Low-density Lipoprotein Receptor-related Protein Research Articles

Therapeutic effects of nanosilibinin in valproic acid-zebrafish model of autism spectrum disorder: Focusing on Wnt signaling pathway and autism spectrum disorder-related cytokines.

In this study, we delved into the intricate world of autism spectrum disorder (ASD) and its connection to the disturbance in the Wnt signaling pathway and immunological abnormalities. Our aim was to evaluate the impact of silibinin, a remarkable modulator of both the Wnt signaling pathway and the immune system, on the neurobehavioral and molecular patterns observed in a zebrafish model of ASD induced by valproic acid (VPA). Because silibinin is a hydrophobic molecule and highly insoluble in water, it was used in the form of silibinin nanoparticles (nanosilibinin, NS). After assessing survival, hatching rate, and morphology of zebrafish larvae exposed to different concentrations of NS, the appropriate concentrations were chosen. Then, zebrafish embryos were exposed to VPA (1 μM) and NS (100 and 200 μM) at the same time for 120 h. Next, anxiety and inattentive behaviors and the expression of CHD8, CTNNB, GSK3beta, LRP6, TNFalpha, IL1beta, and BDNF genes were assessed 7days post fertilization. The results indicated that higher concentrations of NS had adverse effects on survival, hatching, and morphological development. The concentrations of 100 and 200 μM of NS could ameliorate the anxiety-like behavior and learning deficit and decrease ASD-related cytokines (IL1beta and TNFalpha) in VPA-treated larvae. In addition, only 100 μM of NS prevented raising the gene expression of Wnt signaling-related factors (CHD8, CTNNB, GSK3beta, and LRP6). In conclusion, NS treatment for the first 120 h showed therapeutic effect on an autism-like phenotype probably via reducing the expression of pro-inflammatory cytokines genes and changing the expression of Wnt signaling components genes.

Lrp10 suppresses IL7R limiting CD8 T cell homeostatic expansion and anti-tumor immunity

Signals emanating from the T-cell receptor (TCR), co-stimulatory receptors, and cytokine receptors each influence CD8 T-cell fate. Understanding how these signals respond to homeostatic and microenvironmental cues can reveal new ways to therapeutically direct T-cell function. Through forward genetic screening in mice, we discover that loss-of-function mutations in LDL receptor-related protein 10 (Lrp10) cause naive and central memory CD8 T cells to accumulate in peripheral lymphoid organs. Lrp10 encodes a conserved cell surface protein of unknown immunological function. T-cell activation induces Lrp10 expression, which post-translationally suppresses IL7 receptor (IL7R) levels. Accordingly, Lrp10 deletion enhances T-cell homeostatic expansion through IL7R signaling. Lrp10-deficient mice are also intrinsically resistant to syngeneic tumors. This phenotype depends on dense tumor infiltration of CD8 T cells, which display increased memory cell characteristics, reduced terminal exhaustion, and augmented responses to immune checkpoint inhibition. Here, we present Lrp10 as a new negative regulator of CD8 T-cell homeostasis and a host factor that controls tumor resistance with implications for immunotherapy.

Heterogeneous Presentations and Serologies in Myasthenia Gravis Patients Presenting with Dysphagia.

Myasthenia gravis (MG) is an autoimmune disease that affects the neuromuscular junction. MG patients may present de novo with primary otolaryngology complaints, including swallowing dysfunction. This study describes a range of unique presentations and rare diagnostic serologies, which have not previously been fully described. A retrospective review was performed of all patients presenting with primary symptom of dysphagia and subsequently diagnosed with MG. Data collected included demographics, clinical presentation, swallow studies, serology, imaging, treatment, and response. Five patients met the inclusion criteria. Four endorsed dysphagia as primary complaint and one endorsed dysphagia and dysphonia. All patients underwent in-office swallow evaluations that showed vallecular or pyriform sinus residue. Three patients completed modified barium swallow studies that showed pharyngeal weakness and epiglottic dysfunction in all, and upper esophageal sphincter dysfunction in two. One patient with additional symptom of dyspnea was admitted and found to be in myasthenic crisis. Upon serologic evaluation, three patients were positive for acetylcholine receptor (AChR) antibodies only, one for muscle-specific-kinase (MuSK) antibodies only, and one for low density lipoprotein receptor-related protein 4 (LRP4) antibodies only. All patients received neurology evaluation and were treated with steroids, pyridostigmine, plasma exchange, or rituximab. In three patients with over 1 year follow-up, symptoms were significantly improved or resolved. MG is an important differential diagnosis in patients with unexplained pharyngeal dysphagia. While workup can include AChR antibody screening, in seronegative patients with persistent symptoms, additional testing for MuSK and LRP4 may lead to diagnosis and effective treatment. 4 Laryngoscope, 134:4903-4910, 2024.

