Postnatal expression of KLF12 in the inner medullary collecting ducts of kidney and its trans-activation of UT-A1 urea transporter promoter

KLF12 transcriptionally regulates PD-L1 expression in non-small cell lung cancer

Recent studies have pointed to the role of Krüpple-like factor 12 (KLF12) in cancer-associated processes, including cancer proliferation, apoptosis, and metastasis. However, the role of KLF12 in tumor immunity remains obscure. Here, we found that KLF12 expression was significantly higher in non-small cell lung cancer (NSCLC) cells with higher programmed death-ligand 1 (PD-L1) expression. Additionally, a positive correlation between KLF12 and PD-L1 was observed in clinical patient tumor tissues. By chromatin immunoprecipitation (ChIP) analysis, KLF12 was identified to bind to the CACCC motif of the PD-L1 promoter. Overexpression of KLF12 promoted PD-L1 transcription, whereas silencing of KLF12 inhibited PD-L1 transcription. Furthermore, signal transducer and activator of transcription 1 (STAT1)- and STAT3-triggered PD-L1 transcription was abolished in the absence of KLF12, and KLF12 knockdown weakened the binding of STAT1 and STAT3 to the PD-L1 promoter. Mechanistically, KLF12 physically interacted with P300, a histone acetyltransferase. In addition, KLF12 silencing reduced P300 binding to the PD-L1 promoter, which subsequently caused decreased acetylation of histone H3. PD-L1 transcription driven by KLF12 overexpression was eliminated by EP300 silencing. In immunocompetent mice, KLF12 knockout inhibited tumor growth and promoted infiltration of CD8+ T cells. However, this phenomenon was not observed in immunodeficient mice. Overall, this study reveals KLF12-mediated transcriptional regulation of PD-L1 in NSCLC; targeting KLF12 may be a potential therapeutic strategy for NSCLC.

Identification of genetic associations and functional SNPs of bovine KLF6 gene on milk production traits in Chinese holstein

BACKGROUND

Our previous research identified the Kruppel like factor 6 (KLF6) gene as a prospective candidate for milk production traits in dairy cattle. The expression of KLF6 in the livers of Holstein cows during the peak of lactation was significantly higher than that during the dry and early lactation periods. Notably, it plays an essential role in activating peroxisome proliferator-activated receptor α (PPARα) signaling pathways. The primary aim of this study was to further substantiate whether the KLF6 gene has significant genetic effects on milk traits in dairy cattle.

RESULTS

Through direct sequencing of PCR products with pooled DNA, we totally identified 12 single nucleotide polymorphisms (SNPs) within the KLF6 gene. The set of SNPs encompasses 7 located in 5' flanking region, 2 located in exon 2 and 3 located in 3' untranslated region (UTR). Of these, the g.44601035G > A is a missense mutation that resulting in the replacement of arginine (CGG) with glutamine (CAG), consequently leading to alterations in the secondary structure of the KLF6 protein, as predicted by SOPMA. The remaining 7 regulatory SNPs significantly impacted the transcriptional activity of KLF6 following mutation (P < 0.005), manifesting as changes in transcription factor binding sites. Additionally, 4 SNPs located in both the UTR and exons were predicted to influence the secondary structure of KLF6 mRNA using the RNAfold web server. Furthermore, we performed the genotype-phenotype association analysis using SAS 9.2 which found all the 12 SNPs were significantly correlated to milk yield, fat yield, fat percentage, protein yield and protein percentage within both the first and second lactations (P < 0.0001 ~ 0.0441). Also, with Haploview 4.2 software, we found the 12 SNPs linked closely and formed a haplotype block, which was strongly associated with five milk traits (P < 0.0001 ~ 0.0203).

CONCLUSIONS

In summary, our study represented the KLF6 gene has significant impacts on milk yield and composition traits in dairy cattle. Among the identified SNPs, 7 were implicated in modulating milk traits by impacting transcriptional activity, 4 by altering mRNA secondary structure, and 1 by affecting the protein secondary structure of KLF6. These findings provided valuable molecular insights for genomic selection program of dairy cattle.

