Lfng Expression Research Articles

RADT-06. IDENTIFICATION OF NEW RADIATION RESPONSE PREDICTOR GENES FOR GLIOBLASTOMACRUCIAL CONTRIBUTION OF THE LUNATIC FRINGE GENE (LFNG)

Abstract Glioblastoma (GBM) is adults’ most common aggressive primary intracranial tumor. The current standard of care involves maximal safe surgery followed by radiochemotherapy. OBJECTIVE our study was to identify genes that predict response to radiochemotherapy. MATERIALS AND METHODS We collected molecular and clinical data, including primary glioma mRNA expression, from two international online databases - TCGA and CCGA. A total of 76 cases were examined, with 41 patients in the TCGA cohort and 35 in the CCGA cohort. The patients were divided into two groups before assessing the data. Group 1 included patients who were alive at the time of the analysis, and Group 2 included patients who had passed away. Then, we performed a single-center Moroccan transcriptomic study involving 28 cases to assess the impact of the individualized gene in our environment. RESULTS The following genes, namely SRPX, S100A16, LFNG, CD5, CMBL, and TCTN2, are among the top genes co-overexpressed in TCGA and CGGA patients. We conducted a multivariate COX survival test, taking into account known prognostic clinical parameters, and found that the LFNG gene is the only marker of poor prognosis independent of other clinical markers in TCGA and CGGA patients treated with radiotherapy. Our results indicate that patients who overexpress LFNG have elevated IFNg levels and low granzyme B levels, while the levels of perforin and granzyme A remain unaffected by LFNG variation. Furthermore, our results demonstrate positive correlations between LFNG gene expression and four immune checkpoints (PD1, PDL1, CTLA4, and VISTA), but negative correlations only with TIM3. CONCLUSION Our findings suggest that LFNG could serve as a useful biomarker for identifying patients with poor prognosis and that LFNG expression may be associated with specific immune checkpoint expression patterns. These results have important implications for the development of new therapeutic approaches in the treatment of TCGA and CGGA patients.

Abstract A068: Lfng-expressing centroacinar cell is a prime cell-of-origin for p53-deficient pancreatic cancer

Abstract Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal malignancies with poor understanding of etiology. Studies using mouse models showed that both acinar and ductal cells of the pancreas can be transformed by combination of oncogenic Kras and p53 mutations to form PDAC. How the transforming capacities of pancreatic cells are constrained, or whether a unique subset of cells serve as a prime target for oncogenic transformation, remains obscure. We found that expression of a Notch modulator, Lunatic Fringe (Lfng), is confined to a limited number of cells with centroacinar location and morphology in the adult mouse pancreas. These cells are selectively targeted by KrasG12D coupled with p53 loss-of-function (but not gain-of-function) mutations, leading to rapid pancreatic tumor formation, whereas the elimination of Lfng completely blocks the initiation of these tumors. We showed that p53 constrains the progenitor-like property of Lfng-expressing cells and that Lfng is required for hyperproliferation of these cells when p53 is inactivated. We identified Notch3 as a functional Notch receptor for PDAC initiation and progression in this context. Lfng expression is undetectable in normal acinar and ductal cells but upregulated in acinar- as well as ductal-derived precursor lesions, and its deletion hinders both the initiation and progression of these lesions. Collectively, Lfng marks a centroacinar subpopulation that is restrained by p53 and is uniquely susceptible to oncogenic transformation with p53 loss. Furthermore, Lfng functions as an oncogene in all three exocrine lineages in the adult pancreas. Genetic alterations of LFNG, predominantly in the forms of mRNA upregulation and gene amplification, were detected in 9% of PDAC patients and were associated with shortened overall survival. Consistent with its expression in mouse pancreas, LFNG immunostaining was noted in a subset of centroacinar cells in normal adjacent pancreatic tissues from human patients, and its expression in the adenocarcinoma specimens was positively correlated to tumor grade. Thus, LFNG may play an important role in human PDAC, in parallel with the one shown in the murine models. This study offers new insights into the pancreatic cancer cell-of-origin, initiation, and progression, which may lead to the identification of a therapeutic target for the disease. Citation Format: Keli Xu, Wen-Cheng Chung, Shubing Zhang, Azeddine Atfi. Lfng-expressing centroacinar cell is a prime cell-of-origin for p53-deficient pancreatic cancer [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr A068.

