InteractiveFly: GeneBrief

nord: Biological Overview | References

Hedgehog (Hh) and bone morphogenetic proteins (BMPs) pattern the developing Drosophila wing by functioning as short- and long-range morphogens, respectively. This study shows that a previously unknown Hh-dependent mechanism fine-tunes the activity of BMPs. Through genome-wide expression profiling of the Drosophila wing imaginal discs, this study identified nord as a novel target gene of the Hh signaling pathway. Nord is related to the vertebrate Neuron Derived Neurotrophic Factor (NDNF) involved in Congenital Hypogonadotropic Hypogonadism and several types of cancer. Loss- and gain-of-function analyses implicate Nord in the regulation of wing growth and proper crossvein patterning. At the molecular level, biochemical evidence ia presented that Nord is a secreted BMP-binding protein and localizes to the extracellular matrix. Nord binds to Decapentaplegic (Dpp) or the heterodimer Dpp-Glass bottom boat (Gbb) to modulate their release and activity. Furthermore, this study demonstrates that Nord is a dosage-depend BMP modulator, where low levels of Nord promote and high levels inhibit BMP signaling. Taken together, it is proposed that Hh-induced Nord expression fine tunes both the range and strength of BMP signaling in the developing Drosophila wing (Yang, 2022).

In Drosophila, the short-range morphogen Hh and the long-range morphogen BMP function together to organize wing patterning. It has been previously shown that the Hh signal shapes the activity gradient of BMP by both inducing the expression of Dpp and simultaneously downregulating the Dpp receptor Tkv, resulting in lower responsiveness to Dpp in cells at the A/P compartment border. This study showed that the activity of BMP is further fine-tuned by another previously unknown Hh-dependent mechanism. Using a genome-wide expression profiling of the Drosophila wing imaginal discs, this study identfied nord as a novel target gene of the Hh signaling pathway. Nord and its homolog NDNF belong to a family of secreted proteins that can exist in two distinct pools: diffusible Nord/NDNF proteins that can reach a longer distance and membrane/matrix-associated Nord/NDNF proteins spreading within a short distance from the source cells. During larval and early pupal wing development, Nord is expressed together or in close proximity with the BMP ligand Dpp along the A/P compartment boundary. Elimination of nord caused a reduction of overall wing size and resulted in ectopic posterior crossvein (PCV) formation. Both of these phenotypes are attributable to alterations of BMP signaling activity as monitored by the level of Mad phosphorylation, yet in opposite directions: loss of nord led to decreased pMad in larval wing discs, whereas ectopic pMad surrounded the primordial PCV in nord mutant pupal wings. Moreover, expressing exogenous Nord at different levels and during different developmental stages and contexts showed that Nord is a dosage-dependent modulator of BMP signaling both in wing growth and crossvein patterning. At the molecular level, it was further demonstrated that Nord is a BMP-binding protein that directly enhances or inhibits BMP signaling in cultured S2 cells (Yang, 2022).

Combining the genetic and biochemical evidence, it is proposes that Nord mediates BMP signaling activity through binding of the BMP ligands Dpp and Dpp-Gbb. Depending on the levels of Nord proteins and the source/types of BMP ligands, Nord-mediated binding of Dpp and Dpp-Gbb may promote or repress BMP signaling activity. Additionally, the existence of two spatially distinct pools of diffusible and membrane/matrix-associated Nord proteins may introduce further complications in Nord-mediated BMP signaling regulation. In the wild-type wing discs, expressed in a subset of Dpp-secreting cells along the A/P boundary, Nord binds and enhances the local BMP signaling activity by augmenting ligand concentration near the Nord/Dpp-secreting cells. Meanwhile, Nord also impedes the mobilization of Dpp, especially the long-range BMP signaling mediator Dpp-Gbb heterodimer. Loss of nord simultaneously led to reduced local BMP and increased long-range BMP activities, and therefore gave rise to the seemingly opposite phenotypes of reduced wing size and ectopic PCV. In contrast, low levels of ectopic Nord in the P compartment autonomously increased BMP signaling activity, whereas high levels of Nord, either in the P compartment or throughout the wing pouch, inhibited BMP signaling activity likely through interfering with the normal BMP reception. Taken together, it is proposed that Hh-induced Nord expression provides an exquisite regulation of the strength and range of BMP signaling in the developing Drosophila wing (Yang, 2022).

