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Salem O, Wang HT, Alaseem AM, Ciobanu O, Hadjab I, Gawri R, Antoniou J, Mwale F. Naproxen affects osteogenesis of human mesenchymal stem cells via regulation of Indian hedgehog signaling molecules. Arthritis Res Ther 2014; 16:R152. [PMID: 25034046 PMCID: PMC4223691 DOI: 10.1186/ar4614] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2014] [Accepted: 07/04/2014] [Indexed: 12/12/2022] Open
Abstract
INTRODUCTION We previously showed that type X collagen, a marker of late stage chondrocyte hypertrophy (associated with endochondral ossification), is constitutively expressed by mesenchymal stem cells (MSCs) from osteoarthritis patients and this may be related to Naproxen (Npx), a nonsteroidal anti-inflammatory drug used for therapy. Hedgehog (HH) signaling plays an important role during the development of bone. We tested the hypothesis that Npx affected osteogenic differentiation of human MSCs through the expression of Indian hedgehog (IHH), Patched-1 (PTC1) and GLI family members GLI1, GLI2, GLI3 in vitro. METHODS MSCs were cultured in osteogenic differentiation medium without (control) or with 0.5 μM Npx. The expression of collagen type X, alpha 1 (COL10A1), alkaline phosphatase (ALP), osteopontin (OPN), osteocalcin (OC), collagen type I, alpha 1 (COL1A1) was analyzed with real-time reverse transcription (RT) PCR, and the ALP activity was measured. The osteogenesis of MSCs was monitored by mineral staining and quantification with alizarin red S. To examine whether Npx affects osteogenic differentiation through HH signaling, the effect of Npx on the expression of IHH, GLI1, GLI2, GLI3 and PTC1 was analyzed with real-time RT PCR. The effect of cyclopamine (Cpn), a HH signaling inhibitor, on the expression of COL10A1, ALP, OC and COL1A1 was also determined. RESULTS When MSCs were cultured in osteogenic differentiation medium, Npx supplementation led to a significant decrease in ALP gene expression as well as its activity, and had a tendency to decrease mineral deposition. It also decreased the expression of COL1A1 significantly. In contrast, the gene expression of COL10A1 and OPN were upregulated significantly by Npx. No significant effect was found on OC expression. The expression of IHH, PTC1, GLI1, and GLI2 was increased by Npx, while no significant difference was observed on GLI3 expression. Cpn reversed the effect of Npx on the expression of COL10A1, ALP, OPN and COL1A1. CONCLUSIONS These results indicate that Npx can affect gene expression during osteogenic differentiation of MSCs, and downregulate mineral deposition in the extracellular matrix through IHH signaling. Therefore, Npx could affect MSC-mediated repair of subchondral bone in OA patients.
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Transcriptional regulation of graded Hedgehog signaling. Semin Cell Dev Biol 2014; 33:73-80. [PMID: 24862856 DOI: 10.1016/j.semcdb.2014.05.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2014] [Revised: 05/07/2014] [Accepted: 05/08/2014] [Indexed: 02/06/2023]
Abstract
The Hedgehog (Hh) pathway plays conserved roles in regulating a diverse spectrum of developmental processes. In some developmental contexts, a gradient of Hh protein specifies multiple cell types in a dose-dependent fashion, thereby acting as a morphogen. Hh signaling ultimately acts on the transcriptional level through GLI proteins. In the presence of Hh signaling full length GLI proteins act as transcriptional activators of target genes. Conversely, in the absence of Hh, GLI proteins act as transcriptional repressors. This review will highlight mechanisms contributing to how graded Hh signaling might translate to differential GLI activity and be interpreted into distinct transcriptional responses.
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Wu J, Lu X, Wang Z, Shangguan S, Chang S, Li R, Wu L, Bao Y, Niu B, Wang L, Zhang T. Association between PKA gene polymorphism and NTDs in high risk Chinese population in Shanxi. INTERNATIONAL JOURNAL OF CLINICAL AND EXPERIMENTAL PATHOLOGY 2013; 6:2968-2974. [PMID: 24294386 PMCID: PMC3843280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 10/08/2013] [Indexed: 06/02/2023]
Abstract
OBJECTIVE This study aimed to investigate the single nucleotide polymorphisms (SNPs) of PKA and neural tube defects (NTDs) in Chinese population. METHOD A total of 183 NTDs cases and 200 healthy controls were used in this study. 7 selected single nucleotide polymorphism (SNP) sites in the PKA gene were analyzed with MassArray high-throughput DNA analyzer with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. A series of statistical methods were carried out to investigate the correlation between the SNPs and the patient susceptibility to NTDs. RESULTS Statistical analysis showed a significant correlation between the SNP sites rs12132032 in PRKACB and NTDs. The AA genotype, A-allele and dominant AA in rs12132032 significantly increased the incidence of NTDs especially anencephaly (OR=3.87, 95% CI: 1.80-8.34 with genotype; OR=2.08, 95% CI: 1.43-3.04 with allele; OR=3.10, 95% CI: 1.53-6.26 with dominant). The T-allele of rs594631 in PRKACB was correlative with NTDs in male but not in female. CONCLUSIONS The gene polymorphism loci rs12132032 in PRKACB maybe a potential risk factor for anencephaly in Chinese population from Shanxi, while gender susceptibility may influence the correlation.
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Affiliation(s)
- Jian Wu
- Capital University of Physical Education and SportsBeijing 100044, China
| | - Xiaolin Lu
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of PediatricsBeijing 100020, China
| | - Zhen Wang
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of PediatricsBeijing 100020, China
| | - Shaofang Shangguan
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of PediatricsBeijing 100020, China
| | - Shaoyan Chang
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of PediatricsBeijing 100020, China
| | - Rui Li
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of PediatricsBeijing 100020, China
| | - Lihua Wu
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of PediatricsBeijing 100020, China
| | - Yihua Bao
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of PediatricsBeijing 100020, China
| | - Bo Niu
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of PediatricsBeijing 100020, China
| | - Li Wang
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of PediatricsBeijing 100020, China
| | - Ting Zhang
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of PediatricsBeijing 100020, China
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Lu X, Wang Z, Wang J, Shangguan S, Bao Y, Lu P, Wang L. An association study betweenSUFUgene polymorphisms and neural tube defects. Int J Neurosci 2013; 124:436-42. [DOI: 10.3109/00207454.2013.849249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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55
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Wang Z, Shangguan S, Lu X, Chang S, Li R, Wu L, Bao Y, Niu B, Wang L, Zhang T. Association of SMO polymorphisms and neural tube defects in the Chinese population from Shanxi Province. Int J Clin Exp Med 2013; 6:960-966. [PMID: 24260604 PMCID: PMC3832335] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2013] [Accepted: 10/29/2013] [Indexed: 06/02/2023]
Abstract
OBJECTIVE This study aimed to investigate the single nucleotide polymorphisms (SNPs) of SMO and neural tube defects (NTDs) in Chinese population. METHOD A total of 113 NTDs cases and 138 healthy controls were used in this study. 10 selected single nucleotide polymorphism (SNP) sites in the SMO gene were analyzed with MassArray high-throughput DNA analyzer with matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. A series of statistical methods were carried out to investigate the correlation between the SNPs and the patient susceptibility to NTDs. RESULTS The C allele of rs3824 increased the risk of spina bifida (OR=2.52; 95% CI: 1.18, 5.38; p=0.026) but not the risk of anencephaly or encephalocele. Significant differences were found between spina bifida and controls when we compared the GG group with the CC+CG group (OR=2.66; 95% CI: 1.26, 5.61; p=0.011). CC+CG genotype was a risk factor for spina bifida. CONCLUSIONS The gene polymorphism loci rs3824 of SMO was closely related to spina bifida in Chinese population from Shanxi. The haplotype GA in rs3824 and rs9706 increased the risk of NTDs particularly spina bifida in women.
