WNT10B Research Articles

Comparative genomics on Wnt8a and Wnt8b genes

WNT family ligands transduce signals through FZD1, FZD2, FZD3, FZD4, FZD5, FZD6, FZD7, FZD8, FZD9, FZD10, LRP5, LRP6, ROR1, ROR2 and RYK. WNT1, WNT2, WNT2B, WNT3, WNT3A, WNT8A, WNT8B, WNT10A and WNT10B are canonical WNTs to activate WNT - beta-catenin pathway. Human WNT8A mRNA is expressed in NT2 cells with neuronal differentiation potential, while human WNT8B mRNA in diffuse type gastric cancer. Here, we identified and characterized the rat Wnt8a and Wnt8b genes by using bioinformatics. The rat Wnt8a gene, consisting of six exons, was located within AC134361.2 genome sequence. The rat Wnt8b gene, consisting of six exons, was located within AC105487.6 and AC103018.7 genome sequences. The rat Wnt8a (355 aa) and Wnt8b (350 aa) with 60.0% total-amino-acid identity were secreted-type proteins with 22 conserved Cys residues and two Asn-linked glycosylation sites. Wnt8b orthologs were more conserved than Wnt8a orthologs. GATA-binding site was located within conserved region of rat Wnt8b and human WNT8B promoters. GATA6 ESTs were expressed in diffuse type gastric cancer, and FGFR2 gene is reported preferentially amplified in diffuse type gastric cancer. KGF-FGFR2-PI3K-GATA6-WNT8B signaling cascade is predicted to play important roles in diffuse type gastric cancer. This is the first report on the rat Wnt8a and Wnt8b genes as well as on the conserved GATA-binding site within rat Wnt8b and human WNT8B promoters.

Molecular evolution of Wnt2b orthologs

WNT family proteins transduce signals through Frizzled (FZD) receptors with extracellular WNT-binding domain and cytoplasmic Dishevelled-binding domain. WNT2B-ST7L and WNT2-ST7 loci are paralogous regions within the human genome. WNT2B isoform 2 and WNT2 are canonical WNTs to activate the beta-catenin - TCF pathway in human cancer, especially in gastric cancer. Here, the rat Wnt2b gene was identified and characterized by using bioinformatics. The rat Wnt2b gene, consisting of five exons, was located within AC106372.5 genome sequence. Wnt2b core promoter region (nucleotide position 234449-233652 of AC106372.5 rat genome sequence) was identified as an evolutionarily conserved region. GC content of rat Wnt2b promoter was 71.8%. Nucleotide identity between human and rat Wnt2b promoters was 71.2%. E box, CP2-binding site, CCAAT box and ZNFN1A1 (IKAROS)-binding site were located within the conserved region of rat Wnt2b, mouse Wnt2b, and human WNT2B promoters. Rat Wnt2b (391 aa), human WNT2B isoform 2 and other vertebrate Wnt2b orthologs were type II transmembrane proteins with cleavable extracellular WNT domain, while vertebrate Wnt2 orthologs were secreted proteins. Twenty-four Cys residues were conserved among vertebrate Wnt2b and Wnt2 orthologs. Glycosylation sites at Asn 283 of rat Wnt2b and RGD motif were identified within mammalian Wnt2b orthologs, but not within vertebrate Wnt2 orthologs and zebrafish wnt2b. Zebrafish wnt2b acquired N-terminal cytoplasmic region to evolve into type II transmembrane protein, and then mammalian Wnt2b orthologs acquired integrin-targeting RGD motif within the extracellular WNT domain. This is the first report on the rat Wnt2b gene as well as on molecular evolution of the Wnt2b orthologs.

