LRRC37B is a human modifier of voltage-gated sodium channels and axon excitability in cortical neurons.

The enhanced cognitive abilities characterizing the human species result from specialized features of neurons and circuits. Here, we report that the hominid-specific gene LRRC37B encodes a receptor expressed in human cortical pyramidal neurons (CPNs) and selectively localized to the axon initial segment (AIS), the subcellular compartment triggering action potentials. Ectopic expression of LRRC37B in mouse CPNs in vivo leads to reduced intrinsic excitability, a distinctive feature of some classes of human CPNs. Molecularly, LRRC37B binds to the secreted ligand FGF13A and to the voltage-gated sodium channel (Nav) ß-subunit SCN1B. LRRC37B concentrates inhibitory effects of FGF13A on Nav channel function, thereby reducing excitability, specifically at the AIS level. Electrophysiological recordings in adult human cortical slices reveal lower neuronal excitability in human CPNs expressing LRRC37B. LRRC37B thus acts as a species-specific modifier of human neuron excitability, linking human genome and cell evolution, with important implications for human brain function and diseases.

FGF13 enhances the function of TRPV1 by stabilizing microtubules and regulates acute and chronic itch.

Itching is an aversive somatosensation that triggers the desire to scratch. Transient receptor potential (TRP) channel proteins are key players in acute and chronic itch. However, whether the modulatory effect of fibroblast growth factor 13 (FGF13) on acute and chronic itch is associated with TRP channel proteins is unclear. Here, we demonstrated that conditional knockout of Fgf13 in dorsal root ganglion neurons induced significant impairment in scratching behaviors in response to acute histamine-dependent and chronic dry skin itch models. Furthermore, FGF13 selectively regulated the function of the TRPV1, but not the TRPA1 channel on Ca2+ imaging and electrophysiological recordings, as demonstrated by a significant reduction in neuronal excitability and current density induced by TRPV1 channel activation, whereas TRPA1 channel activation had no effect. Changes in channel currents were also verified in HEK cell lines. Subsequently, we observed that selective modulation of TRPV1 by FGF13 required its microtubule-stabilizing effect. Furthermore, in FGF13 knockout mice, only the overexpression of FGF13 with a tubulin-binding domain could rescue TRP channel function and the impaired itch behavior. Our findings reveal a novel mechanism by which FGF13 is involved in TRPV1-dependent itch transduction and provide valuable clues for alleviating pathological itch syndrome.

Missense variants in the N-terminal domain of the A isoform of FHF2/FGF13 cause an X-linked developmental and epileptic encephalopathy.

Fibroblast growth factor homologous factors (FHFs) are intracellular proteins which regulate voltage-gated sodium (Nav) channels in the brain and other tissues. FHF dysfunction has been linked to neurological disorders including epilepsy. Here, we describe two sibling pairs and three unrelated males who presented in infancy with intractable focal seizures and severe developmental delay. Whole-exome sequencing identified hemi- and heterozygous variants in the N-terminal domain of the A isoform of FHF2 (FHF2A). The X-linked FHF2 gene (also known as FGF13) has alternative first exons which produce multiple protein isoforms that differ in their N-terminal sequence. The variants were located at highly conserved residues in the FHF2A inactivation particle that competes with the intrinsic fast inactivation mechanism of Nav channels. Functional characterization of mutant FHF2A co-expressed with wild-type Nav1.6 (SCN8A) revealed that mutant FHF2A proteins lost the ability to induce rapid-onset, long-term blockade of the channel while retaining pro-excitatory properties. These gain-of-function effects are likely to increase neuronal excitability consistent with the epileptic potential of FHF2 variants. Our findings demonstrate that FHF2 variants are a cause of infantile-onset developmental and epileptic encephalopathy and underline the critical role of the FHF2A isoform in regulating Nav channel function.

FGF homologous factors are secreted from cells to induce FGFR-mediated anti-apoptotic response.