The activity of TGF-β type factors, including the BMP subfamily, is modulated by a large variety of binding proteins that can either enhance or inhibit their signaling in a context-dependent manner. These modulator proteins vary broadly in structure, location, and mechanism of action. Well-known extracellular and freely diffusible proteins include Noggin, Tsg, Follistatin, the CR (cysteine-rich) domain containing proteins such as Chordin/Sog, and the Can family named after two founding members, Dan and Cerberus. With the exception of Tsg and Tsg/Sog or Tsg/Chordin complexes that in some cases can promote BMP signaling, all of these factors behave as antagonists, where BMP binding prevents association of the ligand with the receptor complex (Yang, 2022).

The other broad category of BMP-binding proteins includes membrane-bound or matrix-associated proteins and, in contrast to the highly diffusible class of BMP-binding factors, these proteins often act as either agonists or antagonists depending on context. These proteins are also structurally diverse, but to date, none contain FN3 or DUF2369 domains that are characteristic of Nord and NDNF, its vertebrate counterpart. From a mechanistic point of view, perhaps the two most instructive Drosophila members of this class of modulators are the heparan sulfate proteoglycan (HSPG) Dally and the CR-containing protein Cv-2. HSPGs are well characterized as modulators of growth factor signaling. In the case of FGFs, HSPGs act as true co-receptors in which they form a tripartite complex with ligand and FGFR, the signaling receptor. However, they can also mediate signaling in other ways. Analysis of dally loss-of-function clones in imaginal discs demonstrates that it has both cell-autonomous and non-autonomous effects with respect to BMP signaling. In general, low levels tend to promote signaling while high doses attenuate signaling. Many models have been put forth to explain these opposing effects and often come down to balancing ligand sequestration and diffusion properties. For instance, in the absence of HSPGs, Dpp may more freely diffuse away from the disc epithelial cell surface. In this case, HSPG acts to enhance signaling by keeping Dpp tethered to the cell surface where it can engage its signaling receptors. On the other hand, a high level of HSPG may compete with signaling receptors for BMP binding and thereby reduce signal (Yang, 2022).

The situation with respect to signal modulation becomes even more complex for factors such as Nord that bind both HSPGs and BMPs. An instructive example to consider is Cv-2, a secreted factor that, like Nord, binds both to HSPGs and BMPs and is also induced by BMP signaling. Like Dally, Cv-2 also has dose-dependent effects on signaling in wing imaginal discs, where low levels enhance while high levels inhibit BMP signaling. By virtue of being bound to HSPGs, it may simply function as an additional tethering molecule that keeps BMPs localized near the cell surface. However, Cv-2 has the unique property that it is also able to bind Tkv, a Drosophila BMPR type I receptor. This has led to speculation that it could act as an exchange factor that aids in handing off a BMP ligand from the HSPG pool to the type I receptor. Mathematical modeling showed that this mechanism can produce a biphasic signal depending on affinities of the various BMP-binding proteins involved and their concentrations (Yang, 2022).

In the case of Nord, its mechanism of action is likely compatible with a variety of these and/or alternative models. While this study has shown that Nord is a BMP-binding protein and Akiyama (2021) have shown that it also binds HSPGs, it is not clear whether the BMP and HSPG-binding sites overlap or are distinct and where they are positioned relative to the FN3 and DUF2369 domains. This is an important issue to consider with respect to the two CRISPR mutants that were generated that truncate Nord within the DUF2369 domain. Interestingly, the nord^3D allele appears to retain some function since it does not generate ectopic crossveins as do the nord^MI06414 or nord^22A alleles, yet nord^3D still produces small wings in transheterozygous combination with a deficiency or nord^22A, consistent with having lost the BMP growth-promoting ability. The discrepancy in crossvein patterning between the different nord alleles may be explained by a difference in residual function of the various truncated Nord protein products. Because the nord^MI06414 allele yields a much shorter predicted Nord peptide compared to the two CRISPR alleles, it is likely to behave as a protein null with a stronger phenotype. The two nord CRISPR alleles, although similar in the sequence deleted from the C-terminus, differ in how many non-nord encoded amino acids occur between the frameshift and the stop codon. The nord^22A allele has additional 14 amino acids relative to nord^3D. Perhaps this extension of the truncated fragment destabilizes or interferes with residual function found in the nord^3D allele. Additional biochemical studies defining the BMP and HSPG-binding sites, the stability of truncated Nord fragments, and whether Nord can also associate with either the type I or II receptors will aid in formulating a more precise mechanistic model (Yang, 2022).