Identification and characterization of rat Wnt1 and Wnt10b genes in silico

WNT family genes encode WNT family glycoproteins, while Frizzled (FZD) family genes encode seven-transmembrane-type receptors with extracellular WNT-binding domain and cytoplasmic Dishevelled-binding domain. WNT signaling pathway is implicated in carcinogenesis and embryogenesis. WNT1-WNT10B, WNT6-WNT10A, WNT3-WNT9B (WNT14B), WNT3A-WNT9A (WNT14) gene clusters exist within the human genome. Here, we identified and characterized rat Wnt1 and Wnt10b genes by using bioinformatics. Rat Wnt1 gene, consisting of four exons, encoded a 370-aa protein with signal peptide, 22 conserved Cys residues and four Asn-linked glycosylation sites. Rat Wnt10b gene, consisting of five exons, encoded a 389-aa protein with signal peptide, 24 conserved Cys residues and two Asn-linked glycosylation sites. Wnt1 and Wnt10b genes at rat chromosome 7q36 were clustered in head-to-head manner with an interval of about 10 kb within AC096835.4 or AC118760.4 genome sequences. Promoter region, exon 1 and 5'-part of intron 1 were conserved between rat and human Wnt1 orthologs. Intergenic conserved region (IGCR) was identified within the Wnt1-Wnt10b gene cluster. GC content of rat Wnt1-Wnt10b IGCR (nucleotide position 14962-15875 of AC096835.4 genome sequence) was 59.4%. Rat Wnt1-Wnt10b IGCR showed 92.5 and 74.4% nucleotide identity with mouse Wnt1-Wnt10b IGCR and human WNT1-WNT10B IGCR, respectively. Wnt1-Wnt10b IGCR was predicted as regulatory element rather than gene because cDNA or EST derived from Wnt1-Wnt10b IGCR was not identified. This is the first report on rat Wnt1 and Wnt10b genes as well as on Wnt1-Wnt10b IGCR.

Identification and characterization of rat Wnt6 and Wnt10a genes in silico

WNT and Hedgehog signaling pathways are implicated in various types of human cancer, such as gastric and pancreatic cancer. WNT1, WNT2, WNT2B (WNT13), WNT3, WNT3A, WNT4, WNT5A, WNT5B, WNT6, WNT7A, WNT7B, WNT8A, WNT8B, WNT9A (WNT14), WNT9B (WNT14B). WNT10A, WNT10B, WNT11 and WNT16 genes encode WNT family glycoproteins, which transduce signals through Frizzled (FZD) family receptors with extracellular WNT-binding and cytoplasmic Dishevelled-binding domains. WNT6 and WNT10A genes at human chromosome 2q35 are clustered in tail-to-head manner with an interval of <7 kb. Here, we identified and characterized rat Wnt6 and Wnt10a genes by using bioinformatics. Wnt6 and Wnt10a genes were clustered in tail-to-head manner with an interval of about 7 kb within AC127107.3 and AC132020.3 genome sequences. Rat Wnt6 gene, consisting of four exons, encoded a 365-aa protein with signal peptide, 24 conserved Cys residues, two Asn-linked glycosylation sites and an RGD motif. Rat Wnt10a gene, consisting of four exons, encoded a 417-aa protein with 24 conserved Cys residues, two Asn-linked glycosylation sites and an RGD motif. Rat Wnt6 and human WNT6 showed 97.8% total-amino-acid identity, while rat Wnt10a and human WNT10A showed 95.4% total-amino-acid identity. Promoter region was conserved between rat Wnt6 and human WNT6 genes. GATA, FOXA2, and TGIF binding sites were located within the conserved region of rat Wnt6 and human WNT6 promoters. This is the first report on rat Wnt6 and Wnt10a genes as well as on the conserved promoter region of Wnt6 orthologs.

Comparative analysis of the expression patterns of Wnts during chick limb development

Wnts control a number of processes during limb development-from initiating outgrowth and controlling patterning, to regulating cell differentiation in a number of tissues. We analyzed the expression pattern of various Wnts (4, 5a, 5b, 6, 11, and 14) in whole mount in situ hybridization during chick wing development. From HH stage 26, expression of Wnt 4 is observed in the central elbow region and wrist-forming regions, and during later stages, expression is seen in the joint-forming regions of the whole limb. Wnt 5a is expressed throughout the limb mesenchyme during early limb developmental stages, and later, at HH stage 23, it becomes predominantly confined to the distal tip, leaving low expression levels proximally. At HH stage 29, expression at the distal tip is restricted to the interdigital regions, and at day 8, expression is seen in the region surrounding the phalanges. Wnt 5b expression is first observed in the AER at HH stage 20 and later in the dorsal and ventral mesenchyme surrounding the cartilage elements of the limb. Expression of Wnt 6 is observed from HH stage 17 until day 8 in the dorsal and ventral ectoderm and also in the dorsoventral limb boundaries. Expression of Wnt 11 is observed in the proximal dorsal mesenchyme of the limb from HH stage 23 onward and later in the dorsal and ventral subectodermal mesenchyme and in the regions adjacent to the digits at day 8. Weak expression of Wnt 14 is observed at the proximal mesenchyme of the limb at HH stage 23; later, it extends as a transverse strip surrounding the cartilage elements as well as in the interdigital mesenchyme.

The Canonical Wnt/β-Catenin Pathway Is Active in Pre-B Acute Lymphoblastic Leukemia (ALL) Cells and Augments Their Growyh and Survival.

