Charting human development using a multi-endodermal organ atlas and organoid models.

Organs are composed of diverse cell types that traverse transient states during organogenesis. To interrogate this diversity during human development, we generate a single-cell transcriptome atlas from multiple developing endodermal organs of the respiratory and gastrointestinal tract. We illuminate cell states, transcription factors, and organ-specific epithelial stem cell and mesenchyme interactions across lineages. We implement the atlas as a high-dimensional search space to benchmark human pluripotent stem cell (hPSC)-derived intestinal organoids (HIOs) under multiple culture conditions. We show that HIOs recapitulate reference cell states and use HIOs to reconstruct the molecular dynamics of intestinal epithelium and mesenchyme emergence. We show that the mesenchyme-derived niche cue NRG1 enhances intestinal stem cell maturation in vitro and that the homeobox transcription factor CDX2 is required for regionalization of intestinal epithelium and mesenchyme in humans. This work combines cell atlases and organoid technologies to understand how human organ development is orchestrated.

Stromal-derived NRG1 enables oncogenic KRAS bypass in pancreas cancer.

Activating KRAS mutations (KRAS*) in pancreatic ductal adenocarcinoma (PDAC) drive anabolic metabolism and support tumor maintenance. KRAS* inhibitors show initial antitumor activity followed by recurrence due to cancer cell-intrinsic and immune-mediated paracrine mechanisms. Here, we explored the potential role of cancer-associated fibroblasts (CAFs) in enabling KRAS* bypass and identified CAF-derived NRG1 activation of cancer cell ERBB2 and ERBB3 receptor tyrosine kinases as a mechanism by which KRAS*-independent growth is supported. Genetic extinction or pharmacological inhibition of KRAS* resulted in up-regulation of ERBB2 and ERBB3 expression in human and murine models, which prompted cancer cell utilization of CAF-derived NRG1 as a survival factor. Genetic depletion or pharmacological inhibition of ERBB2/3 or NRG1 abolished KRAS* bypass and synergized with KRASG12D inhibitors in combination treatments in mouse and human PDAC models. Thus, we found that CAFs can contribute to KRAS* inhibitor therapy resistance via paracrine mechanisms, providing an actionable therapeutic strategy to improve the effectiveness of KRAS* inhibitors in PDAC patients.

STAT5b is a key effector of NRG-1/ERBB4-mediated myocardial growth.

The growth factor Neuregulin-1 (NRG-1) regulates myocardial growth and is currently under clinical investigation as a treatment for heart failure. Here, we demonstrate in several in vitro and in vivo models that STAT5b mediates NRG-1/EBBB4-stimulated cardiomyocyte growth. Genetic and chemical disruption of the NRG-1/ERBB4 pathway reduces STAT5b activation and transcription of STAT5b target genes Igf1, Myc, and Cdkn1a in murine cardiomyocytes. Loss of Stat5b also ablates NRG-1-induced cardiomyocyte hypertrophy. Dynamin-2 is shown to control the cell surface localization of ERBB4 and chemical inhibition of Dynamin-2 downregulates STAT5b activation and cardiomyocyte hypertrophy. In zebrafish embryos, Stat5 is activated during NRG-1-induced hyperplastic myocardial growth, and chemical inhibition of the Nrg-1/Erbb4 pathway or Dynamin-2 leads to loss of myocardial growth and Stat5 activation. Moreover, CRISPR/Cas9-mediated knockdown of stat5b results in reduced myocardial growth and cardiac function. Finally, the NRG-1/ERBB4/STAT5b signaling pathway is differentially regulated at mRNA and protein levels in the myocardium of patients with pathological cardiac hypertrophy as compared to control human subjects, consistent with a role of the NRG-1/ERBB4/STAT5b pathway in myocardial growth.

The novel antibody fusion protein rhNRG1-HER3i promotes heart regeneration by enhancing NRG1-ERBB4 signaling pathway.