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Affiliation(s)
- Zhen Wang
- Beijing Municipal Key Laboratory of Child Development and Nutriomics, Capital Institute of Pediatrics Beijing 100020, China
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Ma X, Turnbull P, Peterson R, Turnbull J. Trophic and proliferative effects of Shh on motor neurons in embryonic spinal cord culture from wildtype and G93A SOD1 mice. BMC Neurosci 2013; 14:119. [PMID: 24119209 PMCID: PMC3852546 DOI: 10.1186/1471-2202-14-119] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 09/18/2013] [Indexed: 12/01/2022] Open
Abstract
Background The developmental morphogen sonic hedgehog (Shh) may continue to play a trophic role in the support of terminally-differentiated motor neurons, of potential relevance to motor neuron disease. In addition, it may support the proliferation and differentiation of endogenous stem cells along motor neuronal lineages. As such, we have examined the trophic and proliferative effects of Shh supplementation or Shh antagonism in embryonic spinal cord cell cultures derived from wildtype or G93A SOD1 mice, a mouse model of amyotrophic lateral sclerosis. Results Shh supported survival, and stimulated growth of motor neurons, neurite outgrowth, and neurosphere formation in primary culture derived from both G93A SOD1 and WT mice. Shh increased the percentage of ciliated motor neurons, especially in G93A SOD1 culture. Shh-treated cultures showed increased neuronal proliferation compared to controls and especially cyclopamine treated cultures, from G93A SOD1 and WT mice. Moreover, Shh enhanced cell survival and differentiation of motor neuron precursors in WT culture. Conclusions Shh is neurotrophic to motor neurons and has mitogenic effects in WT and mSOD1 G93A culture in vitro.
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Affiliation(s)
- Xiaoxing Ma
- Department of Medicine, McMaster University, 1200 Main St West, Hamilton, ON L8N 3Z5, Canada.
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Abbasi AA, Minhas R, Schmidt A, Koch S, Grzeschik KH. Cis-regulatory underpinnings of human GLI3 expression in embryonic craniofacial structures and internal organs. Dev Growth Differ 2013; 55:699-709. [PMID: 24102645 DOI: 10.1111/dgd.12076] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Revised: 07/24/2013] [Accepted: 08/06/2013] [Indexed: 12/16/2022]
Abstract
The zinc finger transcription factor Gli3 is an important mediator of Sonic hedgehog (Shh) signaling. During early embryonic development Gli3 participates in patterning and growth of the central nervous system, face, skeleton, limb, tooth and gut. Precise regulation of the temporal and spatial expression of Gli3 is crucial for the proper specification of these structures in mammals and other vertebrates. Previously we reported a set of human intronic cis-regulators controlling almost the entire known repertoire of endogenous Gli3 expression in mouse neural tube and limbs. However, the genetic underpinning of GLI3 expression in other embryonic domains such as craniofacial structures and internal organs remain elusive. Here we demonstrate in a transgenic mice assay the potential of a subset of human/fish conserved non-coding sequences (CNEs) residing within GLI3 intronic intervals to induce reporter gene expression at known regions of endogenous Gli3 transcription in embryonic domains other than central nervous system (CNS) and limbs. Highly specific reporter expression was observed in craniofacial structures, eye, gut, and genitourinary system. Moreover, the comparison of expression patterns directed by these intronic cis-acting regulatory elements in mouse and zebrafish embryos suggests that in accordance with sequence conservation, the target site specificity of a subset of these elements remains preserved among these two lineages. Taken together with our recent investigations, it is proposed here that during vertebrate evolution the Gli3 expression control acquired multiple, independently acting, intronic enhancers for spatiotemporal patterning of CNS, limbs, craniofacial structures and internal organs.
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Affiliation(s)
- Amir A Abbasi
- Faculty of Biological Sciences, National Center for Bioinformatics, Program of Comparative and Evolutionary Genomics, Quaid-i-Azam University, Islamabad, 45320, Pakistan
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Yu K, McGlynn S, Matise MP. Floor plate-derived sonic hedgehog regulates glial and ependymal cell fates in the developing spinal cord. Development 2013; 140:1594-604. [PMID: 23482494 DOI: 10.1242/dev.090845] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Cell fate specification in the CNS is controlled by the secreted morphogen sonic hedgehog (Shh). At spinal cord levels, Shh produced by both the notochord and floor plate (FP) diffuses dorsally to organize patterned gene expression in dividing neural and glial progenitors. Despite the fact that two discrete sources of Shh are involved in this process, the individual contribution of the FP, the only intrinsic source of Shh throughout both neurogenesis and gliogenesis, has not been clearly defined. Here, we have used conditional mutagenesis approaches in mice to selectively inactivate Shh in the FP (Shh(FP)) while allowing expression to persist in the notochord, which underlies the neural tube during neurogenesis but not gliogenesis. We also inactivated Smo, the common Hh receptor, in neural tube progenitors. Our findings confirm and extend prior studies suggesting an important requirement for Shh(FP) in specifying oligodendrocyte cell fates via repression of Gli3 in progenitors. Our studies also uncover a connection between embryonic Shh signaling and astrocyte-mediated reactive gliosis in adults, raising the possibility that this pathway is involved in the development of the most common cell type in the CNS. Finally, we find that intrinsic spinal cord Shh signaling is required for the proper formation of the ependymal zone, the epithelial cell lining of the central canal that is also an adult stem cell niche. Together, our studies identify a crucial late embryonic role for Shh(FP) in regulating the specification and differentiation of glial and epithelial cells in the mouse spinal cord.
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Affiliation(s)
- Kwanha Yu
- Department of Neuroscience and Cell Biology, UMDNJ/Robert Wood Johnson Medical School, 675 Hoes Lane, Piscataway, NJ 08840, USA
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Peterson KA, Nishi Y, Ma W, Vedenko A, Shokri L, Zhang X, McFarlane M, Baizabal JM, Junker JP, van Oudenaarden A, Mikkelsen T, Bernstein BE, Bailey TL, Bulyk ML, Wong WH, McMahon AP. Neural-specific Sox2 input and differential Gli-binding affinity provide context and positional information in Shh-directed neural patterning. Genes Dev 2013; 26:2802-16. [PMID: 23249739 DOI: 10.1101/gad.207142.112] [Citation(s) in RCA: 127] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In the vertebrate neural tube, regional Sonic hedgehog (Shh) signaling invokes a time- and concentration-dependent induction of six different cell populations mediated through Gli transcriptional regulators. Elsewhere in the embryo, Shh/Gli responses invoke different tissue-appropriate regulatory programs. A genome-scale analysis of DNA binding by Gli1 and Sox2, a pan-neural determinant, identified a set of shared regulatory regions associated with key factors central to cell fate determination and neural tube patterning. Functional analysis in transgenic mice validates core enhancers for each of these factors and demonstrates the dual requirement for Gli1 and Sox2 inputs for neural enhancer activity. Furthermore, through an unbiased determination of Gli-binding site preferences and analysis of binding site variants in the developing mammalian CNS, we demonstrate that differential Gli-binding affinity underlies threshold-level activator responses to Shh input. In summary, our results highlight Sox2 input as a context-specific determinant of the neural-specific Shh response and differential Gli-binding site affinity as an important cis-regulatory property critical for interpreting Shh morphogen action in the mammalian neural tube.
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Affiliation(s)
- Kevin A Peterson
- Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, Massachusetts 02138, USA
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Oosterveen T, Kurdija S, Alekseenko Z, Uhde CW, Bergsland M, Sandberg M, Andersson E, Dias JM, Muhr J, Ericson J. Mechanistic differences in the transcriptional interpretation of local and long-range Shh morphogen signaling. Dev Cell 2013; 23:1006-19. [PMID: 23153497 DOI: 10.1016/j.devcel.2012.09.015] [Citation(s) in RCA: 83] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 07/20/2012] [Accepted: 09/18/2012] [Indexed: 01/08/2023]
Abstract
Morphogens orchestrate tissue patterning in a concentration-dependent fashion during vertebrate embryogenesis, yet little is known of how positional information provided by such signals is translated into discrete transcriptional outputs. Here we have identified and characterized cis-regulatory modules (CRMs) of genes operating downstream of graded Shh signaling and bifunctional Gli proteins in neural patterning. Unexpectedly, we find that Gli activators have a noninstructive role in long-range patterning and cooperate with SoxB1 proteins to facilitate a largely concentration-independent mode of gene activation. Instead, the opposing Gli-repressor gradient is interpreted at transcriptional levels, and, together with CRM-specific repressive input of homeodomain proteins, comprises a repressive network that translates graded Shh signaling into regional gene expression patterns. Moreover, local and long-range interpretation of Shh signaling differs with respect to CRM context sensitivity and Gli-activator dependence, and we propose that these differences provide insight into how morphogen function may have mechanistically evolved from an initially binary inductive event.
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Affiliation(s)
- Tony Oosterveen
- Department of Cell and Molecular Biology, Karolinska Institutet, 171 77 Stockholm, Sweden.