Wnt signalling is known to play an important regulatory role in hematopoietic progenitors/stem cells during both fetal and adult development. Recently this pathway has been implicated in several hematological malignancies, however, its precise role in pathogenesis of pre-B ALL remains unknown. In this study we examined the expression of genes required for Wnt signalling in 12 ALL cases, normal bone marrow mononuclear cells, bone marrow stroma and the effect of Wnt-3a stimulation on leukemic cell growth and survival. RT-PCR analysis revealed expression of Wnt family members 2b, 5a, 10b and 16b in most ALL cases. Primary BM stroma expressed Wnt-5a alone while BM mononuclear cells expressed Wnts 3a, 5a, 10b and 16b. Wnt receptors Fz-7 and 8 were widely expressed on ALL cases while Fz-3 and 4 showed restricted expression. Together this suggests that Wnt signalling pathway may be active in pre-B ALL cells. To characterise functional consequences of Wnt pathway activation we investigated the effects of Wnt-3a on proliferation, survival and cell cycle status of blasts from three pre-B ALL cell lines, one newly derived stromal dependent cell line (STYG) and one primary patient sample under 3-day serum-free culture conditions. Exposure to Wnt-3a resulted in a mean 5.3-, 5.2-, 1.7-, 2.7- and 5.1- fold stimulation of 3H-thymidine incorporation in NALM6, Reh, LK63, STYG and primary ALL cells, respectively. Cell cycle analysis based on propidium iodide staining confirmed an increased proportion of cells progressing from G0/1 through to S/G2/M phases. Wnt3a augmented survival in all leukemic cells by 18.6% (range 11.7% – 24.6%, p<0.001) in comparison to untreated cells under serum-free conditions as measured by Annexin V/PI staining. Immunofluorescence microscopy revealed elevated nuclear b-catenin levels in Wnt-3a stimulated cells, confirming activation through the canonical pathway. Our results suggest that Wnt proteins may exert a proliferative/survival effect on leukemic cells through an autocrine/paracrine regulatory loop.

Activation of Stem-Cell Specific Genes by HOXA9 and HOXA10 Homeodomain Proteins in CD34+ Human Cord Blood Cells.

There is growing evidence for a role of HOX homeodomain (HD) proteins in normal hematopoiesis. Several HOX genes, including HOXA9 and HOXA10, are expressed in primitive hematopoietic cells, and that expression is down-regulated as cells mature, implying a role in early hematopoietic differentiation. In addition, retrovirally enforced over-expression of either of these two HD proteins results in dramatic expansion of hematopoietic stem cells (HSC). Our laboratory recently published a description of the HOXA9 transcriptome in human leukemic cell lines, using a transient over-expression strategy (Dorsam et al. Blood 2004). In that study we observed changes in the mRNA levels of a large number of genes within 24 hours of introduction of a HOXA9 expression vector in these cells. The modulated targets represented a wide variety of functional groups, including oncogenes, cell-cycle proteins, enzymes, membrane proteins and other transcription factors. Interestingly, a number of these putative targets are known to be part of the transcriptome of normal HSC. This previous study raises questions as to whether the HOXA9 targets identified in aneuploid immortalized myeloid cell lines would match the gene targets in normal hematopoietic cells. To answer this question and to compare target genes of two closely related HD proteins, human CD34+ umbilical cord blood cells were transduced with MSCV-based vectors expressing either HOXA9 or HOXA10, and RNA isolated from these cells was amplified and analyzed with cDNA microarrays. Statistical analysis using the Significance Analysis of Microarrays (SAM) algorithm revealed a common signature of several hundred modulated genes, demonstrating that the transcriptomes of HOXA9 and HOXA10 largely overlap in this cellular context. In a second step, CLUSTER analysis was performed, introducing threshold values to increase the likelihood of the identified genes being truly regulated and of biological significance. Using these more stringent criteria, 115 genes were modulated by one or both of the over-expressed genes. Several genes that were up-regulated by both HOX proteins were validated by quantitative real-time RT-PCR. HOXA9 and HOXA10 showed positive regulation of genes in the Wnt pathway, including Wnt 10b and two Wnt receptors Frizzled 1 and Frizzled 5, a important pathway for hematopoietic stem cell (HSC) self renewal. Other validated targets included Ets-related gene (ERG), alcohol dehydrogenase 1 (ALDH1) and very long chain acyl-CoA synthetase (VLCS-H1), all of which are known to be expressed in normal CD34+ cells. One down-regulated gene in this survey is CYBB, a respiratory burst oxidase component pg91(phox), which is expressed in myeloid cells, and has previously been shown to be repressed by HOXA10. GenMAPP pathway analysis indicated that HOXA9 and HOXA10 repressed expression of several genes involved in heme biosynthesis and three globin genes, indicating a general suppression of the erythroid maturation program. HOXA9 and HOXA10 both appear to activate many HSC-specific genes while repressing genes involved in hematopoietic differentiation.