Stimulating cardiomyocyte proliferation in the adult heart has emerged as a promising strategy for cardiac regeneration following myocardial infarction (MI). The NRG1-ERBB4 signaling pathway has been implicated in the regulation of cardiomyocyte proliferation. However, the therapeutic potential of recombinant human NRG1 (rhNRG1) has been limited due to the low expression of ERBB4 in adult cardiomyocytes. Here, we investigated whether a fusion protein of rhNRG1 and an ERBB3 inhibitor (rhNRG1-HER3i) could enhance the affinity of NRG1 for ERBB4 and promote adult cardiomyocyte proliferation. In vitro and in vivo experiments were conducted using postnatal day 1 (P1), P7, and adult cardiomyocytes. Western blot analysis was performed to assess the expression and activity of ERBB4. Cardiomyocyte proliferation was evaluated using Ki67 and pH 3 immunostaining, while fibrosis was assessed using Masson staining. Our results indicate that rhNRG1-HER3i, but not rhNRG1, promoted P7 and adult cardiomyocyte proliferation. Furthermore, rhNRG1-HER3i improved cardiac function and reduced cardiac fibrosis in post-MI hearts. Administration of rhNRG1-HER3i inhibited ERBB3 phosphorylation while increasing ERBB4 phosphorylation in adult mouse hearts. Additionally, rhNRG1-HER3i enhanced angiogenesis following MI compared to rhNRG1. In conclusion, our findings suggest that rhNRG1-HER3i is a viable therapeutic approach for promoting adult cardiomyocyte proliferation and treating MI by enhancing NRG1-ERBB4 signaling pathway.

Host-Specific and Homologous Pairs of Melampsora larici-populina Effectors Unveil Novel Nicotiana benthamiana Stromule Induction Factors.

The poplar rust fungus Melampsora larici-populina is part of one of the most devastating group of fungi (Pucciniales) and causes important economic losses to the poplar industry. Because M. larici-populina is a heteroecious obligate biotroph, its spread depends on its ability to carry out its reproductive cycle through larch and then poplar parasitism. Genomic approaches have identified more than 1,000 candidate secreted effector proteins (CSEPs) from the predicted secretome of M. larici-populina that are potentially implicated in the infection process. In this study, we selected CSEP pairs (and one triplet) among CSEP gene families that share high sequence homology but display specific gene expression profiles among the two distinct hosts. We determined their subcellular localization by confocal microscopy through expression in the heterologous plant system Nicotiana benthamiana. Five out of nine showed partial or complete chloroplastic localization. We also screened for potential protein interactors from larch and poplar by yeast two-hybrid assays. One pair of CSEPs and the triplet shared common interactors, whereas the members of the two other pairs did not have common targets from either host. Finally, stromule induction quantification revealed that two pairs and the triplet of CSEPs induced stromules when transiently expressed in N. benthamiana. The use of N. benthamiana eds1 and nrg1 knockout lines showed that CSEPs can induce stromules through an eds1-independent mechanism. However, CSEP homologs shared the same impact on stromule induction and contributed to discovering a new stromule induction cascade that can be partially and/or fully independent of eds1. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

PMP2 regulates myelin thickening and ATP production during remyelination.

It is well established that axonal Neuregulin 1 type 3 (NRG1t3) regulates developmental myelin formation as well as EGR2-dependent gene activation and lipid synthesis. However, in peripheral neuropathy disease context, elevated axonal NRG1t3 improves remyelination and myelin sheath thickness without increasing Egr2 expression or activity, and without affecting the transcriptional activity of canonical myelination genes. Surprisingly, Pmp2, encoding for a myelin fatty acid binding protein, is the only gene whose expression increases in Schwann cells following overexpression of axonal NRG1t3. Here, we demonstrate PMP2 expression is directly regulated by NRG1t3 active form, following proteolytic cleavage. Then, using a transgenic mouse model overexpressing axonal NRG1t3 (NRG1t3OE) and knocked out for PMP2, we demonstrate that PMP2 is required for NRG1t3-mediated remyelination. We demonstrate that the sustained expression of Pmp2 in NRG1t3OE mice enhances the fatty acid uptake in sciatic nerve fibers and the mitochondrial ATP production in Schwann cells. In sum, our findings demonstrate that PMP2 is a direct downstream mediator of NRG1t3 and that the modulation of PMP2 downstream NRG1t3 activation has distinct effects on Schwann cell function during developmental myelination and remyelination.