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Abstract
Sonic hedgehog (Shh) signaling is critical for various developmental processes including specification of the midbrain dopamine (mDA) neurons in the ventral mesencephalon (vMes). While the timing of Shh and its response gene Gli1 segregates mDA neurons, their overall lineage contribution to mDA neurons heavily overlaps. Here, we demonstrate that the same set of mDA neuron progenitors sequentially respond to Shh signaling (Gli1 expression), induce Shh expression, and then turn off Shh responsiveness. Thus, at any given developmental stage, cells rarely co-express Shh and Gli1. Using Shh(Cre:GFP) mice to delete the Smoothened receptor in the Shh pathway, we demonstrate that the loss of Shh signaling in Shh expressing cells results in a transient increase in proliferation and subsequent depletion of mDA neuron progenitors in the posterior vMes due to the facilitated cell cycle exit. Moreover, the change in duration of Shh signaling in vMes progenitors altered the timing of the contribution to the ventral tegmental area (VTA) and the substantia nigra pars compacta (SNc) mDA neurons. Taken together, our investigation on the relationship between the Shh-secreting and -responding cells revealed an intricate regulation of induction and cessation of Shh signaling that influences the distribution of mDA neurons in the VTA and SNc.
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Affiliation(s)
- Lindsay Hayes
- Program in Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
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Law KKL, Makino S, Mo R, Zhang X, Puviindran V, Hui CC. Antagonistic and cooperative actions of Kif7 and Sufu define graded intracellular Gli activities in Hedgehog signaling. PLoS One 2012; 7:e50193. [PMID: 23166838 PMCID: PMC3500354 DOI: 10.1371/journal.pone.0050193] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2012] [Accepted: 10/22/2012] [Indexed: 01/18/2023] Open
Abstract
Graded Hedgehog (Hh) signaling governs the balance of Gli transcriptional activators and repressors to specify diverse ventral cell fates in the spinal cord. It remains unclear how distinct intracellular Gli activity is generated. Here, we demonstrate that Sufu acts universally as a negative regulator of Hh signaling, whereas Kif7 inhibits Gli activity in cooperation with, and independent of, Sufu. Together, they deter naïve precursors from acquiring increasingly ventral identity. We show that Kif7 is also required to establish high intracellular Gli activity by antagonizing the Sufu-inhibition of Gli2. Strikingly, by abolishing the negative regulatory action of Sufu, diverse ventral cell fates can be specified in the absence of extracellular Hh signaling. These data suggest that Sufu is the primary regulator of graded Hh signaling and establish that the antagonistic and cooperative actions of Kif7 and Sufu are responsible for setting up distinct Gli activity in ventral cell fate specification.
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Affiliation(s)
- Kelvin King Lo Law
- Program in Developmental & Stem Cell Biology, The Hospital for Sick Children, Toronto Medical Discovery Tower, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Shigeru Makino
- Mutagenesis and Genomics Team, RIKEN BioResource Center, Koyadai, Tsukuba, Ibaraki, Japan
| | - Rong Mo
- Program in Developmental & Stem Cell Biology, The Hospital for Sick Children, Toronto Medical Discovery Tower, Toronto, Ontario, Canada
| | - Xiaoyun Zhang
- Program in Developmental & Stem Cell Biology, The Hospital for Sick Children, Toronto Medical Discovery Tower, Toronto, Ontario, Canada
| | - Vijitha Puviindran
- Program in Developmental & Stem Cell Biology, The Hospital for Sick Children, Toronto Medical Discovery Tower, Toronto, Ontario, Canada
| | - Chi-chung Hui
- Program in Developmental & Stem Cell Biology, The Hospital for Sick Children, Toronto Medical Discovery Tower, Toronto, Ontario, Canada
- Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
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Rapacioli M, Botelho J, Cerda G, Duarte S, Elliot M, Palma V, Flores V. Sonic hedgehog (Shh)/Gli modulates the spatial organization of neuroepithelial cell proliferation in the developing chick optic tectum. BMC Neurosci 2012. [PMID: 23031710 DOI: 10.1186/1471‐2202‐13‐117] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Sonic hedgehog (Shh)/Gli pathway plays an important regulatory role on the neuroepithelial cells (NEc) proliferation in the dorsal regions of the developing vertebrate Central Nervous System. The aim of this paper was to analyze the effect of the Shh/Gli signaling pathway activation on the proliferation dynamics and/or the spatial organization of the NEc proliferation activity during early stages of the developing chick optic tectum (OT). In ovo pharmacological gain and loss of hedgehog function approaches were complemented with in vivo electroporation experiments in order to create ectopic sources of either Shh or Gli activator (GliA) proteins in the OT. NEc proliferating activity was analyzed at ED 4/4.5 by recording the spatial co-ordinates of the entire population of mitotic NEc (mNEc) located along OT dorsal-ventral sections. Several space signals (numerical sequences) were derived from the mNEc spatial co-ordinate records and analyzed by different standardized non-linear methods of signal analysis. RESULTS In ovo pharmacologic treatment with cyclopamine resulted in dramatic failure in the OT expansion while the agonist purmorphamine produced the opposite result, a huge expansion of the OT vesicle. Besides, GliA and Shh misexpressions interfere with the formation of the intertectal fissure located along the dorsal midline. This morphogenetic alteration is accompanied by an increase in the mNEc density. There is a gradient in the response of NEcs to Shh and GliA: the increase in mNEc density is maximal near the dorsal regions and decrease towards the OT-tegmental boundary. Biomathematical analyses of the signals derived from the mNEc records show that both Shh and GliA electroporations change the proliferation dynamics and the spatial organization of the mNEc as revealed by the changes in the scaling index estimated by these methods. CONCLUSIONS The present results show that the Shh/Gli signaling pathway plays a critical role in the OT expansion and modelling. This effect is probably mediated by a differential mitogenic effect that increases the NEc proliferation and modulates the spatial organization of the NEc proliferation activity.
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Affiliation(s)
- Melina Rapacioli
- Interdisciplinary Group in Theoretical Biology, Department Biostructural Sciences, Favaloro University, Solís 453 (1078), Buenos Aires, Argentina
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Yang L, Huang S, Bian Y, Ma X, Zhang H, Xie J. Identification of signature genes for detecting hedgehog signaling activation in gastric cancer. Mol Med Rep 2012; 3:473-8. [PMID: 21472265 DOI: 10.3892/mmr_00000283] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
The aim of this study was to investigate the expression of hedgehog signaling molecules in gastric cancer. In situ hybridization, immunohistochemistry and RT-PCR for hedgehog signaling molecules, smoothened (SMO), suppressor of fused [Su(Fu)], and the target genes hedgehog-interacting protein (HIP) and platelet-derived growth factor receptor α (PDGFRα) were performed in 30 gastric cancer and two gastritis specimens. Using in situ hybridization, SMO expression was detected in 18/30 cancerous specimens (60%) as well as in 1/2 gastritis specimens (50%). Su(Fu) was expressed in 15/30 (50%), HIP in 14/30 (≈47%), and PDGFRα in 6/30 (20%) gastric cancer specimens. Despite the heterogeneous expression pattern, SMO, Su(Fu) and PDGFRα transcripts were highly correlated with the HIP transcript in the 30 gastric cancer specimens (p=0.0006, 0.0003 and 0.0441, respectively). Results from the in situ hybridization were further confirmed by RT-PCR for the expression of all of the genes and by immunohistochemistry for SMO expression. The findings revealed a set of genes for detecting Hh signaling activation in gastric cancer.
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Affiliation(s)
- Ling Yang
- Institute of Developmental Biology, School of Life Sciences, Shandong University, Shandong 250100, P.R. China
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65
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Rapacioli M, Botelho J, Cerda G, Duarte S, Elliot M, Palma V, Flores V. Sonic hedgehog (Shh)/Gli modulates the spatial organization of neuroepithelial cell proliferation in the developing chick optic tectum. BMC Neurosci 2012; 13:117. [PMID: 23031710 PMCID: PMC3564940 DOI: 10.1186/1471-2202-13-117] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 09/26/2012] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND Sonic hedgehog (Shh)/Gli pathway plays an important regulatory role on the neuroepithelial cells (NEc) proliferation in the dorsal regions of the developing vertebrate Central Nervous System. The aim of this paper was to analyze the effect of the Shh/Gli signaling pathway activation on the proliferation dynamics and/or the spatial organization of the NEc proliferation activity during early stages of the developing chick optic tectum (OT). In ovo pharmacological gain and loss of hedgehog function approaches were complemented with in vivo electroporation experiments in order to create ectopic sources of either Shh or Gli activator (GliA) proteins in the OT. NEc proliferating activity was analyzed at ED 4/4.5 by recording the spatial co-ordinates of the entire population of mitotic NEc (mNEc) located along OT dorsal-ventral sections. Several space signals (numerical sequences) were derived from the mNEc spatial co-ordinate records and analyzed by different standardized non-linear methods of signal analysis. RESULTS In ovo pharmacologic treatment with cyclopamine resulted in dramatic failure in the OT expansion while the agonist purmorphamine produced the opposite result, a huge expansion of the OT vesicle. Besides, GliA and Shh misexpressions interfere with the formation of the intertectal fissure located along the dorsal midline. This morphogenetic alteration is accompanied by an increase in the mNEc density. There is a gradient in the response of NEcs to Shh and GliA: the increase in mNEc density is maximal near the dorsal regions and decrease towards the OT-tegmental boundary. Biomathematical analyses of the signals derived from the mNEc records show that both Shh and GliA electroporations change the proliferation dynamics and the spatial organization of the mNEc as revealed by the changes in the scaling index estimated by these methods. CONCLUSIONS The present results show that the Shh/Gli signaling pathway plays a critical role in the OT expansion and modelling. This effect is probably mediated by a differential mitogenic effect that increases the NEc proliferation and modulates the spatial organization of the NEc proliferation activity.
