Altered autophagic flux in GNE mutant cells of Indian origin: Potential drug target for GNE myopathy.

Autophagy phenomenon in the cell maintains proteostasis balance by eliminating damaged organelles and protein aggregates. Imbalance in autophagic flux may cause accumulation of protein aggregates in various neurodegenerative disorders. Regulation of autophagy by either calcium or chaperone play a key role in the removal of protein aggregates from the cell. The neuromuscular rare genetic disorder, GNE Myopathy, is characterized by accumulation of rimmed vacuoles having protein aggregates of ß-amyloid and tau that may result from altered autophagic flux. In the present study, the autophagic flux was deciphered in HEK cell-based model for GNE Myopathy harbouring GNE mutations of Indian origin. The refolding activity of HSP70 chaperone was found to be reduced in GNE mutant cells compared to wild type controls. The autophagic markers LC3II/I ratio was altered with increased number of autophagosome formation in GNE mutant cells compared to wild type cells. The cytosolic calcium levels were also increased in GNE mutant cells of Indian origin. Interestingly, treatment of GNE mutant cells with HSP70 activator, BGP-15, restored the expression and refolding activity of HSP70 along with autophagosome formation. Treatment with calcium chelator, BAPTA-AM restored the cytoplasmic calcium levels and autophagosome formation but not LC3II/I ratio significantly. Our study provides insights towards GNE mutation specific response for autophagy regulation and opens up a therapeutic advancement area in calcium signalling and HSP70 function for GNE related Myopathy.

GNE deficiency impairs Myogenesis in C2C12 cells and cannot be rescued by ManNAc supplementation.

GNE myopathy (GNEM) is a late-onset muscle atrophy, caused by mutations in the gene for the key enzyme of sialic acid biosynthesis, UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE). With an incidence of one to nine cases per million it is an ultra-rare, so far untreatable, autosomal recessive disease. Several attempts have been made to treat GNEM patients by oral supplementation with sialic acid precursors (e.g. N-acetylmannosamine, ManNAc) to restore sarcolemmal sialylation and muscle strength. In most studies, however, no significant improvement was observed. The lack of a suitable mouse model makes it difficult to understand the exact pathomechanism of GNEM and many years of research have failed to identify the role of GNE in skeletal muscle due to the lack of appropriate tools. We established a CRISPR/Cas9-mediated Gne-knockout cell line using murine C2C12 cells to gain insight into the actual role of the GNE enzyme and sialylation in a muscular context. The main aspect of this study was to evaluate the therapeutic potential of ManNAc and N-acetylneuraminic acid (Neu5Ac). Treatment of Gne-deficient C2C12 cells with Neu5Ac, but not with ManNAc, showed a restoration of the sialylation level back to wild type levels-albeit only with long-term treatment, which could explain the rather low therapeutic potential. We furthermore highlight the importance of sialic acids on myogenesis, for C2C12 Gne-knockout myoblasts lack the ability to differentiate into mature myotubes.

A novel variant in the GNE gene in a Malian patient presenting with distal myopathy.

GNE-myopathy (GNE-M) is a rare autosomal recessive disorder caused by variants in the GNE gene. We report a novel variant in GNE causing GNE-M in a Malian family. A 19-year-old male patient from consanguineous marriage was seen for progressive walking difficulty. Neurological examination found predominant distal muscle weakness and atrophy, decreased tendon reflexes, predominating in lower limbs. Electroneuromyography showed an axonal neuropathy pattern. However, whole exome sequencing (WES) revealed a novel biallelic variant in GNE c.1838G > A:p.Gly613Glu, segregating with the phenotype within the family. This study highlights its diagnosis challenges in sub-Saharan Africa and broadens the genetic spectrum of this rare disease.

Pseudoexon activation by deep intronic variation in GNE myopathy with thrombocytopenia.

