Alternative titles; symbols
HGNC Approved Gene Symbol: KLF4
Cytogenetic location: 9q31.2 Genomic coordinates (GRCh38): 9:107,484,852-107,489,769 (from NCBI)
Shields et al. (1996) cloned a mouse cDNA, which they named gut-enriched Kruppel-like factor (Gklf), that encodes a member of the Kruppel family of transcription factors. Immunofluorescence revealed that Gklf is localized to the nucleus and is found at highest levels in growth-arrested cells. Shields et al. (1996) found that mouse Gklf mRNA is most abundant in the colon and is also expressed in the testis, lung, and small intestine.
Garrett-Sinha et al. (1996) identified a novel zinc finger protein whose mRNA is expressed at high levels in the epidermal layer of the skin and in epithelial cells in the tongue, palate, esophagus, stomach, and colon of newborn mice. They named the protein EZF for 'epithelial zinc finger.'
By screening a human umbilical vein endothelial cell cDNA library with a cDNA encoding the C-terminal zinc finger region of EKLF (KLF1; 600599), Yet et al. (1998) isolated a cDNA encoding KLF4, which they called EZF. The predicted 470-amino acid KLF4 protein has a proline- and serine-rich N terminus and contains 3 C2H2 Kruppel-type zinc fingers at the C terminus. KLF4 also contains a potential nuclear localization signal. The human KLF4 protein shares 91% sequence identity with mouse Ezf. Northern blot analysis detected a 3.5-kb KLF4 transcript in RNA from both human umbilical vein endothelial cells and human aortic endothelial cells.
Yet et al. (1998) found that recombinant KLF4 bound specifically to a probe containing the CACCC site of the beta-globin gene (141900) in gel mobility shift assays.
Shields et al. (1996) found that transfection of mouse Gklf into COS-1 cells caused an inhibition of DNA synthesis.
Yet et al. (1998) found that, in contrast to other members of the EKLF family, which are transcriptional activators, KLF4 functioned as a transcriptional repressor in transient transfection studies. The authors identified both the repression domain and the activation domain within KLF4.
Wang et al. (2004) found that both Klf4 and Upar (PLAUR; 173391) were predominantly expressed in luminal surface epithelial cells of the colonic crypt in mice. Colon cells from Klf4-null mice showed a dramatic reduction in Upar protein compared with wildtype mice. Conversely, KLF4 expression in human colon cancer cells increased the amount of UPAR protein and mRNA. Mobility shift experiments and chromatin immunoprecipitation showed that KLF4 bound multiple regions of the UPAR promoter.
Induced pluripotent stem (iPS) cells can be generated from mouse fibroblasts by retrovirus-mediated introduction of 4 transcription factors, Oct3/4 (164177), Sox2 (184429), c-Myc (190080), and Klf4, and subsequent selection for Fbx15 (609093) expression (Takahashi and Yamanaka, 2006). These iPS cells, hereafter called Fbx15 iPS cells, are similar to embryonic stem (ES) cells in morphology, proliferation, and teratoma formation; however, they are different with regard to gene expression and DNA methylation patterns, and fail to produce adult chimeras. Okita et al. (2007) showed that selection for Nanog (607937) expression results in germline-competent iPS cells with increased ES cell-like gene expression and DNA methylation patterns compared with Fbx15 iPS cells. The 4 transgenes were strongly silenced in Nanog iPS cells. Okita et al. (2007) obtained adult chimeras from 7 Nanog iPS cell clones, with one clone being transmitted through the germline to the next generation. Approximately 20% of the offspring developed tumors attributable to reactivation of the c-Myc transgene. Okita et al. (2007) concluded that iPS cells competent for germline chimeras can be obtained from fibroblasts, but retroviral introduction of c-Myc should be avoided for clinical application.
Wernig et al. (2007) independently demonstrated that the transcription factors Oct4, Sox2, c-Myc, and Klf4 can induce epigenetic reprogramming of a somatic genome to an embryonic pluripotent state.
Using microarray analysis, Good and Tangye (2007) showed that naive splenic B cells expressed higher levels of transcription factors KLF4, KLF9 (602902), and PZLF (ZBTB16; 176797) compared with memory B cells. Activation of naive B cells through CD40 (109535) and B-cell receptor downregulated expression of these cellular quiescence-associated transcription factors. Overexpression of KLF4, KLF9, and PZLF in memory B cells delayed their entry into cell division and proliferation. Good and Tangye (2007) concluded that memory B cells undergo a rewiring process that results in a significantly reduced activation threshold compared with naive B cells, allowing them to enter division more quickly, to differentiate into Ig-secreting plasma cells, and to more rapidly produce antibodies.