FGF homologous factors (FHFs) are the least described group of fibroblast growth factors (FGFs). The FHF subfamily consists of four proteins: FGF11, FGF12, FGF13, and FGF14. Until recently, FHFs were thought to be intracellular, non-signaling molecules, despite sharing structural and sequence similarities with other members of FGF family that can be secreted and activate cell signaling by interacting with surface receptors. Here, we show that despite lacking a canonical signal peptide for secretion, FHFs are exported to the extracellular space. Furthermore, we propose that their secretion mechanism is similar to the unconventional secretion of FGF2. The secreted FHFs are biologically active and trigger signaling in cells expressing FGF receptors (FGFRs). Using recombinant proteins, we demonstrated their direct binding to FGFR1, resulting in the activation of downstream signaling and the internalization of the FHF-FGFR1 complex. The effect of receptor activation by FHF proteins is an anti-apoptotic response of the cell.

Inducible Fgf13 ablation alleviates cardiac fibrosis via regulation of microtubule stability.

Fibroblast growth factor (FGF) isoform 13, a distinct type of FGF, boasts significant potential for therapeutic intervention in cardiovascular dysfunctions. However, its impact on regulating fibrosis remains unexplored. This study aims to elucidate the role and mechanism of FGF13 on cardiac fibrosis. Here, we show that following transverse aortic constriction (TAC) surgery, interstitial fibrosis and collagen content increase in mice, along with reduced ejection fraction and fractional shortening, augmented heart mass. However, following Fgf13 deletion, interstitial fibrosis is decreased, ejection fraction and fractional shortening are increased, and heart mass is decreased, compared with those in the TAC group. Mechanistically, incubation of cardiac fibroblasts with transforming growth factor ß (TGFß) increases the expressions of types I and III collagen proteins, as well as α-smooth muscle actin (α-SMA) proteins, and enhances fibroblast proliferation and migration. In the absence of Fgf13, the expressions of these proteins are decreased, and fibroblast proliferation and migration are suppressed, compared with those in the TGFß-stimulated group. Overexpression of FGF13, but not FGF13 mutants defective in microtubule binding and stabilization, rescues the decrease in collagen and α-SMA protein and weakens the proliferation and migration function of the Fgf13 knockdown group. Furthermore, Fgf13 knockdown decreases ROCK protein expression via microtubule disruption. Collectively, cardiac Fgf13 knockdown protects the heart from fibrosis in response to haemodynamic stress by modulating microtubule stabilization and ROCK signaling pathway.

A Heterozygous Variant of FGF13 Caused X-Linked Developmental and Epileptic Encephalopathy 90 in a Chinese Family.

Developmental and epileptic encephalopathy (DEE) refers to a group of severe epilepsy encephalopathy and development disorders, and its typical clinical features include seizures, drug resistance, and developmental delay or regression. To date, limited studies have reported DEEs driven by FGF13. Here, we reported a girl with developmental and epileptic encephalopathy 90 caused by variant of FGF13. Her electroencephalogram (EEG) showed discontinuous hypsarrhythmia, and a heterozygous nonsynonymous variant in FGF13 [NM_004114.4: c.5C>G, p.(Ala2Gly)] was identified from the proband. The variant was not reported in public databases such as gnomAD and Exome Aggregation Consortium (ExAC), and was predicted to be damaging to proteins and classified as likely pathogenic according to the ACMG guidelines. The seizure was finally controlled by a combination of ACTH + zonisamide (10 mg/kg.d) + levetiracetam (52 mg/kg.d) + clonazepam (0.7 mg/kg.d).

Identification of FGF13 as a Potential Biomarker and Target for Diagnosis of Impaired Glucose Tolerance.

Early identification of pre-diabetes provides an opportunity for intervention and treatment to delay its progression to type 2 diabetes mellitus (T2DM). We aimed to identify the biomarkers of impaired glucose tolerance (IGT) through bioinformatics analysis. The GSE76896 dataset, including non-diabetic (ND), IGT, and T2DM clinical samples, was deeply analyzed to identify 309 Co-DEGs for IGT and T2DM. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses indicated that inflammatory responses and the PI3K-AKT signaling pathway are important patho-physiological features of IGT and T2DM. Protein-protein interaction (PPI) network analysis and cytoHubba technolgy identified seven hub genes: namely, CCL2, CXCL1, CXCL8, EDN1, FGF13, MMP1, and NGF. The expression and ROC curves of these hub genes were validated using the GSE38642 dataset. Through an immunofluorescence assay, we found that the expression of FGF13 in islets of mice in the HFD and T2DM groups was significantly lower than in the control group. Similarly, the level of FGF13 in the sera of IGT and T2DM patients was lower than that in the healthy group. Together, these results suggest that FGF13 can be treated as a novel biomarker of IGT, which may provide new targets for the diagnosis and treatment of pre-diabetes and T2DM.