INTRODUCTION/AIMS: GNE myopathy is a rare autosomal recessive disorder caused by pathogenic variants in the GNE gene, which is essential for the sialic acid biosynthesis pathway. Although over 300 GNE variants have been reported, some patients remain undiagnosed with monoallelic pathogenic variants. This study aims to analyze the entire GNE genomic region to identify novel pathogenic variants. METHODS: Patients with clinically compatible GNE myopathy and monoallelic pathogenic variants in the GNE gene were enrolled. The other GNE pathogenic variant was verified using comprehensive methods including exon 2 quantitative polymerase chain reaction and nanopore long-read single-molecule sequencing (LRS). RESULTS: A deep intronic GNE variant, c.862+870C>T, was identified in nine patients from eight unrelated families. This variant generates a cryptic splice site, resulting in the activation of a novel pseudoexon between exons 5 and 6. It results in the insertion of an extra 146 nucleotides into the messengerRNA (mRNA), which is predicted to result in a truncated humanGNE1(hGNE1) protein. Peanut agglutinin（PNA） lectin staining of muscle tissues showed reduced sialylation of mucin O-glycans on sarcolemmal glycoproteins. Notably, a third of patients with the c.862+870C>T variant exhibited thrombocytopenia. A common core haplotype harboring the deep intronic GNE variant was found in all these patients. DISCUSSION: The transcript with pseudoexon activation potentially affects sialic acid biosynthesis via nonsense-mediated mRNA decay, or resulting in a truncated hGNE1 protein, which interferes with normal enzyme function. LRS is expected to be more frequently incorporated in genetic analysis given its efficacy in detecting hard-to-find pathogenic variants.

Ubiquitin-specific protease 7 prevents recurrent spontaneous abortion by targeting enhancer of zeste homolog 2 to regulate trophoblast proliferation, apoptosis, migration, and invasion through the Wnt/ß-catenin pathway†.

Trophoblasts are significant components of the placenta and play crucial roles in maternal-fetal crosstalk. Adequate trophoblast migration and invasion are essential for embryo implantation and healthy pregnancy. Ubiquitin-specific protease 7 (USP7), a member of the deubiquitinating enzyme family, regulates the processes of migration and invasion in multiple tumor cells. However, the effects of USP7 on trophoblasts and its possible mechanism in the development of recurrent spontaneous abortion (RSA) are still unclear. In this study, we analyzed the expression of USP7 in villous tissues obtained from RSA patients and healthy controls, and then GNE-6776 (a USP7-specific inhibitor) and USP7 siRNA were used in a trophoblast cell line, HTR-8/SVneo, to further assess the effect of USP7 on the biological function of trophoblasts. Our results provide convincing evidence that USP7 is downregulated in the placental villous tissues of RSA patients. USP7 was found to have a crucial role in the proliferation, apoptosis, migration, invasion, and epithelial-mesenchymal transition (EMT) process of trophoblast cells. Further experiments revealed that USP7 directly interacted with the enhancer of zeste homolog 2 (EZH2) and regulated the Wnt/ß-catenin signaling pathway in trophoblasts. Taken together, these findings indicate the vital role of USP7 in regulating trophoblast proliferation, migration and invasion, thus affecting the pathogenesis of RSA, providing new insights into the important role of USP7 in the maternal-fetal interface.

Tissue-specific isoform expression of GNE gene in human tissues.

Mutations in the sialic acid biosynthesis enzyme GNE lead to a late-onset, debilitating neuromuscular disorder, GNE myopathy, characterized by progressive skeletal muscle weakness. The mechanisms responsible for skeletal muscle specificity, late-onset, and disease progression are unknown. Our main aim is to understand the reason for skeletal muscle-specific phenotype. To answer this question, we have analyzed the expression profile of the GNE gene and its multiple mRNA variants in different human tissues. A combinatorial approach encompassing bioinformatics tools and molecular biology techniques was used. NCBI, Ensembl, and GTEx were used for data mining. The expression analysis of GNE and its variants was performed with cDNA tissue panel using PCR and targeted RNA-seq. Among nine different GNE isoforms reported in this study, transcript variants 1, X1, and X2 were not tissue specific. Transcript variants 1, 6, X1, and X2, were found in skeletal muscles suggesting their possible role in GNE myopathy. In the current study, we present new data about GNE expression patterns in human tissues. Our results suggest that there may be a link between tissue-specific pathology and isoform pattern in skeletal muscles, which could provide clues for the development of new treatment strategies for GNE myopathy.