SNX5-Rab11a protects against cardiac hypertrophy through regulating LRP6 membrane translocation

BackgroundsPathological cardiac hypertrophy is considered one of the independent risk factors for heart failure, with a rather complex pathogenic machinery. Sorting nexins (SNXs), denoting a diverse family of cytoplasmic- and membrane-associated phosphoinositide-binding proteins, act as a pharmacological target against specific cardiovascular diseases including heart failure. Family member SNX5 was reported to play a pivotal role in a variety of biological processes. However, contribution of SNX5 to the development of cardiac hypertrophy, remains unclear. MethodsMice underwent transverse aortic constriction (TAC) to induce cardiac hypertrophy and simulate pathological conditions. TAC model was validated using echocardiography and histological staining. Expression of SNX5 was assessed by western blotting. Then, SNX5 was delivered through intravenous administration of an adeno-associated virus serotype 9 carrying cTnT promoter (AAV9-cTnT-SNX5) to achieve SNX5 cardiac-specific overexpression. To assess the impact of SNX5, morphological analysis, echocardiography, histological staining, hypertrophic biomarkers, and cardiomyocyte contraction were evaluated. To unravel potential molecular events associated with SNX5, interactome analysis, fluorescence co-localization, and membrane protein profile were evaluated. ResultsOur results revealed significant downregulated protein level of SNX5 in TAC-induced hypertrophic hearts in mice. Interestingly, cardiac-specific overexpression of SNX5 improved cardiac function, with enhanced left ventricular ejection fraction, fraction shortening, as well as reduced cardiac fibrosis. Mechanistically, SNX5 directly bound to Rab11a, increasing membrane accumulation of Rab11a (a Rab GTPase). Afterwards, this intricate molecular interaction upregulated the membrane content of low-density lipoprotein receptor-related protein 6 (LRP6), a key regulator against cardiac hypertrophy. Our comprehensive assessment of siRab11a expression in HL-1 cells revealed its role in antagonism of LRP6 membrane accumulation under SNX5 overexpression. ConclusionsThis study revealed that binding of SNX5 with LRP6 triggers their membrane translocation through Rab11a assisting, defending against cardiac remodeling and cardiac dysfunction under pressure overload. These findings provide new insights into the previously unrecognized role of SNX5 in the progression of cardiac hypertrophy.

The high-bone-mass phenotype of novel transgenic mice with LRP5 A241T mutation

Gain-of-function mutations in the low-density lipoprotein receptor-related protein 5 (LRP5) can cause high-bone-mass (HBM) phenotype, with 19 identified mutations so far. The A242T mutation in LRP5 has been found in 9 families, making it one of the most prevalent mutations. However, the correlation between the A242T mutation and HBM phenotype remains unverified in animal models. This study aimed to investigate the bone properties in a new transgenic mouse model carrying the LRP5 A241T missense mutation, equivalent to A242T in humans. Heterozygous Lrp5A241T mice were generated using CRISPR/Cas9 genome editing. Body weight increased with age from 4 to 16 weeks, higher in males than females, with no difference between Lrp5A241T mice and wild-type control. Micro-CT showed slightly longer femur and notably elevated trabecular bone mass of the femur and fifth lumbar spine with higher bone mineral density, bone volume fraction, and trabecular thickness in Lrp5A241T mice compared to wild-type mice. Additionally, increased cortical bone thickness and volume of the femur shaft and skull were observed in Lrp5A241T mice. Three-point bending tests of the tibia demonstrated enhanced bone strength properties in Lrp5A241T mice. Histomorphometry confirmed that the A241T mutation increased bone formation without affecting osteoblast number and reduced resorption activities in vivo. In vitro experiments indicated that the LRP5 A241T mutation enhanced osteogenic capacity of osteoblasts with upregulation of the Wnt signaling pathway, with no significant impact on the resorptive activity of osteoclasts. In summary, mice carrying the LRP5 A241T mutation displayed high bone mass and quality due to enhanced bone formation and reduced bone resorption in vivo, potentially mediated by the augmented osteogenic potential of osteoblasts. Continued investigation into the regulatory mechanisms of its bone metabolism and homeostasis may contribute to the advancement of novel therapeutic strategies for bone disorders.