Circular noncoding RNA circ_0007334 sequestrates miR-577 to derepress KLF12 and accelerate colorectal cancer progression

Colorectal cancer (CRC) is a prevalent malignant tumor with a poor prognosis. Circular RNA (circRNA) circ_0007334 is related to cell proliferation in CRC. This study is designed to explore the role and mechanism of circ_0007334 in CRC progression. Circ_0007334, microRNA-577 (miR-577) and kruppel-like factor 12 (KLF12) levels were measured by real-time quantitative PCR (RT-qPCR). Exosomes were detected by a transmission electron microscope and nanoparticle tracking analysis (NTA). CD63, TSG101, matrix metallopeptidase-2 (MMP-2), MMP-9, VEGFA and KLF12 protein levels were examined by western blot assay. The binding relationship between miR-577 and circ_0007334 or KLF12 was predicted by circRNA interactome or Starbase and verified by a dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Cell viability, colony number, migration, invasion and angiogenesis were detected by cell counting kit-8 (CCK-8), colony formation, wound healing, transwell and tube formation assays. The biological role of circ_0007334 was examined by the xenograft tumor model in vivo. Circ_0007334 and KLF12 were increased, and miR-577 was decreased in CRC tissues and cells. Also, circ_0007334 expression was upregulated in CRC cell-derived exosomes. Circ_0007334 deficiency repressed cell viability, colony formation, migration, invasion, and angiogenesis in CRC cells. Mechanically, circ_0007334 could regulate KLF12 expression by sponging miR-577. Circ_0007334 downregulation or exosomal circ_0007334 silencing blocked CRC tumor growth in vivo. These results presented that circ_0007334 deficiency exerts a tumor-suppressor by the miR-577/KLF12 axis in CRC, and indicated that exosomal circ_0007334 could hinder CRC tumor growth and angiogenesis in vivo. Our findings provided a novel therapeutic strategy for CRC.

Identification of single nucleotide polymorphisms of PIK3R1 and DUSP1 genes and their genetic associations with milk production traits in dairy cows

Background

Previously, phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) and dual specificity phosphatase 1 (DUSP1) were identified as promising candidate genes for milk production traits due to their being differentially expressed between the dry period and the peak of lactation in livers of dairy cows. Hence, in this study, the single nucleotide polymorphisms (SNPs) of PIK3R1 and DUSP1 genes were identified and their genetic associations with milk yield, fat yield, fat percentage, protein yield, and protein percentage, were investigated using 1067 Chinese Holstein cows from 40 sire families.

Results

By re-sequencing the entire coding region and 2000 bp of the 5′ and 3′ flanking regions of the two genes, one SNP in the 5′ untranslated region (UTR), three in the 3′ UTR, and two in the 3′ flanking region of PIK3R1 were identified, and one in the 5′ flanking region, one in the 3′ UTR, and two in the 3′ flanking region of DUSP1 were found. Subsequent single-locus association analyses showed that five SNPs in PIK3R1, rs42590258, rs210389799, rs208819656, rs41255622, rs133655926, and rs211408208, and four SNPs in DUSP1, rs207593520, rs208460068, rs209154772, and rs210000760, were significantly associated with milk, fat and protein yields in the first or second lactation (P values ≤ 0.0001 and 0.0461). In addition, by the Haploview 4.2 software, the six and four SNPs in PIK3R1 and DUSP1 respectively formed one haplotype block, and the haplotype-based association analyses showed significant associations between their haplotype combinations and the milk traits in both two lactations (P values ≤ 0.0001 and 0.0364). One SNP, rs207593520(T/G), was predicted to alter the transcription factor binding sites (TFBSs) in the 5′ flanking region of DUSP1. Further, the dual-luciferase assay showed that the transcription activity of allele T in rs207593520 was significantly higher than that of allele G, suggesting the activation of transcriptional activity of DUSP1 gene by allele T of rs207593520. Thus, the rs207593520 SNP was highlighted as a potential causal mutation that should be further verified.

