In addition, the ZNFNRG1 fusion spliced from an undocumented exon so would not have been found using software that only considered known exons. A further 20 of the first breast cancer cases had breakpoints within NRG1 by DNA sequencing, 13 of which had multiple breakpoints, which would make fusion prediction difficult Supplementary Table 4.
No fusion transcripts were detected in the matching RNA sequencing, but depth of sequencing might have been limiting. The short-read RNA sequencing did not enable us to determine whether these fusions included the cytoplasmic tail exons. Expression of these exons was detected Supplementary Table 3 —clearly in two cases, FAM91A1-NRG1 and ARHGEFNRG1 but not conclusively in the other two cases where there were too few reads overall—but we could not tell whether these reads were from fusion transcripts or normal transcripts, from tumour or normal cells.
We also confirmed that similar fusions—coding sequence of another gene splicing into genomic exon 3 of NRG1— are found in breast cancers, supporting the use of this fusion as a model example. The structure of these fusions has implications for clinical identification of NRG1 fusions, for understanding the subcellular location and secretion of NRG1 fusion proteins, and explanations of their oncogenicity.
We needed both the DNA and RNA sequencing to detect the fusions in cancers: there were too few supporting reads in the RNA sequencing to call them from RNA alone, while prediction from the DNA rearrangements alone would only have been provisional, particularly in our 14 examples where there were multiple breaks in NRG1.
Although we found 4 examples in cases 0. The importance of correct interpretation is underlined by the probability that some NRG1 rearrangements—including presumably the out-of-frame fusions—are in activating events as discussed below.
In conclusion as noted before [ 6 , 8 , 9 , 10 ] , RNA analysis is probably necessary, and combining with DNA sequencing improves sensitivity and specificity, but, even with both, sensitive identification of fusions is challenging. TENM4 , teneurin4, has been identified as a probable driver target of structural variation, notably in the breast [ 37 ] and Fig. It is a transmembrane protein with a cytoplasmic N-terminus and a large extracellular domain, most of which is lost in the fusion Fig.
The original cDNA cloned by Schaefer et al. The isoforms we found Fig. Some had the full transmembrane and cytoplasmic C terminus designated 1a and 2a forms [ 1 ] while others, including the original cDNA of Schaefer et al. But the multiple splice forms in MDA-MB suggests that these other fusions will also come in multiple isoforms, including forms with the cytoplasmic tail. The oncogenic function of NRG1 fusions is paradoxical and remains to be fully explained. So why are NRG1 fusions oncogenic?
We suggest two alternative explanations: alteration of expression or alteration of subcellular localisation. Simplest would be altered regulation of NRG1 expression, by placing it downstream of an unrelated promoter, allowing one cell to express ligand and receptor. This would be consistent with the wide range of fusion partners. A more intriguing hypothesis is that the fusion proteins have a different subcellular distribution, and, specifically, that one route of nuclear signalling is lost.
NRG1 encodes many isoforms and proteolytically cleaved forms, secreted, membrane-bound, cytoplasmic, and nuclear [ 1 , 43 ]. The latter is intracellular because it lacks a transmembrane domain or signal sequence [ 2 , 43 ], and it has been shown to translocate to the nucleus and alter gene expression [ 44 , 45 ].
Translocation is mediated by sequences around the Ig-like domain [ 44 , 46 ] Breuleux et al. Similarly, as noted by others e. Other fusion partners have a signal sequence, e. However, this is not a universal feature of the fusions, e. Although NRG1 appears to be oncogenic in some tumours, it is in activated in carcinomas at least as often as it is activated. NRG1 is silenced by methylation in some breast and other carcinomas [ 31 , 47 , 48 ] and seems to be at least one target of distal 8p loss, which is one of the most frequent large-scale events in carcinomas [ 49 ].
Many of the rearrangements in NRG1 appear not to fuse the gene or create a fusion that lacks the EGF-like, receptor-binding domain, or are simply out of frame. Many of the rearrangements of NRG1 that we found in breast cancers did not or were unlikely to create an activating fusion Supplementary Table 4 , including the two fusions that were out of frame.
The lack of nuclear signalling by the Ig-like domain might be part of the control mechanism. Whether or not this is the explanation, because many NRG1 rearrangements seem to be inactivating, the correct identification of activating fusions may require care.
This sheds new light on the mechanism of action of NRG1 fusions. Secondly, we confirm that around 0. NRG1 rearrangements will therefore require careful analysis and interpretation for appropriate patient management. The breast cancer data are not publicly available because of patient confidentiality, but application for access may be made jointly to CC Carlos.