Unique Splicing of Lrp5 in the Brain: A New Player in Neurodevelopment and Brain Maturation.

Low-density lipoprotein receptor-related protein 5 (LRP5) is a constitutively expressed receptor with observed roles in bone homeostasis, retinal development, and cardiac metabolism. However, the function of LRP5 in the brain remains unexplored. This study investigates LRP5's role in the central nervous system by conducting an extensive analysis using RNA-seq tools and in silico assessments. Two protein-coding Lrp5 transcripts are expressed in mice: full-length Lrp5-201 and a truncated form encoded by Lrp5-202. Wt mice express Lrp5-201 in the liver and brain and do not express the truncated form. Lrp5-/- mice express Lrp5-202 in the liver and brain and do not express Lrp5-201 in the liver. Interestingly, Lrp5-/- mouse brains show full-length Lrp5-201 expression, suggesting that LRP5 has a role in preserving brain function during development. Functional gene enrichment analysis on RNA-seq unveils dysregulated expression of genes associated with neuronal differentiation and synapse formation in the brains of Lrp5-/- mice compared to Wt mice. Furthermore, Gene Set Enrichment Analysis highlights downregulated expression of genes involved in retinol and linoleic acid metabolism in Lrp5-/- mouse brains. Tissue-specific alternative splicing of Lrp5 in Lrp5-/- mice supports that the expression of LRP5 in the brain is needed for the correct synthesis of vitamins and fatty acids, and it is indispensable for correct brain development.

Astrocytic LRP1 enables mitochondria transfer to neurons and mitigates brain ischemic stroke by suppressing ARF1 lactylation

Low-density lipoprotein receptor-related protein-1 (LRP1) is an endocytic/signaling cell-surface receptor that regulates diverse cellular functions, including cell survival, differentiation, and proliferation. LRP1 has been previously implicated in the pathogenesis of neurodegenerative disorders, but there are inconsistencies in its functions. Therefore, whether and how LRP1 maintains brain homeostasis remains to be clarified. Here, we report that astrocytic LRP1 promotes astrocyte-to-neuron mitochondria transfer by reducing lactate production and ADP-ribosylation factor 1 (ARF1) lactylation. In astrocytes, LRP1 suppressed glucose uptake, glycolysis, and lactate production, leading to reduced lactylation of ARF1. Suppression of astrocytic LRP1 reduced mitochondria transfer into damaged neurons and worsened ischemia-reperfusion injury in a mouse model of ischemic stroke. Furthermore, we examined lactate levels in human patients with stroke. Cerebrospinal fluid (CSF) lactate was elevated in stroke patients and inversely correlated with astrocytic mitochondria. These findings reveal a protective role of LRP1 in brain ischemic stroke by enabling mitochondria-mediated astrocyte-neuron crosstalk.

Identification of genes associated with color characteristics of meat and fat tissue of aberdeen-angus cattle

Currently, full genome association studies and identification of candidate genes for economically useful traits in farm animals are topical, scientifically sound and practice-oriented, and fulfill one of the objectives of the Strategy for Scientific and Technical Development of the Russian Federation. This article presents the results of GWAS on color spectral values of meat and fat tissue of Aberdeen-Angus cattle, known for its meat characteristics of high grade. The animals were genotyped on high-density BovineHD Genotyping BeadChip chips containing ≈53,000 SNPs. After quality control, 39,928 remained. By analysis and structural annotation, 25 and 26 candidate genes for meat and fat color were identified, respectively. According to functional annotation, the genes were categorized into 6 groups: nervous system functions, organ development, vascular, joints, metabolic processes and biosynthesis, cellular processes, muscle, tissue and bone, reproduction and embryonic development. The obtained genes were checked through the Animal QTL database, as a result of which 13 genes were confirmed, of which 3 were localized SNPs, in connection with which the LRP2, SCIN and ANTXR1 genes have advantages for their further application in the molecular diagnostics of cattle not only meat, but also dairy productivity.