Mediterranean diet protects against neuroinflammation and degeneration in female nonhuman primates

AbstractBackgroundMediterranean diets may reduce Alzheimer’s disease (AD) risk and preserve cognitive function relative to Western diets in part by protecting against neuroinflammation. In middle‐aged humans that subsequently develop AD, increased cortical thickness precedes atrophy. It is hypothesized that the initial increase in brain volumes may be due to early neuroinflammation that precedes neurodegeneration (Pegueroles et al. Alzheimers Dement 2017). Long term impacts of diet patterns on health are difficult to quantify in human beings. Thus, we addressed this hypothesis in cynomolgus macaques (Macaca fascicularis), a nonhuman primate that undergoes age‐related changes in brain structure and function, and responds to Western diets, like humans.Method38 middle‐aged (mean = 12 years of age) female macaques were fed a Western or Mediterranean diet for 2.5 years in a randomized nonhuman primate trial. Changes from baseline in volumes of total brain, gray, cortical gray, and white matter, cerebrospinal fluid and (CSF), were determined by structural MRI. We also generated thickness‐based AD temporoparietal meta‐ROIs based on the AD clinical literature as previously described (Frye et al., 2021 Alzheimers Dement. 2021;17:733). Transcriptional profiles in the temporal cortex were determined at the end of the study by RNAseq.ResultWestern diet led to increases in temporoparietal cortical thicknesses, total brain and gray matter volumes, and diminished cerebrospinal fluid and white matter volumes. Diet significantly altered expression of seven genes (FDR<0.05). The Mediterranean group had lower expression of CDK14, a proinflammatory regulator, and higher expression of BTN2A1, KATNB1, LFNG, MRC2, SLCA32, and TMEM268, many of which have anti‐inflammatory associations. Several differentially expressed genes were correlated with AD‐relevant brain volumes. CDK14 was positively correlated with total brain, total gray, and cortical gray matter volumes and temporoparietal cortical thickness (Figure, Mediterranean = yellow), and negatively correlated with total white matter and CSF volumes. LFNG, MRC2, and SLCA32 were negatively correlated with total brain, total gray, and cortical gray matter volume, as well as temporoparietal cortical thickness, and positively correlated with CSF volume (all p’s<0.05).ConclusionThese results suggest that the Mediterranean diet protects against, whereas the Western diet promotes, AD‐relevant neuroinflammation associated with early increases in gray matter volumes.

PATH-42. UNCOVERING AN ASSOCIATION BETWEEN OLIGODENDROGLIOMA AND THE HUMAN PAPILLOMAVIRUS (HPV) THROUGH MOLECULAR SUBPOPULATION ANALYSIS USING NETRAAI

Abstract Oligodendrogliomas (OGs) are a rare subset of primary brain tumors, accounting for approximately 5% of all brain tumors. While the etiology of OG has yet to be fully characterized, genomic heterogeneity is linked to clinical heterogeneity with variability in progression and survival. Currently, OGs are stratified into three molecular subtypes based on IDH mutation and 1p/19q co-deletion with additional molecular heterogeneity related to EGFR, PTEN, 10q deletion, and several other markers observed among 1p/19q co-deleted OGs. Using a public OG dataset, we assembled a set consisting of 156 primary OG tumors, 14 primary glioma samples, and 9 normal samples profiled using mRNA expression arrays. Using NetraAI, a novel machine learning platform, we identified three OG patient subpopulations based on survival and differentially expressed genes. Examining low- versus high-grade OG, we identified two subpopulations: (1) 26 low-grade and 21 high-grade OGs characterized by higher RPS6KV1 expression, and (2) 6 low-grade and 61 high-grade OGs characterized by higher LFNG expression. A third subpopulation emerged examining 1p/19p co-deletion, consisting of 60 no co-deletion and 3 co-deletion OGs characterized by higher HDAC1 expression. These driving genes have a common link to human papillomavirus (HPV) infection based on functional genomic analysis. HDAC1 is a histone deacetylase involved in gene expression regulation, LFNG is implicated in the Notch signaling pathway, and RPS6KB1 is a kinase regulating protein synthesis and cell growth. We hypothesize that concomitant HPV infection may negatively impact OG prognosis, warranting further investigation into the precise molecular interactions linking HPV infection to clinical outcomes. Furthermore, exploring the link between HPV infection and vaccination to OG outcomes on a population basis may provide valuable insights. The identification of these subpopulations, not previously described by other groups, demonstrates the utility of the NetraAI approach in uncovering subpopulations with potential implications in developing targeted therapies for OG.

Two NOTCH1 O-fucose sites have opposing functions in mouse retinal angiogenesis.