Association of the Gene Encoding Wingless-Type Mammary Tumor Virus Integration-Site Family Member 5B ( WNT5B) with Type 2 Diabetes

Recent reports have suggested that WNT signaling is an important regulator for adipogenesis or insulin secretion and might be involved in the pathogenesis of type 2 diabetes. To investigate possible roles of the WNT genes in conferring susceptibility to type 2 diabetes, we examined the association of the genes that encode members of the WNT family with type 2 diabetes in the Japanese population. First, 40 single-nucleotide polymorphism (SNP) loci within 11 WNT genes were analyzed in 188 subjects with type 2 diabetes (case-1) and 564 controls (control-1). Among them, six SNP loci exhibited a significant difference (P<.05) in the allele and/or genotype distributions between case and control subjects. These SNP loci were further analyzed in another set of case (case-2; n=733) and control (control-2; n=375) subjects to confirm their statistical significance. As a result, one SNP locus in the WNT5B gene was strongly associated with type 2 diabetes ( chi 2=15.6; P=.00008; odds ratio=1.74; 95% confidence interval 1.32-2.29). Expression of the WNT5B gene was detectable in several tissues, including adipose, pancreas, and liver. Subsequent in vitro experiments identified the fact that expression of the Wnt5b gene was increased at an early phase of adipocyte differentiation in mouse 3T3-L1 cells. Furthermore, overexpression of the Wnt5b gene in preadipocytes resulted in the promotion of adipogenesis and the enhancement of adipocytokine-gene expression. These results indicate that the WNT5B gene may contribute to conferring susceptibility to type 2 diabetes and may be involved in the pathogenesis of this disease through the regulation of adipocyte function.

Regulating the Balance between Peroxisome Proliferator-activated Receptor γ and β-Catenin Signaling during Adipogenesis: A GLYCOGEN SYNTHASE KINASE 3β PHOSPHORYLATION-DEFECTIVE MUTANT OF β-CATENIN INHIBITS EXPRESSION OF A SUBSET OF ADIPOGENIC GENES

The differentiation of preadipocytes into adipocytes requires the suppression of canonical Wnt signaling, which appears to involve a peroxisome proliferator-activated receptor gamma (PPARgamma)-associated targeting of beta-catenin to the proteasome. In fact, sustained activation of beta-catenin by expression of Wnt1 or Wnt 10b in preadipocytes blocks adipogenesis by inhibiting PPARgamma-associated gene expression. In this report, we investigated the mechanisms regulating the balance between beta-catenin and PPARgamma signaling that determines whether mouse fibroblasts differentiate into adipocytes. Specifically, we show that activation of PPARgamma by exposure of Swiss mouse fibroblasts to troglitazone stimulates the degradation of beta-catenin, which depends on glycogen synthase kinase (GSK) 3beta activity. Mutation of serine 37 (a target of GSK3beta) to an alanine renders beta-catenin resistant to the degradatory action of PPARgamma. Ectopic expression of the GSK3beta phosphorylation-defective S37A-beta-catenin in Swiss mouse fibroblasts expressing PPARgamma stimulates the canonical Wnt signaling pathway without blocking their troglitazone-dependent differentiation into lipid-laden cells. Analysis of protein expression in these cells, however, shows that S37A-beta-catenin inhibits a select set of adipogenic genes because adiponectin expression is completely blocked, but FABP4/aP2 expression is unaffected. Furthermore, the mutant beta-catenin appears to have no affect on the ability of PPARgamma to bind to or transactivate a PPAR response element. The S37A-beta-catenin-associated inhibition of adiponectin expression coincides with an extensive decrease in the abundance of C/EBPalpha in the nuclei of the differentiated mouse fibroblasts. Taken together, these data suggest that GSKbeta is a key regulator of the balance between beta-catenin and PPARgamma activity and that activation of canonical Wnt signaling downstream of PPARgamma blocks expression of a select subset of adipogenic genes.