Fibroblast growth factor homologous factor 2 attenuates excitability of DRG neurons.

Fibroblast growth factor homologous factors (FHFs) are cytosolic members of the superfamily of the FGF proteins. Four members of this subfamily (FHF1-4) are differentially expressed in multiple tissues in an isoform-dependent manner. Mutations in FHF proteins have been associated with multiple neurological disorders. FHF proteins bind to the COOH terminus of voltage-gated sodium (Nav) channels and regulate current amplitude and gating properties of these channels. FHF2, which is expressed in dorsal root ganglia (DRG) neurons, has two main splicing isoforms: FHF2A and FHF2B, which differ in the length and sequence of their NH2 termini, have been shown to differentially regulate gating properties of Nav1.7, a channel that is a major driver of DRG neuron firing. FHF2 expression levels are downregulated after peripheral nerve axotomy, which suggests that they may regulate neuronal excitability via an action on Nav channels after injury. We have previously shown that knockdown of FHF2 leads to gain-of-function changes in Nav1.7 gating properties: enhanced repriming, increased current density, and hyperpolarized activation. From this we posited that knockdown of FHF2 might also lead to DRG hyperexcitability. Here we show that knockdown of either FHF2A alone or all isoforms of FHF2 results in increased DRG neuron excitability. In addition, we demonstrate that supplementation of FHF2A and FHF2B reduces DRG neuron excitability. Overexpression of FHF2A or FHF2B also reduced excitability of DRG neurons treated with a cocktail of inflammatory mediators, a model of inflammatory pain. Our data suggest that increased neuronal excitability after nerve injury might be triggered, in part, via a loss of FHF2-Nav1.7 interaction.NEW & NOTEWORTHY FHF2 is known to bind to and modulate the function of Nav1.7. FHF2 expression is also reduced after nerve injury. We demonstrate that knockdown of FHF2 expression increases DRG neuronal excitability. More importantly, overexpression of FHF2 reduces DRG excitability in basal conditions and in the presence of inflammatory mediators (a model of inflammatory pain). These results suggest that FHF2 could potentially be used as a tool to reduce DRG neuronal excitability and to treat pain.

MiR-421 regulates goat intramuscular preadipocytes differentiation via targeting FGF13.

As a member of the MicroRNA s (miRNAs) family, miR-421 has been widely studied in regulating the proliferation and apoptosis of cancer cells a. However, there are still no reports on miR-421 in regulating adipocyte differentiation and its related mechanisms. Accordingly, this study aimed to investigate the potential involvement of miR-421 in goat intramuscular preadipocytes (P_IMA). The expression level of miR-421 was measured via quantitative real-time PCR during goat P_IMA differentiation. And the effects of miR-421 on goat P_IMA differentiation were studied by liposome transfection, Oil red O staining and qRT-PCR. Furthermore, the miR-421 target was searched and the underlying mechanism was clarified by luciferase reporter assay and rescue experiment. Our results showed that inhibition of miR-421 could accumulation of lipid droplets by upregulation the expression level of AP2, LPL, C/EBPα and SREBP1. Further studies showed that fibroblast growth factor 13 (FGF13) was the direct target of miR-421. Knocking down of FGF13 expression could inhibit lipid droplet formation and down-regulated the expression of key adipogenic regulatory genes. In addition, the rescue experiment revealed that FGF13 is involved in miR-421-induced differentiation of goat P_IMA as a key factor. Overall, these findings indicate that miR-421 is a negative regulator in the progression of differentiation of goat P_IMA by inhibiting the expression of FGF13.