Using Oct4, Sox2, Klf4, and Myc, Park et al. (2008) derived iPS cells from fetal, neonatal, and adult human primary cells, including dermal fibroblasts isolated from a skin biopsy of a healthy research subject. Human iPS cells resemble embryonic stem cells in morphology and gene expression and in the capacity to form teratomas in immune-deficient mice. Park et al. (2008) concluded that defined factors can reprogram human cells to pluripotency, and they established a method whereby patient-specific cells might be established in culture.
Kim et al. (2008) showed that adult mouse neural stem cells express higher endogenous levels of Sox2 and c-Myc than embryonic stem cells and that exogenous Oct4 together with either Klf4 or c-Myc is sufficient to generate induced pluripotent stem (iPS) cells from neural stem cells. These 2-factor iPS cells are similar to embryonic stem cells at the molecular level, contribute to development of the germ line, and form chimeras. Kim et al. (2008) proposed that, in inducing pluripotency, the number of reprogramming factors can be reduced when using somatic cells that endogenously express appropriate levels of complementing factors.
Stadtfeld et al. (2008) generated mouse iPS cells from fibroblasts and liver cells by using nonintegrating adenoviruses transiently expressing Oct4, Sox2, Klf4, and c-Myc. These adenoviral iPS cells showed DNA demethylation characteristic of reprogrammed cells, expressed endogenous pluripotency genes, formed teratomas, and contributed to multiple tissues, including the germ cell line, in chimeric mice. Stadtfeld et al. (2008) concluded that their results provided strong evidence that insertional mutagenesis is not required for in vitro reprogramming.
Okita et al. (2008) independently reported the generation of mouse iPS cells without viral vectors. Repeated transfection of 2 expression plasmids, one containing the cDNAs of Oct3/4 (164177), Sox2 (184429), and Klf4 and the other containing the c-Myc (190080) cDNA, into mouse embryonic fibroblasts resulted in iPS cells without evidence of plasmid integration, which produced teratomas when transplanted into mice and contributed to adult chimeras. Okita et al. (2008) concluded that the production of virus-free iPS cells, albeit from embryonic fibroblasts, addresses a critical safety concern for potential use of iPS cells in regenerative medicine.
Niwa et al. (2009) showed that 2 LIF (159540) signaling pathways are each connected to the core circuitry required to maintain pluripotency via different transcription factors. In mouse embryonic stem cells, Klf4 is mainly activated by the Jak-Stat3 pathway and preferentially activates Sox2, whereas Tbx3 (601621) is preferentially regulated by the phosphatidylinositol-3-OH kinase-Akt and mitogen-activated protein kinase pathways and predominantly stimulates Nanog (607937). In the absence of Lif, artificial expression of Klf4 or Tbx3 was sufficient to maintain pluripotency while maintaining the expression of Oct3/4. Notably, overexpression of Nanog supported Lif-independent self-renewal of mouse embryonic stem cells in the absence of Klf4 and Tbx3 activity. Therefore, Niwa et al. (2009) concluded that KLF4 and TBX3 are involved in mediating LIF signaling to the core circuitry but are not directly associated with the maintenance of pluripotency, because embryonic stem cells keep pluripotency without their expression in the particular context.
Moore et al. (2009) screened genes developmentally regulated in retinal ganglion cells (RGCs) and identified KLF4 as a transcriptional repressor of axon growth in RGCs and other central nervous system (CNS) neurons. RGCs lacking KLF4 showed increased axon growth both in vitro and after optic nerve injury in vivo. Related KLF family members suppressed or enhanced axon growth to differing extents, and several growth-suppressive KLFs were upregulated postnatally, whereas growth-enhancing KLFs were downregulated. Coexpression of KLF4 or KLF9 (602902) blocked the growth-promoting effects of KLF6 (602053) or KLF7 (604865) in vitro. Thus, Moore et al. (2009) concluded that coordinated activities of different KLFs regulate the regenerative capacity of CNS neurons.