Nord shows some sequence similarity to the NDNF family of proteins. Based on a very recent study, like many other neurotrophic factors, NDNF arose in the ancestor of bilaterians or even later. In agreement, by analyzing the genome and EST sequences from various organisms, this study found that nearly all bilaterian animals have either single or multiple orthologous genes for Nord/Ndnf. Of note, no Ndnf homologs were identiied in the flatworm Planarian, but these factors are highly conserved across vertebrates. All vertebrate family members contain a signal peptide, two FN3-like repeats, and a domain of unknown function (DUF2369) that is now referred to as the NDNF domain. The NDNF domain partially overlaps with the first FN3 but shows some additional conservation that extends between the two FN3 domains. The FN3 module is quite diverse in sequence but is thought to exhibit a common fold that is used as an interaction surface or spacer. The function of the NDNF domain is not clear, but it may also provide a protein interaction surface (Yang, 2022).

Although the vertebrate NDNFs are highly conserved throughout the entire protein length, the Caenorhabditis elegans and Drosophila relatives are quite divergent in primary sequence and show little conservation beyond a few key residues that define the second FN3 and NDNF domains. Notably, the Drosophila protein is missing the first FN3 domain, and therefore it is not clear the extent to which Nord and the vertebrate NDNFs may exhibit functional conservation. Ironically, the original human NDNF clone was identified on the basis of domain structure conservation with Drosophila Nord, which was identified via enhancer trapping to be a gene expressed in mushroom bodies and whose loss leads to defects in olfactory learning and memory (Dubnau et al., 2003). Unfortunately, that particular LacZ enhancer trap line that disrupted the nord locus is no longer available. The use of these new alleles should prove helpful for either confirming or eliminating the involvement of Nord as a modulator of learning and memory and/or other neuronal functions in larva and adult Drosophila (Yang, 2022).

In the mouse, NDNF is highly expressed in many neurons of the brain and spinal cord. Studies using cultured mouse hippocampal neurons revealed that it promotes neuron migration and neurite outgrowth, hence its name. In later studies, NDNF was also found to be upregulated in mouse endothelial cells in response to hindlimb ischemia, where it promotes endothelial cell and cardiomyocyte survival through integrin-mediated activation of AKT/endothelial NOS signaling. Additionally, recent studies have shown that NDNF expression is significantly downregulated in human lung adenocarcinoma (LUAD) and renal cell carcinoma (RCC), indicating that NDNF may also provide a beneficial function as a tumor suppressor (Yang, 2022).

Taken together, these studies have suggested some possible functions for vertebrate NDNF. However, they have primarily relied on in vitro cell culture models, and only recently have in vivo loss-of-function studies been reported. Remarkably, NDNF mutants were discovered in the genomes of several probands with congenital hypogonadotropic hypogonadism (CHH), a rare genetic disorder that is characterized by absence of puberty, infertility, and anosmia (loss of smell). This phenotype is very similar to that produced by loss of the anos¹, which also encodes an FN3 superfamily member and is responsible for Kallmann syndrome, a condition that similarly presents with CHH and anosmia due to lack of proper GnRH and olfactory neuron migration. Although in vitro studies indicated that NDNF modulates FGFR1 signaling after FGF8 stimulation, the in vivo molecular mechanism responsible for the neuronal migration defects is not clear. The results of the current study on the function of Drosophila Nord raise the issue of whether any of the ascribed vertebrate NDNF functions could involve alterations in BMP signaling. In the case of angiogenesis and EMT, BMPs, as well as other TGF-β family members, participate at many levels. At present, however, no involvement of BMP or TGF-β signaling has been implicated in migration of the GnRH neurons, although BMP signaling does define neurogenic permissive areas in which the olfactory placode forms. A clear objective for the future is to determine if the vertebrate NDNF factors bind BMPs and/or HSPG proteins such as Dally-like glypicans to modulate BMP signaling activity. On the Drosophila side, additional non-BMP-modulating roles for Nord should also be examined (Yang, 2022).