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Affiliation(s)
- Melina Rapacioli
- Interdisciplinary Group in Theoretical Biology, Department Biostructural Sciences, Favaloro University, Solís 453 (1078), Buenos Aires, Argentina
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Matise MP. Molecular genetic control of cell patterning and fate determination in the developing ventral spinal cord. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 2:419-25. [DOI: 10.1002/wdev.83] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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Bayly RD, Brown CY, Agarwala S. A novel role for FOXA2 and SHH in organizing midbrain signaling centers. Dev Biol 2012; 369:32-42. [PMID: 22750257 DOI: 10.1016/j.ydbio.2012.06.018] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Revised: 06/06/2012] [Accepted: 06/20/2012] [Indexed: 02/04/2023]
Abstract
The floor plate (FP) is a midline signaling center, known to direct ventral cell fates and axon guidance in the neural tube. The recent identification of midbrain FP as a source of dopaminergic neurons has renewed interest in its specification and organization, which remain poorly understood. In this study, we have examined the chick midbrain and spinal FP and show that both can be partitioned into medial (MFP) and lateral (LFP) subdivisions. Although Hedgehog (HH) signaling is necessary and sufficient for LFP specification, it is not sufficient for MFP induction. By contrast, the transcription factor FOXA2 can execute the full midbrain and spinal cord FP program via HH-independent and dependent mechanisms. Interestingly, although HH-independent FOXA2 activity is necessary and sufficient for inducing MFP-specific gene expression (e.g., LMX1B, BMP7), it cannot confer ventral identity to midline cells without also turning on Sonic hedgehog (SHH). We also note that the signaling centers of the midbrain, the FP, roof plate (RP) and the midbrain-hindbrain boundary (MHB) are physically contiguous, with each expressing LMX1B and BMP7. Possibly as a result, SHH or FOXA2 misexpression can transform the MHB into FP and also suppress RP induction. Conversely, HH or FOXA2 knockdown expands the endogenous RP and transforms the MFP into a RP and/or MHB fate. Finally, combined HH blockade and FOXA2 misexpression in ventral midbrain induces LMX1B expression, which triggers the specification of the RP, rather than the MFP. Thus we identify HH-independent and dependent roles for FOXA2 in specifying the FP. In addition, we elucidate for the first time, a novel role for SHH in determining whether a midbrain signaling center will become the FP, MHB or RP.
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Affiliation(s)
- Roy D Bayly
- Institute for Cell and Molecular Biology, University of Texas at Austin, Austin, TX 78712-0248, USA
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68
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Christopher KJ, Wang B, Kong Y, Weatherbee SD. Forward genetics uncovers Transmembrane protein 107 as a novel factor required for ciliogenesis and Sonic hedgehog signaling. Dev Biol 2012; 368:382-92. [PMID: 22698544 DOI: 10.1016/j.ydbio.2012.06.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 06/01/2012] [Accepted: 06/04/2012] [Indexed: 12/28/2022]
Abstract
Cilia are dynamic organelles that are essential for a vast array of developmental patterning events, including left-right specification, skeletal formation, neural development, and organogenesis. Despite recent advances in understanding cilia form and function, many key ciliogenesis components have yet to be identified. By using a forward genetics approach, we isolated a novel mutant allele (schlei) of the mouse Transmembrane protein 107 (Tmem107) gene, which we show here is critical for cilia formation and embryonic patterning. Tmem107 is required for normal Sonic hedgehog (Shh) signaling in the neural tube and acts in combination with Gli2 and Gli3 to pattern ventral and intermediate neuronal cell types. schlei mutants also form extra digits, and we demonstrate that Tmem107 acts in the Shh pathway to determine digit number, but not identity, by regulating a subset of Shh target genes. Phenotypically, schlei mutants share several features with other cilia mutants; however, spatial restriction of mutant phenotypes and lack of left-right patterning defects in schlei animals suggest differential requirements for Tmem107 in cilia formation in distinct tissues. Also, in contrast to mutants with complete loss of cilia, schlei mutants retain some function of both Gli activator and repressor forms. Together, these studies identify a previously unknown regulator of ciliogenesis and provide insight into how ciliary factors affect Shh signaling and cilia biogenesis in distinct tissues.
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MESH Headings
- Amino Acid Sequence
- Animals
- Body Patterning/genetics
- Cells, Cultured
- Cilia/genetics
- Embryo, Mammalian/cytology
- Embryo, Mammalian/embryology
- Embryo, Mammalian/metabolism
- Extremities/embryology
- Female
- Gene Expression Regulation, Developmental
- Hedgehog Proteins/genetics
- In Situ Hybridization
- Kruppel-Like Transcription Factors/genetics
- Male
- Membrane Proteins/genetics
- Mice
- Mice, Inbred C3H
- Mice, Inbred C57BL
- Mice, Mutant Strains
- Microscopy, Electron, Scanning
- Molecular Sequence Data
- Mutation
- Nerve Tissue Proteins/genetics
- Neural Tube/embryology
- Neural Tube/metabolism
- Neural Tube/ultrastructure
- Sequence Homology, Amino Acid
- Signal Transduction/genetics
- Zinc Finger Protein Gli2
- Zinc Finger Protein Gli3
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69
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Sasai N, Briscoe J. Primary cilia and graded Sonic Hedgehog signaling. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2012; 1:753-72. [PMID: 23799571 DOI: 10.1002/wdev.43] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cilia are evolutionary-conserved microtubule-containing organelles protruding from the surface of cells. They are classified into two types--primary and motile cilia. Primary cilia are nearly ubiquitous, at least in vertebrate cells, and it has become apparent that they play an essential role in the intracellular transduction of a range of stimuli. Most notable among these is Sonic Hedgehog. In this article we briefly summarize the structure and biogenesis of primary cilia. We discuss the evidence implicating cilia in the transduction of extrinsic signals. We focus on the involvement and molecular mechanism of cilia in signaling by Sonic Hedgehog in embryonic tissues, specifically the neural tube, and we discuss how cilia play an active role in the interpretation of gradients of Sonic Hedgehog (Shh) signaling.
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Affiliation(s)
- Noriaki Sasai
- Developmental Biology, National Institute for Medical Research, Mill Hill, London, UK
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70
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Haddad-Tóvolli R, Heide M, Zhou X, Blaess S, Alvarez-Bolado G. Mouse thalamic differentiation: gli-dependent pattern and gli-independent prepattern. Front Neurosci 2012; 6:27. [PMID: 22371696 PMCID: PMC3283895 DOI: 10.3389/fnins.2012.00027] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2011] [Accepted: 02/08/2012] [Indexed: 12/17/2022] Open
Abstract
Sonic hedgehog (Shh) signaling is essential for thalamic development. The Gli transcription factors act downstream of Shh – while Gli2 is the major activator (GliA), Gli3 acts primarily as a repressor (GliR). The thalamus is remarkable among dorsal structures because of its proximity to the mid-diencephalic organizer, a unique dorsal Shh source. This lends complexity to the interactions between Shh, Gli2, and Gli3, suggesting the presence of a dorsal Gli activator which elsewhere is found only ventrally, and making the dissection of thalamic Gli functions particularly interesting. A current model based on mutant phenotypes in telencephalon and midbrain postulates a degree of reciprocal antagonism of Shh and Gli3 in dorsal brain regions. To approach the role of Gli factors in thalamic specification we first analyzed mice deficient in Gli2 or Gli3. In Gli2 mutants, the thalamus is small and poorly differentiated with the exception of the medial and intralaminar nuclei which, in contrast, are specifically and severely affected by Gli3 inactivation. Gbx2 expression is very reduced in the Gli3 mutant. Most thalamic nuclei are present in both mutants, although incompletely differentiated, as reflected by the loss of specific markers. The ventral posterior group, revealed by novel specific marker Hes1, is present in both mutants and extends axons to the telencephalon. To test the Gli3/Shh interaction we generated a novel mutant deficient in Gli3 and neuroepithelial Shh. The thalamus of the n-Shh/Gli3 double mutants is very large and very poorly differentiated except for a broad domain of Gbx2, Lhx2, and Calb2 expression. In utero electroporation experiments on wild type embryos suggest that a stage-specific factor acting early is responsible for this prepattern. We show that, in the thalamus, GliA acts downstream of Shh to specify pattern and size of the thalamic nuclei to the exception of the medial and intralaminar groups. Gli3A can partially substitute for Gli2A in the Gli2 mutant. GliR is essential for specification and growth of the medial and intralaminar nuclei, contributes to the specification of other thalamic nuclei and reduces thalamic size. GliA (from neuroepithelial Shh signaling) and GliR do not show reciprocal antagonism in the thalamus, and their joint abolition does not rescue the wild type phenotype.