Assessment of thrombocytopenia, sleep apnea, and cardiac involvement in GNE myopathy patients.

INTRODUCTION: We previously identified UDP-N-acetylglucosamine 2-epimerase (GNE) myopathy patients with sleep apnea and a past history of thrombocytopenia, but without disease-specific cardiac involvement. This study aimed to clarify the occurrence, severity, and serial changes of these complications. METHODS: Thirty-three genetically confirmed GNE myopathy patients who participated in a 5-y longitudinal observational history study underwent platelet count and platelet-associated immunoglobulin G (PA-IgG) measurements, a sleep study, and electrocardiography (ECG), Holter ECG, and echocardiogram examinations. RESULTS: Among the 33 patients, three had low platelet counts and 17 out of 26 were PA-IgG positive. No patient exhibited bleeding tendencies, and 3 out of 28 had low platelet counts. Muscle weakness was more pronounced, and summed MMT and grip power significantly lower, in PA-IgG-positive patients than in PA-IgG-negative patients. Of 19 patients, 7, 4, and 3 who underwent a sleep study had mild, moderate, and severe sleep apnea, respectively, and three started continuous positive airway pressure (CPAP). The respiratory disturbance index was not significantly correlated with physical evaluation items or forced vital capacity. All patients underwent ECG, 32 underwent cardiac ultrasound, and 25 underwent Holter ECG. No disease-specific cardiac involvement was noted, no serial changes during the follow-up period were observed for ECG and echocardiography, and none of the patients required therapy for cardiac abnormalities. DISCUSSION: PA-IgG is a potential disease biomarker in GNE myopathy patients, although its significance needs to be clarified. While none of the patients in this study experienced cardiomyopathy or arrythmia due to myopathy, sleep apnea was identified as a frequent complication.

Clinical, genetic, and pathological characterization of GNE myopathy in China.

BACKGROUND: GNE myopathy is the most common distal myopathy in China. We summarized the clinical, genetic, and pathological characteristics of 125 Chinese patients with GNE myopathy. METHODS: We collected clinical data of 21 patients diagnosed at our hospital and 104 patients from previous reports. Clinical, genetic, and pathological characteristics were summarized. According to the location of mutations, patients were classified into groups to analyze genotype-phenotype correlation. We reviewed the pathological features and studied the expressions of neural cell adhesion molecule. RESULTS: The severity of involvement of lower limb muscles was in the following order: tibialis anterior > biceps femoris > gastrocnemius > iliopsoas > quadriceps femoris. Mutation p.D207V was the most common variant in China. Patients carrying p.D207V tended to show later disease onset. In the epimerase/epimerase group, men had earlier disease onset than women (p < 0.05). In other groups, age at disease onset in females was earlier than that in males. Protein analysis showed decreased sialylation of NCAM and upregulation of LC3 in patients with different mutations. CONCLUSIONS: Mutation p.D207V is the most common GNE variant in China. Involvement of flexor muscles in lower limbs was more obvious than extensor muscles. NCAM expression in patients with various mutations may be a useful diagnostic biomarker in GNE myopathy.

Gene analysis and clinical features of 22 GNE myopathy patients.

