Identification of sonic hedgehog-responsive genes using cDNA microarray

Ontogeny of inter-alpha inhibitor protein (IAIP) expression in human brain

Inter-alpha inhibitor proteins (IAIPs) are naturally occurring immunomodulatory molecules found in most tissues. We have reported ontogenic changes in the expression of IAIPs in brain during development in sheep and abundant expression of IAIPs in fetal and neonatal rodent brain in a variety of cellular types and brain regions. Although a few studies identified bikunin, light chain of IAIPs, in adult human brain, the presence of the complete endogenous IAIP protein complex has not been reported in human brain. In this study, we examined the immunohistochemical expression of endogenous IAIPs in human cerebral cortex from early in development through the neonatal period and in adults using well-preserved postmortem brains. We examined total, nuclear, and cytoplasmic staining of endogenous IAIPs and their expression in neurofilament light polypeptide-positive neurons and glial fibrillary acidic protein (GFAP)-positive astrocytes. IAIPs were ubiquitously detected for the first time in cerebral cortical cells at 24-26, 27-28, 29-36, and 37-40 weeks of gestation and in adults. Quantitative analyses revealed that IAIPs were predominately localized in the nucleus in all age groups, but cytoplasmic IAIP expression was more abundant in adult than in the younger ages. Immunoreactivity of IAIPs was expressed in neurons and astrocytes in all age groups. In addition, IAIP co-localization with GFAP-positive astrocytes was more abundant in adults than in the developing brain. We conclude that IAIPs exhibit ubiquitous expression, and co-localize with neurons and astrocytes in the developing and adult human brain suggesting a potential role for IAIPs in development and endogenous neuroprotection.

Kruppel-Like Factor 4 represses osteoblast differentiation via ciliary Hedgehog signaling

Primary cilia are appendages observed in most types of cells, and serve as cellular antennae for sensing environmental signals. Evidence is accumulating that correct ciliogenesis and ciliary functions are indispensable for normal skeletal development by regulating signaling pathways important for bone development. However, whether ciliogenesis is regulated by bone-related factors in osteoblasts is largely unknown. Here we show that Kruppel-Like Factor 4 (KLF4), which is known to repress osteoblast differentiation, supports the formation and maintenance of cilia in cultured osteoblasts; however, the length of the cilia observed in KLF4-induced cells were significantly shorter compared to the control cells. Basal Hedgehog signaling was repressed by KLF4. Significantly, activating Hedgehog signaling using a Smoothened agonist significantly rescued osteoblast mineralization and osteoblastic gene expressions. Global gene expression analysis showed that KLF4 induced number of genes including the nuclear receptor, Pregnane X receptor (PXR), and PXR repressed calvarial osteoblast mineralization and repressed Gli1 expression similar as the effect observed by inducing KLF4. Our results implicate that KLF4 plays important roles for maintaining osteoblasts in an immature state by repressing basal activation of the Hedgehog signaling.

Ontogeny of inter-alpha inhibitor proteins in ovine brain and somatic tissues

Inter-alpha inhibitor proteins (IAIPs) found in relatively high concentrations in human plasma are important in inflammation. IAIPs attenuate brain damage in young and adult subjects, decrease during sepsis and necrotizing enterocolitis in premature infants, and attenuate sepsis-related inflammation in newborn rats. Although a few studies have reported adult organ-specific IAIP expression, information is not available on age-dependent IAIP expression. Given evidence suggesting IAIPs attenuate brain damage in young and adult subjects, and inflammation in newborns, we examined IAIP expression in plasma, cerebral cortex (CC), choroid plexus (CP), cerebral spinal fluid (CSF), and somatic organs in fetal, newborn, and adult sheep to determine the endogenous expression patterns of these proteins during development. IAIPs (enzyme-linked immunosorbent assay) were higher in newborn and adult than fetal plasma (P < 0.05). Western immunoblot detected 125 kDa PaI (Pre-alpha Inhibitor) and 250 kDa IaI (Inter-alpha Inhibitor) in plasma, CNS, and somatic organs. PaI expression in CC and CP was higher in fetuses than newborns and adults, but IaI expression was higher in adults than fetuses and newborns. Both PaI and IaI were higher in fetal than newborn CSF. IAIPs exhibited organ-specific ontogenic patterns in placenta, liver, heart, and kidney. These results provide evidence for the first time that plasma, brain, placenta, liver, heart, and kidney express IAIPs throughout ovine development and that expression patterns are unique to each organ. Although exact functions of IAIPs in CNS and somatic tissues are not known, their presence in relatively high amounts during development suggests their potential importance in brain and organ development.