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Affiliation(s)
- Roberta Haddad-Tóvolli
- Department of Neuroanatomy, Institute of Anatomy and Cell Biology, University of Heidelberg Heidelberg, Germany
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71
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Sivakumar KC, Dhanesh SB, Shobana S, James J, Mundayoor S. A systems biology approach to model neural stem cell regulation by notch, shh, wnt, and EGF signaling pathways. OMICS-A JOURNAL OF INTEGRATIVE BIOLOGY 2012; 15:729-37. [PMID: 21978399 DOI: 10.1089/omi.2011.0011] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The Notch, Sonic Hedgehog (Shh), Wnt, and EGF pathways have long been known to influence cell fate specification in the developing nervous system. Here we attempted to evaluate the contemporary knowledge about neural stem cell differentiation promoted by various drug-based regulations through a systems biology approach. Our model showed the phenomenon of DAPT-mediated antagonism of Enhancer of split [E(spl)] genes and enhancement of Shh target genes by a SAG agonist that were effectively demonstrated computationally and were consistent with experimental studies. However, in the case of model simulation of Wnt and EGF pathways, the model network did not supply any concurrent results with experimental data despite the fact that drugs were added at the appropriate positions. This paves insight into the potential of crosstalks between pathways considered in our study. Therefore, we manually developed a map of signaling crosstalk, which included the species connected by representatives from Notch, Shh, Wnt, and EGF pathways and highlighted the regulation of a single target gene, Hes-1, based on drug-induced simulations. These simulations provided results that matched with experimental studies. Therefore, these signaling crosstalk models complement as a tool toward the discovery of novel regulatory processes involved in neural stem cell maintenance, proliferation, and differentiation during mammalian central nervous system development. To our knowledge, this is the first report of a simple crosstalk map that highlights the differential regulation of neural stem cell differentiation and underscores the flow of positive and negative regulatory signals modulated by drugs.
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72
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England S, Batista MF, Mich JK, Chen JK, Lewis KE. Roles of Hedgehog pathway components and retinoic acid signalling in specifying zebrafish ventral spinal cord neurons. Development 2012; 138:5121-34. [PMID: 22069186 DOI: 10.1242/dev.066159] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In mouse, Hedgehog (Hh) signalling is required for most ventral spinal neurons to form. Here, we analyse the spinal cord phenotype of zebrafish maternal-zygotic smoothened (MZsmo) mutants that completely lack Hh signalling. We find that most V3 domain cells and motoneurons are lost, whereas medial floorplate still develops normally and V2, V1 and V0v cells form in normal numbers. This phenotype resembles that of mice that lack both Hh signalling and Gli repressor activity. Ventral spinal cord progenitor domain transcription factors are not expressed at 24 hpf in zebrafish MZsmo mutants. However, pMN, p2 and p1 domain markers are expressed at early somitogenesis stages in these mutants. This suggests that Gli repressor activity does not extend into zebrafish ventral spinal cord at these stages, even in the absence of Hh signalling. Consistent with this, ectopic expression of Gli3R represses ventral progenitor domain expression at these early stages and knocking down Gli repressor activity rescues later expression. We investigated whether retinoic acid (RA) signalling specifies ventral spinal neurons in the absence of Hh signalling. The results suggest that RA is required for the correct number of many different spinal neurons to form. This is probably mediated, in part, by an effect on cell proliferation. However, V0v, V1 and V2 cells are still present, even in the absence of both Hh and RA signalling. We demonstrate that Gli1 has a Hh-independent role in specifying most of the remaining motoneurons and V3 domain cells in embryos that lack Hh signalling, but removal of Gli1 activity does not affect more dorsal neurons.
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Affiliation(s)
- Samantha England
- Biology Department, Syracuse University, 107 College Place, Syracuse, NY 13244, USA
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73
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Differentiation of human ES cell-derived neural progenitors to neuronal cells with regional specific identity by co-culturing of notochord and somite. Stem Cell Res 2012; 8:120-33. [DOI: 10.1016/j.scr.2011.08.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Revised: 08/26/2011] [Accepted: 08/28/2011] [Indexed: 01/08/2023] Open
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74
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75
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Mazur MD, Couldwell WT. Investigating a Candidate Cell of Origin for Diffuse Intrinsic Pontine Glioma. World Neurosurg 2011; 76:368-9. [DOI: 10.1016/j.wneu.2011.08.027] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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76
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Bangs F, Antonio N, Thongnuek P, Welten M, Davey MG, Briscoe J, Tickle C. Generation of mice with functional inactivation of talpid3, a gene first identified in chicken. Development 2011; 138:3261-72. [PMID: 21750036 PMCID: PMC3133916 DOI: 10.1242/dev.063602] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/16/2011] [Indexed: 01/28/2023]
Abstract
Specification of digit number and identity is central to digit pattern in vertebrate limbs. The classical talpid(3) chicken mutant has many unpatterned digits together with defects in other regions, depending on hedgehog (Hh) signalling, and exhibits embryonic lethality. The talpid(3) chicken has a mutation in KIAA0586, which encodes a centrosomal protein required for the formation of primary cilia, which are sites of vertebrate Hh signalling. The highly conserved exons 11 and 12 of KIAA0586 are essential to rescue cilia in talpid(3) chicken mutants. We constitutively deleted these two exons to make a talpid3(-/-) mouse. Mutant mouse embryos lack primary cilia and, like talpid(3) chicken embryos, have face and neural tube defects but also defects in left/right asymmetry. Conditional deletion in mouse limb mesenchyme results in polydactyly and in brachydactyly and a failure of subperisoteal bone formation, defects that are attributable to abnormal sonic hedgehog and Indian hedgehog signalling, respectively. Like talpid(3) chicken limbs, the mutant mouse limbs are syndactylous with uneven digit spacing as reflected in altered Raldh2 expression, which is normally associated with interdigital mesenchyme. Both mouse and chicken mutant limb buds are broad and short. talpid3(-/-) mouse cells migrate more slowly than wild-type mouse cells, a change in cell behaviour that possibly contributes to altered limb bud morphogenesis. This genetic mouse model will facilitate further conditional approaches, epistatic experiments and open up investigation into the function of the novel talpid3 gene using the many resources available for mice.
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Affiliation(s)
- Fiona Bangs
- Biology and Biochemistry Department, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Nicole Antonio
- Biology and Biochemistry Department, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Peerapat Thongnuek
- Biology and Biochemistry Department, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Monique Welten
- Biology and Biochemistry Department, University of Bath, Claverton Down, Bath BA2 7AY, UK
| | - Megan G. Davey
- Division of Developmental Biology, The Roslin Institute, The University of Edinburgh, Easter Bush, Midlothian, EH25 9RG, Scotland, UK
| | - James Briscoe
- Developmental Neurobiology, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK
| | - Cheryll Tickle
- Biology and Biochemistry Department, University of Bath, Claverton Down, Bath BA2 7AY, UK
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77
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Abstract
Gli zinc-finger proteins are transcription factors involved in the intracellular signal transduction controlled by the Hedgehog family of secreted molecules. They are frequently mutated in human congenital malformations, and their abnormal regulation leads to tumorigenesis. Genetic studies in several model systems indicate that their activity is tightly regulated by Hedgehog signaling through various posttranslational modifications, including phosphorylation, ubiquitin-mediated degradation, and proteolytic processing, as well as through nucleocytoplasmic shuttling. In vertebrate cells, primary cilia are required for the sensing of Hedgehog pathway activity and involved in the processing and activation of Gli proteins. Two evolutionarily conserved Hedgehog pathway components, Suppressor of fused and Kif7, are core intracellular regulators of mammalian Gli proteins. Recent studies revealed that Gli proteins are also regulated transcriptionally and posttranslationally through noncanonical mechanisms independent of Hedgehog signaling. In this review, we describe the regulation of Gli proteins during development and discuss possible mechanisms for their abnormal activation during tumorigenesis.