Previous in vitro studies demonstrated that Fringe glycosylation of the NOTCH1 extracellular domain at O-fucose residues in Epidermal Growth Factor-like Repeats (EGFs) 6 and 8 is a significant contributor to suppression of NOTCH1 activation by JAG1 or enhancement of NOTCH1 activation by DLL1, respectively. In this study, we sought to evaluate the significance of these glycosylation sites in a mammalian model by generating 2 C57BL/6J mouse lines carrying NOTCH1 point mutations, which eliminate O-fucosylation and Fringe activity at EGFs 6 (T232V) or 8 (T311V). We assessed changes to morphology during retinal angiogenesis, a process in which expression of Notch1, Jag1, Dll4, Lfng, Mfng, and Rfng genes coordinate cell-fate decisions to grow vessel networks. In the EGF6 O-fucose mutant (6f/6f) retinas, we observed reduced vessel density and branching, suggesting that this mutant is a Notch1 hypermorph. This finding agrees with prior cell-based studies showing that the 6f mutation increased JAG1 activation of NOTCH1 during co-expression with inhibitory Fringes. Although we predicted that the EGF8 O-fucose mutant (8f/8f) would not complete embryonic development due to the direct involvement of the O-fucose in engaging ligand, the 8f/8f mice were viable and fertile. In the 8f/8f retina, we measured increased vessel density consistent with established Notch1 hypomorphs. Overall, our data support the importance of NOTCH1 O-fucose residues for pathway function and confirms that single O-glycan sites are rich in signaling instructions for mammalian development.

Total glycosides from Eucommia ulmoides seed promoted osteogenic differentiation of adipose-derived mesenchymal stem cells and bone formation in ovariectomized rats through regulating Notch signaling pathway

BackgroundOsteoporosis (OP) is a well-known chronic degenerative disease, with impaired mesenchymal stem cells (MSCs) function and suppressed osteogenic differentiation. Total glycosides from Eucommia ulmoides seed (TGEUS) was a Chinese medicine and have rich pharmacological effects. This study was designed to explore the mechanism of TGEUS in promoting osteogenic differentiation and bone formation in ovariectomized (OVX) rats.MethodsAdipose‐derived mesenchymal stem cells (ADSCs) were isolated and treated with different concentration of TGEUS. Cell viability was assessed using cell counting kit-8 (CCK-8) assay. Osteogenic capacity was identified by ALP staining and ARS staining. Moreover, RNA sequencing between control and TGEUS treated ADSCs were further performed to reveal the mechanism of TGEUS in promoting osteogenic differentiation. The expression of Jag1, Lfng and Hey1 were measured using quantitative real-time polymerase chain reaction (qRTPCR). Osteogenic markers were further assessed by western blot. DAPT and NICD were further used to identify whether Notch signaling pathway involved into TGEUS promoting osteogenic differentiation of ADSCs. Ovariectomy-induced bone loss rats model was established and divided into three groups: sham, OVX and OVX + TGEUS groups. HE staining and immunohistochemical staining were further performed to identify whether TGEUS could promote bone formation.ResultsTGEUS treatment significantly enhanced the cell viability and ALP activity than control group, the optimal dose of TGEUS was 5 μM. We selected 5 μM TGEUS for further study. TGEUS significantly enhanced ALP activity and calcium deposition than that of control group. Activation of Notch signaling fully blocked TGEUS-induced osteogenic differentiation of ADSCs. Following TGEUS treatment, the trabecular bone of the rats was significantly increased, thickened, and more connected compared to the OVX group. With the treatment of TGEUS, the expression of Osterix (Osx), Osteocalcin (OCN) and RUNX Family Transcription Factor 2 (RUNX2) increased than OVX group.ConclusionTGEUS enhanced osteogenic differentiation of ADSCs and promoted bone formation in ovariectomy-induced bone loss rats. Our study broadened the understanding of TGEUS as a therapeutic target against osteoporosis.

NOTCH activation promotes glycosyltransferase expression in human myeloid leukemia cells.

NOTCH signaling diversely regulates the growth of acute myeloid leukemia (AML) cells. It is known that glycosylation of NOTCH receptors modulates NOTCH activation. However, little is known about glycosylation of NOTCH in AML cells. We examined the effects of ligand-induced NOTCH activation on the expression of NOTCHmodifying glycosyltransferases in two AML cell lines, THP-1 and TMD7. The cells were stimulated with recombinant NOTCH ligands JAGGED1 and DELTA1, and subjected to immunoblot analysis to evaluate the expression levels of glycosyltransferases. Ligand stimulation promoted the expression of POFUT1, LFNG, MFNG, RFNG, GXYLT1, GXYLT2, and XXYLT1 in THP-1 cells, and that of RFNG and GXYLT1 in TMD7 cells. We found that NOTCH activation promoted the expression of several glycosyltransferases in AML cells. This suggests that NOTCH activation modulates its sensitivity to NOTCH ligands by increased glycosylation of NOTCH receptors in AML cells. Further investigation is needed to elucidate its biological significance.