Hanna et al. (2009) demonstrated that the reprogramming by Oct4, Sox2, Klf4, and Myc transcription factors is a continuous stochastic process where almost all mouse donor cells eventually give rise to iPS cells on continued growth and transcription factor expression. Additional inhibition of the p53 (191170)/p21 (116899) pathway or overexpression of Lin28 (611043) increased the cell division rate and resulted in an accelerated kinetics of iPS cell formation that was directly proportional to the increase in cell proliferation. In contrast, Nanog overexpression accelerated reprogramming in a predominantly cell division rate-independent manner. Quantitative analyses defined distinct cell division rate-dependent and -independent modes for accelerating the stochastic course of reprogramming, and suggested that the number of cell divisions is a key parameter driving epigenetic reprogramming to pluripotency.
Using bone marrow chimera Klf -/- mice and flow cytometric analysis, Lebson et al. (2010) found that Klf4 was required for development of Th17 cells and Il17 (603149) production. Chromatin immunoprecipitation analysis showed that Klf4 bound the Il17 promoter. Wildtype and Klf4 -/- T cells upregulated expression of Rorgt (602943) similarly during Th17 polarization, suggesting that the 2 transcription factors are regulated independently. Adoptive transfer of T cells from Klf4 -/- mice did not result in development of experimental autoimmune encephalomyelitis. Lebson et al. (2010) concluded that KLF4 has a role in Th17 cell differentiation.
Hoffmeyer et al. (2012) reported a molecular link between Wnt/beta-catenin (116806) signaling and the expression of the telomerase subunit Tert (187270). Beta-catenin-deficient mouse embryonic stem (ES) cells have short telomeres; conversely, ES cells expressing an activated form of beta-catenin (beta-catenin(deltaEx3/+)) have long telomeres. Hoffmeyer et al. (2012) showed that beta-catenin regulates Tert expression through the interaction with Klf4, a core component of the pluripotency transcriptional network. Beta-catenin binds to the Tert promoter in a mouse intestinal tumor model and in human carcinoma cells. Hoffmeyer et al. (2012) uncovered a theretofore unknown link between the stem cell and oncogenic potential whereby beta-catenin regulates Tert expression, and thereby telomere length, which could be critical in human regenerative therapy and cancer.
Rais et al. (2013) showed that depleting MBD3 (603573), a core member of the MBD3/NURD (nucleosome remodeling and deacetylation) repressor complex, together with OSKM (OCT4, SOX2, KLF4, and MYC) transduction and reprogramming in naive pluripotency-promoting conditions, result in deterministic and synchronized iPS cell reprogramming (nearly 100% efficiency within 7 days from mouse and human cells). Rais et al. (2013) stated that their findings uncovered a dichotomous molecular function for the reprogramming factors, serving to reactivate endogenous pluripotency networks while simultaneously directly recruiting the MBD3/NURD repressor complex that potently restrains the reactivation of OSKM downstream target genes. Subsequently, the latter interactions, which are largely depleted during early preimplantation development in vivo, lead to a stochastic and protracted reprogramming trajectory toward pluripotency in vitro. Rais et al. (2013) concluded that their deterministic reprogramming approach offered a novel platform for the dissection of molecular dynamics leading to establishing pluripotency at unprecedented flexibility and resolution.
By radiation hybrid mapping, Yet et al. (1998) mapped the KLF4 gene to chromosome 9q31.
Garrett-Sinha et al. (1996) mapped the mouse Ezf (Klf4) gene to chromosome 4, in close proximity to the thioredoxin gene (187700).
Located at the interface between body and environment, the epidermis must protect the body against toxic agents and dehydration, and protect itself against physical and mechanical stresses. Acquired just before birth and at the last stage of epidermal differentiation, the skin's proteinaceous/lipid barrier creates a surface seal essential for protecting animals against microbial infections and dehydration. Segre et al. (1999) showed that Kruppel-like factor-4, which is highly expressed in the differentiating layers of epidermis, is both vital to and selective for barrier acquisition. Klf4 -/- mice die shortly after birth due to loss of skin barrier function, as measured by penetration of external dyes and rapid loss of body fluids. The defect was not corrected by grafting of Klf4 -/- skin onto nude mice. Loss of the barrier occurred without morphologic or biochemical alterations to the well-known structural features of epidermis that are essential for mechanical integrity. Instead, late-stage differentiation structures were selectively perturbed, including the cornified envelope, a likely scaffold for lipid organization. Using suppressive hybridization, Segre et al. (1999) identified 3 transcripts encoding cornified envelope proteins with altered expression in the absence of Klf4. Sprr2a (182267) was one, this being the only epidermal gene whose promoter is known to possess a functional Klf4 binding site. These studies provide a new insight into transcriptional governance of barrier function, and pave the way for unraveling the molecular events that orchestrate this essential process.