KRAS-mutant non-small cell lung cancer (NSCLC) therapy based on tepotinib and omeprazole combination

BackgroundKRAS-mutant non-small cell lung cancer (NSCLC) shows a relatively low response rate to chemotherapy, immunotherapy and KRAS-G12C selective inhibitors, leading to short median progression-free survival, and overall survival. The MET receptor tyrosine kinase (c-MET), the cognate receptor of hepatocyte growth factor (HGF), was reported to be overexpressed in KRAS-mutant lung cancer cells leading to tumor-growth in anchorage-independent conditions.MethodsCell viability assay and synergy analysis were carried out in native, sotorasib and trametinib-resistant KRAS-mutant NSCLC cell lines. Colony formation assays and Western blot analysis were also performed. RNA isolation from tumors of KRAS-mutant NSCLC patients was performed and KRAS and MET mRNA expression was determined by real-time RT-qPCR. In vivo studies were conducted in NSCLC (NCI-H358) cell-derived tumor xenograft model.ResultsOur research has shown promising activity of omeprazole, a V-ATPase-driven proton pump inhibitor with potential anti-cancer properties, in combination with the MET inhibitor tepotinib in KRAS-mutant G12C and non-G12C NSCLC cell lines, as well as in G12C inhibitor (AMG510, sotorasib) and MEK inhibitor (trametinib)-resistant cell lines. Moreover, in a xenograft mouse model, combination of omeprazole plus tepotinib caused tumor growth regression. We observed that the combination of these two drugs downregulates phosphorylation of the glycolytic enzyme enolase 1 (ENO1) and the low-density lipoprotein receptor-related protein (LRP) 5/6 in the H358 KRAS G12C cell line, but not in the H358 sotorasib resistant, indicating that the effect of the combination could be independent of ENO1. In addition, we examined the probability of recurrence-free survival and overall survival in 40 early lung adenocarcinoma patients with KRAS G12C mutation stratified by KRAS and MET mRNA levels. Significant differences were observed in recurrence-free survival according to high levels of KRAS mRNA expression. Hazard ratio (HR) of recurrence-free survival was 7.291 (p = 0.014) for high levels of KRAS mRNA expression and 3.742 (p = 0.052) for high MET mRNA expression.ConclusionsWe posit that the combination of the V-ATPase inhibitor omeprazole plus tepotinib warrants further assessment in KRAS-mutant G12C and non G12C cell lines, including those resistant to the covalent KRAS G12C inhibitors.

Coxsackievirus A10 impairs nail regeneration and induces onychomadesis by mimicking DKK1 to attenuate Wnt signaling.

Coxsackievirus A10 (CV-A10) infection, a prominent cause of childhood hand-foot-and-mouth disease (HFMD), frequently manifests with the intriguing phenomenon of onychomadesis, characterized by nail shedding. However, the underlying mechanism is elusive. Here, we found that CV-A10 infection in mice could suppress Wnt/β-catenin signaling by restraining LDL receptor-related protein 6 (LRP6) phosphorylation and β-catenin accumulation and lead to onychomadesis. Mechanistically, CV-A10 mimics Dickkopf-related protein 1 (DKK1) to interact with Kringle-containing transmembrane protein 1 (KRM1), the CV-A10 cellular receptor. We further found that Wnt agonist (GSK3β inhibitor) CHIR99021 can restore nail stem cell differentiation and protect against nail shedding. These findings provide novel insights into the pathogenesis of CV-A10 and related viruses in onychomadesis and guide prognosis assessment and clinical treatment of the disease.

Repeated trans-spinal magnetic stimulation promotes microglial phagocytosis of myelin debris after spinal cord injury through LRP-1

Spinal cord injury (SCI) is a serious trauma of the central nervous system. The clearance of myelin debris is a critical step in the functional recovery following spinal cord injury (SCI). Recent studies have begun to reveal critical roles for professional phagocytes in the central nervous system, microglia, and their receptors in the control of myelin debris in neurodegenerative disease. Repeated trans-spinal magnetic stimulation (rTSMS) has been demonstrated as a noninvasive SCI treatment that enhances tissue repair and functional recovery. In this study, we investigated the role and molecular mechanism of rTSMS on microglial phagocytosis of myelin debris in a rat SCI model. In our studies, we found that rTSMS significantly promoted the motor function recovery of SCI rats associated with the inhibition the neuroinflammation and glia scar formation. Immunofluorescence results further showed that the rTSMS promotes the clearance of myelin debris by microglia in vivo and in vitro. Additionally, receptor-associated protein (RAP), a Low-density lipoprotein receptor-related protein-1 (LRP-1) inhibitor, could cancel the accelerated microglial phagocytosis of myelin debris after rTSMS in vitro experiments. Simultaneously, Elisa's results and western blotting respectively showed that rTSMS significantly decreased the levels of soluble LRP-1(sLRP-1) and the LRP-1 splicing enzyme of ADAM17. In conclusion, rTSMS could promote the clearance of myelin debris by microglia through LRP-1 to improve the functional recovery of SCI rats.