Supt20 is required for development of the axial skeleton

Somitogenesis and subsequent axial skeletal development is regulated by the interaction of pathways that determine the periodicity of somite formation, rostrocaudal somite polarity and segment identity. Here we use a hypomorphic mutant mouse line to demonstrate that Supt20 (Suppressor of Ty20) is required for development of the axial skeleton. Supt20 hypomorphs display fusions of the ribs and vertebrae at lower thoracic levels along with anterior homeotic transformation of L1 to T14. These defects are preceded by reduction of the rostral somite and posterior shifts in Hox gene expression. While cycling of Notch target genes in the posterior presomitic mesoderm (PSM) appeared normal, expression of Lfng was reduced. In the anterior PSM, Mesp2 expression levels and cycling were unaffected; yet, expression of downstream targets such as Lfng, Ripply2, Mesp1 and Dll3 in the prospective rostral somite was reduced accompanied by expansion of caudal somite markers such as EphrinB2 and Hes7. Supt20 interacts with the Gcn5-containing SAGA histone acetylation complex. Gcn5 hypomorphic mutant embryos show similar defects in axial skeletal development preceded by posterior shift of Hoxc8 and Hoxc9 gene expression. We demonstrate that Gcn5 and Supt20 hypomorphs show similar defects in rostral-caudal somite patterning potentially suggesting shared mechanisms.

Reconstitution of TGFBR2 in HCT116 colorectal cancer cells causes increased LFNG expression and enhanced N-acetyl-d-glucosamine incorporation into Notch1

Transforming growth factor-β (TGF-β) signaling plays a key role in regulating normal cell growth and differentiation, and mutations affecting members of this pathway contribute to cancer development and metastasis. In DNA mismatch repair (MMR)-deficient colorectal cancers that exhibit the microsatellite instability (MSI) phenotype, biallelic frameshift mutations in the transforming growth factor β receptor type 2 (TGFBR2) gene occur at high frequency that lead to altered signal transduction and downstream target gene expression. Although recent evidence suggests that altered TGF-β signaling can modulate protein glycosylation patterns in MSI-high colorectal tumor cells, affected genes have not been identified. Here, we investigated in a more systematic approach, expression changes of TGFBR2-regulated genes, involved in glycosylation using a TGFBR2-reconstituted colorectal cancer cell line (HCT116–TGFBR2) and Glyco-Gene Chip analysis. Based on this oligonucleotide array of about 1000 human glycosylation-related genes, several candidates including HES1, PDGFB, JUNB and LFNG were found to be upregulated in a TGFBR2-dependent manner and subsequently validated by real-time RT-PCR analyses. Focusing on the glycosyltransferase LFNG and its target signaling protein Notch1, dual labeling with [3H]-N-acetyl-d-glucosamine ([3H]-GlcNAc) and [35S]-l-methionine revealed a significant increase in N-acetyl-d-glucosamine incorporation into immunoprecipitated Notch1 receptor upon TGFBR2 expression whereas the protein level remained unaffected. These data suggest that TGFBR2 signaling can affect Notch1 glycosylation via regulation of glycosyltransferase LFNG expression and provide a first mechanistic example for altered glycosylation in MSI colorectal tumor cells.

Breast cancer regulated by Fringe.