Conclusions

We demonstrated novel and significant genetic effects of the PIK3R1 and DUSP1 genes on milk production traits in dairy cows, and our findings provide information for use in dairy cattle breeding.

KLF12 Regulates Mouse NK Cell Proliferation

NK cells are innate lymphocytes that play an integral role in tumor rejection and viral clearance. Unlike their other lymphocyte counterparts, NK cells have the unique ability to recognize and lyse target cells without prior exposure. However, there are no known NK cell-specific genes that are exclusively expressed by all NK cells. Therefore, identification of NK cell-specific genes would allow a better understanding of why NK cells are unique cytotoxic lymphocytes. From the Immunological Genome (ImmGen) Consortium studies, we identified kruppel-like factor 12 (Klf12), encoding a novel transcription factor, preferentially expressed in C57BL/6 mouse NK cells. KLF12 was dispensable for NK cell development, IFN-γ production, degranulation, and proliferation in Klf12 knockout mice. RNA-sequencing analysis revealed increased expression of Btg3, an antiproliferative gene, in KLF12-deficient NK cells compared with wild-type NK cells. Interestingly, competitive mixed bone marrow chimeric mice exhibited reduced development of KLF12-deficient NK cells, altered IFN-γ production and degranulation, and impairment of NK cell proliferation in vitro and in vivo in response to mouse CMV infection. KLF12-deficient NK cells from bone marrow chimeric mice also expressed higher levels of the IL-21R, which resulted in increased IL-21R signaling and correlated with greater inhibition of NK cell proliferation. Furthermore, IL-21 induced Btg3 expression, which correlated with arrested NK cell maturation and proliferation. In summary, we found that KLF12 regulates mouse NK cell proliferation potentially by regulating expression of Btg3 via IL-21.

Regulation of KLF12 by microRNA-20b and microRNA-106a in cystogenesis

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most common inherited disorders. ADPKD is caused by mutations in the gene encoding either polycystic kidney disease 1 ( PKD1) or polycystic kidney disease 2 ( PKD2). Patients with ADPKD show progressive growth of cystic fluid-filled renal cysts. Here, we used Pkd2^f/f control mice and Pkd2^f/f:HoxB7-Cre experimental mice, which are bred to have a conditional deletion of Pkd2 in the collecting ducts, and analyzed the expression pattern of microRNAs (miRNAs) of kidney tissues from Pkd2^f/f and Pkd2^f/f:HoxB7-Cre mice. Decreased expression of miR-20b-5p and miR-106a-5p in Pkd2^f/f:HoxB7-Cre mice compared to that in Pkd2^f/f mice was observed. These miRNAs target Klf12 (Krüppel-like factor 12), which has low expression in kidney tissues of Pkd2^f/f mice; however, its expression is enhanced in Pkd2^f/f:HoxB7-Cre mice over time. Moreover, miR-20b-5p and miR-106a-5p directly target Klf12 mRNA by binding to the 3'-UTR of Klf12. In addition, human and mouse cell lines exhibit similar patterns. These findings were also consistent with the data from Pkd2 knockout mouse embryonic fibroblasts. Furthermore, direct and indirect knockdown of Klf12 slows cyst growth and cell proliferation in mouse inner medullary collecting duct cells. Taken together, we suggest that the induction of miR-20b-5p or miR-106a-5p or the down-regulation of KLF12 could be used as potential novel therapies for inhibiting cyst growth in patients with ADPKD.-Shin, Y., Kim, D. Y., Ko, J. Y., Woo, Y. M., Park, J. H. Regulation of KLF12 by microRNA-20b and microRNA-106a in cystogenesis.