FGF13 promotes metastasis of triple-negative breast cancer.

Triple-negative breast cancer (TNBC) represents 10-20% of all human ductal adenocarcinomas and has a poor prognosis relative to other subtypes, due to the high propensity to develop distant metastases. Hence, new molecular targets for therapeutic intervention are needed for TNBC. We recently conducted a rigorous phenotypic and genomic characterization of four isogenic populations of MDA-MB-231 human triple-negative breast cancer cells that possess a range of intrinsic spontaneous metastatic capacities in vivo, ranging from nonmetastatic (MDA-MB-231_ATCC) to highly metastatic to lung, liver, spleen and spine (MDA-MB-231_HM). Gene expression profiling of primary tumours by RNA-Seq identified the fibroblast growth factor homologous factor, FGF13, as highly upregulated in aggressively metastatic MDA-MB-231_HM tumours. Clinically, higher FGF13 mRNA expression was associated with significantly worse relapse free survival in both luminal A and basal-like human breast cancers but was not associated with other clinical variables and was not upregulated in primary tumours relative to normal mammary gland. Stable FGF13 depletion restricted in vitro colony forming ability in MDA-MB-231_HM TNBC cells but not in oestrogen receptor (ER)-positive MCF-7 or MDA-MB-361 cells. However, despite augmenting MDA-MB-231_HM cell migration and invasion in vitro, FGF13 suppression almost completely blocked the spontaneous metastasis of MDA-MB-231_HM orthotopic xenografts to both lung and liver while having negligible impact on primary tumour growth. Together, these data indicate that FGF13 may represent a therapeutic target for blocking metastatic outgrowth of certain TNBCs. Further evaluation of the roles of individual FGF13 protein isoforms in progression of the different subtypes of breast cancer is warranted.

Inducible Fgf13 ablation enhances caveolae-mediated cardioprotection during cardiac pressure overload.

The fibroblast growth factor (FGF) homologous factor FGF13, a noncanonical FGF, has been best characterized as a voltage-gated Na+ channel auxiliary subunit. Other cellular functions have been suggested, but not explored. In inducible, cardiac-specific Fgf13 knockout mice, we found-even in the context of the expected reduction in Na+ channel current-an unanticipated protection from the maladaptive hypertrophic response to pressure overload. To uncover the underlying mechanisms, we searched for components of the FGF13 interactome in cardiomyocytes and discovered the complete set of the cavin family of caveolar coat proteins. Detailed biochemical investigations showed that FGF13 acts as a negative regulator of caveolae abundance in cardiomyocytes by controlling the relative distribution of cavin 1 between the sarcolemma and cytosol. In cardiac-specific Fgf13 knockout mice, cavin 1 redistribution to the sarcolemma stabilized the caveolar structural protein caveolin 3. The consequent increase in caveolae density afforded protection against pressure overload-induced cardiac dysfunction by two mechanisms: (i) enhancing cardioprotective signaling pathways enriched in caveolae, and (ii) increasing the caveolar membrane reserve available to buffer membrane tension. Thus, our results uncover unexpected roles for a FGF homologous factor and establish FGF13 as a regulator of caveolae-mediated mechanoprotection and adaptive hypertrophic signaling.

Regulatory module involving FGF13, miR-504, and p53 regulates ribosomal biogenesis and supports cancer cell survival.

The microRNA miR-504 targets TP53 mRNA encoding the p53 tumor suppressor. miR-504 resides within the fibroblast growth factor 13 (FGF13) gene, which is overexpressed in various cancers. We report that the FGF13 locus, comprising FGF13 and miR-504, is transcriptionally repressed by p53, defining an additional negative feedback loop in the p53 network. Furthermore, we show that FGF13 1A is a nucleolar protein that represses ribosomal RNA transcription and attenuates protein synthesis. Importantly, in cancer cells expressing high levels of FGF13, the depletion of FGF13 elicits increased proteostasis stress, associated with the accumulation of reactive oxygen species and apoptosis. Notably, stepwise neoplastic transformation is accompanied by a gradual increase in FGF13 expression and increased dependence on FGF13 for survival ("nononcogene addiction"). Moreover, FGF13 overexpression enables cells to cope more effectively with the stress elicited by oncogenic Ras protein. We propose that, in cells in which activated oncogenes drive excessive protein synthesis, FGF13 may favor survival by maintaining translation rates at a level compatible with the protein quality-control capacity of the cell. Thus, FGF13 may serve as an enabler, allowing cancer cells to evade proteostasis stress triggered by oncogene activation.