Neuregulin-1 and ALS19 (ERBB4): at the crossroads of amyotrophic lateral sclerosis and cancer.

BACKGROUND: Neuregulin-1 (NRG1) is implicated in both cancer and neurologic diseases such as amyotrophic lateral sclerosis (ALS); however, to date, there has been little cross-field discussion between neurology and oncology in regard to these genes and their functions. MAIN BODY: Approximately 0.15-0.5% of cancers harbor NRG1 fusions that upregulate NRG1 activity and hence that of the cognate ERBB3/ERBB4 (HER3/HER4) receptors; abrogating this activity with small molecule inhibitors/antibodies shows preliminary tissue-agnostic anti-cancer activity. Notably, ERBB/HER pharmacologic suppression is devoid of neurologic toxicity. Even so, in ALS, attenuated ERBB4/HER4 receptor activity (due to loss-of-function germline mutations or other mechanisms in sporadic disease) is implicated; indeed, ERBB4/HER4 is designated ALS19. Further, secreted-type NRG1 isoforms may be upregulated (perhaps via a feedback loop) and could contribute to ALS pathogenesis through aberrant glial cell stimulation via enhanced activity of other (e.g., ERBB1-3/HER1-3) receptors and downstream pathways. Hence, pan-ERBB inhibitors, already in use for cancer, may be agents worthy of testing in ALS. CONCLUSION: Common signaling cascades between cancer and ALS may represent novel therapeutic targets for both diseases.

Anti-inflammatory effects of neuregulin-1 in HaCaT keratinocytes and atopic dermatitis-like mice stimulated with Der p 38.

Neuregulin (NRG)-1 plays fundamental roles in several organ systems after binding to its receptors, ErbB2 and ErbB4. This study examines the role of NRG-1 in atopic dermatitis (AD), a chronic skin disease that causes dryness, pruritus, and inflammation. In mice administered Der p 38, the skin presents AD-like symptoms including filaggrin downregulation and infiltration of neutrophils and eosinophils. Noticeably, there is an increased expression of NRG-1, ErbB2, and ErbB4 in the skin. Upregulation of these proteins is significantly correlated to the clinical skin severity score. In human keratinocyte HaCaT cells, exposure to Der p 38 decreased filaggrin expression, and NRG-1 alone had no effect on the expression. However, co-treatment of Der p 38 with NRG-1 enhanced the filaggrin expression decreased by Der p 38. Pre-treatment with AG879 (an ErbB2 inhibitor) or ErbB4 siRNA blocked the recovery of filaggrin expression in the cells after co-treatment with Der p 38 and NRG-1. Der p 38 treatment enhanced the secretion of interleukin-6 (IL-6), IL-8, and monocyte chemoattractant protein-1 (MCP-1). Co-treatment of Der p 38 with NRG-1 lowered the cytokine secretion increased by Der p 38, although NRG-1 alone was not effective on cytokine alteration. Neutrophil apoptosis was not altered by NRG-1 or supernatants of cells treated with NRG-1, but the cell supernatants co-treated with Der p 38 and NRG-1 blocked the anti-apoptotic effects of Der p 38-treated supernatants on neutrophils, which was involved in the activation of caspase 9 and caspase 3. Taken together, we determined that NRG-1 has anti-inflammatory effects in AD triggered by Der p 38. These results will pave the way to understanding the functions of NRG-1 and in the future development of AD treatment.

Pulmonary invasive mucinous adenocarcinoma.

Invasive mucinous adenocarcinoma (IMA) is a relatively rare subtype of lung adenocarcinoma, composed of goblet and/or columnar tumour cells containing abundant intracytoplasmic mucin vacuoles. While a majority of IMAs are driven by KRAS mutations, recent studies have identified distinct genomic alterations, such as NRG1 and ERBB2 fusions. IMAs also more frequently present as a pneumonic-like pattern with multifocal and multilobar involvement, and comparative genomic profiling predominantly shows a clonal relationship, suggesting intrapulmonary metastases rather than synchronous primary tumours. Accordingly, these unique features require different therapeutic approaches when compared to nonmucinous adenocarcinomas in general. In this article, we review recent updates on the histopathological, clinical, and molecular features of IMAs, and also highlight some unresolved issues for future studies.