INTRODUCTION: GNE myopathy is an autosomal recessive distal myopathy caused by a biallelic mutation in UDP-N-acetylglucosamine 2-epomerase/N-acetylmannosamine kinase. In this study, we discuss the clinical features, pathological characteristics, genetic profiles, and atypical clinical manifestations of 22 Chinese GNE patients. MATERIALS AND METHODS: Retrospective analysis was performed for GNE myopathy patients at our institute between 2005 and 2021. Histopathological analysis and gene testing were done according to standard protocols. RESULTS: Molecular analysis revealed 14-reported and 7 novel mutations, including c.125G > A (p.P42Q), c.226G > A (p.V76I), c.970C > G (p.H324D), c.155A > G (p.D52G), c.1055G > A (p.R352H), c.1064G > A (p.G355E), and c.491 T > C (p.I164T) in GNE. D207V was the most frequent mutation showing an allele frequency of 25%. A total of 21 patients presented classic clinical manifestation, and only 1 patient had signs of proximal muscle weakness. A patient containing p.V603L and p.R160X mutations showed idiopathic thrombocytopenia and distal weakness. There were 4 female patients who experienced rapid deterioration after pregnancy. DISCUSSION: Our study revealed 7 novel mutations in GNE, where p.D207V was shown as a potential hotspot mutation in Chinese patients. Idiopathic thrombocytopenia should be a concern in GNE myopathy patients. Twenty-seven percent of female patients experienced rapid deterioration during pregnancy or after delivery.

The role of amyloid ß in the pathological mechanism of GNE myopathy.

GNE myopathy is a hereditary muscle disorder characterized by muscle atrophy and weakness initially involving the lower distal extremities. The treatment of GNE myopathy mainly focuses on a sialic acid deficiency caused by a mutation in the GNE gene, but it has not achieved the expected effect. The main pathological features of GNE myopathy are myofiber atrophy and rimmed vacuoles, including accumulation of amyloid ß, which is mainly found in atrophic muscle fibers. Although the role of amyloid ß and other misfolded proteins on the nervous system has been widely recognized, the cause and process of the formation of amyloid ß in the pathological process of GNE myopathy are unclear. In addition, amyloid ß has been reported to be linked to quality control mechanisms of proteins, such as molecular chaperones, the ubiquitin-proteasome system, and the autophagy-lysosome system. Herein, we summarize the possible reasons for amyloid ß deposition and illustrate amyloid ß-mediated events in the cells and their role in muscle atrophy in GNE myopathy. This review represents an overview of amyloid ß and GNE myopathy that could help identify a potential mechanism and thereby a plausible therapeutic for the disease.

The Synthesis of UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine Kinase (GNE), α-dystroglycan, and ß-galactoside α-2,3-sialyltransferase 6 (ST3Gal6) By Skeletal Muscle Cell As a Response To Infection with Trichinella Spiralis.

The Nurse cell of the parasitic nematode Trichinella spiralis is a unique structure established after genetic, morphological and functional modification of a small portion of invaded skeletal muscle fiber. Even if the newly developed cytoplasm of the Nurse cell is no longer contractile, this structure remains well integrated within the surrounding healthy tissue. Our previous reports suggested that this process is accompanied by an increased local biosynthesis of sialylated glycoproteins. In this work we examined the expressions of three proteins, functionally associated with the process of sialylation. The enzyme UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) is a key initiator of the sialic acid biosynthetic pathway. The α-dystroglycan was the only identified sialylated glycoprotein in skeletal muscles by now, bearing sialyl-α-2,3-Gal-ß-1,4-Gl-cNAc-ß-1,2-Man-α-1-O-Ser/Thr glycan. The third protein of interest for this study was the enzyme ß-galactoside α-2,3-sialyltransferase 6 (ST3Gal6), which transfers sialic acid preferably onto Gal-ß-1,4-GlcNAc as an acceptor, and thus it was considered as a suitable candidate for the sialylation of the α-dystroglycan. The expressions of the three proteins were analyzed by real time-PCR and immunohistochemistry on modified methacarn fixed paraffin tissue sections of mouse skeletal muscle samples collected at days 0, 14 and 35 post infection. According to our findings, the up-regulation of GNE was a characteristic of the early and the late stage of the Nurse cell development. Additional features of this process were the elevated expressions of α-dystroglycan and the enzyme ST3Gal6. We provided strong evidence that an increased local synthesis of sialic acids is a trait of the Nurse cell of T. spiralis, and at least in part due to an overexpression of α-dystroglycan. In addition, circumstantially we suggest that the enzyme ST3Gal6 is engaged in the process of sialylation of the major oligosaccharide component of α-dystroglycan.