Krüppel-like factors in mammalian stem cells and development

Krüppel-like factors (KLFs) are a family of zinc-finger transcription factors that are found in many species. Recent studies have shown that KLFs play a fundamental role in regulating diverse biological processes such as cell proliferation, differentiation, development and regeneration. Of note, several KLFs are also crucial for maintaining pluripotency and, hence, have been linked to reprogramming and regenerative medicine approaches. Here, we review the crucial functions of KLFs in mammalian embryogenesis, stem cell biology and regeneration, as revealed by studies of animal models. We also highlight how KLFs have been implicated in human diseases and outline potential avenues for future research.

The critical role of Krüppel-like factors in kidney disease

Krüppel-like factors (KLFs) are a family of zinc-finger transcription factors critical to mammalian embryonic development, regeneration, and human disease. There is emerging evidence that KLFs play a vital role in key physiological processes in the kidney, ranging from maintenance of glomerular filtration barrier to tubulointerstitial inflammation to progression of kidney fibrosis. Seventeen members of the KLF family have been identified, and several have been well characterized in the kidney. Although they may share some overlap in their downstream targets, their structure and function remain distinct. This review highlights our current knowledge of KLFs in the kidney, which includes their pattern of expression and their function in regulating key biological processes. We will also critically examine the currently available literature on KLFs in the kidney and offer some key areas in need of further investigation.

Krüppel-Like Factor 12 Promotes Colorectal Cancer Growth through Early Growth Response Protein 1

Krüppel-like factor 12 (KLF12) is a transcription factor that plays a role in normal kidney development and repression of decidualization. KLF12 is frequently elevated in esophageal adenocarcinoma and has been reported to promote gastric cancer progression. Here, we examined the role of KLF12 in colorectal cancer (CRC). Indeed, KLF12 promotes tumor growth by directly activating early growth response protein 1 (EGR1). The levels of KLF12 and EGR1 correlate synergistically with a poor prognosis. These results indicate that KLF12 likely plays an important role in CRC and could serve as a potential prognostic marker and therapeutic target.

Loss of Krüppel-like factor 6 cripples podocyte mitochondrial function

Krüppel-like factors (KLFs) are zinc finger transcription factors that share homology in three C-terminal zinc finger domains. KLF family members are expressed in most if not all tissues and have diverse roles in organismal development and cell differentiation, function, and death. The glomerular podocyte is particularly sensitive to mitochondrial dysfunction, as seen in various genetic disorders manifesting as progressive glomerulosclerosis. In this issue of the JCI, Mallipattu and coworkers show that KLF6 expression is reduced in mouse and human glomerular disease. Podocyte-specific deletion of Klf6 expression in mice leads to mitochondrial dysfunction and apoptosis, followed by glomerulosclerosis. This is the first demonstration that defective transcriptional regulation of nuclear-encoded mitochondrial genes can result in experimental glomerular disease.

PKC-α contributes to high NaCl-induced activation of NFAT5 (TonEBP/OREBP) through MAPK ERK1/2

High NaCl in the renal medullary interstitial fluid powers the concentration of urine but can damage cells. The transcription factor nuclear factor of activated T cells 5 (NFAT5) activates the expression of osmoprotective genes. We studied whether PKC-α contributes to the activation of NFAT5. PKC-α protein abundance was greater in the renal medulla than in the cortex. Knockout of PKC-α reduced NFAT5 protein abundance and expression of its target genes in the inner medulla. In human embryonic kidney (HEK)-293 cells, high NaCl increased PKC-α activity, and small interfering RNA-mediated knockdown of PKC-α attenuated high NaCl-induced NFAT5 transcriptional activity. Expression of ERK1/2 protein and phosphorylation of ERK1/2 were higher in the renal inner medulla than in the cortex. Knockout of PKC-α decreased ERK1/2 phosphorylation in the inner medulla, as did knockdown of PKC-α in HEK-293 cells. Also, knockdown of ERK2 reduced high NaCl-dependent NFAT5 transcriptional activity in HEK-293 cells. Combined knockdown of PKC-α and ERK2 had no greater effect than knockdown of either alone. Knockdown of either PKC-α or ERK2 reduced the high NaCl-induced increase of NFAT5 transactivating activity. We have previously found that the high NaCl-induced increase of phosphorylation of Ser(591) on Src homology 2 domain-containing phosphatase 1 (SHP-1-S591-P) contributes to the activation of NFAT5 in cell culture, and here we found high levels of SHP-1-S591-P in the inner medulla. PKC-α has been previously shown to increase SHP-1-S591-P, which raised the possibility that PKC-α might be acting through SHP-1. However, we did not find that knockout of PKC-α in the renal medulla or knockdown in HEK-293 cells affected SHP-1-S591-P. We conclude that PKC-α contributes to high NaCl-dependent activation of NFAT5 through ERK1/2 but not through SHP-1-S591.