Packaging of supplemented urokinase into alpha granules of in vitro–grown megakaryocytes for targeted nascent clot lysis

AbstractFibrinolytics delivered into the general circulation lack selectivity for nascent thrombi, reducing efficacy and increasing the risk of bleeding. Urokinase-type plasminogen activator (uPA) transgenically expressed within murine platelets provided targeted thromboprophylaxis without causing bleeding but is not clinically feasible. Recent advances in generating megakaryocytes prompted us to develop a potentially clinically relevant means to produce “antithrombotic” platelets from CD34+ hematopoietic stem cell–derived in vitro–grown megakaryocytes. CD34+ megakaryocytes internalize and store in alpha granules (α-granules) single-chain uPA (scuPA) and a plasmin-resistant thrombin-activatable variant (uPAT). Both uPAs colocalized with internalized factor V (FV), fibrinogen and plasminogen, low-density lipoprotein receptor–related protein 1 (LRP1), and interferon-induced transmembrane protein 3, but not with endogenous von Willebrand factor (VWF). Endocytosis of uPA by CD34+ megakaryocytes was mediated, in part, via LRP1 and αIIbβ3. scuPA-containing megakaryocytes degraded endocytosed intragranular FV but not endogenous VWF in the presence of internalized plasminogen, whereas uPAT-megakaryocytes did not significantly degrade either protein. We used a carotid artery injury model in nonobese diabetic-severe combined immunodeficiency IL2rγnull (NSG) mice homozygous for VWFR1326H (a mutation switching binding VWF specificity from mouse to human glycoprotein Ibα) to test whether platelets derived from scuPA- or uPAT-megakaryocytes would prevent thrombus formation. NSG/VWFR1326H mice exhibited a lower thrombotic burden after carotid artery injury compared with NSG mice unless infused with human platelets or megakaryocytes, whereas intravenous injection of uPA-megakaryocytes generated sufficient uPA-containing human platelets to lyse nascent thrombi. These studies describe the use of in vitro–generated megakaryocytes as a potential platform for delivering uPA or other ectopic proteins within platelet α-granules to sites of vascular injury.

Neuronal LRP4 directs the development, maturation and cytoskeletal organization of Drosophila peripheral synapses.

Synaptic development requires multiple signaling pathways to ensure successful connections. Transmembrane receptors are optimally positioned to connect the synapse and the rest of the neuron, often acting as synaptic organizers to synchronize downstream events. One such organizer, the LDL receptor-related protein LRP4, is a cell surface receptor that has been most well-studied postsynaptically at mammalian neuromuscular junctions. Recent work, however, identified emerging roles, but how LRP4 acts as a presynaptic organizer and the downstream mechanisms of LRP4 are not well understood. Here, we show that LRP4 functions presynaptically at Drosophila neuromuscular synapses, acting in motoneurons to instruct pre- and postsynaptic development. Loss of presynaptic LRP4 results in multiple defects, impairing active zone organization, synapse growth, physiological function, microtubule organization, synaptic ultrastructure and synapse maturation. We further demonstrate that LRP4 promotes most aspects of presynaptic development via a downstream SR-protein kinase, SRPK79D. These data demonstrate a function for presynaptic LRP4 as a peripheral synaptic organizer, highlight a downstream mechanism conserved with its CNS function in Drosophila, and underscore previously unappreciated but important developmental roles for LRP4 in cytoskeletal organization, synapse maturation and active zone organization.

Evolutionary and functional analyses of LRP5 in archaic and extant modern humans

BackgroundThe human lineage has undergone a postcranial skeleton gracilization (i.e. lower bone mass and strength relative to body size) compared to other primates and archaic populations such as the Neanderthals. This gracilization has been traditionally explained by differences in the mechanical load that our ancestors exercised. However, there is growing evidence that gracilization could also be genetically influenced.ResultsWe have analyzed the LRP5 gene, which is known to be associated with high bone mineral density conditions, from an evolutionary and functional point of view. Taking advantage of the published genomes of archaic Homo populations, our results suggest that this gene has a complex evolutionary history both between archaic and living humans and within living human populations. In particular, we identified the presence of different selective pressures in archaics and extant modern humans, as well as evidence of positive selection in the African and South East Asian populations from the 1000 Genomes Project. Furthermore, we observed a very limited evidence of archaic introgression in this gene (only at three haplotypes of East Asian ancestry out of the 1000 Genomes), compatible with a general erasing of the fingerprint of archaic introgression due to functional differences in archaics compared to extant modern humans. In agreement with this hypothesis, we observed private mutations in the archaic genomes that we experimentally validated as putatively increasing bone mineral density. In particular, four of five archaic missense mutations affecting the first β-propeller of LRP5 displayed enhanced Wnt pathway activation, of which two also displayed reduced negative regulation.ConclusionsIn summary, these data suggest a genetic component contributing to the understanding of skeletal differences between extant modern humans and archaic Homo populations.