Effects of inter-alpha inhibitor proteins on neonatal brain injury: Age, task and treatment dependent neurobehavioral outcomes

Hypoxic-ischemic (HI) brain injury is frequently associated with premature and/or full term birth related complications. HI injury often results in learning and processing deficits that reflect widespread damage to an extensive range of cortical and sub-cortical brain structures. Further, inflammation has been implicated in the long-term progression and severity of HI injury. Recently, inter-alpha inhibitor proteins (IAIPs) have been shown to attenuate inflammation in models of systemic infection. Importantly, preclinical studies of neonatal HI injury and neuroprotection often focus on single time windows of assessment or single behavioral domains. This approach limits translational validity, given evidence for a diverse spectrum of neurobehavioral deficits that may change across developmental windows following neonatal brain injury. Therefore, the aims of this research were to assess the effects of human IAIPs on early neocortical cell death (72h post-insult), adult regional brain volume measurements (cerebral cortex, hippocampus, striatum, corpus callosum) and long-term behavioral outcomes in juvenile (P38-50) and adult (P80+) periods across two independent learning domains (spatial and non-spatial learning), after postnatal day 7 HI injury in rats. Here, for the first time, we show that IAIPs reduce acute neocortical neuronal cell death and improve brain weight outcome 72h following HI injury in the neonatal rat. Further, these longitudinal studies are the first to show age, task and treatment dependent improvements in behavioral outcome for both spatial and non-spatial learning following systemic administration of IAIPs in neonatal HI injured rats. Finally, results also show sparing of brain regions critical for spatial and non-spatial learning in adult animals treated with IAIPs at the time of injury onset. These data support the proposal that inter-alpha inhibitor proteins may serve as novel therapeutics for brain injury associated with premature birth and/or neonatal brain injury and highlight the importance of assessing multiple ages, brain regions and behavioral domains when investigating experimental treatment efficacy.

Gi proteins mediate activation of the canonical hedgehog pathway in the myocardium

During myocardial ischemia, upregulation of the hedgehog (Hh) pathway promotes neovascularization and increases cardiomyocyte survival. The canonical Hh pathway activates a transcriptional program through the Gli family of transcription factors by derepression of the seven-transmembrane protein smoothened (Smo). The mechanisms linking Smo to Gli are complex and, in some cell types, involve coupling of Smo to Gi proteins. In the present study, we investigated, for the first time, the transcriptional response of cardiomyocytes to sonic hedgehog (Shh) and the role of Gi protein utilization. Our results show that Shh strongly activates Gli1 expression by quantitative PCR in a Smo-dependent manner in neonatal rat ventricular cardiomyocytes. Microarray analysis of gene expression changes elicited by Shh and sensitive to a Smo inhibitor identified a small subset of 37 cardiomyocyte-specific genes regulated by Shh, including some in the PKA and purinergic signaling pathways. In addition, neonatal rat ventricular cardiomyocytes infected with an adenovirus encoding GiCT, a peptide that impairs receptor-Gi protein coupling, showed reduced activation of Hh targets. In vitro data were confirmed in transgenic mice with cardiomyocyte-inducible GiCT expression. Transgenic GiCT mice showed specific reduction of Gli1 expression in the heart under basal conditions and failed to upregulate the Hh pathway upon ischemia and reperfusion injury, unlike their littermate controls. This study characterizes, for the first time, the transcriptional response of cardiomyocytes to Shh and establishes a critical role for Smo coupling to Gi in Hh signaling in the normal and ischemic myocardium.