PKC-α contributes to high NaCl-induced activation of NFAT5 (TonEBP/OREBP) through MAPK ERK1/2

High NaCl in the renal medullary interstitial fluid powers the concentration of urine but can damage cells. The transcription factor nuclear factor of activated T cells 5 (NFAT5) activates the expression of osmoprotective genes. We studied whether PKC-α contributes to the activation of NFAT5. PKC-α protein abundance was greater in the renal medulla than in the cortex. Knockout of PKC-α reduced NFAT5 protein abundance and expression of its target genes in the inner medulla. In human embryonic kidney (HEK)-293 cells, high NaCl increased PKC-α activity, and small interfering RNA-mediated knockdown of PKC-α attenuated high NaCl-induced NFAT5 transcriptional activity. Expression of ERK1/2 protein and phosphorylation of ERK1/2 were higher in the renal inner medulla than in the cortex. Knockout of PKC-α decreased ERK1/2 phosphorylation in the inner medulla, as did knockdown of PKC-α in HEK-293 cells. Also, knockdown of ERK2 reduced high NaCl-dependent NFAT5 transcriptional activity in HEK-293 cells. Combined knockdown of PKC-α and ERK2 had no greater effect than knockdown of either alone. Knockdown of either PKC-α or ERK2 reduced the high NaCl-induced increase of NFAT5 transactivating activity. We have previously found that the high NaCl-induced increase of phosphorylation of Ser(591) on Src homology 2 domain-containing phosphatase 1 (SHP-1-S591-P) contributes to the activation of NFAT5 in cell culture, and here we found high levels of SHP-1-S591-P in the inner medulla. PKC-α has been previously shown to increase SHP-1-S591-P, which raised the possibility that PKC-α might be acting through SHP-1. However, we did not find that knockout of PKC-α in the renal medulla or knockdown in HEK-293 cells affected SHP-1-S591-P. We conclude that PKC-α contributes to high NaCl-dependent activation of NFAT5 through ERK1/2 but not through SHP-1-S591.

Genetic variants in transcription factors are associated with the pharmacokinetics and pharmacodynamics of metformin

One-third of type 2 diabetes patients do not respond to metformin. Genetic variants in metformin transporters have been extensively studied as a likely contributor to this high failure rate. Here, we investigate, for the first time, the effect of genetic variants in transcription factors on metformin pharmacokinetics (PK) and response. Overall, 546 patients and healthy volunteers contributed their genome-wide, pharmacokinetic (235 subjects), and HbA1c data (440 patients) for this analysis. Five variants in specificity protein 1 (SP1), a transcription factor that modulates the expression of metformin transporters, were associated with changes in treatment HbA1c (P < 0.01) and metformin secretory clearance (P < 0.05). Population pharmacokinetic modeling further confirmed a 24% reduction in apparent clearance in homozygous carriers of one such variant, rs784888. Genetic variants in other transcription factors, peroxisome proliferator-activated receptor-α and hepatocyte nuclear factor 4-α, were significantly associated with HbA1c change only. Overall, our study highlights the importance of genetic variants in transcription factors as modulators of metformin PK and response.

Krüppel -like factor 8 is a stress-responsive transcription factor that regulates expression of HuR

BACKGROUND/AIMS

HuR is an RNA-binding protein that regulates the post-transcriptional life of thousands of cellular mRNAs and promotes cell survival. HuR is expressed as two mRNA transcripts that are differentially regulated by cell stress. The goal of this study is to define factors that promote transcription of the longer alternate form.