Caldas cam. Falls DL. Neuregulins: functions, forms, and signaling strategies. Exp Cell Res. The neuregulin family of genes and their multiple splice variants in breast cancer. J Mammary Gland Biol Neoplasia. The EGFR family: not so prototypical receptor tyrosine kinases. Cold Spring Harbor Perspect Biol. Article Google Scholar. CDNRG1 fusions in lung adenocarcinoma.
Cancer Discov. Transcriptome meta-analysis of lung cancer reveals recurrent aberrations in NRG1 and Hippo pathway genes. Nat Commun. Detection of NRG1 gene fusions in solid tumors. Clin Cancer Res. J Thorac Oncol. Gamma-heregulin: a novel heregulin isoform that is an autocrine growth factor for the human breast cancer cell line, MDA-MB Cancer Cell.
Neuregulinmediated autocrine signaling underlies sensitivity to HER2 kinase inhibitors in a subset of human cancers. A case of invasive mucinous pulmonary adenocarcinoma with a CDNRG1 fusion protein targeted with afatinib. Durable response to afatinib in lung adenocarcinoma harboring NRG1 gene fusions. Successful targeting of the NRG1 pathway indicates novel treatment strategy for metastatic cancer. Ann Oncol. Wilson FH, Politi K. ERBB signaling interrupted: targeting ligand-induced pathway activation.
NRG1 gene fusions are recurrent, clinically actionable gene rearrangements in KRAS wild-type pancreatic ductal adenocarcinoma. Gamma-heregulin: a fusion gene of DOC-4 and neuregulin-1 derived from a chromosome translocation. Weinstein EJ, Leder P. The extracellular region of heregulin is sufficient to promote mammary gland proliferation and tumorigenesis but not apoptosis. Cancer Res. Analysis of proviral integration in human mammary epithelial cell lines immortalized by retroviral infection with a temperature-sensitive SV40 T-antigen construct.
Int J Cancer. Molecular cytogenetic analysis of breast cancer cell lines. Br J Cancer. Kim D, Salzberg SL. TopHat-Fusion: an algorithm for discovery of novel fusion transcripts. Genome Biol. Mobile element insertions are frequent in oesophageal adenocarcinomas and can mislead paired-end sequencing analysis. BMC Genomics. The driver mutational landscape of ovarian squamous cell carcinomas arising in mature cystic teratoma. Vermeer et al. This physical arrangement creates a ligand-receptor pair poised for activation whenever epithelial integrity is disrupted.
Indeed, immediately following a mechanical injury, heregulin-alpha activates ERBB2 in cells at the edge of the wound, and this process hastens restoration of epithelial integrity. Likewise, when epithelial cells are not separated into apical and basolateral membranes polarized , or when tight junctions between adjacent cells are opened, heregulin-alpha activates its receptor.
This mechanism of ligand-receptor segregation on either side of epithelial tight junctions may be vital for rapid restoration of integrity following injury, and hence critical for survival. This model also suggests a mechanism for abnormal receptor activation in diseases with increased epithelial permeability. Michailov et al. Reduced Nrg1 expression caused hypomyelination and reduced nerve conduction velocity.
Neuronal overexpression of Nrg1 induced hypermyelination and demonstrated that Nrg1 type III is the responsible isoform. Bao et al. The findings identified a molecular basis for activity-dependent synaptic plasticity. Flames et al. They showed that the membrane-bound type III isoform acted as a substrate for cell adhesion, while the soluble and diffusible types I and II isoforms were chemoattractive and induced cell migration. Lemmens et al. Both effects were attenuated by a nitric oxide synthase NOS inhibitor.
Lopez-Bendito et al. This migration was essential to form a permissive corridor for thalamocortical axons TCAs to navigate through the telencephalon. Ky et al. In various adjusted models factoring for demographics, NRG1-beta covariates, and potential confounders, NRG1-beta was independently associated with an increased risk of death or cardiac transplantation p values ranging from 0.
These findings were all independent of brain natriuretic peptide BNP; Combining avian blood vessel-specific gene manipulation and mouse genetics, Saito et al. They found that the dorsal aorta acts as a morphogenetic signaling center that coordinates neural crest cell migration and cell lineage segregation.