Expanding the clinicopathological-genetic spectrum of GNE myopathy by a Chinese neuromuscular centre.

GNE myopathy is a heterogeneous group of ultrarare neuromuscular disorders caused by mutations in the GNE gene. An estimated prevalence of 1~21/1,000,000 leads to a deficiency of data and a lack of availability of samples to conduct clinical research on this neuromuscular disorder. Although GNE, which is the mutated gene responsible for the disease, is well known as the key enzyme in the biosynthesis pathway of sialic acid, the clinicopathological-genetic spectrum of GNE mutant patients is still unclear and expanding. This study presents ten unrelated patients with GNE myopathy, discovering five novel missense mutations. Clinical, electrophysiological, imaging, pathological and genetic data are presented in a retrospective manner. Interestingly, several patients in the cohort were found to have peripheral neuropathy and inflammatory cell infiltration in muscle biopsies, which have seldom been reported. This study, conducted by a neuromuscular centre in China, is the first attempt to highlight these abnormal clinicopathological features and associate them with genetic mutations in GNE myopathy.

Uridine diphosphate-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase deletion in mice leads to lethal intracerebral hemorrhage during embryonic development.

Among the enzymes of the biosynthesis of sialoglycoconjugates, uridine diphosphate-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE), catalyzing the first essential step of the sialic acid (Sia) de novo biosynthesis, and cytidine monophosphate (CMP)-Sia synthase (CMAS), activating Sia to CMP-Sia, are particularly important. The knockout of either of these enzymes in mice is embryonically lethal. While the lethality of Cmas-/- mice has been attributed to a maternal complement attack against asialo fetal placental cells, the cause of lethality in Gne-deficient embryos has remained elusive. Here, we advanced the significance of sialylation for embryonic development through detailed histological analyses of Gne-/- embryos and placentae. We found that Gne-/- embryonic and extraembryonic tissues are hyposialylated rather than being completely deficient of sialoglycans, which holds true for Cmas-/- embryos. Residual sialylation of Gne-/- cells can be explained by scavenging free Sia from sialylated maternal serum glycoconjugates via the lysosomal salvage pathway. The placental architecture of Gne-/- mice was unaffected, but severe hemorrhages in the neuroepithelium with extensive bleeding into the cephalic ventricles were present at E12.5 in the mutants. At E13.5, the vast majority of Gne-/- embryos were asystolic. This phenotype persisted when Gne-/- mice were backcrossed to a complement component 3-deficient background, confirming distinct pathomechanisms of Cmas-/- and Gne-/- mice. We conclude that the low level of sialylation observed in Gne-/- mice is sufficient both for immune homeostasis at the fetal-maternal interface and for embryonic development until E12.5. However, formation of the neural microvasculature is the first critical process, depending on a higher degree of sialylation during development of the embryo proper.

Elucidation of ER stress and UPR pathway in sialic acid-deficient cells: Pathological relevance to GNEM.