Quantitative proteomic profiling studies of pancreatic cancer stem cells

Analyzing subpopulations of tumor cells in tissue is a challenging subject in proteomic studies. Pancreatic cancer stem cells (CSCs) are such a group of cells that only constitute 0.2-0.8% of the total tumor cells but have been found to be the origin of pancreatic cancer carcinogenesis and metastasis. Global proteome profiling of pancreatic CSCs from xenograft tumors in mice is a promising way to unveil the molecular machinery underlying the signaling pathways. However, the extremely low availability of pancreatic tissue CSCs (around 10,000 cells per xenograft tumor or patient sample) has limited the utilization of currently standard proteomic approaches which do not work effectively with such a small amount of material. Herein, we describe the profiling of the proteome of pancreatic CSCs using a capillary scale shotgun technique by coupling offline capillary isoelectric focusing(cIEF) with nano reversed phase liquid chromatography(RPLC) followed by spectral counting peptide quantification. A whole cell lysate from 10,000 cells which corresponds to approximately 1 microg of protein material is equally divided for three repeated cIEF separations where around 300 ng of peptide material is used in each run. In comparison with a nontumorigenic tumor cell sample, among 1159 distinct proteins identified with FDR less than 0.2%, 169 differentially expressed proteins are identified after multiple testing corrections where 24% of the proteins are upregulated in the CSCs group. Ingenuity Pathway analysis of these differential expression signatures further suggests significant involvement of signaling pathways related to apoptosis, cell proliferation, inflammation, and metastasis.

Hyaluronan regulates ceruloplasmin production by gliomas and their treatment-resistant multipotent progenitors

Ceruloplasmin (glycosylphosphatidylinositol-linked ferroxidase associated with normal astrocytes) can also be secreted by glioma cells, where its function is unknown. Ceruloplasmin is not only present in glioma cells and in human glioma specimens but also is enriched in highly malignant glioma stem-like cells. Hyaluronan is a large extracellular glycosaminoglycan that enhances malignant glioma behaviors by interacting with CD44 receptors and by downstream activation of signaling proteins and transporters associated with malignancy. We examined the relationship between hyaluronan and ceruloplasmin expression in glioma stem-like cells. Antagonism of hyaluronan interactions with short-fragment hyaluronan oligomers decreased ceruloplasmin expression in parental and stem-like glioma cells in vivo and in cell culture, implying that hyaluronan regulates ceruloplasmin expression. Further gain and loss-of-function studies are needed to fully define the relationship between hyaluronan and ceruloplasmin, and ceruloplasmin's effect on malignant behaviors.

Thyroid hormone action in the adult brain: gene expression profiling of the effects of single and multiple doses of triiodo-L-thyronine in the rat striatum

Thyroid hormones have profound effects on mood and behavior, but the molecular basis of thyroid hormone action in the adult brain is relatively unknown. In particular, few thyroid hormone-dependent genes have been identified in the adult brain despite extensive work carried out on the developing brain. In this work we performed global analysis of gene expression in the adult rat striatum in search for genomic changes taking place after administration of T(3) to hypothyroid rats. The hormone was administered in two different schedules: 1) a single, large dose of 25 microg per 100 g body weight (SD) or 2) 1.5 microg per 100 g body weight once daily for 5 d (RD). Twenty-four hours after the single or last of multiple doses, gene expression in the striatum was analyzed using Codelink microarrays. SD caused up-regulation of 149 genes and down-regulation of 88 genes. RD caused up-regulation of 18 genes and down-regulation of one gene. The results were confirmed by hybridization to Affymetrix microarrays and by TaqMan PCR. Among the genes identified are genes involved in circadian regulation and the regulation of signaling pathways in the striatum. These results suggest that thyroid hormone is involved in regulation of striatal physiology at multiple control points. In addition, they may explain the beneficial effects of large doses of thyroid hormone in bipolar disorders.