The feedback regulator Nord controls Dpp/BMP signaling via extracellular interaction with Dally in the Drosophila wing

The Drosophila BMP 2/4 homologue Decapentaplegic (Dpp) acts as a morphogen to regulate diverse developmental processes, including wing morphogenesis. Transcriptional feedback regulation of this pathway ensures tightly controlled signaling outputs to generate the precise pattern of the adult wing. Nevertheless, few direct Dpp target genes have been explored and understanding of feedback regulation remains incomplete. This study employed transcriptional profiling following dpp conditional knockout to identify nord, a novel Dpp/BMP feedback regulator. nord mutants generated by CRISPR/Cas9 mutagenesis produce a smaller wing and display low penetrance venation defects. At the molecular level, nord encodes a secreted heparin-binding protein, and this study shows that its overexpression is sufficient to antagonize Dpp/BMP signaling. Mechanistically, it was demonstrated that Nord physically interacts with the Dpp/BMP co-receptor Dally and promotes its degradation. In sum, it is proposed that Nord fine-tunes Dpp/BMP signaling by regulating Dally availability on the cell surface, with implications for both developmental and disease models (Akiyama, 2022).

Transcriptomic analyses using dpp^FO revealed a novel Dpp/BMP target gene nord. Analysis of mRNA FISH and a Gal4-based transcriptional reporter revealed strong nord expression in the stripe of cells along with the A/P compartment and little or weak expression in the D/V boundary in the wing disc. A similar Nord expression pattern was observed using the Nord-GFP protein trap. Surprisingly, unlike other well-studied Dpp/BMP targets, nord expression was restricted in the anterior compartment. Dpp/BMP signaling activity was essential but not sufficient to induce nord expression, indicating that other factors are required for its activation. Indeed, a recent study reports that Hh signaling regulates nord expression in the developing wing (Yang, 2022). Thus, nord expression is positively regulated by both Dpp/BMP and Hh inputs, although the molecular basis for nord suppression at the D/V boundary remains elusive. Interestingly, these signaling pathways also control dally expression. dally expression is activated by Hh signaling in the central stripe region of the wing disc, while Dpp/BMP signaling downregulates dally expression outside the stripe domain. Thus, nord and dally are co-expressed in part of the central stripe region through transcriptional regulation. This expression pattern may allow Nord to efficiently modulate functions of HSPG Dally to fine-tune the Dpp/BMP signaling pathway in the extracellular space (Akiyama, 2022).

BMP positive feedback loop mechanisms provide an optimal extracellular environment that allows BMP ligands to precisely distribute through the wing vein lumen and direct posterior crossvein (PCV) cell fate. Accordingly, partial attenuation of the pathway often results in an ectopic PCV formation. This study found that while nord^Δ1728 homozygotes rarely exhibited ectopic vein formation in the PCV region under normal conditions, PCV phenotypes were enhanced by genetic and environmental stress. It is inferred that BMP feedback mechanisms are sensitive to stress, thus enhancing the nord PCV phenotype. Intriguingly, Nord protein was detected in hemocytes distributed within the wing veins even though it was only expressed in a row of distal anterior pupal wing cells. These observations indicate that either wing cells or other sources deposit Nord protein on hemocytes. Similarly, although crossveinless d (cv-d), which encodes a vitellogenin-like lipoprotein, is expressed in the fat body and other non-imaginal disc tissues, Cv-d proteins circulate to the pupal wing via hemocytes, bind BMPs and HSPGs, and regulate PCV development. It is thus inferred that Nord may travel far from its site of expression via hemocytes and play a critical role in establishing a BMP positive feedback loop to ensure proper PCV formation (Akiyama, 2022).

Lastly, while performing the genetic interaction experiments, we noticed that nord^Δ1728 ; dally^gem double mutant animals exhibited a male larval gonad developmental defect. Further, it was found that the nord transcriptional reporter, nord-Gal4, was strongly expressed in male-specific somatic gonadal precursor cells and the terminal epithelium of testis derived from the precursor cells. These results suggest that Nord is not only essential for wing development but also plays an essential role with the HSPG Dally during testis development. It is of great interest to examine how nord and dally are involved in testis development in the future (Akiyama, 2022).