Impairments of GABAergic transmission in hippocampus mediate increased susceptibility of epilepsy in the early stage of Alzheimer's disease.

BACKGROUND: Patients with Alzheimer's disease (AD) are often co-morbid with unprovoked seizures, making clinical diagnosis and management difficult. Although it has an important role in both AD and epilepsy, abnormal γ-aminobutyric acid (GABA)ergic transmission is recognized only as a compensative change for glutamatergic damage. Neuregulin 1 (NRG1)-ErbB4 signaling can promote GABA release and suppress epileptogenesis, but its effects on cognition in AD are still controversial. METHODS: Four-month-old APPswe/PS1dE9 mice (APP mice) were used as animal models in the early stage of AD in this study. Acute/chronic chemical-kindling epilepsy models were established with pentylenetetrazol. Electroencephalogram and Racine scores were performed to assess seizures. Behavioral tests were used to assess cognition and emotion. Electrophysiology, western blot and immunofluorescence were performed to detect the alterations in synapses, GABAergic system components and NRG1-ErbB4 signaling. Furthermore, NRG1 was administrated intracerebroventricularly into APP mice and then its antiepileptic and cognitive effects were evaluated. RESULTS: APP mice had increased susceptibility to epilepsy and resulting hippocampal synaptic damage and cognitive impairment. Electrophysiological analysis revealed decreased GABAergic transmission in the hippocampus. This abnormal GABAergic transmission involved a reduction in the number of parvalbumin interneurons (PV+ Ins) and decreased levels of GABA synthesis and transport. We also found impaired NRG1-ErbB4 signaling which mediated by PV+ Ins loss. And NRG1 administration could effectively reduce seizures and improve cognition in four-month-old APP mice. CONCLUSION: Our results indicated that abnormal GABAergic transmission mediated hippocampal hyperexcitability, further excitation/inhibition imbalance, and promoted epileptogenesis in the early stage of AD. Appropriate NRG1 administration could down-regulate seizure susceptibility and rescue cognitive function. Our study provided a potential direction for intervening in the co-morbidity of AD and epilepsy.

Imbalance of NRG1-ERBB2/3 signalling underlies altered myelination in Charcot-Marie-Tooth disease 4H.

Charcot-Marie-Tooth (CMT) disease is one of the most common inherited neurological disorders, affecting either axons from the motor and/or sensory neurons or Schwann cells of the peripheral nervous system (PNS) and caused by more than 100 genes. We previously identified mutations in FGD4 as responsible for CMT4H, an autosomal recessive demyelinating form of CMT disease. FGD4 encodes FRABIN, a GDP/GTP nucleotide exchange factor, particularly for the small GTPase Cdc42. Remarkably, nerves from patients with CMT4H display excessive redundant myelin figures called outfoldings that arise from focal hypermyelination, suggesting that FRABIN could play a role in the control of PNS myelination. To gain insights into the role of FGD4/FRABIN in Schwann cell myelination, we generated a knockout mouse model (Fgd4SC-/-), with conditional ablation of Fgd4 in Schwann cells. We show that the specific deletion of FRABIN in Schwann cells leads to aberrant myelination in vitro, in dorsal root ganglia neuron/Schwann cell co-cultures, as well as in vivo, in distal sciatic nerves from Fgd4SC-/- mice. We observed that those myelination defects are related to an upregulation of some interactors of the NRG1 type III/ERBB2/3 signalling pathway, which is known to ensure a proper level of myelination in the PNS. Based on a yeast two-hybrid screen, we identified SNX3 as a new partner of FRABIN, which is involved in the regulation of endocytic trafficking. Interestingly, we showed that the loss of FRABIN impairs endocytic trafficking, which may contribute to the defective NRG1 type III/ERBB2/3 signalling and myelination. Using RNA-Seq, in vitro, we identified new potential effectors of the deregulated pathways, such as ERBIN, RAB11FIP2 and MAF, thereby providing cues to understand how FRABIN contributes to proper ERBB2 trafficking or even myelin membrane addition through cholesterol synthesis. Finally, we showed that the re-establishment of proper levels of the NRG1 type III/ERBB2/3 pathway using niacin treatment reduces myelin outfoldings in nerves of CMT4H mice. Overall, our work reveals a new role of FRABIN in the regulation of NRG1 type III/ERBB2/3 NRG1signalling and myelination and opens future therapeutic strategies based on the modulation of the NRG1 type III/ERBB2/3 pathway to reduce CMT4H pathology and more generally other demyelinating types of CMT disease.