Bone morphogenetic proteins BMPs produced by the dorsal aorta are critical for the production of the chemokine stromal cell-derived factor-1 SDF1; and neuregulin-1 in the paraaortic region, which act as chemoattractants for early migration. Later, BMP signaling is directly involved in the sympathomedullary segregation. Saito et al. Early social isolation results in adult behavioral and cognitive dysfunction that correlates with white matter alterations.
Makinodan et al. These alterations, which occur only during this critical period, are phenocopied by loss of oligodendrocyte ErbB3 receptors, and social isolation leads to reduced expression of the ErbB3 ligand neuregulin Hahn et al. The findings were consistent with the hypothesis that NMDA receptor hypofunction may play a role in schizophrenia.
Using human constructs and RNA interference against endogenous rat proteins, Li et al. Synaptic activity led to the activation and recruitment of ERBB4 into the synapse. Li et al. Woo et al. Studies using the endogenous rodent protein and an exogenous human construct indicated a role for NRG1 in regulation of GABAergic transmission. This effect was blocked by inhibition or mutation of rodent Erbb4, suggesting the involvement of ERBB4.
Fazzari et al. In contrast to the view that supports a role for these genes in the formation and function of excitatory synapses between pyramidal cells, Fazzari et al. In particular, ErbB4 is expressed by many parvalbumin -expressing chandelier and basket cells, where it localizes to axon terminals and postsynaptic densities receiving glutamatergic input.
Gain- and loss-of-function experiments, both in vitro and in vivo, demonstrated that ErbB4 cell-autonomously promotes the formation of axo-axonic inhibitory synapses over pyramidal cells, and that this function is probably mediated by Nrg1.
In addition, ErbB4 expression in GABA-containing interneurons regulates the formation of excitatory synapses onto the dendrites of these cells. By contrast, ErbB4 is dispensable for excitatory transmission between pyramidal neurons. Using whole cell recordings of mouse hippocampal slices, Pitcher et al. Similar results were observed in pyramidal cells in the prefrontal cortex.
Nrg1-beta also prevented long-term potentiation of synaptic transmission induced by theta-burst stimulation. The study identified Src as a downstream target of the Nrg1-beta-ErbB4 signaling pathway, and indicated that Src activity is an essential step in regulating synaptic plasticity.
Del Monte-Nieto et al. Notch1 signaling promotes extracellular matrix degradation during the formation of endocardial projections that are critical for individualization of trabecular units, whereas Nrg1 promotes myocardial ECM synthesis, which is necessary for trabecular rearrangement and growth. These systems interconnect through Nrg1 control of Vegfa , but act antagonistically to establish trabecular architecture.
By a genomewide scan of schizophrenia families in Iceland, Stefansson et al. Stefansson et al. They genotyped markers representing a core at-risk haplotype found in Icelanders at the 5-prime end of the NRG1 gene in unrelated Scottish patients and unrelated Scottish control subjects.
The frequency of the 7-marker haplotype among the Scottish patients was significantly greater than that among the control subjects The estimated risk ratio was 1. They genotyped 25 microsatellite markers and SNPs spanning the NRG1 gene, including markers of the 7-marker haplotype found in excess in Icelandic and Scottish schizophrenia subjects.
However, none of these haplotypes was significantly associated with schizophrenia after correcting for multiple testing.
To determine if the underlying cause of the association discrepancies between schizophrenia and polymorphisms in the NRG1 gene might be due to population-specific genetic variation, Gardner et al. Most of the SNPs analyzed displayed differing frequencies according to geographic areas.
These differences were especially relevant in 2 SNPs located in a large intron of the gene, which revealed genetic stratification related to broad continental areas. Furthermore, haplotype analysis revealed a clear clustering according to geographic areas. Gardner et al. Go et al. Type I Nrg1 was required for generation of neural crest-derived neurons in cranial ganglia and for trabeculation of the heart ventricle, whereas type III Nrg1 was required for early development of Schwann cells.
Mice homozygous for disruptions of all NRG1 isoforms, all Ig-NRG1 isoforms, and all cytoplasmic tail-containing isoforms die at embryonic day In particular, these mice die before significant expression of CRD-NRG1 isoforms, which predominate after midgestation. By histologic analyses, Wolpowitz et al. Newborn mutants had immature skeletal muscle. Schwann cells were generated in the mutants but failed to survive, consistent with the designation of NRG1 as a Schwann cell survival factor.
Schwann cells in turn appeared to provide trophic support only after the nerve had entered its target field and had begun synapse formation.