Frequent expression loss of Inter-alpha-trypsin inhibitor heavy chain (ITIH) genes in multiple human solid tumors: a systematic expression analysis

Background

The inter-alpha-trypsin inhibitors (ITI) are a family of plasma protease inhibitors, assembled from a light chain – bikunin, encoded by AMBP – and five homologous heavy chains (encoded by ITIH1, ITIH2, ITIH3, ITIH4, and ITIH5), contributing to extracellular matrix stability by covalent linkage to hyaluronan. So far, ITIH molecules have been shown to play a particularly important role in inflammation and carcinogenesis.

Methods

We systematically investigated differential gene expression of the ITIH gene family, as well as AMBP and the interacting partner TNFAIP6 in 13 different human tumor entities (of breast, endometrium, ovary, cervix, stomach, small intestine, colon, rectum, lung, thyroid, prostate, kidney, and pancreas) using cDNA dot blot analysis (Cancer Profiling Array, CPA), semiquantitative RT-PCR and immunohistochemistry.

Results

We found that ITIH genes are clearly downregulated in multiple human solid tumors, including breast, colon and lung cancer. Thus, ITIH genes may represent a family of putative tumor suppressor genes that should be analyzed in greater detail in the future. For an initial detailed analysis we chose ITIH2 expression in human breast cancer. Loss of ITIH2 expression in 70% of cases (n = 50, CPA) could be confirmed by real-time PCR in an additional set of breast cancers (n = 36). Next we studied ITIH2 expression on the protein level by analyzing a comprehensive tissue micro array including 185 invasive breast cancer specimens. We found a strong correlation (p < 0.001) between ITIH2 expression and estrogen receptor (ER) expression indicating that ER may be involved in the regulation of this ECM molecule.

Conclusion

Altogether, this is the first systematic analysis on the differential expression of ITIH genes in human cancer, showing frequent downregulation that may be associated with initiation and/or progression of these malignancies.

Squamous cell carcinoma related oncogene/DCUN1D1 is highly conserved and activated by amplification in squamous cell carcinomas

Chromosomal amplification at 3q is common to multiple human cancers, but has a specific predilection for squamous cell carcinomas (SCC) of mucosal origin. We identified and characterized a novel oncogene, SCC-related oncogene (SCCRO), which is amplified along the 3q26.3 region in human SCC. Amplification and overexpression of SCCRO in these tumors correlate with poor clinical outcome. The importance of SCCRO amplification in malignant transformation is established by the apoptotic response to short hairpin RNA against SCCRO, exclusively in cancer cell lines carrying SCCRO amplification. The oncogenic potential of SCCRO is underscored by its ability to transform fibroblasts (NIH-3T3 cells) in vitro and in vivo. We show that SCCRO regulates Gli1--a key regulator of the hedgehog (HH) pathway. Collectively, these data suggest that SCCRO is a novel component of the HH signaling pathway involved in the malignant transformation of squamous cell lineage.

Sonic Hedgehog regulates Hes1 through a novel mechanism that is independent of canonical Notch pathway signalling

Aberrant regulation of signalling mechanisms that normally orchestrate embryonic development, such as the Hedgehog, Wnt and Notch pathways, is a common feature of tumorigenesis. In order to better understand the neoplastic events mediated by Hedgehog signalling, we identified over 200 genes regulated by Sonic Hedgehog in multipotent mesodermal cells. Widespread crosstalk with other developmental signalling pathways is evident, suggesting a complex network of interactions that challenges the often over-simplistic representation of these pathways as simple linear entities. Hes1, a principal effector of the Notch pathway, was found to be a target of Sonic Hedgehog in both C3H/10T1/2 mesodermal and MNS70 neural cells. Desert Hedgehog also elicited a strong Hes1 response. While Smoothened function was found necessary for upregulation of Hes1 in response to Sonic Hedgehog, the mechanism does not require gamma-secretase-mediated cleavage of Notch receptors, and appears to involve transcription factors other than RBP-Jkappa. Thus, we have defined a novel mechanism for Hes1 regulation in stem-like cells that is independent of canonical Notch signalling.