Extracellular regulation of HSPGs, such as shedding of membrane-localized HSPGs from the cell surface and digestion and modification of HS chains, is tightly regulated during development and homeostasis, and its misregulation has been recognized as a hallmark of cancer. Matrix Metallopeptidase 9 cleaves a transmembrane HSPG syndecan-1 from the cell membrane, facilitating tumor growth, metastasis, and angiogenesis. In addition, the Drosophila endo-6-O-sulfatase Sulf1, which selectively removes 6-O-sulfate groups from the HS chains in the extracellular space, controls molecular interactions between HSPGs and signaling molecules including BMP and Wg, and regulates diverse biological processes such as wing development and intestinal stem cell activity. In the developing Drosophila wing, transcription of the secreted Dpp/BMP feedback regulator Pent is restricted to the lateral regions of the wing disc by Dpp/BMP-dependent repression in the central domain. Pent-mediated endocytosis and degradation of glypicans shape the Dpp and Wg morphogen gradients. This study identified the novel secreted factor Nord through transcriptional profiling of Dpp/BMP target genes. Nord inhibits Dpp/BMP signaling and interacts with the HSPG Dally. Subsequent analyses revealed that Nord promotes Dally internalization for degradation. It was further demonstrated that Nord neutralizes the ability of Dally to promote Dpp/BMP signaling. Based on these results, a model is proposed in which 1) Dpp/BMP signaling induces nord expression at the A/P compartment boundary, 2) Nord is secreted into the extracellular space and binds to the co-receptor Dally, and 3) Nord enhances Dally degradation via endocytosis, thus downregulating the Dpp/BMP signaling pathway. Although the precise molecular mechanisms underlying the phenotypic enhancements observed in nord^Δ1728; dally^gem double mutant animals need to be addressed in the future, the current model explains how nord mutations suppress the L5 vein defect observed in dally mutants. In this scenario, the lack of Nord function would help to stabilize Dally protein in a dally^gem hypomorphic mutant background, and this slight increase in Dally activity is in turn sufficient to rescue the L5 vein phenotype. Further, it is speculated that the same molecular mechanism can account for the downregulation of Wg signaling observed in wing discs overexpressing nord. In this case, nord overexpression destabilizes Dally on the cell surface, leading to reduced Wg signaling activity. Lastly, a recent study demonstrated that Nord also directly interacts with BMPs and acts as a biphasic Dpp/BMP regulator that promotes the pathway at low levels but inhibits it at high concentrations (Yang, 2022). In the future, deciphering how Nord controls BMP ligand and co-receptor availability in the extracellular space with other secreted factors will provide a more concrete picture of the molecular mechanisms regulating the Dpp/BMP morphogen gradient formation. It will be particularly exciting to investigate how Nord and Pent cooperate to modulate glypican activity to fine-tune Dpp/BMP signaling since they possess a similar protein function with distinct expression patterns in the developing wing disc (Akiyama, 2022).

nord encodes a Drosophila NDNF protein. Human NDNF acts as a tumor suppressor (Xia, 2019; Zhang, 2019). NDNF expression is decreased in lung adenocarcinoma, and downregulation of NDNF promotes tumor growth in a mouse xenograft model (Zhang, 2019). NDNF is also known as a causative gene for congenital hypogonadotropic hypogonadism (CHH), which is characterized by infertility and delayed/absence of puberty (Messina, 2020). CHH is rooted in the abnormal development of gonadotropin-releasing hormone (GnRH) neurons. Many CHH-linked genes are involved in the regulation of the Fibroblast growth factor (FGF) signaling pathway. Indeed, NDNF overexpression inhibits FGF signaling in cell culture, and ndnf mutant mice exhibit a GnRH neuronal migration defect. Further, NDNF improves cardiac function after ischemia and myocardial infarction by reducing cardiomyocyte apoptosis and promoting angiogenesis through activation of the AKT signaling pathway. Nevertheless, the molecular mechanisms by which NDNF modulates multiple signaling pathways remain unclear. Intriguingly, it has been shown that HSPGs play essential roles in these biological processes. For instance, mutations in heparan sulfate 6-O-sulfotransferase-1 and anosimin-1 are found in CHH patients. Anosmin-1 is an HSPG interacting protein and regulates GnRH neuronal migration by promoting FGF signaling. Taken together, it is speculated that vertebrate NDNF may modulate HSPG activity to fine-tune multiple downstream signaling pathways. In this regard, the present study not only reveals a new mode of extracellular morphogen regulation, but also opens up a new avenue for investigating the molecular basis for NDNF-associated disorders in humans (Akiyama, 2022).