The phase I/II eNRGy trial: Zenocutuzumab in patients with cancers harboring NRG1 gene fusions.

Neuregulin 1 (NRG1) fusions are oncogenic drivers that have been detected in non-small-cell lung cancer (NSCLC), pancreatic ductal adenocarcinoma (PDAC) and other solid tumors. NRG1 fusions are rare, occurring in less than 1% of solid tumors. Patients with NRG1 fusion positive (NRG1+) cancer have limited therapeutic options. Zenocutuzumab is a novel, bispecific IgG1 antibody that targets both HER2 and HER3 proteins and inhibits NRG1 binding through a 'Dock & Block®' mechanism of action. Here, we describe the rationale and design of the phase II component of the eNRGy trial, part of the overall, open-label phase I/II, multicenter trial exploring the safety, tolerability, pharmacokinetics, pharmacodynamics, immunogenicity and antitumor activity of zenocutuzumab in patients with NRG1+ NSCLC, PDAC or other solid tumors.

eNRGy: a clinical trial of zenocutuzumab for cancer caused by NRG1 gene fusionsNRG1 gene fusions are rare mutations that cause cancer cells to grow. These fusions are found in many different types of cancer. Tumors with NRG1 gene fusions do not respond well to standard treatment options. Zenocutuzumab, or Zeno, is a treatment that is being tested to see if it can stop cancer that is growing because of NRG1 gene fusions. Here, we describe the reasoning for and design of an ongoing clinical trial (eNRGy) designed to study the efficacy (how well it works) and safety of Zeno in patients with cancer that has NRG1 gene fusions. The eNRGy trial is recruiting patients with cancer that has NRG1 gene fusions, including non-small-cell lung cancer, pancreatic cancer and others. Patients who join this trial will receive Zeno once every 2 weeks until their cancer grows. The main goal (primary end point) of this trial is to determine the percentage of patients whose tumors decrease in size by 30% or more. The eNRGy trial is currently enrolling patients. For more information, refer to ClinicalTrials.gov (Identifier: NCT02912949), visit https://nrg1.com/, or call 1-833-NRG-1234.

ErbB4 deficiency exacerbates olfactory dysfunction in an early-stage Alzheimer's disease mouse model.