Fate map of the diencephalon and the zona limitans at the 10-somites stage in chick embryos

The diencephalon is a central area of the vertebrate developing brain, where the thalamic nuclear complex, the pretectum and the anterior tegmental structures are generated. It has been subdivided into prosomeres, which are transversal domains defined by morphological and molecular criteria. The zona limitans intrathalamica is a central boundary in the diencephalon that separates the posterior diencephalon (prosomeres 1 and 2), from the anterior diencephalon (prosomere 3). This intrathalamic limit appears early on in neural tube development, and the molecular pattern that it reveals suggests an important role in the diencephalic histogenesis. We hereby present a fate map of the presumptive territories in the diencephalon of a chick embryo at the 10–11 somite stages (HH9–10), by homotopic and isochronic quail–chick grafts. The anatomical interpretation of chimeric brains was aided by correlative whole-mount in situ hybridization with RNA probes for chicken genes expressed in specific diencephalic territories. The resulting fate map describes the distribution of the presumptive diencephalic prosomeres in the neural tube, and demonstrates their topologically conserved relationships throughout the neural development. Moreover, we show that the presumptive epithelium of ZLI can be localized at early developmental stages in the diencephalic alar plate at the anterior limit of the Wnt8b gene expression domain.

Spatial and temporal expression of Wnt and Dickkopf genes during murine lens development

Recent studies indicate a role for Wnt signalling in regulating lens cell differentiation ( Stump et al., 2003). To further our understanding of this, we investigated the expression patterns of Wnts and Wnt signalling regulators, the Dickkopfs ( Dkks), during murine lens development. In situ hybridisation showed that Wnt5a, Wnt5b, Wnt7a, Wnt7b, Wnt8a and Wnt8b genes are expressed throughout the early lens primordia. At embryonic day 14.5 (E14.5), Wnt5a, Wnt5b, Wnt7a, Wnt8a and Wnt8b are reduced in the primary fibres, whereas Wnt7b remains strongly expressed. This trend persists up to E15.5. At later embryonic stages, Wnt expression is predominantly localised to the epithelium and elongating cells at the lens equator. As fibre differentiation progresses, Wnt expression becomes undetectable in the cells of the lens cortex. The one exception is Wnt7b, which continues to be weakly expressed in cortical fibres. This pattern of expression continues through to early postnatal stages. However, by postnatal day 21 (P21), expression of all Wnts is distinctly weaker in the central lens epithelium compared with the equatorial region. This is most notable for Wnt5a, which is barely detectable in the central lens epithelium at P21. Dkk1, Dkk2 and Dkk3 have similar patterns of expression to each other and to the majority of the Wnts during lens development. This study shows that multiple Wnt and Dkk genes are expressed during lens development. Expression is predominantly in the epithelial compartment but is also associated, particularly in the case of Wnt7b, with early events in fibre differentiation.

BMP treatment of C3H10T1/2 mesenchymal stem cells induces both chondrogenesis and osteogenesis.

The molecular mechanisms by which bone morphogenetic proteins (BMPs) promote skeletal cell differentiation were investigated in the murine mesenchymal stem cell line C3H10T1/2. Both BMP-7 and BMP-2 induced C3H10T1/2 cells to undergo a sequential pattern of chondrogenic followed by osteogenic differentiation that was dependent on both the concentration and the continuous presence of BMP in the growth media. Differentiation was determined by the expression of chondrogenesis and osteogenesis associated matrix genes. Subsequent experiments using BMP-7 demonstrated that withdrawal of BMP from the growth media led to a complete loss of skeletal cell differentiation accompanied by adipogenic differentiation of these cells. Continuous treatment with BMP-7 increased the expression of Sox9, Msx 2, and c-fos during the periods of chondrogenic differentiation after which point their expression decreased. In contrast, Dlx 5 expression was induced by BMP-7 treatment and remained elevated throughout the time-course of skeletal cell differentiation. Runx2/Cbfa1 was not detected by ribonuclease protection assay (RPA) and did not appear to be induced by BMP-7. The sequential nature of differentiation of chondrocytic and osteoblastic cells and the necessity for continuous BMP treatment to maintain skeletal cell differentiation suggests that the maintenance of selective differentiation of the two skeletal cell lineages might be dependent on BMP-7-regulated expression of other morphogenetic factors. An examination of the expression of Wnt, transforming growth factor-beta (TGF-beta), and the hedgehog family of morphogens showed that Wnt 5b, Wnt 11, BMP-4, growth and differentiation factor-1 (GDF-1), Sonic hedgehog (Shh), and Indian hedgehog (Ihh) were endogenously expressed by C3H10T1/2 cells. Wnt 11, BMP-4, and GDF-1 expression were inhibited by BMP-7 treatment in a dose-dependent manner while Wnt 5b and Shh were selectively induced by BMP-7 during the period of chondrogenic differentiation. Ihh expression also showed induction by BMP-7 treatment, however, the period of maximal expression was during the later time-points, corresponding to osteogenic differentiation. An interesting phenomenon was that BMP-7 activity could be further enhanced twofold by growing the cells in a more nutrient-rich media. In summary, the murine mesenchymal stem cell line C3H10T1/2 was induced to follow an endochondral sequence of chondrogenic and osteogenic differentiation dependent on both dose and continual presence of BMP-7 and enhanced by a nutrient-rich media. Our preliminary results suggest that the induction of osteogenesis is dependent on the secondary regulation of factors that control osteogenesis through an autocrine mechanism.