Accumulation of misfolded proteins in endoplasmic reticulum (ER) generates a stress condition in the cell. The cell combats ER stress by activating unfolded protein response (UPR) and ERAD (ER stress-associated degradation) pathway. Failure to restore favorable folding environment results in cell dysfunction and apoptosis. Various neurodegenerative disorders are characterized by the accumulation of misfolded protein, protein aggregates, and ER stress. GNE myopathy (GNEM) is a neuromuscular disorder pathologically characterized by rimmed vacuole formation due to the accumulation of protein aggregates. More than 200 mutations in key sialic acid biosynthetic enzyme UDP-N-acetylglucosamine 2-epimerase/N-acetylmannosamine kinase (GNE) have been identified worldwide in the muscle biopsies of GNE myopathy patients. However, the cellular and molecular pathomechanism leading to the disease ar poorly understood. In the present study, the phenomenon of ER stress has been elucidated in GNE mutant cells overexpressing GNE mutations of Indian origin. The effect of GNE mutations on activation of UPR signaling via inositol-requiring transmembrane kinase/endoribonuclease 1 (IRE-1), protein kinase RNA-like endoplasmic reticulum kinase (PERK), and activating transcription factor-6 (ATF6) were deciphered to understand the effect of GNE mutations on these proteins. GRP78 was upregulated with increased X-box-binding protein-1 (XBP-1) splicing and CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) upregulation leading to increased apoptosis of GNE mutant cells. Insulin-like growth factor 1 (IGF-1) ligand rescued the cells from apoptotic phenotype by supporting cell survival mechanism. Our study indicates a balance of cell death and survival that decides cell fate and offers potential therapeutic targets to combat ER stress in diseases associated with dysfunctional UPR pathway.

Distal myopathy due to TCAP variants in four unrelated Chinese patients.

Distal myopathies are a group of clinically and genetically heterogeneous hereditary muscle disorders characterized by progressive muscular weakness starting in the distal parts of the limbs. The most common subtype of distal myopathy is GNE myopathy, a rare muscle disease with autosomal recessive inheritance. Limb-girdle muscular dystrophy 2G (LGMD2G) is a rare autosomal recessive subtype of LGMDs caused by TCAP variant. Patients with LGMD2G can present with distal myopathy and rimmed vacuoles on muscle pathology. Thus far, the most reported TCAP mutations related to LGMD2G were recessive frameshift or nonsense variants. Here, we described four Chinese patients from unrelated families with LGMD2G due to TCAP mutations. The clinical symptoms of our patients were similar to those previously reported in LGMD2G patients. Three different pathogenic TCAP variants were identified in these patients, including two frameshift variants and one intronic variant. Autophagolysosomes have been observed in one patient by electron microscopy. Our research expands the genetic spectrum of TCAP mutations in China, indicating c.165-166insG is likely the common pathogenic variant. We also provide evidences that autophagy may be involved in the pathophysiology of LGMD2G.

Visualizing the effects of lactate dehydrogenase (LDH) inhibition and LDH-A genetic ablation in breast and lung cancer with hyperpolarized pyruvate NMR.

In many tumors, cancer cells take up large quantities of glucose and metabolize it into lactate, even in the presence of sufficient oxygen to support oxidative metabolism. It has been hypothesized that this malignant metabolic phenotype supports cancer growth and metastasis, and that reversal of this so-called "Warburg effect" may selectively harm cancer cells. Conversion of glucose to lactate can be reduced by ablation or inhibition of lactate dehydrogenase (LDH), the enzyme responsible for conversion of pyruvate to lactate at the endpoint of glycolysis. Recently developed inhibitors of LDH provide new opportunities to investigate the role of this metabolic pathway in cancer. Here we show that magnetic resonance spectroscopic imaging of hyperpolarized pyruvate and its metabolites in models of breast and lung cancer reveal that inhibition of LDH was readily visualized through reduction in label exchange between pyruvate and lactate, while genetic ablation of the LDH-A isoform alone had smaller effects. During the acute phase of LDH inhibition in breast cancer, no discernible bicarbonate signal was observed and small signals from alanine were unchanged.

Tissue specific expression of sialic acid metabolic pathway: role in GNE myopathy.