Olfactory dysfunction is increasingly recognized as an early indicator of Alzheimer's disease (AD). Aberrations in GABAergic function and the excitatory/inhibitory (E/I) balance within the olfactory bulb (OB) have been implicated in olfactory impairment during the initial stages of AD. While the neuregulin 1 (NRG1)/ErbB4 signaling pathway is known to regulate GABAergic transmission in the brain and is associated with various neuropsychiatric disorders, its specific role in early AD-related olfactory impairment remains incompletely understood. This study demonstrated that olfactory dysfunction preceded cognitive decline in young adult APP/PS1 mice and was characterized by reduced levels of NRG1 and ErbB4 in the OB. Further investigation revealed that deletion of ErbB4 in parvalbumin interneurons reduced GABAergic transmission and increased hyperexcitability in mitral and tufted cells (M/Ts) in the OB, thereby accelerating olfactory dysfunction in young adult APP/PS1 mice. Additionally, ErbB4 deficiency was associated with increased accumulation of Aß and BACE1-mediated cleavage of APP, along with enhanced CDK5 signaling in the OB. NRG1 infusion into the OB was found to enhance GABAergic transmission in M/Ts and alleviate olfactory dysfunction in young adult APP/PS1 mice. These findings underscore the critical role of NRG1/ErbB4 signaling in regulating GABAergic transmission and E/I balance within the OB, contributing to olfactory impairment in young adult APP/PS1 mice, and provide novel insights for early intervention strategies in AD. This work has shown that ErbB4 deficiency increased the burden of Aß, impaired GABAergic transmission, and disrupted the E/I balance of mitral and tufted cells (M/Ts) in the OB, ultimately resulting in olfactory dysfunction in young adult APP/PS1 mice. NRG1 could enhance GABAergic transmission, rescue E/I imbalance in M/Ts, and alleviate olfactory dysfunction in young adult APP/PS1 mice. OB: olfactory bulb, E/I: excitation/inhibition, Pr: probability of release, PV: parvalbumin interneurons, Aß: ß-amyloid, GABA: gamma-aminobutyric acid.

Durable response to afatinib in advanced lung adenocarcinoma harboring a novel NPTN-NRG1 fusion: a case report.

BACKGROUND: NRG1 fusions are rare oncogenic drivers in solid tumors, and the incidence of NRG1 fusions in non-small cell lung cancer (NSCLC) was 0.26%. It is essential to explore potential therapeutic strategies and efficacy predictors for NRG1 fusion-positive cancers. CASE PRESENTATION: We report an advanced lung adenocarcinoma patient harboring a novel NPTN-NRG1 fusion identified by RNA-based next-generation sequencing (NGS), which was not detected by DNA-based NGS at initial diagnosis. Transcriptomics data of the tissue biopsy showed NRG1α isoform accounted for 30% of total NRG1 reads, and NRG1ß isoform was undetectable. The patient received afatinib as fourth-line treatment and received a progression-free survival (PFS) of 14 months. CONCLUSIONS: This report supports afatinib can provide potential benefit for NRG1 fusion patients, and RNA-based NGS is an accurate and cost-effective strategy for fusion detection and isoform identification.

Involvement of CXCL10 in Neuronal Damage under the Condition of Spinal Cord Injury and the Potential Therapeutic Effect of Nrg1.

OBJECTIVE: Few studies have reported the direct effect of C-X-C motif chemokine ligand 10 (CXCL10) and Neuregulin 1 (Nrg1) on neurons after spinal cord injury (SCI). This study reports the role of CXCL10 in the regulation of neuronal damage after SCI and the potential therapeutic effect of Nrg1. METHODS: The expression level of CXCL10 and Nrg1 in SCI mice was analyzed in the Gene Expression Omnibus DataSets, followed by immunohistochemical confirmation using a mouse SCI model. HT22 cells and NSC34 cells were treated with CXCL10 and Nrg1, individually or in combination, and then assayed for cell viability. The percentage of wound closure was determined through the cell scratch injury model using HT22 and NSC34 cells. Potential molecular mechanisms were also tested in response to either the individual administration of CXCL10 and Nrg1 or a mixture of both molecules. RESULTS: CXCL10 expression was significantly increased in both young and old mice subjected to SCI, while Nrg1 expression was significantly decreased. CXCL10 induced a decrease in cell viability, which was partially reversed by Nrg1. CXCL10 failed to inhibit scratch healing in HT22 and NSC34 cells, while Nrg1 promoted scratch healing. At the molecular level, CXCL10-activated cleaved caspase 9 and cleaved caspase 3 were both inhibited by Nrg1 through pERK1/2 signaling in HT22 and NSC34 cells. CONCLUSIONS: CXCL10 is upregulated in SCI. Despite the negative effect on cell viability, CXCL10 failed to inhibit the scratch healing of HT22 and NSC34 cells. Nrg1 may protect neurons by partially antagonizing the effect of CXCL10.

Jatrorrhizine ameliorates Schwann cell myelination via inhibiting HDAC3 ability to recruit Atxn2l for regulating the NRG1-ErbB2-PI3K-AKT pathway in diabetic peripheral neuropathy mice.