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Affiliation(s)
- Chi-Chung Hui
- Program in Developmental and Stem Cell Biology, Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.
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78
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Wang H, Lei Q, Oosterveen T, Ericson J, Matise MP. Tcf/Lef repressors differentially regulate Shh-Gli target gene activation thresholds to generate progenitor patterning in the developing CNS. Development 2011; 138:3711-21. [PMID: 21775418 DOI: 10.1242/dev.068270] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During neural tube development, Shh signaling through Gli transcription factors is necessary to establish five distinct ventral progenitor domains that give rise to unique classes of neurons and glia that arise in specific positions along the dorsoventral axis. These cells are generated from progenitors that display distinct transcription factor gene expression profiles in specific domains in the ventricular zone. However, the molecular genetic mechanisms that control the differential spatiotemporal transcriptional responses of progenitor target genes to graded Shh-Gli signaling remain unclear. The current study demonstrates a role for Tcf/Lef repressor activity in this process. We show that Tcf3 and Tcf7L2 (Tcf4) are required for proper ventral patterning and function by independently regulating two Shh-Gli target genes, Nkx2.2 and Olig2, which are initially induced in a common pool of progenitors that ultimately segregate into unique territories giving rise to distinct progeny. Genetic and functional studies in vivo show that Tcf transcriptional repressors selectively elevate the strength and duration of Gli activity necessary to induce Nkx2.2, but have no effect on Olig2, and thereby contribute to the establishment of their distinct expression domains in cooperation with graded Shh signaling. Together, our data reveal a Shh-Gli-independent transcriptional input that is required to shape the precise spatial and temporal response to extracellular morphogen signaling information during lineage segregation in the CNS.
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Affiliation(s)
- Hui Wang
- Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, 675 Hoes Lane, Piscataway, NJ 08854, USA
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79
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Dowdle WE, Robinson JF, Kneist A, Sirerol-Piquer MS, Frints SGM, Corbit KC, Zaghloul NA, van Lijnschoten G, Mulders L, Verver DE, Zerres K, Reed RR, Attié-Bitach T, Johnson CA, García-Verdugo JM, Katsanis N, Bergmann C, Reiter JF. Disruption of a ciliary B9 protein complex causes Meckel syndrome. Am J Hum Genet 2011; 89:94-110. [PMID: 21763481 DOI: 10.1016/j.ajhg.2011.06.003] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2011] [Revised: 05/24/2011] [Accepted: 06/03/2011] [Indexed: 02/06/2023] Open
Abstract
Nearly every ciliated organism possesses three B9 domain-containing proteins: MKS1, B9D1, and B9D2. Mutations in human MKS1 cause Meckel syndrome (MKS), a severe ciliopathy characterized by occipital encephalocele, liver ductal plate malformations, polydactyly, and kidney cysts. Mouse mutations in either Mks1 or B9d2 compromise ciliogenesis and result in phenotypes similar to those of MKS. Given the importance of these two B9 proteins to ciliogenesis, we examined the role of the third B9 protein, B9d1. Mice lacking B9d1 displayed polydactyly, kidney cysts, ductal plate malformations, and abnormal patterning of the neural tube, concomitant with compromised ciliogenesis, ciliary protein localization, and Hedgehog (Hh) signal transduction. These data prompted us to screen MKS patients for mutations in B9D1 and B9D2. We identified a homozygous c.301A>C (p.Ser101Arg) B9D2 mutation that segregates with MKS, affects an evolutionarily conserved residue, and is absent from controls. Unlike wild-type B9D2 mRNA, the p.Ser101Arg mutation failed to rescue zebrafish phenotypes induced by the suppression of b9d2. With coimmunoprecipitation and mass spectrometric analyses, we found that Mks1, B9d1, and B9d2 interact physically, but that the p.Ser101Arg mutation abrogates the ability of B9d2 to interact with Mks1, further suggesting that the mutation compromises B9d2 function. Our data indicate that B9d1 is required for normal Hh signaling, ciliogenesis, and ciliary protein localization and that B9d1 and B9d2 are essential components of a B9 protein complex, disruption of which causes MKS.
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Affiliation(s)
- William E Dowdle
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, 94158, USA
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80
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Ascl1/Mash1 is a novel target of Gli2 during Gli2-induced neurogenesis in P19 EC cells. PLoS One 2011; 6:e19174. [PMID: 21559470 PMCID: PMC3084770 DOI: 10.1371/journal.pone.0019174] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2010] [Accepted: 03/29/2011] [Indexed: 12/23/2022] Open
Abstract
The Sonic Hedgehog (Shh) signaling pathway is important for neurogenesis in vivo. Gli transcription factors, effector proteins of the Shh signaling pathway, have neurogenic properties in vivo, which are still poorly understood. To study the molecular basis of neurogenic properties of Gli2, we used a well-established embryonic stem cell model, the P19 embryonal carcinoma (EC) cell line, which can be induced to differentiate into neurons in the presence of retinoic acid (RA). We found that, in the absence of RA, overexpression of Gli2 induced P19 EC cells to differentiate into neurons, but not astrocytes during the first ten days of differentiation. To our knowledge, this is the first indication that the expression of Gli factors can convert EC cells into neurons. Furthermore, Gli2 upregulated expression of the neurogenic basic helix-loop-helix (bHLH) factors, such as NeuroD, Neurog1 and Ascl1/Mash1 in P19 EC cells. Using chromatin immunoprecipitation assays, we showed that Gli2 bound to multiple regulatory regions in the Ascl1 gene, including promoter and enhancer regions during Gli2-induced neurogenesis. In addition, Gli2 activated the Ascl1/Mash1 promoter in vitro. Using the expression of a dominant-negative form of Gli2, fused to the Engrailed repression domain, we observed a reduction in gliogenesis and a significant downregulation of the bHLH factors Ascl1/Mash1, Neurog1 and NeuroD, leading to delayed neurogenesis in P19 EC cells, further supporting the hypothesis that Ascl1/Mash1 is a direct target of Gli2. In summary, Gli2 is sufficient to induce neurogenesis in P19 stem cells at least in part by directly upregulating Ascl1/Mash1. Our results provide mechanistic insight into the neurogenic properties of Gli2 in vitro, and offer novel plausible explanations for its in vivo neurogenic properties.
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81
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Mizutani CM, Bier E. EvoD/Vo: the origins of BMP signalling in the neuroectoderm. Nat Rev Genet 2011; 9:663-77. [PMID: 18679435 DOI: 10.1038/nrg2417] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The genetic systems controlling body axis formation trace back as far as the ancestor of diploblasts (corals, hydra, and jellyfish) and triploblasts (bilaterians). Comparative molecular studies, often referred to as evo-devo, provide powerful tools for elucidating the origins of mechanisms for establishing the dorsal-ventral and anterior-posterior axes in bilaterians and reveal differences in the evolutionary pressures acting upon tissue patterning. In this Review, we focus on the origins of nervous system patterning and discuss recent comparative genetic studies; these indicate the existence of an ancient molecular mechanism underlying nervous system organization that was probably already present in the bilaterian ancestor.
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Affiliation(s)
- Claudia Mieko Mizutani
- Section of Cell and Developmental Biology, University of California, San Diego, La Jolla, 92093-0349, USA.
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82
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Hudson C, Ba M, Rouvière C, Yasuo H. Divergent mechanisms specify chordate motoneurons: evidence from ascidians. Development 2011; 138:1643-52. [DOI: 10.1242/dev.055426] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Ascidians are members of the vertebrate sister group Urochordata. Their larvae exhibit a chordate body plan, which forms by a highly accelerated embryonic strategy involving a fixed cell lineage and small cell numbers. We report a detailed analysis of the specification of three of the five pairs of motoneurons in the ascidian Ciona intestinalis and show that despite well-conserved gene expression patterns and embryological outcomes compared with vertebrates, key signalling molecules have adopted different roles. We employed a combination of cell ablation and gene manipulation to analyse the function of two signalling molecules with key roles in vertebrate motoneuron specification that are known to be expressed equivalently in ascidians: the inducer Sonic hedgehog, produced ventrally by the notochord and floorplate; and the inhibitory BMP2/4, produced on the lateral/dorsal side of the neural plate. Our surprising conclusion is that neither BMP2/4 signalling nor the ventral cell lineages expressing hedgehog play crucial roles in motoneuron formation in Ciona. Furthermore, BMP2/4 overexpression induced ectopic motoneurons, the opposite of its vertebrate role. We suggest that the specification of motoneurons has been modified during ascidian evolution, such that BMP2/4 has adopted a redundant inductive role rather than a repressive role and Nodal, expressed upstream of BMP2/4 in the dorsal neural tube precursors, acts as a motoneuron inducer during normal development. Thus, our results uncover significant differences in the mechanisms used for motoneuron specification within chordates and also highlight the dangers of interpreting equivalent expression patterns as indicative of conserved function in evo-devo studies.