NDNF inhibits the migration and invasion of human renal cancer cells through epithelial-mesenchymal transition

Neuron-derived neurotrophic factor (NDNF) is a glycosylated, disulfide-bonded secretory protein that contains a fibronectin type III domain. NDNF has been identified as a neurotrophic factor; however, its role in carcinogenesis has not yet been identified. To investigate the expression and role of NDNF in carcinogenesis, the expression of NDNF in human Renal cell carcinoma (RCC) cell lines and tissues was detected by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. Cell proliferation was investigated using CCK-8 and colony formation assays, and the cell invasion and immigration capacity was evaluated using the transwell assay. The results demonstrated that NDNF expression was downregulated in RCC cell lines and RCC tissues. Restoring NDNF expression significantly inhibited the proliferation, migration and invasion of RCC cells. The study also demonstrated that the inhibitory effect of NDNF on invasive ability was mediated by suppressing the epithelial-mesenchymal transition (EMT) in RCC cells. NDNF may therefore be considered an important regulator of EMT in RCC progression and may represent a novel promising target for antimetastatic therapy (Xia, 2019).

Secretome profiling identifies neuron-derived neurotrophic factor as a tumor-suppressive factor in lung cancer

Clinical and preclinical studies show tissue-specific differences in tumorigenesis. Tissue specificity is controlled by differential gene expression. This study prioritized genes that encode secreted proteins according to their preferential expression in normal lungs to identify candidates associated with lung cancer. Indeed, most of the lung-enriched genes identified in this analysis have known or suspected roles in lung cancer. This study focused on the gene encoding neuron-derived neurotrophic factor (NDNF), which had not yet been associated with lung cancer. It was determined that NDNF was preferentially expressed in the normal adult lung and that its expression was decreased in human lung adenocarcinoma and a mouse model of this cancer. Higher expression of NDNF was associated with better clinical outcome of patients with lung adenocarcinoma. Purified NDNF inhibited proliferation of lung cancer cells, whereas silencing NDNF promoted tumor cell growth in culture and in xenograft models. It was determined that NDNF is downregulated through DNA hypermethylation near CpG island shores in human lung adenocarcinoma. Furthermore, the lung cancer-related DNA hypermethylation sites corresponded to the methylation sites that occurred in tissues with low NDNF expression. Thus, by analyzing the tissue-specific secretome, a tumor-suppressive factor, NDNF, was identified that is associated with patient outcomes in lung adenocarcinoma (Zhang, 2019).

Neuron-Derived Neurotrophic Factor Is Mutated in Congenital Hypogonadotropic Hypogonadism

Congenital hypogonadotropic hypogonadism (CHH) is a rare genetic disorder characterized by infertility and the absence of puberty. Defects in GnRH neuron migration or altered GnRH secretion and/or action lead to a severe gonadotropin-releasing hormone (GnRH) deficiency. Given the close developmental association of GnRH neurons with the olfactory primary axons, CHH is often associated with anosmia or hyposmia, in which case it is defined as Kallmann syndrome (KS). The genetics of CHH are heterogeneous, and >40 genes are involved either alone or in combination. Several CHH-related genes controlling GnRH ontogeny encode proteins containing fibronectin-3 (FN3) domains, which are important for brain and neural development. Therefore, it was hypothesized that defects in other FN3-superfamily genes would underlie CHH. Next-generation sequencing was performed for 240 CHH unrelated probands and filtered for rare, protein-truncating variants (PTVs) in FN3-superfamily genes. Compared to gnomAD controls the CHH cohort was statistically enriched for PTVs in neuron-derived neurotrophic factor (NDNF). Three heterozygous PTVs, all absent from the gnomAD database) and an additional heterozygous missense mutation (p.Thr201Ser) were found in four KS probands. Notably, NDNF is expressed along the GnRH neuron migratory route in both mouse embryos and human fetuses and enhances GnRH neuron migration. Further, knock down of the zebrafish ortholog of NDNF resulted in altered GnRH migration. Finally, mice lacking Ndnf showed delayed GnRH neuron migration and altered olfactory axonal projections to the olfactory bulb; both results are consistent with a role of NDNF in GnRH neuron development. Altogether, the results highlight NDNF as a gene involved in the GnRH neuron migration implicated in KS (Messina, 2020).