Breast cancers are heterogeneous at clinical and molecular levels. In recent years gene expression profiling has been used to classify breast cancers into at least five molecular subtypes, including basal-like, claudin-low, luminal A/B, HER2-enriched and normal-like. Among them, basal-like and claudin-low subtypes account for the majority of triple negative breast cancer (TNBC), a group of diseases that are defined on the basis of being negative for estrogen receptor, progesterone receptor and human epidermal growth factor receptor 2 [1]. TNBC preferentially affects younger patients, is more prevalent in women with African ancestry, and is often more aggressive than other types of breast cancer. Basal-like breast cancer (BLBC) expresses markers of myoepithelium/basal cells and shares features with bipotent progenitor cells, and is thought to have originated from mammary bipotent/luminal progenitor cells. Claudin-low breast cancer (CLBC) shares more features with mammary stem cells and cells that have undergone epithelial-to-mesenchymal transition. Fringe proteins are β3N-acteylglucosaminyl-transferases that are known to modify EGF repeats in the extracellular domains of Notch receptor thereby modulating ligand-mediated Notch activation [2]. There are three Fringe genes in mammals, namely, Lunatic Fringe (Lfng), Manic Fringe (Mfng), and Radical Fringe (Rfng). In the mouse mammary gland, Lfng expression is restricted to the stem/progenitor cell-enriched cap cell layer of the terminal end bud [3]. Deletion of Lfng in mouse mammary epithelium (Lfngflox/flox;MMTV-Cre) resulted in ectopic proliferation, expansion of the basal compartment, and ultimately, development of mammary tumors, in which two-thirds resemble BLBC and one-third are similar to CLBC. In agreement with the mouse experiment, the vast majority of BLBC and a subset of CLBC in humans exhibit significantly decreased LFNG expression [3]. While Lfng deficiency is a hallmark of BLBC, we recently reported that Mfng is highly expressed in CLBC and functions as an oncogene in this context [4]. We showed that Mfng regulates Notch activation in human and mouse CLBC cell lines, as well as in mouse mammary gland. Knockdown of Mfng in CLBC cell lines reduced cell migration and tumorsphere formation associated with a decrease in the stem-like cell population, as well as diminished in vivo tumorigenicity. Deletion of Mfng in Lfngflox/flox;MMTV-Cre mice caused a tumor subtype shift away from CLBC. We identified the phosphoinositide kinase Pik3cg as a direct transcriptional target of Mfng-facilitated RBPJk-dependent Notch signaling in CLBC cells. PIK3CG is aberrantly expressed in many invasive human breast tumors and its expression level correlates with metastatic potential of breast cancer cell lines [5]. We showed that pharmacologic inhibition of PI3Kγ in CLBC cell lines blocked migration and tumorsphere formation, suggesting that Mfng-induced Pik3cg contributes to breast cancer aggressiveness by promoting cell migration and invasion, as well as maintaining cancer cell stemness. Identification of Pik3cg as a Notch target prompts a PI3Kγ-targeting strategy for the treatment of CLBC and perhaps other poor prognosis breast cancers. Interestingly, Met proto-oncogene was amplified in both basal-like and claudin-low subtypes of the Lfngflox/flox;MMTV-Cre mammary tumors [3], and Met synergized with p53 loss to induce mouse mammary tumors resembling CLBC [6]. Therefore combination targeting of both Met and PI3Kγ may prove beneficial for the treatment of this disease. Indeed, we observed synergistic effects of Met and PI3Kγ inhibitors on growth of multiple human CLBC cell lines (Chung and Xu, unpublished data). MFNG expression in human breast cancer is highly correlated with the expression of NOTCH4, but not other Notch receptors. In addition, Mfng silencing in CLBC cell lines consistently decreased Notch4 activation, while Mfng deletion in the mouse mammary gland resulted in decreased Notch4 activation [4]. Thus, Mfng appears to control primarily Notch4-mediated signaling in the mammary epithelium. Given that Notch4 is enriched in mammary stem cells, a putative cell-of-origin of CLBC, the Mfng-Notch4-Pik3cg signaling cascade may be a driving force for CLBC pathogenesis. Next question is what regulates Mfng in this context. To this end, we have found that overexpression of Myc upregulates Mfng in mouse mammary epithelium as well as in human breast cancer cell lines (Zhang and Xu, unpublished data). Intriguingly, Myc was found amplified in almost half of human CLBC cases [7]. A link between Myc and Mfng during CLBC development warrants further investigation. Different subtypes of breast cancer are thought to have different cellular origins. Notch pathway may utilize different Fringes to precisely control signaling in distinct cell types of mammary epithelial hierarchy. Altered Fringe expression/activities may cause dysregulation of Notch signaling in different cells-of-origin, and ultimately, leading to breast cancer of different subtypes. Lfng inhibits Notch activation in luminal progenitor cells to prevent BLBC, whereas Mfng may enhance Notch4 signaling in mammary stem cells to promote CLBC initiation and progression. Of note, loss of both Lfng and Mfng in the mammary epithelium dramatically decreased activation of multiple Notch receptors and induced adenosquamous carcinoma [4], suggesting a redundant role of two genes in certain mammary cell types.

Hoxb6 can interfere with somitogenesis in the posterior embryo through a mechanism independent of its rib-promoting activity.