Polarized localization of voltage-gated Na+ channels is regulated by concerted FGF13 and FGF14 action.

Clustering of voltage-gated sodium channels (VGSCs) within the neuronal axon initial segment (AIS) is critical for efficient action potential initiation. Although initially inserted into both somatodendritic and axonal membranes, VGSCs are concentrated within the axon through mechanisms that include preferential axonal targeting and selective somatodendritic endocytosis. How the endocytic machinery specifically targets somatic VGSCs is unknown. Here, using knockdown strategies, we show that noncanonical FGF13 binds directly to VGSCs in hippocampal neurons to limit their somatodendritic surface expression, although exerting little effect on VGSCs within the AIS. In contrast, homologous FGF14, which is highly concentrated in the proximal axon, binds directly to VGSCs to promote their axonal localization. Single-point mutations in FGF13 or FGF14 abrogating VGSC interaction in vitro cannot support these specific functions in neurons. Thus, our data show how the concerted actions of FGF13 and FGF14 regulate the polarized localization of VGSCs that supports efficient action potential initiation.

C-terminal phosphorylation of NaV1.5 impairs FGF13-dependent regulation of channel inactivation.

Voltage-gated Na+ (NaV) channels are key regulators of myocardial excitability, and Ca2+/calmodulin-dependent protein kinase II (CaMKII)-dependent alterations in NaV1.5 channel inactivation are emerging as a critical determinant of arrhythmias in heart failure. However, the global native phosphorylation pattern of NaV1.5 subunits associated with these arrhythmogenic disorders and the associated channel regulatory defects remain unknown. Here, we undertook phosphoproteomic analyses to identify and quantify in situ the phosphorylation sites in the NaV1.5 proteins purified from adult WT and failing CaMKIIδc-overexpressing (CaMKIIδc-Tg) mouse ventricles. Of 19 native NaV1.5 phosphorylation sites identified, two C-terminal phosphoserines at positions 1938 and 1989 showed increased phosphorylation in the CaMKIIδc-Tg compared with the WT ventricles. We then tested the hypothesis that phosphorylation at these two sites impairs fibroblast growth factor 13 (FGF13)-dependent regulation of NaV1.5 channel inactivation. Whole-cell voltage-clamp analyses in HEK293 cells demonstrated that FGF13 increases NaV1.5 channel availability and decreases late Na+ current, two effects that were abrogated with NaV1.5 mutants mimicking phosphorylation at both sites. Additional co-immunoprecipitation experiments revealed that FGF13 potentiates the binding of calmodulin to NaV1.5 and that phosphomimetic mutations at both sites decrease the interaction of FGF13 and, consequently, of calmodulin with NaV1.5. Together, we have identified two novel native phosphorylation sites in the C terminus of NaV1.5 that impair FGF13-dependent regulation of channel inactivation and may contribute to CaMKIIδc-dependent arrhythmogenic disorders in failing hearts.

Conditional knockout of Fgf13 in murine hearts increases arrhythmia susceptibility and reveals novel ion channel modulatory roles.