METHODS

Effects of transcription factors on HuR expression were determined by inhibition or overexpression of these factors followed by competitive RT-PCR, gel mobility shift, and chromatin immunoprecipitation. Transcription factor expression patterns were identified through competitive RT-PCR and Western analysis. Stress responses were assayed in thapsigargin-treated proximal tubule cells and in ischemic rat kidney.

RESULTS

A previously described NF-κB site and a newly identified Sp/KLF factor binding site were shown to be important for transcription of the long HuR mRNA. KLF8, but not Sp1, was shown to bind this site and increase HuR mRNA levels. Cellular stress in cultured or native proximal tubule cells resulted in a rapid decrease of KLF8 levels that paralleled those of the long HuR mRNA variant.

CONCLUSIONS

These results demonstrate that KLF8 can participate in regulating expression of alternate forms of HuR mRNA along with NF-κB and other factors, depending on cellular contexts.

The urea transporter family (SLC14): physiological, pathological and structural aspects

Urea transporters (UTs) belonging to the solute carrier 14 (SLC14) family comprise two genes with a total of eight isoforms in mammals, UT-A1 to -A6 encoded by SLC14A2 and UT-B1 to -B2 encoded by SLC14A1. Recent efforts have been directed toward understanding the molecular and cellular mechanisms involved in the regulation of UTs using transgenic mouse models and heterologous expression systems, leading to important new insights. Urea uptake by UT-A1 and UT-A3 in the kidney inner medullary collecting duct and by UT-B1 in the descending vasa recta for the countercurrent exchange system are chiefly responsible for medullary urea accumulation in the urinary concentration process. Vasopressin, an antidiuretic hormone, regulates UT-A isoforms via the phosphorylation and trafficking of the glycosylated transporters to the plasma membrane that occurs to maintain equilibrium with the exocytosis and ubiquitin-proteasome degradation pathways. UT-B isoforms are also important in several cellular functions, including urea nitrogen salvaging in the colon, nitric oxide pathway modulation in the hippocampus, and the normal cardiac conduction system. In addition, genomic linkage studies have revealed potential additional roles for SLC14A1 and SLC14A2 in hypertension and bladder carcinogenesis. The precise role of UT-A2 and presence of the urea recycling pathway in normal kidney are issues to be further explored. This review provides an update of these advances and their implications for our current understanding of the SLC14 UTs.

Krüppel-like factor 12 negatively regulates human endometrial stromal cell decidualization

Members of the KLFs family of transcription factors play roles in maternal endometrium development during embryo implantation. However, the specific role of KLF12 in endometrium development has not yet been described. In this study, we showed that KLF12 expression in human endometrial stromal cells (HESCs) was significantly decreased after decidualization stimulated by 8-Br-cAMP and medroxyprogesterone acetate (MPA). The adenovirus-mediated overexpression of KLF12 in HESCs significantly repressed the expression and secretion of decidualization biomarker genes and their products decidual prolactin (PRL) and insulin-like growth factor binding protein-1 (IGFBP-1) induced by 8-Br-cAMP and MPA. Moreover, CHIP and luciferase reporter assays demonstrated that KLF12 bound to a CAGTGGG element within the decidual prolactin promoter and decreased decidual PRL promoter (dPRL/-2000Luc) activation in a sequence-specific manner. Taken together, these findings suggest KLF12 is a negative regulator of human endometrial stromal cell decidualization.