GNE myopathy is an adult-onset degenerative muscle disease that leads to extreme disability in patients. Biallelic mutations in the rate-limiting enzyme UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine-kinase (GNE) of sialic acid (SA) biosynthetic pathway, was shown to be the cause of this disease. Other genetic disorders with muscle pathology where defects in glycosylation are known. It is yet not clear why a defect in SA biosynthesis and glycosylation affect muscle cells selectively even though they are ubiquitously present in all tissues. Here we have comprehensively examined the complete SA metabolic pathway involving biosynthesis, sialylation, salvage, and catabolism. To understand the reason for tissue-specific phenotype caused by mutations in genes of this pathway, we analysed the expression of different SA pathway genes in various tissues, during the muscle tissue development and in muscle tissues from GNE myopathy patients (p.Met743Thr) using publicly available databases. We have also analysed gene co-expression networks with GNE in different tissues as well as gene interactions that are unique to muscle tissues only. The results do show a few muscle specific interactions involving ANLN, MYO16 and PRAMEF25 that could be involved in specific phenotype. Overall, our results suggest that SA biosynthetic and catabolic genes are expressed at a very low level in skeletal muscles that also display a unique gene interaction network.

Early and consistent pattern of proximal weakness in GNE myopathy.

BACKGROUND: GNE myopathy is widely regarded as a distal myopathy. Involvement of proximal musculature in this condition has not been systematically studied. METHODS: The phenotype of genetically confirmed patients with GNE myopathy was analyzed. Fourteen groups of muscles were evaluated with Medical Research Council (MRC) grading and the average muscle scores (AMS:1-10) were calculated. RESULTS: Fully documented AMS data was available in 31 of 65 patients. It showed a consistent pattern of severe weakness of hip adductors, hip flexors, knee flexors, and foot dorsiflexors, with milder weakness of the hip extensors and abductors. The knee extensors were largely unaffected. The proximal weakness appeared early in the course of the disease. Proximal muscle weakness was also present in the remaining 34 patients in whom the data were limited. A variant in exon 13 (c.2179G > A) was very common (81.5%). CONCLUSIONS: The GNE phenotype in this Indian cohort exhibited mixed proximal and distal involvement. Weakness of adductors and flexors of the hip formed an integral part of the phenotype.

Motor axonal neuropathy associated with GNE mutations.

BACKGROUND: Mutations in the GNE gene have been so far described as predominantly associated with distal lower-limb myopathies. Recent reports describe mutations in this gene in patients with peripheral neuropathy and motor neuron disease. METHODS: We describe three patients displaying motor neuropathy in association with GNE mutations. Clinical, electrophysiological, imaging, pathological, and genetic data are presented in a retrospective manner. RESULTS: The three patients had different phenotypes, ranging from mildly progressive lower limb weakness to a rapidly progressive 4-limb weakness. Genetic testing revealed GNE gene mutations in all patients; of those mutations, p.(His186Arg) has not been previously reported. All patients showed evidence of axonal motor nerve involvement on electrodiagnostic examination and/or muscle biopsy. CONCLUSIONS: Nerve involvement associated with GNE gene mutations may be an underdiagnosed pathology and may influence clinical presentation and disease progression.

Discovery of GNE-502 as an orally bioavailable and potent degrader for estrogen receptor positive breast cancer.

Fulvestrant is an FDA-approved drug with a dual mechanism of action (MOA), acting as a full antagonist and degrader of the estrogen receptor protein. A significant limitation of fulvestrant is the dosing regimen required for efficacy. Due to its high lipophilicity and poor pharmacokinetic profile, fulvestrant needs to be administered through intramuscular injections which leads to injection site soreness. This route of administration also limits the dose and target occupancy in patients. We envisioned a best-in-class molecule that would function with the same dual MOA as fulvestrant, but with improved physicochemical properties and would be orally bioavailable. Herein we report our progress toward that goal, resulting in a new lead GNE-502 which addressed some of the liabilities of our previously reported lead molecule GNE-149.