Agrin-Lrp4 pathway in hippocampal astrocytes restrains development of temporal lobe epilepsy through adenosine signaling

BackgroundHuman patients often experience an episode of serious seizure activity, such as status epilepticus (SE), prior to the onset of temporal lobe epilepsy (TLE), suggesting that SE can trigger the development of epilepsy. Yet, the underlying mechanisms are not fully understood. The low-density lipoprotein receptor related protein (Lrp4), a receptor for proteoglycan-agrin, has been indicated to modulate seizure susceptibility. However, whether agrin-Lrp4 pathway also plays a role in the development of SE-induced TLE is not clear.MethodsLrp4f/f mice were crossed with hGFAP-Cre and Nex-Cre mice to generate brain conditional Lrp4 knockout mice (hGFAP-Lrp4−/−) and pyramidal neuron specific knockout mice (Nex-Lrp4−/−). Lrp4 was specifically knocked down in hippocampal astrocytes by injecting AAV virus carrying hGFAP-Cre into the hippocampus. The effects of agrin-Lrp4 pathway on the development of SE-induced TLE were evaluated on the chronic seizure model generated by injecting kainic acid (KA) into the amygdala. The spontaneous recurrent seizures (SRS) in mice were video monitored.ResultsWe found that Lrp4 deletion from the brain but not from the pyramidal neurons elevated the seizure threshold and reduced SRS numbers, with no change in the stage or duration of SRS. More importantly, knockdown of Lrp4 in the hippocampal astrocytes after SE induction decreased SRS numbers. In accord, direct injection of agrin into the lateral ventricle of control mice but not mice with Lrp4 deletion in hippocampal astrocytes also increased the SRS numbers. These results indicate a promoting effect of agrin-Lrp4 signaling in hippocampal astrocytes on the development of SE-induced TLE. Last, we observed that knockdown of Lrp4 in hippocampal astrocytes increased the extracellular adenosine levels in the hippocampus 2 weeks after SE induction. Blockade of adenosine A1 receptor in the hippocampus by DPCPX after SE induction diminished the effects of Lrp4 on the development of SE-induced TLE.ConclusionThese results demonstrate a promoting role of agrin-Lrp4 signaling in hippocampal astrocytes in the development of SE-induced development of epilepsy through elevating adenosine levels. Targeting agrin-Lrp4 signaling may serve as a potential therapeutic intervention strategy to treat TLE.

#1941 About a case: ABBA disease in a patient with thymoma

Abstract Background and Aims ABBA (antibrush border antibody) disease is a rare autoimmune tubulointerstitial kidney disease with few descriptions in the literature. Diagnosis is based on light microscopy, immunofluorescence, electron microscopy and immunostaining for LRP2 (LDL receptor related protein 2), also known as megalin. Method We report the case of a 47-year-old Caucasian man admitted in January 2023 for oedema and acute kidney injury (creatinine 3 mg/dl). Biology revealed nephrotic syndrome with hypoalbuminemia (12 g/L) and albuminuria (13 g/g). Haematuria was also noted (75/mm3). His medical history was notable for myasthenia gravis and epithelial Gougerot. Serological tests were negative for HIV, hepatitis B and hepatitis C. Anti-GBM and anti-PLA2R were negative, antinuclear antibodies and antineutrophil cytoplasmic antibodies were both positive at 1/80 without specificity. Serum complement (C3 and C4) and protein electrophoresis were normal. Renal biopsy showed membranous nephropathy, anti-PLA2R, anti-THSD7A, NELL1 and EXT1/2 negative. There was also IgG staining along Bowman's capsule and along part of the tubular basement membrane (TBM). The acute tubular injury was severe. Morphological studies with thoracic tomodensitometry, thoracic MRI and PET scan revealed a thymoma. The patient underwent surgery in May. It was a stage 3 thymoma with pulmonary and pericardial invasion. In June 2023, the patient started haemodialysis due to progression of chronic renal failure. We performed a second renal biopsy, which confirmed the atypical membranous nephropathy with glomerular and tubular deposits and 10% interstitial sclerosis. The patient received two injections of RITUXIMAB (30 June and 14 July 2023). Results In October 2023, we performed a third renal biopsy due to dialysis dependency three months after RITUXIMAB. The glomerular lesions were similar to the previous biopsy, with minimal extra-membranous deposits. However, tubulointerstitial lesions were more pronounced than before. There was 25% tubular atrophy and 25% interstitial sclerosis associated with interstitial inflammation. We also identified anti-LRP2 immune deposits along the TBM. All these histopathological features lead to the diagnosis of ABBA. Conclusion Anti-LRP2 nephropathy is an orphan disease. It's caused by autoantibodies directed against the proximal tubular brush border, leading to a progressive decline in kidney function. The largest recently published cohort includes 67 patients. Many patients may be misdiagnosed due to the insidious onset and atypical presentation with concomitant glomerular or tubulointerstitial disease. In the cohort, 30% of patients had cancer, including solid organ malignancies (including 1 thymoma). It seems that combined treatment with corticosteroids and another immunosuppressive therapy (cyclophosphamide or rituximab) has better results. In our case, despite his thymoma surgery and rituximab perfusions, the patient is still on dialysis. The immunosuppressive treatment will be discussed with the oncologist soon.