A novel long-range enhancer regulates postnatal expression of Zeb2: implications for Mowat-Wilson syndrome phenotypes

The zinc-finger, E-box-binding homeobox-2 (Zeb2) gene encodes a SMAD-interacting transcription factor that has diverse roles in development and disease. Mutations at the hZeb2 locus cause Mowat-Wilson syndrome (MWS), a genetic disorder that is associated with mental retardation and other, case- and sex-dependent clinical features. Recent studies have detailed microRNA-mediated control of Zeb2, but little is known about the genomic context of this gene or of enhancer sequences that may direct its diverse functions. Here, we describe a novel transgenic rodent model in which Zeb2 regulatory sequence has been disrupted, resulting in a postnatal developmental phenotype that is autosomal dominant. The phenotype exhibits a genotype-by-sex interaction and manifests primarily as an acute attenuation of postnatal kidney development in males. Other aspects of embryonic and neonatal development, including neuronal, are unaffected. The transgene insertion site is associated with a 12 kb deletion, 1.2 Mb upstream of Zeb2, within a 4.1 Mb gene desert. A conserved sequence, derived from the deleted region, enhanced Zeb2 promoter activity in transcription assays. Tissue and temporal restriction of this enhancer activity may involve postnatal changes in proteins that bind this sequence. A control human/mouse VISTA enhancer (62 kb upstream of Zeb2) also up-regulated the Zeb2 promoter, providing evidence of a string of conserved distal enhancers. The phenotype arising from deletion of one copy of the extreme long-range enhancer indicates a critical role for this enhancer at one developmental stage. Haploinsufficiency of Zeb2 in this developmental context reflects inheritance of MWS and may underlie some sex-dependent, non-neural characteristics of this human inherited disorder.

Control of mesenchymal lineage progression by microRNAs targeting skeletal gene regulators Trps1 and Runx2

Multiple microRNAs (miRNAs) that target the osteogenic Runt-related transcription factor 2 (RUNX2) define an interrelated network of miRNAs that control osteoblastogenesis. We addressed whether these miRNAs have functional targets beyond RUNX2 that coregulate skeletal development. Here, we find that seven RUNX2-targeting miRNAs (miR-23a, miR-30c, miR-34c, miR-133a, miR-135a, miR-205, and miR-217) also regulate the chondrogenic GATA transcription factor tricho-rhino-phalangeal syndrome I (TRPS1). Although the efficacy of each miRNA to target RUNX2 or TRPS1 differs in osteoblasts and chondrocytes, each effectively blocks maturation of precommitted osteoblasts and chondrocytes. Furthermore, these miRNAs can redirect mesenchymal stem cells into adipogenic cell fate with concomitant up-regulation of key lineage-specific transcription factors. Thus, a program of multiple miRNAs controls mesenchymal lineage progression by selectively blocking differentiation of osteoblasts and chondrocytes to control skeletal development.

Urea transport in the kidney

Urea transport proteins were initially proposed to exist in the kidney in the late 1980s when studies of urea permeability revealed values in excess of those predicted by simple lipid-phase diffusion and paracellular transport. Less than a decade later, the first urea transporter was cloned. Currently, the SLC14A family of urea transporters contains two major subgroups: SLC14A1, the UT-B urea transporter originally isolated from erythrocytes; and SLC14A2, the UT-A group with six distinct isoforms described to date. In the kidney, UT-A1 and UT-A3 are found in the inner medullary collecting duct; UT-A2 is located in the thin descending limb, and UT-B is located primarily in the descending vasa recta; all are glycoproteins. These transporters are crucial to the kidney's ability to concentrate urine. UT-A1 and UT-A3 are acutely regulated by vasopressin. UT-A1 has also been shown to be regulated by hypertonicity, angiotensin II, and oxytocin. Acute regulation of these transporters is through phosphorylation. Both UT-A1 and UT-A3 rapidly accumulate in the plasma membrane in response to stimulation by vasopressin or hypertonicity. Long-term regulation involves altering protein abundance in response to changes in hydration status, low protein diets, adrenal steroids, sustained diuresis, or antidiuresis. Urea transporters have been studied using animal models of disease including diabetes mellitus, lithium intoxication, hypertension, and nephrotoxic drug responses. Exciting new animal models are being developed to study these transporters and search for active urea transporters. Here we introduce urea and describe the current knowledge of the urea transporter proteins, their regulation, and their role in the kidney.