The intracellular fibroblast growth factors (iFGF/FHFs) bind directly to cardiac voltage gated Na+ channels, and modulate their function. Mutations that affect iFGF/FHF-Na+ channel interaction are associated with arrhythmia syndromes. Although suspected to modulate other ionic currents, such as Ca2+ channels based on acute knockdown experiments in isolated cardiomyocytes, the in vivo consequences of iFGF/FHF gene ablation on cardiac electrical activity are still unknown. We generated inducible, cardiomyocyte-restricted Fgf13 knockout mice to determine the resultant effects of Fgf13 gene ablation. Patch clamp recordings from ventricular myocytes isolated from Fgf13 knockout mice showed a ~25% reduction in peak Na+ channel current density and a hyperpolarizing shift in steady-state inactivation. Electrocardiograms on Fgf13 knockout mice showed a prolonged QRS duration. The Na+ channel blocker flecainide further prolonged QRS duration and triggered ventricular tachyarrhythmias only in Fgf13 knockout mice, suggesting that arrhythmia vulnerability resulted, at least in part, from a loss of functioning Na+ channels. Consistent with these effects on Na+ channels, action potentials in Fgf13 knockout mice, compared to Cre control mice, exhibited slower upstrokes and reduced amplitude, but unexpectedly had longer durations. We investigated candidate sources of the prolonged action potential durations in myocytes from Fgf13 knockout mice and found a reduction of the transient outward K+ current (Ito). Fgf13 knockout did not alter whole-cell protein levels of Kv4.2 and Kv4.3, the Ito pore-forming subunits, but did decrease Kv4.2 and Kv4.3 at the sarcolemma. No changes were seen in the sustained outward K+ current or voltage-gated Ca2+ current, other candidate contributors to the increased action potential duration. These results implicate that FGF13 is a critical cardiac Na+ channel modulator and Fgf13 knockout mice have increased arrhythmia susceptibility in the setting of Na+ channel blockade. The unanticipated effect on Ito revealed new FGF13 properties and the unexpected lack of an effect on voltage-gated Ca2+ channels highlight potential compensatory changes in vivo not readily revealed with acute Fgf13 knockdown in cultured cardiomyocytes.

Disruption of Fgf13 causes synaptic excitatory-inhibitory imbalance and genetic epilepsy and febrile seizures plus.

We identified a family in which a translocation between chromosomes X and 14 was associated with cognitive impairment and a complex genetic disorder termed "Genetic Epilepsy and Febrile Seizures Plus" (GEFS(+)). We demonstrate that the breakpoint on the X chromosome disrupted a gene that encodes an auxiliary protein of voltage-gated Na(+) channels, fibroblast growth factor 13 (Fgf13). Female mice in which one Fgf13 allele was deleted exhibited hyperthermia-induced seizures and epilepsy. Anatomic studies revealed expression of Fgf13 mRNA in both excitatory and inhibitory neurons of hippocampus. Electrophysiological recordings revealed decreased inhibitory and increased excitatory synaptic inputs in hippocampal neurons of Fgf13 mutants. We speculate that reduced expression of Fgf13 impairs excitability of inhibitory interneurons, resulting in enhanced excitability within local circuits of hippocampus and the clinical phenotype of epilepsy. These findings reveal a novel cause of this syndrome and underscore the powerful role of FGF13 in control of neuronal excitability.

Increased expression of fibroblast growth factor 13 in prostate cancer is associated with shortened time to biochemical recurrence after radical prostatectomy.

Fibroblast growth factor homologous factors (FHFs) belong to the fibroblast growth factor (FGF) superfamily, which plays an important role in prostate cancer (PCa). Mining of public database suggests that FGF13 (FHF2) mRNA expression is altered in over 30% of PCa cases. This study examined the FGF13 expression pattern in human PCa specimens and evaluated its potential as a biomarker for patient outcome after radical prostatectomy (RP). Immunohistochemistry (IHC) showed that FGF13 was detectable in the majority of human PCa samples, and FGF13 IHC scores were higher in high-grade prostatic intraepithelial neoplasia, in primary PCa and in metastatic PCa than in benign prostatic tissue. There was a significant association between high cytoplasmic FGF13 staining and a risk of biochemical recurrence (BCR) after RP. This was also evident in the intermediate to high-risk patient groups. In contrast, positive nuclear FGF13 staining along with low cytoplasmic FGF13 group showed a decreased BCR risk. Multivariate regression analysis indicated that high cytoplasmic FGF13 staining was associated with BCR and that this could serve as an independent prognostic marker in PCa. Several PCa cell lines showed increased FGF13 expression at the mRNA and protein levels compared to the immortalized prostate epithelial cell line PNT1a. Analysis of co-labeled cells suggested a possible interaction of FGF13 with α-tubulin and the voltage-gated sodium channel proteins (Na(V)s/VGSCs). Our data indicate that, for PCa patients after RP, FGF13 serves as a potential novel prognostic marker that improves prediction of BCR-free survival, in particular if combined with other clinical parameters.