Djalilian et al. (2006) found significant upregulation of connexin-26 (CX26; GJB2; 121011) in the skin of newborn Klf4 -/- mice. Ectopic expression of Cx26 demonstrated that downregulation of Cx26 was required for barrier acquisition during development.
Patel et al. (2006) showed that Klf4 and corticosteroid treatments coordinately accelerated barrier acquisition in mouse skin. Transcriptional profiling revealed that the genes regulated by corticosteroids and Klf4 during the critical window of epidermal development significantly overlapped, and Klf4 activated the proximal promoters of a significant subset of these genes.
Djalilian, A. R., McGaughey, D., Patel, S., Seo, E. Y., Yang, C., Cheng, J., Tomic, M., Sinha, S., Ishida-Yamamoto, A., Segre, J. A. Connexin 26 regulates epidermal barrier and wound remodeling and promotes psoriasiform response. J. Clin. Invest. 116: 1243-1253, 2006. [PubMed: 16628254] [Full Text: https://doi.org/10.1172/JCI27186]
Garrett-Sinha, L. A., Eberspaecher, H., Seldin, M. F., de Crombrugghe, B. A gene for a novel zinc-finger protein expressed in differentiated epithelial cells and transiently in certain mesenchymal cells. J. Biol. Chem. 271: 31384-31390, 1996. [PubMed: 8940147] [Full Text: https://doi.org/10.1074/jbc.271.49.31384]
Good, K. L., Tangye, S. G. Decreased expression of Kruppel-like factors in memory B cells induces the rapid response typical of secondary antibody responses. Proc. Nat. Acad. Sci. 104: 13420-13425, 2007. [PubMed: 17673551] [Full Text: https://doi.org/10.1073/pnas.0703872104]
Hanna, J., Saha, K., Pando, B., van Zon, J., Lengner, C. J., Creyghton, M. P., van Oudenaarden, A., Jaenisch, R. Direct cell reprogramming is a stochastic process amenable to acceleration. Nature 462: 595-601, 2009. [PubMed: 19898493] [Full Text: https://doi.org/10.1038/nature08592]
Hoffmeyer, K., Raggioli, A., Rudloff, S., Anton, R., Hierholzer, A., Del Valle, I., Hein, K., Vogt, R., Kemler, R. Wnt/beta-catenin signaling regulates telomerase in stem cells and cancer cells. Science 336: 1549-1554, 2012. [PubMed: 22723415] [Full Text: https://doi.org/10.1126/science.1218370]
Kim, J. B., Zaehres, H., Wu, G., Gentile, L., Ko, K., Sebastiano, V., Arauzo-Bravo, M. J., Ruau, D., Han, D. W., Zenke, M., Scholer, H. R. Pluripotent stem cells induced from adult neural stem cells by reprogramming with two factors. Nature 454: 646-650, 2008. [PubMed: 18594515] [Full Text: https://doi.org/10.1038/nature07061]
Lebson, L., Gocke, A., Rosenzweig, J., Alder, J., Civin, C., Calabresi, P. A., Whartenby, K. A. Cutting edge: the transcription factor Kruppel-like factor 4 regulates the differentiation of Th17 cells independently of ROR-gamma-t. J. Immun. 185: 7161-7164, 2010. [PubMed: 21076063] [Full Text: https://doi.org/10.4049/jimmunol.1002750]
Moore, D. L., Blackmore, M. G., Hu, Y., Kaestner, K. H., Bixby, J. L., Lemmon, V. P., Goldberg, J. L. KLF family members regulate intrinsic axon regeneration ability. Science 326: 298-301, 2009. [PubMed: 19815778] [Full Text: https://doi.org/10.1126/science.1175737]
Niwa, H., Ogawa, K., Shimosato, D., Adachi, K. A parallel circuit of LIF signalling pathways maintains pluripotency of mouse ES cells. Nature 460: 118-122, 2009. [PubMed: 19571885] [Full Text: https://doi.org/10.1038/nature08113]