Gli-1 expression is associated with lymph node metastasis and tumor progression in esophageal squamous cell carcinoma

OBJECTIVE

We investigated the expression and function of the hedgehog (Hh) pathway in human esophageal squamous cell carcinoma (ESCC).

METHODS

The expression of Hh pathway molecules were detected in 34 human ESCC cell lines by RT-PCR. Subsequently, we investigated the effects of cyclopamine, a specific inhibitor of the Hh pathway, on cell proliferation, migration and invasion. Next, the effects of siRNA targeting Gli-1 were examined. Immunohistochemically, the expression of Gli-1 was studied in 104 ESCC specimens and compared with the clinicopathological characteristics of the patients.

RESULTS

Gli-1 were expressed in 31 of 34 cell lines (91%), while Sonic hedgehog (SHh), Patched (Ptch), and Smoothened (Smo) expression was noted in all 34 cell lines. Cyclopamine significantly inhibited cell proliferation and migration in ESCC cells that expressed Gli-1. siRNA targeting Gli-1 inhibited cell growth in ESCC cells. Gli-1 was expressed in 52 of 104 cancer specimens (50%). Gli-1 expression was associated with tumor depth (p < 0.001), positive lymph node metastasis (p = 0.004) and a poor prognosis (p = 0.0047).

CONCLUSION

Our results raise the possibility that the inhibition of the Hh pathway could be a novel target for esophageal cancer therapy.

Hedgehog Morphogen in Cardiovascular Disease

In this review, we focus on the basic biology of the important developmental Hedgehog (Hh) protein family, its general function in development, pathway mechanisms, and gene discovery and nomenclature. Hh function in cardiovascular development and recent findings concerning Hh signaling in ischemia models are discussed in more detail, and future perspectives are proposed. In light of the recent discovery of Hh transport by insect lipophorin, we also hypothesize a role for low-density lipoprotein (LDL) in mammalian Hh transport, creating a surprising role for LDL in cardiovascular disease.

Activation of genes for growth factor and cytokine pathways late in chondrogenic differentiation of ATDC5 cells

The mouse embryonal carcinoma cell line ATDC5 provides an excellent model system for chondrogenesis in vitro. To understand better the molecular mechanisms of endochondral bone formation, we investigated gene expression profiles during the differentiation course of ATDC5 cells, using an in-house microarray harboring full-length-enriched cDNAs. For 28 days following chondrogenic induction, 507 genes were up- or down-regulated at least 1.5-fold. These genes were classified into five clusters based on their expression patterns. Genes for growth factor and cytokine pathways were significantly enriched in the cluster characterized by increases in expression during late stages of chondrocyte differentiation. mRNAs for decorin and osteoglycin, which have been shown to bind to transforming growth factors-beta and bone morphogenetic proteins, respectively, were found in this cluster and were detected in hypertrophic chondrocytes of developing mouse bones by in situ hybridization analysis. Taken together with assigned functions of individual genes in the cluster, interdigitated interaction between a number of intercellular signaling molecules is likely to take place in the late chondrogenic stage for autocrine and paracrine regulation among chondrocytes, as well as for chemoattraction and stimulation of progenitor cells of other lineages.

Molecular genetic analysis of a de novo balanced translocation t(6;17)(p21.31;q11.2) associated with hypospadias and anorectal malformation