#1148 Polycystic kidney disease—beyond PKD1 and PKD2

Abstract Background and Aims Autosomal dominant polycystic kidney disease (ADPKD) is a common form of hereditary kidney disease, with an estimated prevalence of 1 out of 1000 individuals worldwide. Although its key clinical manifestation is progressive formation and growth of renal cysts, extra-renal manifestations such as hypertension, cysts in other organs, cardiac valve disease and cerebral aneurysms reflect that it is a systemic disorder. Classical ADPKD is associated with heterozygous PKD1 and PKD2 pathogenic gene variants. Less common involved genes that may present as atypical cystic disease include GNAB, DNAJB11 and more recently ALG5/9. Genes associated to syndromic ciliopathies such IFT140 and OFD1 have also been related to atypical ADPKD. Literature reports that 10% patients with ADPKD phenotype will have de novo pathogenic variant. Around 7% of families have negative genetic testing despite clinical phenotype. Failure to consider broader genetic panels or exome sequencing if available may lessen diagnostic yield. Method We performed descriptive analysis on patients with no family history cystic disease and negative PKD1/PKD2 gene testing in our hereditary nephropathy clinic. Atypical cystic disease was defined as non-enlarged kidneys despite multiple cysts and asymmetrical kidney cyst affection in terms of size and quantity, determined through imaging studies. Results From January 2019 until December 2023, n = 39 genetic tests were performed in patients with cystic disease phenotype, n = 28 (13%) without family history. Twelve patients (31%) had positive PKD1/PKD2 variants analysed by PCR long range multiplex. Fig. 1 represents the genetic test results in the remaining patients (n = 16) with cystic disease phenotype and no family history. Positive genetic testing was obtained in n = 7 (43%). Ten patients (63%) presented features of atypical cystic disease. These had a median referral age of 48 years (IQR 34-58), n = 3 (30%) male. Three causal genetic variants were identified (1 with variants in IFT140 and 2 in OFD1 gene), the remaining with negative genetic test result. Patients without atypical features had a median age of referral 55 years (IQR 38-58), n = 4 (60%) were male. Variants in GANAB, LRP5 and PKHD1 genes were identified in this subgroup. Extra-renal manifestations were seen in in 70% and 50% of patients with and without atypical cystic disease, respectively. The main extra-renal manifestation encountered was hepatic cysts. One patient with a pathogenic OFD1 variant presented syndactyly. Conclusion In recent years, growing knowledge in the field and identification of genes involved in ciliopathies associated with atypical forms polycystic kidney disease have allowed for genetic diagnosis of non-PKD1/PKD2 forms. The identification of new genes associated with atypical forms of polycystic kidney disease has called attention to a potential overlap between polycystic and tubulointerstitial phenotypes. With growing knowledge in genetics leading to improvement of cystic kidney disease panels and increased experience in exome sequencing, diagnostic yield is likely to increase in the coming years. Genetic basis of disease is important considering possibility of avoiding primary transmission through pre-implantatory genetic diagnosis but also in the management and diagnosis of gene-specific systemic manifestations.