FGF13 suppresses acute myeloid leukemia by regulating bone marrow niches.

Fibroblast growth factor 13 (FGF13) is aberrantly expressed in multiple cancer types, suggesting its essential role in tumorigenesis. Hence, we aimed to explore its definite role in the development of acute myeloid leukemia (AML) and emphasize its associations with bone marrow niches. Results showed that FGF13 was lowly expressed in patients with AML and that its elevated expression was related to prolonged overall survival (OS). Univariate and multivariate Cox regression analyses identified FGF13 as an independent prognostic factor. A prognostic nomogram integrating FGF13 and clinicopathologic variables was constructed to predict 1-, 3-, and 5-year OS. Gene mutation and functional analyses indicated that FGF13 was not associated with AML driver mutations but was related to bone marrow niches. As for immunity, FGF13 was remarkably associated with T cell count, immune checkpoint genes, and cytokines. In addition, FGF13 overexpression substantially inhibited the growth and significantly induced the early apoptosis of AML cells. The xenograft study indicated that FGF13 overexpression prolonged the survival of recipient mice. Overall, FGF13 could serve as an independent prognostic factor for AML, and it was closely related to the bone marrow microenvironment.

Nuclear isoform of FGF13 regulates post-natal neurogenesis in the hippocampus through an epigenomic mechanism.

The hippocampus is one of two niches in the mammalian brain with persistent neurogenesis into adulthood. The neurogenic capacity of hippocampal neural stem cells (NSCs) declines with age, but the molecular mechanisms of this process remain unknown. In this study, we find that fibroblast growth factor 13 (FGF13) is essential for the post-natal neurogenesis in mouse hippocampus, and FGF13 deficiency impairs learning and memory. In particular, we find that FGF13A, the nuclear isoform of FGF13, is involved in the maintenance of NSCs and the suppression of neuronal differentiation during post-natal hippocampal development. Furthermore, we find that FGF13A interacts with ARID1B, a unit of Brahma-associated factor chromatin remodeling complex, and suppresses the expression of neuron differentiation-associated genes through chromatin modification. Our results suggest that FGF13A is an important regulator for maintaining the self-renewal and neurogenic capacity of NSCs in post-natal hippocampus, revealing an epigenomic regulatory function of FGFs in neurogenesis.

FGF13 interaction with SHCBP1 activates AKT-GSK3α/ß signaling and promotes the proliferation of A549 cells.

FGF13, a member of the FGF subfamily, has been found to be highly expressed in cancer cells such as prostate cancer, melanoma, glioma and multiple myeloma. However, the mechanism of FGF13 function during cancer cell proliferation remains to be unexplored, especially Non-small cell lung cancer (NSCLC). In this study, the cell proliferation effect of FGF13 on A549 cells was checked by CCK-8, clone formation, Ki67 immunofluorescence staining and Flow Cytometry assay. Localization of FGF13 within A549 cells was performed with confocal laser scanning microscope. The protein variations and interaction were measured by western blotting and co-immunoprecipitation analysis. It showed that FGF13 was mainly distributed in the cytoplasm and exhibited a high expression level in A549 cells. High expression of FGF13 activated AKT-GSK3 signaling pathway, and inhibited the activity of p21 and p27. Thus, FGF13 enhanced the process of transition from G1 to S phase and promoted A549 cells proliferation. Furthermore, the interaction between FGF13 and SHCBP1 was confirmed. Meanwhile, FGF13 and SHCBP1 had a cooperative effect to accelerate the cell cycle progression, especially the ability to promote cell proliferation is significantly enhanced via protein interaction. Hence, we conclude that FGF13 played a positive regulation role during A549 cells proliferation. FGF13 interacted with SHCBP1 to facilitate cell cycle progression, providing new insights into deep understanding of non-small cell lung cancer mechanisms of proliferation and regulation function of FGF13.