Rentschler et al. This inductive effect was restricted to a window of sensitivity between 8. They described the electrical activation pattern of the 9. Thus, endocardial-derived neuregulins may be the major endogenous ligands responsible for inducing murine embryonic cardiomyocytes to differentiate into cells of the conduction system. Mutant mice heterozygous for either NRG1 or its receptor, ERBB4, showed a behavioral phenotype that overlapped with mouse models of schizophrenia.
Hippenmeyer et al. Elimination of all Nrg1 isoforms from DRG and motor neurons impaired muscle spindle differentiation and resulted in failure of proprioceptive afferents to elaborate annulospiral terminals. Muscle spindle differentiation proceeded normally in mice that selectively lacked type III Nrg1. Duchenne muscular dystrophy DMD; is a fatal disorder caused by absence of dystrophin Utrophin UTRN; is a chromosome 6-encoded dystrophin-related protein that has functional motifs in common with dystrophin.
The ability of utrophin to compensate for dystrophin during development and when transgenically overexpressed provided an important impetus for identifying activators of utrophin expression. Therefore, this pathway offers a potential mechanism to modulate utrophin expression in muscle. Krag et al. Intraperitoneal injections of the small peptide encoding the epidermal growth factor-like region of heregulin ectodomain for 3 months in vivo resulted in upregulation of utrophin, a marked improvement in the mechanical properties of muscle as evidenced by resistance to eccentric contraction-mediated damage, and a reduction of muscle pathology.
The amelioration of dystrophic phenotype by heregulin-mediated utrophin upregulation offered a pharmacologic therapeutic modality that obviates many of the toxicity and delivery issues associated with viral vector-based gene therapy for DMD. Escher et al. Postsynaptic differentiation was, however, induced by agrin The effects of neuregulin signaling to muscle may be mediated indirectly through Schwann cells.
Wood et al. Gene name :. NRG1 ;. Family name :. Family Neuregulin. Suggestions for updates and submission of functional predictions are welcome! Please contact us. Show evidences Annotations in this section apply to all the isoforms if not specified otherwise. Ligand discrimination in signaling through an ErbB4 receptor homodimer. J Biol Chem , [Full text: C ] [PubMed: ]. Cell 69, [PubMed: ]. Nature , [Full text: Providing the environmental signal that initiates the directed movement of a motile cell or organism towards a lower concentration of that signal.
Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium. Brief Bioinform 12, [Full text: The activity of a soluble extracellular gene product that interacts with a receptor to effect a change in the activity of the receptor to control the survival, growth, differentiation and effector function of tissues and cells.
Receptor binding and biological activity of mammalian expressed sensory and motor neuron-derived factor SMDF. Growth Factors 16, [PubMed: ]. Cancer Res 61, [PubMed: ]. The function that stimulates a cell to grow or proliferate. Most growth factors have other actions besides the induction of cell growth or proliferation.
Glial growth factors are alternatively spliced erbB2 ligands expressed in the nervous system. Interacting selectively and non-covalently with an integrin. Increases the activity of a protein tyrosine kinase, an enzyme which phosphorylates a tyrosyl phenolic group on a protein. Interacting selectively and non-covalently with a receptor that possesses protein tyrosine kinase activity.
Identification of heregulin, a specific activator of perbB2. Science , [PubMed: ]. Interacting selectively and non-covalently with one or more specific sites on a receptor molecule, a macromolecule that undergoes combination with a hormone, neurotransmitter, drug or intracellular messenger to initiate a change in cell function. Coexpression of erbB2 and erbB3 proteins reconstitutes a high affinity receptor for heregulin. J Biol Chem , [PubMed: ].
A protein or a member of a complex that interacts specifically and non-covalently with a DNA-bound DNA-binding transcription factor to either activate or repress the transcription of specific genes.
Coregulators often act by altering chromatin structure and modifications. For example, one class of transcription coregulators modifies chromatin structure through covalent modification of histones. A second ATP-dependent class modifies the conformation of chromatin. A third class modulates interactions of DNA-binding transcription factor with other transcription coregulators. Heregulin regulates the ability of the ErbB3-binding protein Ebp1 to bind E2F promoter elements and repress E2F-mediated transcription.
M ] [PubMed: ]. Binds to and increases the activity of a transmembrane receptor protein tyrosine kinase. Neuregulins promote survival and growth of cardiac myocytes. Persistence of ErbB2 and ErbB4 expression in neonatal and adult ventricular myocytes. Isoforms Iso 10, Iso 6, Iso 7.
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