Neuron-derived neurotrophic factor functions as a novel modulator that enhances endothelial cell function and revascularization processes

Strategies to stimulate revascularization are valuable for cardiovascular diseases. This study identified neuron-derived neurotrophic factor (NDNF)/epidermacan as a secreted molecule that is up-regulated in endothelial cells in ischemic limbs of mice. NDNF was secreted from cultured human endothelial cells, and its secretion was stimulated by hypoxia. NDNF promoted endothelial cell network formation and survival in vitro through activation of Akt/endothelial NOS (eNOS) signaling involving integrin alphavbeta3. Conversely, siRNA-mediated knockdown of NDNF in endothelial cells led to reduction of cellular responses and basal Akt signaling. Intramuscular overexpression of NDNF led to enhanced blood flow recovery and capillary density in ischemic limbs of mice, which was accompanied by enhanced phosphorylation of Akt and eNOS. The stimulatory actions of NDNF on perfusion recovery in ischemic muscles of mice were abolished by eNOS deficiency or NOS inhibition. Furthermore, siRNA-mediated reduction of NDNF in muscles of mice resulted in reduction of perfusion recovery and phosphorylation of Akt and eNOS in response to ischemia. These data indicate that NDNF acts as an endogenous modulator that promotes endothelial cell function and ischemia-induced revascularization through eNOS-dependent mechanisms. Thus, NDNF can represent a therapeutic target for the manipulation of ischemic vascular disorders (Ohashi, 2014).

Search PubMed for articles about Drosophila Nord

Akiyama, T., Seidel, C. W. and Gibson, M. C. (2022). The feedback regulator Nord controls Dpp/BMP signaling via extracellular interaction with Dally in the Drosophila wing. Dev Biol 488: 91-103. PubMed ID: 35609633

Messina, A., Pulli, K., Santini, S., Acierno, J., Kansakoski, J., Cassatella, D., Xu, C., Casoni, F., Malone, S. A., Ternier, G., Conte, D., Sidis, Y., Tommiska, J., Vaaralahti, K., Dwyer, A., Gothilf, Y., Merlo, G. R., Santoni, F., Niederlander, N. J., Giacobini, P., Raivio, T. and Pitteloud, N. (2020). Neuron-Derived Neurotrophic Factor Is Mutated in Congenital Hypogonadotropic Hypogonadism. Am J Hum Genet 106(1): 58-70. PubMed ID: 31883645

Ohashi, K., Enomoto, T., Joki, Y., Shibata, R., Ogura, Y., Kataoka, Y., Shimizu, Y., Kambara, T., Uemura, Y., Yuasa, D., Matsuo, K., Hayakawa, S., Hiramatsu-Ito, M., Murohara, T. and Ouchi, N. (2014). Neuron-derived neurotrophic factor functions as a novel modulator that enhances endothelial cell function and revascularization processes. J Biol Chem 289(20): 14132-14144. PubMed ID: 24706764

Xia, L., Li, S., Liu, Y., Huang, Y., Ni, B., Wan, L., Mei, H., Li, X., Cai, Z. and Li, Z. (2019). NDNF inhibits the migration and invasion of human renal cancer cells through epithelial-mesenchymal transition. Oncol Lett 17(3): 2969-2975.

Yang, S., Wu, X., Daoutidou, E. I., Zhang, Y., Shimell, M., Chuang, K. H., Peterson, A. J., O'Connor, M. B. and Zheng, X. (2022). The NDNF-like factor Nord is a Hedgehog-induced extracellular BMP modulator that regulates Drosophila wing patterning and growth. Elife 11. PubMed ID: 35037619

Zhang, Y., Wu, X., Kai, Y., Lee, C. H., Cheng, F., Li, Y., Zhuang, Y., Ghaemmaghami, J., Chuang, K. H., Liu, Z., Meng, Y., Keswani, M., Gough, N. R., Wu, X., Zhu, W., Tzatsos, A., Peng, W., Seto, E., Sotomayor, E. M. and Zheng, X. (2019). Secretome profiling identifies neuron-derived neurotrophic factor as a tumor-suppressive factor in lung cancer. JCI Insight 4(24). PubMed ID: 31852841

date revised: 22 December 2022

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