We report a young boy with penoscrotal hypospadias, anal atresia (AA) with a recto-urethral fistula, a hypoplastic kidney and a balanced translocation t(6;17)(p21.31;q11.2). Physical mapping of the breakpoints localized the chromosome 6 breakpoint within an intron of the gene lipoma HMGIC fusion partner-like 5 (LHFPL5) whereas the chromosome 17 breakpoint was mapped to the first intron of the 182-FIP gene encoding the Fragile X Mental Retardation Protein Interacting Protein. Sequence analysis across the breakpoints revealed an almost perfectly balanced translocation with a 2 bp deletion on the derivative chromosome 6 and a 7 bp duplication on the derivative chromosome 17. We identified a fusion transcript consisting of the first exon of 182-FIP and the last exon of LHFPL5 in patient-derived cells. Quantitative expression analysis of the genes flanking the breakpoints, revealed increased transcript levels for SFRS protein kinase 1 (SRPK1) and TAO kinase 1 (TAOK1) which suggests a positional effect due to the translocation. We hypothesize that the urogenital and anorectal malformations in the patient result from one or several mechanisms including disruption of the genes 182-FIP and LHFPL5, altered expression of the genes flanking the translocation breakpoints and, a gain of function mechanism mediated by the 182-FIP-LHFPL5 fusion transcript.

Microarray analysis of the genes induced by tetracycline-regulated expression of NDRF/NeuroD2 in P19 cells

NeuroD-related factor (NDRF)/NeuroD2 is a basic helix-loop-helix (bHLH) protein that plays important roles in neuronal development. To elucidate the NDRF transcription network, we used mouse cDNA microarray analysis combined with a tetracycline-regulatable expression system in P19 embryonal carcinoma cells. Five genes were identified to be up-regulated in the presence of NDRF protein. RNA hybridization analysis confirmed that brain-lipid-binding protein (BLBP) and inhibitor of differentiation 1 (Id1) genes were among the five genes that were rapidly and significantly up-regulated after induction of NDRF. When a dominant negative form of NDRF protein was expressed during retinoic acid-induced neuronal differentiation of P19 cells, the BLBP gene, but not the Id1 gene, was potently repressed. Immunohistochemical analysis revealed that both NDRF and Id1 immunoreactivities were observed in some granule cells of the cerebellum in the postnatal period. These results suggest that NDRF or its related bHLH proteins may act upstream of these genes in a subset of developing neurons.

Purmorphamine induces osteogenesis by activation of the hedgehog signaling pathway

Previously, a small molecule, purmorphamine, was identified that selectively induces osteogenesis in multipotent mesenchymal progenitor cells. In order to gain insights into the mechanism of action of purmorphamine, high-density oligonucleotide microarrays were used to profile gene expression in multipotent mesenchymal progenitor cells treated with either purmorphamine or bone morphogenetic protein-4 (BMP-4). In contrast to BMP-4 treatment, purmorphamine activates the Hedgehog (Hh) signaling pathway, resulting in the up- and downregulation of its downstream target genes, including Gli1 and Patched. Moreover, the known Hh signaling antagonists, cyclopamine and forskolin, completely block the osteogenesis and Glimediated transcription induced by purmorphamine. These results demonstrate that purmorphamine is a small molecule agonist of Hedgehog signaling, and it may ultimately be useful in the treatment of bone-related disease and neurodegenerative disease.

Sonic hedgehog gene-enhanced tissue engineering for bone regeneration

Improved methods of bone regeneration are needed in the craniofacial rehabilitation of patients with significant bone deficits secondary to tumor resection, congenital deformities, and prior to prosthetic dental reconstruction. In this study, a gene-enhanced tissue-engineering approach was used to assess bone regenerative capacity of Sonic hedgehog (Shh)-transduced gingival fibroblasts, mesenchymal stem cells, and fat-derived cells delivered to rabbit cranial bone defects in an alginate/collagen matrix. Human Shh cDNA isolated from fetal lung tissue was cloned into the replication-incompetent retroviral expression vector LNCX, in which the murine leukemia virus retroviral LTR drives expression of the neomycin-resistance gene. The rat beta-actin enhancer/promoter complex was engineered to drive expression of Shh. Reverse transcriptase-polymerase chain reaction analysis demonstrated that the transduced primary rabbit cell populations expressed Shh RNA. Shh protein secretion was confirmed by enzyme-linked immunosorbent assay (ELISA). Alginate/ type I collagen constructs containing 2 x 10(6) Shh-transduced cells were introduced into male New Zealand White rabbit calvarial defects (8 mm). A total of eight groups (N=6) were examined: unrestored empty defects, matrix alone, matrix plus the three cell populations transduced with both control and Shh expression vectors. The bone regenerative capacity of Shh gene enhanced cells was assessed grossly, radiographically and histologically at 6 and 12 weeks postimplantation. After 6 weeks, new full thickness bone was seen emanating directly from the alginate/collagen matrix in the Shh-transduced groups. Quantitative two-dimensional digital analysis of histological sections confirmed statistically significant (P<0.05) amounts of bone regeneration in all three Shh-enhanced groups compared to controls. Necropsy failed to demonstrate any evidence of treatment-related side effects. This is the first study to demonstrate that Shh delivery to bone defects, in this case through a novel gene-enhanced tissue-engineering approach, results in significant bone regeneration. This encourages further development of the Shh gene-enhanced tissue-engineering approach for bone regeneration.