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Affiliation(s)
- Clare Hudson
- UPMC University of Paris 06, UMR7009, Developmental Biology Unit, Observatoire Océanologique de Villefranche-sur-mer, BP28, 06230, Villefranche-sur-mer, France
- CNRS, UMR7009, Developmental Biology Unit, Observatoire Océanologique de Villefranche-sur-mer, 06230, BP28, Villefranche-sur-mer, France
| | - Moly Ba
- UPMC University of Paris 06, UMR7009, Developmental Biology Unit, Observatoire Océanologique de Villefranche-sur-mer, BP28, 06230, Villefranche-sur-mer, France
- CNRS, UMR7009, Developmental Biology Unit, Observatoire Océanologique de Villefranche-sur-mer, 06230, BP28, Villefranche-sur-mer, France
| | - Christian Rouvière
- UPMC University of Paris 06, UMR7009, Developmental Biology Unit, Observatoire Océanologique de Villefranche-sur-mer, BP28, 06230, Villefranche-sur-mer, France
- CNRS, UMR7009, Developmental Biology Unit, Observatoire Océanologique de Villefranche-sur-mer, 06230, BP28, Villefranche-sur-mer, France
| | - Hitoyoshi Yasuo
- UPMC University of Paris 06, UMR7009, Developmental Biology Unit, Observatoire Océanologique de Villefranche-sur-mer, BP28, 06230, Villefranche-sur-mer, France
- CNRS, UMR7009, Developmental Biology Unit, Observatoire Océanologique de Villefranche-sur-mer, 06230, BP28, Villefranche-sur-mer, France
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83
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Wang CKL, Tsugane MH, Scranton V, Kosher RA, Pierro LJ, Upholt WB, Dealy CN. Pleiotropic patterning response to activation of Shh signaling in the limb apical ectodermal ridge. Dev Dyn 2011; 240:1289-302. [PMID: 21465622 DOI: 10.1002/dvdy.22628] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/05/2011] [Indexed: 11/07/2022] Open
Abstract
Sonic hedgehog (Shh) signaling in the limb plays a central role in coordination of limb patterning and outgrowth. Shh expression in the limb is limited to the cells of the zone of polarizing activity (ZPA), located in posterior limb bud mesoderm. Shh is not expressed by limb ectoderm or apical ectodermal ridge (AER), but recent studies suggest a role for AER-Shh signaling in limb patterning. Here, we have examined the effects of activation of Shh signaling in the AER. We find that targeted expression of Shh in the AER activates constitutive Shh signaling throughout the AER and subjacent limb mesoderm, and causes a range of limb patterning defects with progressive severity from mild polydactyly, to polysyndactyly with proximal defects, to severe oligodactyly with phocomelia and partial limb ventralization. Our studies emphasize the importance of control of the timing, level and location of Shh pathway signaling for limb anterior-posterior, proximal-distal, and dorsal-ventral patterning.
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Affiliation(s)
- Chi-Kuang Leo Wang
- Department of Reconstructive Sciences, University of Connecticut Health Center, Farmington, Connecticut, USA
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84
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An atlas of gene regulatory networks reveals multiple three-gene mechanisms for interpreting morphogen gradients. Mol Syst Biol 2011; 6:425. [PMID: 21045819 PMCID: PMC3010108 DOI: 10.1038/msb.2010.74] [Citation(s) in RCA: 116] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 08/04/2010] [Indexed: 11/15/2022] Open
Abstract
Although >450 different topologies can achieve the same multicellular patterning function, they can be grouped into six main classes, which operate using different underlying dynamics. Alternative designs for the same functions can therefore split into two types: (a) topology alterations that retain the same underlying dynamics and (b) alterations that utilize a completely different underlying dynamical mechanism. This segregation of networks into distinct dynamical mechanisms can be revealed by the shape of the topology atlas itself. Cell–cell communication is not usually part of the causal mechanism underlying a band-pass response during morphogen interpretation, but it can tune the result or increase robustness.
Understanding how gene regulatory networks (GRNs) achieve particular biological functions is a central question in systems biology. Systems biology promises to go beyond a case-by-case understanding of individual networks to map out the complete design space of mechanistic possibilities that underlie biological functions. Can such maps serve as useful theoretical frameworks in which to explore the general design principles for these functions? Towards addressing these questions, we created the first design space for a morphogen interpretation function. In order to generate a design space for such a function, we enumerated all possible wiring designs of GRNs consisting of three genes and tested their ability to perform one particular morphogen interpretation function; stripe formation, as it represents a simplified form of the much studied French flag problem and is a commonly found gene expression pattern (Figure 1A). We found that only 5% of GRNs had the ability to generate a single stripe of gene expression when simulated with a fixed morphogen input in a one-dimensional model. We hypothesized that the core mechanisms for producing the stripe of gene expression should be represented by topologies that contain only the necessary and sufficient gene–gene interactions for that function. Hence, we utilized the notions of complexity and neighborhood to generate a complexity atlas. GRNs of such an atlas (represented by nodes) are considered neighbors if they differ by a single gene–gene interaction (neighboring GRN nodes are connected by edges). Such a metagraph (graph of graphs) can then be reorganized using complexity (number of gene–gene interactions) to determine a GRNs position in the y axis, whereas GRNs are spaced in the x axis with the aim of reducing edge crossing (Figure 5A). This reorganization reveals a striking structure, where ‘stalactites' of complexity can be seen protruding from the bottom of the atlas. Each of these stalactites converges on a single ‘core' topology that by extensive analysis we find represents a distinct mechanism. The mechanisms employ a diverse range of distinct space–time behaviors, and the underlying core topologies display design features such as modularity and feed-forward. We mapped the mechanisms to the complexity atlas by analyzing how each particular GRN of the atlas was working. The GRNs functioning via the different mechanisms are highlighted by the different colors in Figure 5A. Mechanisms thus occupy large regions of separated topology space, suggesting them to be discrete. Analyzing transitions between mechanisms through parameter space confirms this to be the case. We find that three of the mechanisms are employed in real patterning systems, including both blastoderm patterning in Drosophila and mesoderm specification in Xenopus (Figure 5B). The remaining three mechanisms are thus candidates for employment in other patterning systems. We explored the performance features of these mechanisms, which suggest that some have features such as robustness to parameter variation that make them highly likely to be employed in particular patterning contexts. Only one of the six-core mechanisms absolutely requires cell–cell communication for functionality, prompting us to predict that cell–cell communication will rarely be responsible for the basic dose response of morphogen interpretation networks. However, we show how cell–cell communication has an important role in robust stripe generation in the face of a noisy morphogen input and in fine tuning the quantitative details of stripe patterning. In summary, the complexity atlas approach is an amendable approach to any system with a clear genotype–function relationship. We demonstrate how certain functions such as morphogen interpretation may have a range of potential solutions in contrast to previous studies that analyzed more constrained functions. Furthermore, we demonstrate how such an approach can be utilized to define a ‘design space' for a given biological function that describes the different mechanistic possibilities and how they relate to one another (Figure 5). Such a design space can be used practically as a guide to discern which patterning mechanisms are likely be at work in a particular context throwing up less intuitive possibilities with powerful performance features. The interpretation of morphogen gradients is a pivotal concept in developmental biology, and several mechanisms have been proposed to explain how gene regulatory networks (GRNs) achieve concentration-dependent responses. However, the number of different mechanisms that may exist for cells to interpret morphogens, and the importance of design features such as feedback or local cell–cell communication, is unclear. A complete understanding of such systems will require going beyond a case-by-case analysis of real morphogen interpretation mechanisms and mapping out a complete GRN ‘design space.' Here, we generate a first atlas of design space for GRNs capable of patterning a homogeneous field of cells into discrete gene expression domains by interpreting a fixed morphogen gradient. We uncover multiple very distinct mechanisms distributed discretely across the atlas, thereby expanding the repertoire of morphogen interpretation network motifs. Analyzing this diverse collection of mechanisms also allows us to predict that local cell–cell communication will rarely be responsible for the basic dose-dependent response of morphogen interpretation networks.
