK), a transmembrane protein mediating ATP and citrate efflux, cause the autosomal dominant form of CMD. How ANK mutations in CMD affect ATP/citrate homeostasis and downstream targets remains unknown. We determined that cellular ATP export, intracellular ATP levels, and plasma citric acid were significantly reduced in ANKF377del knock-in (AnkKI/KI) mice. Enrichment and pathway analyses of the plasma metabolome suggested the involvement of the citric acid cycle. It is known that AMPK is phosphorylated and activated when ATP is low. Phospho-AMPK was significantly upregulated in fusing AnkKI/KI osteoclasts, major contributors to CMD. AMPK inhibitor treatment only during the fusion stage of osteoclasts significantly restored dysfunctional AnkKI/KI osteoclasts, partly by modulating actin structures. Systemic administration of the AMPK inhibitor SBI-0206965 improved the positioning of cervical loops of incisors but failed to correct other skeletal abnormalities in AnkKI/KI mice. Limitations of systemic administration of SBI-0206965 include its off-target effects on other cell types and the inability to inhibit AMPK only on fusing osteoclasts. Nonetheless, this proof-of-principle study reveals an important role of the ATP-AMPK axis in CMD pathogenesis. Take-home messageSuppression of increased activation of AMPK restores the function of osteoclasts, suggesting that abnormal energy metabolism is an integral component of the disease phenotype in CMD.

Mutations in platelet-derived growth factor receptor beta (PDGFR{beta}) cause Kosaki overgrowth syndrome (KOGS). Patients exhibit increased linear growth, craniosynostosis, and thin skin with increased elasticity and scarring. Of the KOGS patients identified to date, three unrelated individuals carried a P584R mutation in the juxtamembrane domain of PDGFR{beta}, resulting in constitutive receptor activation. Due to the limited number of patients, extensive phenotyping and exploration of the molecular basis of disease, including modifier genes, has not been completed. We generated conditional knock-in mice to express mouse PDGFR{beta} with a P583R mutation, corresponding to human P584R, under control of the endogenous Pdgfrb gene. Mutant mice were born at the expected ratio and appeared normal at birth. At 3 weeks of age, mutants began to exhibit connective tissue changes: increased body weight and bone length, craniosynostosis, ectopic bone in the tail and tendons, thin lipodystrophic skin, and high incidence of penile and rectal prolapse. To identify signaling changes caused by mutant PDGFR{beta} signaling, we performed western blotting and phosphoproteomics on dermal fibroblasts. This uncovered increased phosphorylation of PDGFR{beta}, PLC{gamma}, Akt1, Shp2, STAT1, STAT2, STAT3, and STAT5. Analysis of 6,621 proteins and 5,386 phosphopeptides identified upregulation of interferon signaling genes linked to STAT1. In many cell types, STAT1 has tumor-suppressor functions and acts to inhibit cell cycle. We generated Stat1-/- Pdgfrb+/P583R mice to test the contribution of STAT1 to KOGS phenotypes. Stat1-deletion exacerbated overgrowth and calvaria dysmorphogensis, and caused keloid-like skin fibrosis. No phenotypes present in the original Pdgfrb+/P583R mice were reverted to normal after Stat1 deletion. Therefore, the P583R mouse model mirrored KOGS phenotypes and increased activation of multiple PDGFR{beta} signaling mediators; in this context, STAT1 activity opposes PDGFR{beta}-driven overgrowth and fibrosis.