Formation of the vertebrate axial skeleton requires coordinated Hox gene activity. Hox group 6 genes are involved in the formation of the thoracic area owing to their unique rib-promoting properties. Here we show that the linker region (LR) connecting the homeodomain and the hexapeptide is essential for Hoxb6 rib-promoting activity in mice. The LR-defective Hoxb6 protein was still able to bind a target enhancer together with Pax3, producing a dominant-negative effect, indicating that the LR brings additional regulatory factors to target DNA elements. We also found an unexpected association between Hoxb6 and segmentation in the paraxial mesoderm. In particular, Hoxb6 can disturb somitogenesis and anterior-posterior somite patterning by dysregulation of Lfng expression. Interestingly, this interaction occurred differently in thoracic versus more caudal embryonic areas, indicating functional differences in somitogenesis before and after the trunk-to-tail transition. Our results suggest the requirement of precisely regulated Hoxb6 expression for proper segmentation at tailbud stages.

Targeting Met and Notch in the Lfng-deficient, Met-amplified triple-negative breast cancer

Triple negative breast cancer (TNBC) accounts for 15–20% of breast carcinomas and represents one of the most aggressive forms of this disease. Basal and claudin-low are the two main molecular subtypes among TNBCs. We previously reported that deletion of Lfng in mouse mammary gland caused deregulated Notch activation and induced basal-like and claudin-low tumors with co-selection for Met amplification. In human breast cancers, the vast majority of basal tumors and a subset of claudin-low tumors show reduced Lfng expression. Elevated Met expression and activation is associated with basal as well as claudin-low subtypes. To examine roles of Met and Notch in TNBC cells, we established two cell lines that harbor Met amplification as well as Lfng deletion, and possess features of basal and claudin-low breast cancer subtypes. Pharmacological inhibition of Met not only suppressed cell growth, tumorsphere and colony formation, but also reversed epithelial-to-mesenchymal transition and inhibited cell migration in both cell lines. In contrast, inhibition of Notch signaling using a γ-secretase inhibitor (GSI) only suppressed colony formation. Interestingly, GSI had no effect as single agent, but exerted a synergistic effect with Met inhibitor, on cell growth in 2D culture. We found that inhibition of Met resulted in downregulation of Dll ligands and upregulation of Jagged ligands, leading to differential modulation of Notch signaling. Our results suggest that combination targeting of Met and Notch may prove beneficial for TNBC patients with Met overexpression and Notch hyperactivation.

Posterior skeletal development and the segmentation clock period are sensitive to Lfng dosage during somitogenesis

The segmental structure of the axial skeleton is formed during somitogenesis. During this process, paired somites bud from the presomitic mesoderm (PSM), in a process regulated by a genetic clock called the segmentation clock. The Notch pathway and the Notch modulator Lunatic fringe (Lfng) play multiple roles during segmentation. Lfng oscillates in the posterior PSM as part of the segmentation clock, but is stably expressed in the anterior PSM during presomite patterning. We previously found that mice lacking overt oscillatory Lfng expression in the posterior PSM (Lfng∆FCE) exhibit abnormal anterior development but relatively normal posterior development. This suggests distinct requirements for segmentation clock activity during the formation of the anterior skeleton (primary body formation), compared to the posterior skeleton and tail (secondary body formation). To build on these findings, we created an allelic series that progressively lowers Lfng levels in the PSM. Interestingly, we find that further reduction of Lfng expression levels in the PSM does not increase disruption of anterior development. However tail development is increasingly compromised as Lfng levels are reduced, suggesting that primary body formation is more sensitive to Lfng dosage than is secondary body formation. Further, we find that while low levels of oscillatory Lfng in the posterior PSM are sufficient to support relatively normal posterior development, the period of the segmentation clock is increased when the amplitude of Lfng oscillations is low. These data support the hypothesis that there are differential requirements for oscillatory Lfng during primary and secondary body formation and that posterior development is less sensitive to overall Lfng levels. Further, they suggest that modulation of the Notch signaling by Lfng affects the clock period during development.

Tumor-Suppressive Activity of Lunatic Fringe in Prostate through Differential Modulation of Notch Receptor Activation

Elevated Notch ligand and receptor expression has been associated with aggressive forms of prostate cancer, suggesting a role for Notch signaling in regulation of prostate tumor initiation and progression. Here, we report a critical role for Lunatic Fringe (Lfng), which encodes an O-fucosylpeptide 3-ß-N-acetylglucosaminyltransferase known to modify epidermal growth factor repeats of Notch receptor proteins, in regulation of prostate epithelial differentiation and proliferation, as well as in prostate tumor suppression. Deletion of Lfng in mice caused altered Notch activation in the prostate, associated with elevated accumulation of Notch1, Notch2, and Notch4 intracellular domains, decreased levels of the putative Notch3 intracellular fragment, as well as increased expression of Hes1, Hes5, and Hey2. Loss of Lfng resulted in expansion of the basal layer, increased proliferation of both luminal and basal cells, and ultimately, prostatic intraepithelial neoplasia. The Lfng-null prostate showed down-regulation of prostatic tumor suppressor gene NKX3.1 and increased androgen receptor expression. Interestingly, expression of LFNG and NKX3.1 were positively correlated in publically available human prostate cancer data sets. Knockdown of LFNG in DU-145 prostate cancer cells led to expansion of CD44+CD24− and CD49f+CD24− stem/progenitor-like cell population associated with enhanced prostatosphere-forming capacity. Taken together, these data revealed a tumor-suppressive role for Lfng in the prostate through differential regulation of Notch signaling.