Okita, K., Ichisaka, T., Yamanaka, S. Generation of germline-competent induced pluripotent stem cells. Nature 448: 313-317, 2007. [PubMed: 17554338] [Full Text: https://doi.org/10.1038/nature05934]
Okita, K., Nakagawa, M., Hyenjong, H., Ichisaka, T., Yamanaka, S. Generation of mouse induced pluripotent stem cells without viral vectors. Science 322: 949-953, 2008. [PubMed: 18845712] [Full Text: https://doi.org/10.1126/science.1164270]
Park, I.-H., Zhao, R., West, J. A., Yabuuchi, A., Huo, H., Ince, T. A., Lerou, P. H., Lensch, M. W., Daley, G. Q. Reprogramming of human somatic cells to pluripotency with defined factors. Nature 451: 141-146, 2008. [PubMed: 18157115] [Full Text: https://doi.org/10.1038/nature06534]
Patel, S., Xi, Z. F., Seo, E. Y., McGaughey, D., Segre, J. A. Klf4 and corticosteroids activate an overlapping set of transcriptional targets to accelerate in utero epidermal barrier acquisition. Proc. Nat. Acad. Sci. 103: 18668-18673, 2006. [PubMed: 17130451] [Full Text: https://doi.org/10.1073/pnas.0608658103]
Rais, Y., Zviran, A., Geula, S., Gafni, O., Chomsky, E., Viukov, S., Mansour, A. A., Caspi, I., Krupalnik, V., Zerbib, M., Maza, I., Mor, N., and 14 others. Deterministic direct reprogramming of somatic cells to pluripotency. Nature 502: 65-70, 2013. Note: Erratum: Nature 520: 710 only, 2015. [PubMed: 24048479] [Full Text: https://doi.org/10.1038/nature12587]
Segre, J. A., Bauer, C., Fuchs, E. Klf4 is a transcription factor required for establishing the barrier function of the skin. Nature Genet. 22: 356-360, 1999. [PubMed: 10431239] [Full Text: https://doi.org/10.1038/11926]
Shields, J. M., Christy, R. J., Yang, V. W. Identification and characterization of a gene encoding a gut-enriched Kruppel-like factor expressed during growth arrest. J. Biol. Chem. 271: 20009-20017, 1996. [PubMed: 8702718] [Full Text: https://doi.org/10.1074/jbc.271.33.20009]
Stadtfeld, M., Nagaya, M., Utikal, J., Weir, G., Hochedlinger, K. Induced pluripotent stem cells generated without viral integration. Science 322: 945-949, 2008. [PubMed: 18818365] [Full Text: https://doi.org/10.1126/science.1162494]
Takahashi, K., Yamanaka, S. Induction of pluripotent stem cells from mouse embryonic and adult fibroblast cultures by defined factors. Cell 126: 663-676, 2006. [PubMed: 16904174] [Full Text: https://doi.org/10.1016/j.cell.2006.07.024]
Wang, H., Yang, L., Jamaluddin, M. S., Boyd, D. D. The Kruppel-like KLF4 transcription factor, a novel regulator of urokinase receptor expression, drives synthesis of this binding site in colonic crypt luminal surface epithelial cells. J. Biol. Chem. 279: 22674-22683, 2004. [PubMed: 15031282] [Full Text: https://doi.org/10.1074/jbc.M401257200]
Wernig, M., Meissner, A., Foreman, R., Brambrink, T., Ku, M., Hochedlinger, K., Bernstein, B. E., Jaenisch, R. In vitro reprogramming of fibroblasts into a pluripotent ES-cell-like state. Nature 448: 318-324, 2007. [PubMed: 17554336] [Full Text: https://doi.org/10.1038/nature05944]
Yet, S.-F., McA'Nulty, M. M., Folta, S. C., Yen, H.-W., Yoshizumi, M., Hsieh, C.-M., Layne, M. D., Chin, M. T., Wang, H., Perrella, M. A., Jain, M. K., Lee, M.-E. Human EZF, a Kruppel-like zinc finger protein, is expressed in vascular endothelial cells and contains transcriptional activation and repression domains. J. Biol. Chem. 273: 1026-1031, 1998. [PubMed: 9422764] [Full Text: https://doi.org/10.1074/jbc.273.2.1026]