Mammalian Krüppel-like factors in health and diseases

The Krüppel-like factor (KLF) family of transcription factors regulates diverse biological processes that include proliferation, differentiation, growth, development, survival, and responses to external stress. Seventeen mammalian KLFs have been identified, and numerous studies have been published that describe their basic biology and contribution to human diseases. KLF proteins have received much attention because of their involvement in the development and homeostasis of numerous organ systems. KLFs are critical regulators of physiological systems that include the cardiovascular, digestive, respiratory, hematological, and immune systems and are involved in disorders such as obesity, cardiovascular disease, cancer, and inflammatory conditions. Furthermore, KLFs play an important role in reprogramming somatic cells into induced pluripotent stem (iPS) cells and maintaining the pluripotent state of embryonic stem cells. As research on KLF proteins progresses, additional KLF functions and associations with disease are likely to be discovered. Here, we review the current knowledge of KLF proteins and describe common attributes of their biochemical and physiological functions and their pathophysiological roles.

Krüppel-like factor 12 plays a significant role in poorly differentiated gastric cancer progression

Gastric cancer is the second common malignant neoplasia in Japan, and its poorly differentiated form is a deadly disease. To identify novel candidate oncogenes contributing to its genesis, we examined copy-number alterations in 50 primary poorly differentiated gastric cancers using an array-based comparative genomic hybridization (array-CGH). Many genetic changes were identified, including a novel amplification of the 13q22 locus. Several genes are located in this locus, and selective knockdown of one for the Krüppel-like factor 12 (KLF12) induced significant growth-arrest in the HGC27 gastric cancer cell line. Microarray analysis also demonstrated that genes associated with cell proliferation were mostly changed by KLF12 knockdown. To explore the oncogenic function of KLF12, we introduced a full length of human KLF12 cDNA into NIH3T3 and AZ-521 cell lines and found that overexpression significantly enhanced their invasive potential. In clinical samples, KLF12 mRNA in cancer tissue was increased in 11 of 28 cases (39%) when compared with normal gastric epithelium. Clinicopathological analysis further demonstrated a significant correlation between KLF12mRNA levels and tumor size (p = 0.038). These data suggest that the KLF12 gene plays an important role in poorly differentiated gastric cancer progression and is a potential target of therapeutic measures.

Transcriptional profiling of native inner medullary collecting duct cells from rat kidney

Vasopressin acts on the inner medullary collecting duct (IMCD) in the kidney to regulate water and urea transport. To obtain a "parts list" of gene products expressed in the IMCD, we carried out mRNA profiling of freshly isolated rat IMCD cells using Affymetrix Rat 230 2.0 microarrays with approximately 31,000 features; 7,913 annotated transcripts were found to be expressed above background in the IMCD cells. We have created a new online database (the "IMCD Transcriptome Database;" http://dir.nhlbi.nih.gov/papers/lkem/imcdtr/) to make the results publicly accessible. Among the 30 transcripts with the greatest signals on the arrays were 3 water channels: aquaporin-2, aquaporin-3, and aquaporin-4, all of which have been reported to be targets for regulation by vasopressin. In addition, the transcript with the greatest signal among members of the solute carrier family of genes was the UT-A urea transporter (Slc14a2), which is also regulated by vasopressin. The V2 vasopressin receptor was strongly expressed, but the V1a and V1b vasopressin receptors did not produce signals above background. Among the 200 protein kinases expressed, the serum-glucocorticoid-regulated kinase (Sgk1) had the greatest signal intensity in the IMCD. WNK1 and WNK4 were also expressed in the IMCD with a relatively high signal intensity, as was protein kinase A (beta-catalytic subunit). In addition, a large number of transcripts corresponding to A kinase anchoring proteins and 14-3-3 proteins (phospho-S/T-binding proteins) were expressed. Altogether, the results combine with proteomics studies of the IMCD to provide a framework for modeling complex interaction networks responsible for vasopressin action in collecting duct cells.