WNT2 and human gastrointestinal cancer (Review)

WNT2 gene on human chromosome 7q31 is a paralog of the WNT2B gene on human chromosome 1p13. Rat Wnt2 gene was identified within rat genome draft sequence AC095247.4. Human WNT2 showed 96.4% total-amino-acid identity with rat Wnt2, 96.1% with mouse Wnt2, 68.6% with zebrafish wnt2, and 67.8% with fugu wnt2. WNT2 is an evolutionarily conserved secreted-type glycoprotein belonging to the WNT family. WNT2 mRNA is expressed in human fetal lung and placenta, but almost undetectable in normal gastrointestinal tract. WNT2 mRNA is frequently up-regulated in human gastric cancer due to tumor-stromal interaction, and WNT2 gene is rarely amplified in human gastric cancer. WNT2 mRNA is also frequently up-regulated in colorectal polyps, primary colorectal cancer of stage A-C, and also in liver metastasis from colorectal cancer. Putative biding sites for estrogen receptor, GATA-1, AP-2, TCF-1, BHLH, MBF-I, p53, and HNF-5 are located within the 5'-flanking region of human WNT2 gene. WNT2 is up-regulated by beta-estradiol in human MCF-7 cells; however, the mechanism of WNT2 up-regulation in most cases of gastrointestinal cancer remains to be elucidated. WNT2 is a tumor marker of gastric and colorectal cancer. Detection of theWNT2 protein in feces by immunohistochemistry or ELISA and WNT2 mRNA in feces by cDNA-PCR or custom-made microarray could be applied for screening of colorectal cancer. Because WNT2 up-regulation leads to carcinogenesis through activation of the WNT-beta-catenin pathway, WNT2 specific antagonist might be applied for chemoprevention or treatment of gastrointestinal cancer. WNT2 gene is one of the targets for pharmacogenomics in the field of oncology.

Wnt Regulation of Progenitor Maturation in the Cortex Depends on Shh or Fibroblast Growth Factor 2

In the embryonic mouse cerebral cortex, progenitors in the ventricular zone (VZ) undergo a developmental change between embryonic day 13 (E13) and E15. This results in the generation of a secondary proliferative population and the appearance of a second germinal layer, the subventricular zone (SVZ). We have shown previously that bone morphogenetic proteins (BMPs) and fibroblast growth factor 2 (FGF2) act antagonistically to regulate the development of a subset of SVZ progenitors that normally express a high level of epidermal growth factor (EGF) receptors and divide in response to EGF. In the present study, we show that Wnt 7a, Wnt 7b, and Sonic hedgehog (Shh) promote progenitor maturation in explant cultures, as reported for FGF2. Wnts 7a and 7b also stimulate the proliferation of neurogenic progenitors and increase the number of cells that can generate primary neurospheres. To determine whether Wnts, FGF2, and Shh act independently or in a common pathway, each factor was inhibited in cortical explants. This revealed that endogenous Wnts, FGF2, and Shh normally contribute to progenitor maturation. Moreover, Wnt 7a depends on FGF2 or Shh to promote maturation but not proliferation. Maturation induced by blocking BMPs also depends on Shh. In contrast, FGF2 promotes maturation by a Shh-independent mechanism. In vivo, progenitors infected with a Wnt 7a retrovirus at E10.5 were found preferentially in the SVZ at E16.5. These findings suggest that Wnts depend on Shh or FGF2 to promote progenitor maturation to an SVZ state in the embryonic cortex.

Functional development of the mammary gland: use of expression profiling and trajectory clustering to reveal changes in gene expression during pregnancy, lactation, and involution.