Diabetic peripheral neuropathy (DPN) is a chronic complication associated with nerve dysfunction and uncontrolled hyperglycemia. Unfortunately, due to its complicated etiology, there has been no successful therapy for DPN. Our research recently revealed that jatrorrhizine (JAT), one of the active constituents of Rhizoma Coptidis, remarkably ameliorated DPN. This work highlighted the potential mechanism through which JAT relieves DPN using db/db mice. The results indicated that JAT treatment significantly decreased the threshold for thermal and mechanical stimuli and increased nerve conduction velocity. Histopathological analysis revealed that JAT significantly increased the number of sciatic nerve fibers and axons, myelin thickness, and axonal diameters. Additionally, JAT markedly elevated the expression of myelination-associated proteins (MBP, MPZ, and Pmp22). The screening of histone deacetylases (HDAC) determined that histone deacetylase 3 (HDAC3) is an excellent target for JAT-induced myelination enhancement. Liquid chromatography-mass spectrometry-(MS)/MS and coimmunoprecipitation analyses further confirmed that HDAC3 antagonizes the NRG1-ErbB2-PI3K-AKT signaling axis by interacting with Atxn2l to augment SCs myelination. Thus, JAT ameliorates SCs myelination in DPN mice via inhibiting the recruitment of Atxn2l by HDAC3 to regulate the NRG1-ErbB2-PI3K-AKT pathway.

Analysis of CD74 Occurrence in Oncogenic Fusion Proteins.

CD74 is a type II cell surface receptor found to be highly expressed in several hematological and solid cancers, due to its ability to activate pathways associated with tumor cell survival and proliferation. Over the past 16 years, CD74 has emerged as a commonly detected fusion partner in multiple oncogenic fusion proteins. Studies have found CD74 fusion proteins in a range of cancers, including lung adenocarcinoma, inflammatory breast cancer, and pediatric acute lymphoblastic leukemia. To date, there are five known CD74 fusion proteins, CD74-ROS1, CD74-NTRK1, CD74-NRG1, CD74-NRG2α, and CD74-PDGFRB, with a total of 16 different variants, each with unique genetic signatures. Importantly, the occurrence of CD74 in the formation of fusion proteins has not been well explored despite the fact that ROS1 and NRG1 families utilize CD74 as the primary partner for the formation of oncogenic fusions. Fusion proteins known to be oncogenic drivers, including those of CD74, are typically detected and targeted after standard chemotherapeutic plans fail and the disease relapses. The analysis reported herein provides insights into the early intervention of CD74 fusions and highlights the need for improved routine assessment methods so that targeted therapies can be applied while they are most effective.

Neuregulin 1 (NRG1) fusion-positive high-grade spindle cell sarcoma: A distinct group of soft tissue tumors with metastatic potential.

Neuregulin 1 (NRG1) is an epidermal growth factor (EGF)-like ligand that activates receptor tyrosine kinases of the ErbB family of receptors. NRG1 gene fusions, which are rare (<1%) but recurrent events in solid tumors, are an emerging oncogenic driver that is potentially actionable using ErbB-targeted tyrosine kinase inhibitors. Largely characterized only in carcinomas, we describe three cases of NRG1-rearranged sarcomas. The patients were all female, aged 32-47 years old. Two cases were deep-seated tumors in the lower extremities (right thigh and calf); one case presented as a uterine mass. The tumors measured 9-11.5 cm in the greatest dimensions. Histologically, all three tumors were high-grade spindle cell sarcomas composed of monomorphic spindle cells arranged in interlacing fascicles. The tumor cells were set in the loose collagenous stroma with branching, curvilinear thin-walled vasculature in the background. Cytologically, the neoplastic cells displayed ovoid to fusiform nuclei with finely stippled chromatin, inconspicuous nucleoli, scant to moderate clear to eosinophilic cytoplasm, occasional cytoplasmic vacuoles, and elongated cytoplasmic processes. Mitotic activity was elevated (> 20/10 high power fields) and tumor necrosis was present. None of the tumors expressed lineage-specific immunophenotypical markers. Targeted RNA-sequencing uncovered gene fusions involving NRG1 and the 5' untranslated regions of PPHLN1, HMBOX1, or MTUS1. In all cases, the C-terminal EGF-like domain of NRG1 was preserved in the predicted chimeric protein product. All three patients developed metastatic disease within 2 years from initial presentation and were alive with disease at last follow-up (mean follow-up period = 19 months). In conclusion, we present the first case series of NRG1-rearranged sarcomas characterized by high-grade fascicular spindle cell morphology, non-specific immunoprofile, and aggressive clinical behavior. Further studies are needed to determine whether this distinct subgroup of spindle cell sarcomas are amenable to targeted therapies.