The Gene Expression Profile of Cyst Epithelial Cells in Autosomal Dominant Polycystic Kidney Disease Patients

Autosomal dominant polycystic kidney disease (ADPKD) is a common genetic disorder characterized by the formation of fluid-filled cysts in the kidney and progressive renal failure. Other manifestations of ADPKD include the formation of cysts in other organs (liver, pancreas, and spleen), hypertension, cardiac defects, and cerebral aneurysms. The loss of function of the polycystin -1 and -2 results in the formation of epithelium-lined cysts, a process that depends on initial epithelial proliferation. cDNA microarrays powerfully monitor gene expression and have led to the discoveries of pathways regulating complex biological processes. We undertook to profile the gene expression patterns of epithelial cells derived from the cysts of ADPKD patients using the cDNA microarray technique. Candidate genes that were differently expressed in cyst tissues were identified. 19 genes were up-regulated, and 6 down-regulated. Semi-quantitative RT-PCR results were consistent with the microarray findings. To distinguish between normal and epithelial cells, we used the hierarchical method. The results obtained may provide a molecular basis for understanding the biological meaning of cytogenesis.

Hedgehog: an unusual signal transducer

Hedgehog proteins are of pivotal importance for development and maintenance of tissue patterns in adult organisms. Despite the role of Hedgehogs in differentiation and tumorigenesis, signal transduction of Hedgehog remains a relatively uncharted area of signalling biochemistry. For proper Hedgehog distribution into tissues, two highly unusual covalent modifications are necessary, palmitoylation of a secreted protein and the attachment of a cholesterol group, making Hedgehog the only established sterolated protein in nature. Hedgehog exerts its function via two membrane-bound receptors, Patched and Smoothened; presumably, Patched transports a cholesterol derivate out of cells which inhibits Smoothened. Binding of Hedgehog to Patched impedes this proposed pump function and thus Inhibition of Smoothened, which leads to expression of genetic Hedgehog targets via relief of transcriptional repression. These atypical features make Hedgehog physiology unique in biology and may explain why this field has attracted such significant attention.

BMPR1A signaling is necessary for hair follicle cycling and hair shaft differentiation in mice

Interactions between ectodermal and mesenchymal extracellular signaling pathways regulate hair follicle (HF) morphogenesis and hair cycling. Bone morphogenetic proteins (BMPs) are known to be important in hair follicle development by affecting the local cell fate modulation. To study the role of BMP signaling in the HF, we disrupted Bmpr1a, which encodes the BMP receptor type IA (BMPR1A) in an HF cell-specific manner, using the Cre/loxP system. We found that the differentiation of inner root sheath, but not outer root sheath, was severely impaired in mutant mice. The number of HFs was reduced in the dermis and subcutaneous tissue, and cycling epithelial cells were reduced in mutant mice HFs. Our results strongly suggest that BMPR1A signaling is essential for inner root sheath differentiation and is indispensable for HF renewal in adult skin.