Reprint of: Disrupting Jagged1–Notch signaling impairs spatial memory formation in adult mice

It is well-known that Notch signaling plays a critical role in brain development and growing evidence implicates this signaling pathway in adult synaptic plasticity and memory formation. The Notch1 receptor is activated by two subclasses of ligands, Delta-like (including Dll1 and Dll4) and Jagged (including Jag1 and Jag2). Ligand-induced Notch1 receptor signaling is modulated by a family of Fringe proteins, including Lunatic fringe (Lfng). Although Dll1, Jag1 and Lfng are critical regulators of Notch signaling, their relative contribution to memory formation in the adult brain is unknown. To investigate the roles of these important components of Notch signaling in memory formation, we examined spatial and fear memory formation in adult mice with reduced expression of Dll1, Jag1, Lfng and Dll1 plus Lfng. We also examined motor activity, anxiety-like behavior and sensorimotor gating using the acoustic startle response in these mice. Of the lines of mutant mice tested, we found that only mice with reduced Jag1 expression (mice heterozygous for a null mutation in Jag1, Jag1+/−) showed a selective impairment in spatial memory formation. Importantly, all other behavior including open field activity, conditioned fear memory (both context and discrete cue), acoustic startle response and prepulse inhibition, was normal in this line of mice. These results provide the first in vivo evidence that Jag1–Notch signaling is critical for memory formation in the adult brain.

Disrupting Jagged1–Notch signaling impairs spatial memory formation in adult mice

It is well-known that Notch signaling plays a critical role in brain development and growing evidence implicates this signaling pathway in adult synaptic plasticity and memory formation. The Notch1 receptor is activated by two subclasses of ligands, Delta-like (including Dll1 and Dll4) and Jagged (including Jag1 and Jag2). Ligand-induced Notch1 receptor signaling is modulated by a family of Fringe proteins, including Lunatic fringe (Lfng). Although Dll1, Jag1 and Lfng are critical regulators of Notch signaling, their relative contribution to memory formation in the adult brain is unknown. To investigate the roles of these important components of Notch signaling in memory formation, we examined spatial and fear memory formation in adult mice with reduced expression of Dll1, Jag1, Lfng and Dll1 plus Lfng. We also examined motor activity, anxiety-like behavior and sensorimotor gating using the acoustic startle response in these mice. Of the lines of mutant mice tested, we found that only mice with reduced Jag1 expression (mice heterozygous for a null mutation in Jag1, Jag1+/−) showed a selective impairment in spatial memory formation. Importantly, all other behavior including open field activity, conditioned fear memory (both context and discrete cue), acoustic startle response and prepulse inhibition, was normal in this line of mice. These results provide the first in vivo evidence that Jag1–Notch signaling is critical for memory formation in the adult brain.

Lunatic Fringe Deficiency Cooperates with the Met/Caveolin Gene Amplicon to Induce Basal-like Breast Cancer

Basal-like breast cancers (BLBC) express a luminal progenitor gene signature. Notch receptor signaling promotes luminal cell fate specification in the mammary gland, while suppressing stem cell self-renewal. Here we show that deletion of Lfng, a sugar transferase that prevents Notch activation by Jagged ligands, enhances stem/progenitor cell proliferation. Mammary-specific deletion of Lfng induces basal-like and claudin-low tumors with accumulation of Notch intracellular domain fragments, increased expression of proliferation-associated Notch targets, amplification of the Met/Caveolin locus, and elevated Met and Igf-1R signaling. Human BL breast tumors, commonly associated with JAGGED expression, elevated MET signaling, and CAVEOLIN accumulation, express low levels of LFNG. Thus, reduced LFNG expression facilitates JAG/NOTCH luminal progenitor signaling and cooperates with MET/CAVEOLIN basal-type signaling to promote BLBC.