To characterize the molecular mechanisms by which progesterone withdrawal initiates milk secretion, we examined global gene expression during pregnancy and lactation in mice, focusing on the period around parturition. Trajectory clustering was used to profile the expression of 1358 genes that changed significantly between pregnancy day 12 and lactation day 9. Predominantly downward trajectories included stromal and proteasomal genes and genes for the enzymes of fatty acid degradation. Milk protein gene expression increased throughout pregnancy, whereas the expression of genes for lipid synthesis increased sharply at the onset of lactation. Examination of regulatory genes with profiles similar or complementary to those of lipid synthesis genes led to a model in which progesterone stimulates synthesis of TGF-beta, Wnt 5b, and IGFBP-5 during pregnancy. These factors are suggested to repress secretion by interfering with PRL and IGF-1 signaling. With progesterone withdrawal, PRL and IGF-1 signaling are activated, in turn activating Akt/PKB and the SREBPs, leading to increased lipid synthesis.

Thymic epithelial cells provide WNT signals to developing thymocytes.

Interactions with thymic stromal cells are known to be critical for the development of T cells from progenitors entering the thymus, yet the molecular mechanisms of stromal cell function remain poorly understood. Accumulating evidence has highlighted the importance of beta-catenin-mediated activation of T cell factor (TCF)/lymphoid enhancer factor (LEF) transcription during thymocyte development. As regulation of this signaling pathway is controlled by binding of soluble Wnt proteins to cell surface Frizzled (Fz) receptors, we studied components of Wnt/Fz-mediated signaling in thecontext of stromal cell regulation of thymocyte development. We show that mRNA for a variety of Wnt family members, notably Wnt-4, Wnt-7a and 7b, and Wnt-10a and 10b, are expressed by thymic epithelium rather then by thymocytes, while thymocytes demonstrate a developmentally regulated pattern of Fz receptor expression. Collectively these findings suggest (1) a functional role for Wnt-producing thymic epithelium in determining TCF/LEF-mediated transcriptional regulation in Fz-bearing thymocytes, and (2) a role for defined Wnt-Fz interactions at successive stages of thymocyte maturation. In support of this we show that separation of thymocytes from Wnt-producing epithelial cells and the thymic microenvironment, triggers beta-catenin phosphorylation and degradation in thymocytes. Thus, sustained exposure to Wnt in the context of an intact stromal microenvironment is necessary for stabilization of beta-catenin-mediated signaling in thymocytes.

Expression of Wnt, Frizzled, sFRP, and DKK Genes in Adult Human Pancreas

Wnts are important signaling molecules involved in many normal developmental processes in the human body as well as some forms of cancer. Nineteen Wnt genes are found in the human genome, as well as 10 Wnt receptor genes called Frizzled. Two coreceptors called LRP 5 and 6 are critical for Wnt signal transduction. The interaction of the Wnts with the receptors is regulated by two classes of extracellular Wnt or LRP binding proteins called sFRP and Dickkopf (DKK), which modulate Wnt signaling. We have examined the expression of all Wnt family members both in the exocrine portion and in isolated islets of adult human pancreas. RT-PCR analysis of the 1-day cultured exocrine pellet fraction from the islet isolation procedure showed that Wnt 2, 2b, 3, 4, 5a, 5b, 7a, 7b, 14, and 15 were detectable. All 10 Frizzled (Frz) receptors were expressed but only Frizzled 1, 2, 4, 5, and 6 strongly. RT-PCR performed on purified human islets revealed that Wnt 2b, 3, 4, 5a, 7b, 10a, and 14 and Frz 4, 5, and 6 were the most highly expressed. DKK 1, 3, and 4 as well as sFRP 1, 4, and 5 were expressed in the exocrine fraction. sFRP 2 and 3 were detectable but only at low levels. In situ hybridization for Frz 1-7 showed that expression colocalized with the islets of Langerhans. Together the data suggest that active Wnt signaling occurs in adult pancreas and is probably important for physiological functions.