Partial loss-of-function variant in neuregulin 1 identified in family with heritable peripheral neuropathy.

Neuregulin 1 signals are essential for the development and function of Schwann cells, which form the myelin sheath on peripheral axons. Disruption of myelin in the peripheral nervous system can lead to peripheral neuropathy, which is characterized by reduced axonal conduction velocity and sensorimotor deficits. Charcot-Marie-Tooth disease is a group of heritable peripheral neuropathies that may be caused by variants in nearly 100 genes. Despite the evidence that Neuregulin 1 is essential for many aspects of Schwann cell development, previous studies have not reported variants in the neuregulin 1 gene (NRG1) in patients with peripheral neuropathy. We have identified a rare missense variant in NRG1 that is homozygous in a patient with sensory and motor deficits consistent with mixed axonal and de-myelinating peripheral neuropathy. Our in vivo functional studies in zebrafish indicate that the patient variant partially reduces NRG1 function. This study tentatively suggests that variants at the NRG1 locus may cause peripheral neuropathy and that NRG1 should be investigated in families with peripheral neuropathy of unknown cause.

mTOR kinase inhibition disrupts neuregulin 1-ERBB3 autocrine signaling and sensitizes NF2-deficient meningioma cellular models to IGF1R inhibition.

Meningiomas (MNs), arising from the arachnoid/meningeal layer, are nonresponsive to chemotherapies, with ∼50% showing loss of the Neurofibromatosis 2 (NF2) tumor suppressor gene. Previously, we established NF2 loss activates mechanistic target of rapamycin complex 1 (mTORC1) and mechanistic target of rapamycin complex 2 (mTORC2) signaling, leading to clinical trials for NF2 and MN. Recently our omics studies identified activated ephrin (EPH) receptor and Src family kinases upon NF2 loss. Here, we report increased expression of several ligands in NF2-null human arachnoidal cells (ACs) and the MN cell line Ben-Men-1, particularly neuregulin-1/heregulin (NRG1), and confirm increased NRG1 secretion and activation of V-ERB-B avian erythroblastic leukemia viral oncogene homolog 3 (ERBB3) receptor kinase. Conditioned-medium from NF2-null ACs or exogenous NRG1 stimulated ERBB3, EPHA2, and mTORC1/2 signaling, suggesting pathway crosstalk. NF2-null cells treated with an ERBB3-neutralizing antibody partially downregulated mTOR pathway activation but showed no effect on viability. mTORC1/2 inhibitor treatment decreased NRG1 expression and downregulated ERBB3 while re-activating pAkt T308, suggesting a mechanism independent of NRG1-ERBB3 but likely involving activation of another upstream receptor kinase. Transcriptomics after mTORC1/2 inhibition confirmed decreased ERBB3/ERBB4 while revealing increased expression of insulin-like growth factor receptor 1 (IGF1R). Drug treatment co-targeting mTORC1/2 and IGF1R/insulin receptor attenuated pAkt T308 and showed synergistic effects on viability. Our findings indicate potential autocrine signaling where NF2 loss leads to secretion/activation of NRG1-ERBB3 signaling. mTORC1/2 inhibition downregulates NRG1-ERBB3, while upregulating pAkt T308 through an adaptive response involving IGF1R/insulin receptor and co-targeting these pathways may prove effective for treatment of NF2-deficient MN.