Modifying transcript lengths of cycling mouse segmentation genes

Regular production of somites, precursors of the axial skeleton and attached muscles is controlled by a molecular oscillator, the segmentation clock, which drives cyclic transcription of target genes in the unsegmented presomitic mesoderm (PSM). The clock is based on a negative feedback loop which generates pulses of transcription that oscillate with the same periodicity as somite formation. Mutants in several oscillating genes including the Notch pathway gene Lunatic fringe (Lfng) and the Notch target Hes7, result in defective somitogenesis and disorganised axial skeletons. Both genes encode negative regulators of Notch signalling output, but it is not yet clear if they are just secondary clock targets or if they encode components of a primary, pacemaker oscillator.In this paper, we try to identify components in the primary oscillator by manipulating delays in the feedback circuitry. We characterise recombinant mice in which Lfng and Hes7 introns are lengthened in order to delay mRNA production. Lengthening the third Hes7 intron by 10 or 20kb disrupts accurate RNA splicing and inactivates the gene. Lfng expression and activity is normal in mice whose Lfng is lengthened by 10kb, but no effects on segmentation are evident. We discuss these results in terms of the relative contributions of transcriptional and post-transcriptional delays towards defining the pace of segmentation, and of alternative strategies for manipulating the period of the clock.

Somitogenesis in the anole lizard and alligator reveals evolutionary convergence and divergence in the amniote segmentation clock

The axial skeleton is a defining feature of vertebrates and is patterned during somitogenesis. Cyclically expressed members of the notch and other signaling pathways, described as the ‘segmentation clock’, regulate the formation of somite boundaries. Comparisons among vertebrate model systems have revealed fundamental shifts in the regulation of expression among critical genes in the notch pathway. However, insights into the evolution of these expression differences have been limited by the lack of information from non-avian reptiles. We analyzed the segmentation clock of the first Lepidosaurian reptile sequenced, the green anole lizard, Anolis carolinensis, for comparison with avian and mammalian models. Using genomic sequence, RNA-Seq transcriptomic data, and in situ hybridization analysis of somite-stage embryos, we carried out comparative analyses of key genes and found that the anole segmentation clock displays features common to both amniote and anamniote vertebrates. Shared features with anamniotes, represented by Xenopus laevis and Danio rerio, include an absence of lunatic fringe (lfng) expression within the presomitic mesoderm (PSM), a hes6a gradient in the PSM not observed in the chicken or mouse, and EGF repeat structure of the divergent notch ligand, dll3. The anole and mouse share cycling expression of dll1 ligand in the PSM. To gain insight from an Archosaurian reptile, we analysed LFNG and DLL1 expressions in the American alligator. LFNG expression was absent in the alligator PSM, like the anole but unlike the chicken. In contrast, DLL1 expression does not cycle in the PSM of the alligator, similar to the chicken but unlike the anole. Thus, our analysis yields novel insights into features of the segmentation clock that are evolutionarily basal to amniotes versus those that are specific to mammals, Lepidosaurian reptiles, or Archosaurian reptiles.

Lunatic Fringe prolongs Delta/Notch-induced self-renewal of committed αβ T-cell progenitors

AbstractLunatic Fringe (Lfng) enhances Notch1 activation by Delta-like 4 (DL4) to promote Notch1-dependent T-lineage commitment of thymus-seeding progenitors. Subsequently, Notch1 and T-cell receptor-β (TCRβ)–containing pre-TCR complexes signal CD4/CD8 double-negative 3 (DN3) committed T-cell progenitors to survive, proliferate, and differentiate into CD4/CD8 double-positive (DP) αβ T-cell precursors. Few DP thymocytes develop without Notch1 or pre-TCR signals, whereas ectopic Notch1 activation causes T-cell leukemia. However, mechanisms of a Notch-pre-TCR collaboration during this “β-selection” process are poorly understood. We genetically manipulated Lfng to attenuate or enhance Notch1 activation in DN3 thymocytes without inducing leukemogenesis. We show that Lfng temporally sustains DL-induced Notch1 signaling to prolong proliferative self-renewal of pre-DP thymocytes. Pre-TCR signaling greatly augmented Notch trophic functions to promote robust proliferation of pre-DP progenitors. In contrast, in the absence of DL/Notch signaling, pre-TCR-expressing progenitors rapidly atrophied and differentiated into DP thymocytes. Thus, Lfng prolongs Notch1 signaling to promote self-renewal more than differentiation during the early stages of β-selection. Our data provide novel insights into the Notch-pre-TCR collaboration, and suggest that decreasing Lfng expression during the DN3-DP transition minimizes the potent leukemogenic potential of Notch1 signaling.