Cryo-EM structures elucidate the multiligand receptor nature of megalin

Megalin (low-density lipoprotein receptor-related protein 2) is a giant glycoprotein of about 600 kDa, mediating the endocytosis of more than 60 ligands, including those of proteins, peptides, and drug compounds [S. Goto, M. Hosojima, H. Kabasawa, A. Saito, Int. J. Biochem. Cell Biol. 157, 106393 (2023)]. It is expressed predominantly in renal proximal tubule epithelial cells, as well as in the brain, lungs, eyes, inner ear, thyroid gland, and placenta. Megalin is also known to mediate the endocytosis of toxic compounds, particularly those that cause renal and hearing disorders [Y. Hori et al., J. Am. Soc. Nephrol. 28, 1783-1791 (2017)]. Genetic megalin deficiency causes Donnai-Barrow syndrome/facio-oculo-acoustico-renal syndrome in humans. However, it is not known how megalin interacts with such a wide variety of ligands and plays pathological roles in various organs. In this study, we elucidated the dimeric architecture of megalin, purified from rat kidneys, using cryoelectron microscopy. The maps revealed the densities of endogenous ligands bound to various regions throughout the dimer, elucidating the multiligand receptor nature of megalin. We also determined the structure of megalin in complex with receptor-associated protein, a molecular chaperone for megalin. The results will facilitate further studies on the pathophysiology of megalin-dependent multiligand endocytic pathways in multiple organs and will also be useful for the development of megalin-targeted drugs for renal and hearing disorders, Alzheimer's disease [B. V. Zlokovic et al., Proc. Natl. Acad. Sci. U.S.A. 93, 4229-4234 (1996)], and other illnesses.

A multi-trait GWAS identifies novel genes influencing albuminuria.

Albuminuria is common and associated with increased risks of end-stage kidney disease and cardiovascular diseases, yet its underlying mechanism remains obscure. Previous genome-wide association studies (GWAS) for albuminuria did not consider gene pleiotropy and primarily focused on European ancestry populations. This study adopted a multi-trait analysis of GWAS (MTAG) approach to jointly analyze two vital kidney traits, estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio (UACR) to identify and prioritize the genes associated with UACR. Data from the Taiwan Biobank from 2012 to 2023 were analyzed. GWAS of UACR and eGFR were performed separately and the summary statistics from these GWAS were jointly analyzed using MTAG. The polygenic risk scores (PRS) of UACR were constructed for validation. The UACR-associated loci were further fine-mapped and prioritized based on their deleteriousness, eQTL associations, and relatedness to Mendelian kidney diseases. MTAG analysis of the UACR revealed 15 genetic loci, including 12 novel loci. The PRS for UACR was significantly associated with urinary albumin level (P<0.001) and microalbuminuria (P=0.001 ∼ 0.045). A list of priority genes was generated. Twelve genes with high priority included the albumin endocytic receptor gene LRP2 and ciliary genes IFT172. The findings of this multi-trait GWAS suggest that primary cilia play a role in sensing mechanical stimuli, leading to albumin endocytosis. The priority list of genes warrants further translational investigation to reduce albuminuria.

Activation of lipophagy ameliorates cadmium-induced neural tube defects via reducing low density lipoprotein cholesterol levels in mouse placentas

Neural tube defects (NTDs) represent a prevalent and severe category of congenital anomalies in humans. Cadmium (Cd) is an environmental teratogen known to cause fetal NTDs. However, its underlying mechanisms remain elusive. This study aims to investigate the therapeutic potential of lipophagy in the treatment of NTDs, providing valuable insights for future strategies targeting lipophagy activation as a means to mitigate NTDs.We successfully modeled NTDs by Cd exposure during pregnancy. RNA sequencing was employed to investigate the transcriptomic alterations and functional enrichment of differentially expressed genes in NTD placental tissues. Subsequently, pharmacological/genetic (Atg5-/- placentas) experiments confirmed that inducing placental lipophagy can alleviate Cd induced-NTDs. We found that Cd exposure caused NTDs. Further analyzed transcriptomic data from the placentas with NTDs which revealed significant downregulation of low-density lipoprotein receptor associated protein 1(Lrp1) gene expression responsible for positive regulation of low-density lipoprotein cholesterol (LDL-C) transport. Correspondingly, there was an increase in maternal serum/placenta/amniotic fluid LDL-C content. Subsequently, we have discovered that Cd exposure activated placental lipophagy. Pharmacological/genetic (Atg5-/- placentas) experiments confirmed that inducing placental lipophagy can alleviate Cd induced-NTDs. Furthermore, our findings demonstrate that activation of placental lipophagy effectively counteracts the Cd-induced elevation in LDL-C levels. Lipophagy serves to mitigate Cd-induced NTDs by reducing LDL-C levels within mouse placentas.