Expression of ST7R (ST7-like, ST7L) in normal tissues and cancer

We have recently cloned and characterized ST7R (ST7-like, ST7L), WNT3, WNT3A, WNT5B, WNT6, WNT7B, WNT8A, WNT8B, WNT10A, WNT10B, WNT11, WNT14, WNT14B/WNT15, NKD1, NKD2, ARHU/WRCH1, ARHV/WRCH2, and VANGL1/STB2 using bioinformatics, cDNA-PCR and RACE. ST7R is a paralog of tumor suppressor gene ST7 in the human genome. ST7R gene is clustered with WNT2B gene in human chromo-some 1p13 region, while ST7 gene is clustered with WNT2 gene in human chromosome 7q31 region. Multiple ST7R mRNAs (ST7R1-ST7R4) are transcribed due to alternative splicing. ST7R4 is divergent from ST7R1-ST7R3 in the C-terminal region. Here, we investigated expression of ST7R mRNAs in normal human tissues and human cancer. Northern blot analysis with S7S1 probe corresponding to ST7R1, ST7R2 and ST7R3 isoforms detected 4.2 kb ST7R mRNA in various normal tissues, and also large amounts of 2.2-2.4 kb ST7R mRNAs in testis. Northern blot analysis with S7S4 probe corresponding to ST7R4 isoform detected 2.0 kb ST7R mRNA in testis. Expression of ST7R mRNAs in human cancer was next investigated using cDNA-PCR. Although ST7R mRNAs were almost ubiquitously expressed in 7 gastric cancer cell lines, expression levels of ST7R mRNAs were relatively lower in TMK1 cells. ST7R mRNAs were expressed in most cases of primary gastric cancer, and were up-regulated in 2 out of 10 cases of primary gastric cancer. This is the first report on expression analyses on ST7R.

Molecular cloning and characterization of mouse St7r (St7-like, St7l)

Human ST7R (ST7-like, ST7L) is a paralog of tumor suppressor gene ST7 in the human genome. ST7R gene is clustered with WNT2B gene in human chromosome 1p13, while ST7 gene is clustered with WNT2 gene in human chromosome 7q31. Here, we have cloned mouse ortholog of human ST7R using bioinformatics and cDNA-PCR. Mouse St7r was found to encode 559 amino-acid polypeptide. Mouse St7r showed 90.7% total-amino-acid identity with human ST7R isoform 4 (ST7R4), and 71.6% total-amino-acid identity with human ST7 and mouse St7. Three tyrosine-phosphorylation sites as well as ST7R homologous domains (S7H1, S7H2, and S7H3) were conserved among mouse St7r, human ST7R, mouse St7, and human ST7. Leucine zipper domain of mouse St7r was conserved in human ST7R, but not in mouse St7 and human ST7. Mouse St7r was expressed almost ubiquitously in adult mouse tissues and also in mouse embryos. Although mouse genome draft sequence including mouse St7r gene has not yet been identified, rat genome draft sequence AC106372.1 was found to include rat St7r gene as well as rat Wnt2b gene. These results indicate evolutional conservation of ST7R-WNT2B gene cluster. This is the first report on molecular cloning and initial characterization of mouse St7r.

Molecular cloning and characterization of ST7R (ST7-like, ST7L) on human chromosome 1p13, a novel gene homologous to tumor suppressor gene ST7 on human chromosome 7q31

ST7 is a tumor suppressor gene, which is clustered with WNT2 gene in human chromosome 7q31 region. WNT2 gene is homologous to WNT2B gene. WNT2B gene encodes two isoforms due to alternative splicing of alternative promoter type. WNT2 and WNT2B isoform 2 (WNT2B2) are positive regulators of the WNT - beta-catenin - TCF signaling pathway. Here, a novel ST7-related gene ST7R (ST7-like, ST7L) was identified by using bioinformatics, and ST7R cDNAs were isolated by using cDNA-PCR. ST7R gene encoded 575-amino-acid polypeptide with leucine zipper domain and 3 tyrosine-phosphorylation sites. Human ST7R was homologous to human ST7 (72.1% total-amino-acid identity) and Drosophila CG3634 (56.8% total-amino-acid identity). Leucine zipper domain was unique to ST7R. Tyr 268 and Tyr 441 of ST7R were conserved in ST7 and CG3634. ST7R-homologous domains (S7H1, S7H2, and S7H3) were conserved among ST7R, ST7, and CG3634. ST7R gene consisted of at least 15 exons, and four ST7R isoforms were transcribed due to alternative splicing. ST7R and WNT2B genes, located in human chromosome 1p13 region, were clustered in tail-to-tail manner with an interval of less than 5.0-kb. ST7R-WNT2B and ST7-WNT2 gene clusters might be generated due to duplication of an ancestral gene cluster. Because allelic loss or rearrangements of human chromosome 1p13 region are reported in breast cancer, germ cell tumors, squamous cell carcinoma of head and neck, non-small cell lung cancer, gastrointestinal stromal/smooth muscle tumors (GIST), meningioma, melanoma, acute megakaryoblastic leukemia (M7), and Kaposi's sarcoma, ST7R might be a novel tumor suppressor gene on human chromosome 1p13.