Application of microarray technology in environmental and comparative physiology

DNA microarray technology is revolutionizing many aspects of biological research, allowing the expression of many thousands of gene transcripts to be monitored simultaneously. This provides powerful tools for the genome-wide correlation of gene transcript levels with physiological responses and alterations in physiological states. To date, microarray analyses have been applied almost exclusively to a few model species for which the abundant gene sequence data permit the fabrication of whole-genome microarrays. However, many interesting physiological traits and responses are poorly expressed or absent in model species and may be better illustrated in nonmodel organisms. Comparative approaches to understanding function traditionally focus on species that by virtue of their unusual adaptations, lifestyles, and phylogeny are particularly suited to address a specific biological process or problem. In this review, we show that microarray technology can be successfully applied to these nonmodel species and used to generate new insights of comparative and evolutionary significance into animal function.

Novel genes regulated by Sonic Hedgehog in pluripotent mesenchymal cells

Sonic Hedgehog is a secreted morphogen involved in patterning a wide range of structures in the developing embryo. Disruption of the Hedgehog signalling cascade leads to a number of developmental disorders and plays a key role in the formation of a range of human cancers. The identification of genes regulated by Hedgehog is crucial to understanding how disruption of this pathway leads to neoplastic transformation. We have used a Sonic Hedgehog (Shh) responsive mouse cell line, C3H/10T1/2, to provide a model system for hedgehog target gene discovery. Following activation of cell cultures with Shh, RNA was used to interrogate microarrays to investigate downstream transcriptional consequences of hedgehog stimulation. As a result 11 target genes have been identified, seven of which are induced (Thrombomodulin, GILZ, BF-2, Nr4a1, IGF2, PMP22, LASP1) and four of which are repressed (SFRP-1, SFRP-2, Mip1-gamma, Amh) by Shh. These targets have a diverse range of putative functions and include transcriptional regulators and molecules known to be involved in regulating cell growth or apoptosis. The corroboration of genes previously implicated in hedgehog signalling, along with the finding of novel targets, demonstrates both the validity and power of the C3H/10T1/2 system for Shh target gene discovery.

The human prostate expresses sonic hedgehog during fetal development

PURPOSE

The keynote event of prostate ductal development is the formation of epithelial buds that invade the urogenital sinus mesenchyma. Studies in mice have shown that budding requires the signaling peptide, which is expressed in the epithelium of the prostatic anlagen. We report our characterization of (SHH) expression in the human fetal prostate.

MATERIALS AND METHODS

Reverse transcriptase-polymerase chain reaction was performed in fetal prostate RNA isolated at 15.5 and 18 weeks of gestation, respectively. Immunostaining was performed on sections from 7 male fetuses at 9.5 to 34 and in 4 female fetuses at 9 to 18 weeks of gestation.

RESULTS

Weak staining for was seen in the prostatic urethra at 9.5 weeks. Intense staining was seen at 11.5 and 13 weeks in the prostatic urothelium and nascent prostatic buds. Staining was slightly diminished at 16.5, further diminished at 18 to 20 and absent at 34 weeks. expression at 15.5 and 18 weeks was confirmed by reverse transcriptase-polymerase chain reaction assay of freshly isolated prostate tissue. Comparative immunostaining in the female showed urothelial staining at 9 and 12 weeks with staining greatest above the entrance of the müllerian ducts. Staining diminished earlier in the female (14 weeks) than in the male and was almost absent at 18 weeks.

CONCLUSIONS

expression in the human fetal prostate is contemporaneous with the fetal testosterone surge and with ductal budding of the prostatic urothelium. expression is also present in the female urogenital sinus but in the absence of testosterone it is not associated with ductal budding.

Gli and hedgehog in cancer: tumours, embryos and stem cells

Do tumours arise from stem cells, or are they derived from more differentiated cells that, for some reason, begin to recapitulate developmental programmes? Inappropriate activation of the Sonic hedgehog-Gli signalling pathway occurs in several types of tumour, including those of the brain and the skin. Studies in these and other systems suggest that inappropriate function of the Gli transcription factors in stem or precursor cells might lead to the onset of a tumorigenic programme and that these factors are prime targets for anticancer therapies.