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85
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Peyrot SM, Wallingford JB, Harland RM. A revised model of Xenopus dorsal midline development: differential and separable requirements for Notch and Shh signaling. Dev Biol 2011; 352:254-66. [PMID: 21276789 DOI: 10.1016/j.ydbio.2011.01.021] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Revised: 01/18/2011] [Accepted: 01/19/2011] [Indexed: 11/30/2022]
Abstract
The development of the vertebrate dorsal midline (floor plate, notochord, and hypochord) has been an area of classical research and debate. Previous studies in vertebrates have led to contrasting models for the roles of Shh and Notch signaling in specification of the floor plate, by late inductive or early allocation mechanisms, respectively. Here, we show that Notch signaling plays an integral role in cell fate decisions in the dorsal midline of Xenopus laevis, similar to that observed in zebrafish and chick. Notch signaling promotes floor plate and hypochord fates over notochord, but has variable effects on Shh expression in the midline. In contrast to previous reports in frog, we find that Shh signaling is not required for floor plate vs. notochord decisions and plays a minor role in floor plate specification, where it acts in parallel to Notch signaling. As in zebrafish, Shh signaling is required for specification of the lateral floor plate in the frog. We also find that the medial floor plate in Xenopus comprises two distinct populations of cells, each dependent upon different signals for its specification. Using expression analysis of several midline markers, and dissection of functional relationships, we propose a revised allocation mechanism of dorsal midline specification in Xenopus. Our model is distinct from those proposed to date, and may serve as a guide for future studies in frog and other vertebrate organisms.
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Affiliation(s)
- Sara M Peyrot
- Dept of Molecular and Cell Biology and Center for Integrative Genomics, University of California, Berkeley, CA 94720, USA
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86
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Matise MP, Wang H. Sonic hedgehog signaling in the developing CNS where it has been and where it is going. Curr Top Dev Biol 2011; 97:75-117. [PMID: 22074603 DOI: 10.1016/b978-0-12-385975-4.00010-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Sonic Hedgehog (Shh) is one of three mammalian orthologs of the Hedgehog (Hh) family of secreted proteins first identified for their role in patterning the Drosophila embryo. In this review, we will highlight some of the outstanding questions regarding how Shh signaling controls embryonic development. We will mainly consider its role in the developing mammalian central nervous system (CNS) where the pathway plays a critical role in orchestrating the specification of distinct cell fates within ventral regions, a process of exquisite complexity that is necessary for the proper wiring and hence function of the mature system. Embryonic development is a process that plays out in both the spatial and the temporal dimensions, and it is becoming increasingly clear that our understanding of Shh signaling in the CNS is grounded in an appreciation for the dynamic nature of this process. In addition, any consideration of Hh signaling must by necessity include a consideration of data from many different model organisms and systems. In many cases, the extent to which insights gained from these studies are applicable to the CNS remains to be determined, yet they provide a strong framework in which to explore its role in CNS development. We will also discuss how Shh controls cell fate diversification through the regulation of patterned target gene expression in the spinal cord, a region where our understanding of the morphogenetic action of graded Shh signaling is perhaps the furthest advanced.
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Affiliation(s)
- Michael P Matise
- UMDNJ/Robert Wood Johnson Medical School, Piscataway, New Jersey, USA
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87
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Lek M, Dias JM, Marklund U, Uhde CW, Kurdija S, Lei Q, Sussel L, Rubenstein JL, Matise MP, Arnold HH, Jessell TM, Ericson J. A homeodomain feedback circuit underlies step-function interpretation of a Shh morphogen gradient during ventral neural patterning. Development 2010; 137:4051-60. [PMID: 21062862 DOI: 10.1242/dev.054288] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The deployment of morphogen gradients is a core strategy to establish cell diversity in developing tissues, but little is known about how small differences in the concentration of extracellular signals are translated into robust patterning output in responding cells. We have examined the activity of homeodomain proteins, which are presumed to operate downstream of graded Shh signaling in neural patterning, and describe a feedback circuit between the Shh pathway and homeodomain transcription factors that establishes non-graded regulation of Shh signaling activity. Nkx2 proteins intrinsically strengthen Shh responses in a feed-forward amplification and are required for ventral floor plate and p3 progenitor fates. Conversely, Pax6 has an opposing function to antagonize Shh signaling, which provides intrinsic resistance to Shh responses and is important to constrain the inductive capacity of the Shh gradient over time. Our data further suggest that patterning of floor plate cells and p3 progenitors is gated by a temporal switch in neuronal potential, rather than by different Shh concentrations. These data establish that dynamic, non-graded changes in responding cells are essential for Shh morphogen interpretation, and provide a rationale to explain mechanistically the phenomenon of cellular memory of morphogen exposure.
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Affiliation(s)
- Madelen Lek
- Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden
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88
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Hunkapiller J, Singla V, Seol A, Reiter JF. The ciliogenic protein Oral-Facial-Digital 1 regulates the neuronal differentiation of embryonic stem cells. Stem Cells Dev 2010; 20:831-41. [PMID: 20873986 DOI: 10.1089/scd.2010.0362] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Oral-Facial-Digital 1 (OFD1) Syndrome is an X-linked developmental disorder caused by mutations in the gene Ofd1. OFD1 syndrome involves malformation of the face, oral cavity, and digits and may be characterized by cystic kidneys and mental retardation. Deletion or missense mutations in Ofd1 also result in loss of primary cilia, a microtubule-based cellular projection that mediates multiple signaling pathways. Ofd1 mutant mice display pleiotropic developmental phenotypes, including neural, skeletal, and cardiac defects. To address how loss of Ofd1 and loss of primary cilia affect early differentiation decisions, we analyzed embryoid bodies (EBs) derived from Ofd1 mutant embryonic stem (ES) cells. Ofd1 mutant EBs do not form primary cilia and display defects in Hedgehog and Wnt signaling. Additionally, we show that ES cells lacking Ofd1 display an increased capacity to differentiate into neurons. Nevertheless, neurons derived from Ofd1 mutant ES cells fail to differentiate into V3 interneurons, a cell type dependent on ciliary function and Hedgehog signaling. Thus, loss of Ofd1 affects ES cell interpretation of developmental cues and reveals that EBs model some aspects of ciliopathies, providing insights into the developmental origins of OFD1 syndrome and functions of cilia.
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Affiliation(s)
- Julie Hunkapiller
- Department of Biochemistry and Biophysics, Cardiovascular Research Institute, University of California, San Francisco, San Francisco, California 94158, USA
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89
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Liu Z, Owen T, Zhang L, Zuo J. Dynamic expression pattern of Sonic hedgehog in developing cochlear spiral ganglion neurons. Dev Dyn 2010; 239:1674-83. [PMID: 20503364 DOI: 10.1002/dvdy.22302] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Sonic hedgehog (Shh) signaling plays important roles in the formation of the auditory epithelium. However, little is known about the detailed expression pattern of Shh and the cell sources from which Shh is secreted. By analyzing Shh(CreEGFP/+) mice, we found that Shh was first expressed in all cochlear spiral ganglion neurons by embryonic day 13.5, after which its expression gradually decreased from base to apex. By postnatal day 0, it was not detected in any spiral ganglion neurons. Genetic cell fate mapping results also confirmed that Shh was exclusively expressed in all spiral ganglion neurons and not in surrounding glia cells. The basal-to-apical wave of Shh decline strongly resembles that of hair cell differentiation, supporting the idea that Shh signaling inhibits hair cell differentiation. Furthermore, this Shh(CreEGFP/+) mouse is a useful Cre line in which to delete floxed genes specifically in spiral ganglion neurons of the developing cochlea.
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Affiliation(s)
- Zhiyong Liu
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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90
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Murdoch JN, Copp AJ. The relationship between sonic Hedgehog signaling, cilia, and neural tube defects. BIRTH DEFECTS RESEARCH. PART A, CLINICAL AND MOLECULAR TERATOLOGY 2010; 88:633-52. [PMID: 20544799 PMCID: PMC3635124 DOI: 10.1002/bdra.20686] [Citation(s) in RCA: 144] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The Hedgehog signaling pathway is essential for many aspects of normal embryonic development, including formation and patterning of the neural tube. Absence of the sonic hedgehog (shh) ligand is associated with the midline defect holoprosencephaly, whereas increased Shh signaling is associated with exencephaly and spina bifida. To complicate this apparently simple relationship, mutation of proteins required for function of cilia often leads to impaired Shh signaling and to disruption of neural tube closure. In this article, we review the literature on Shh pathway mutants and discuss the relationship between Shh signaling, cilia, and neural tube defects.
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Affiliation(s)
- Jennifer N Murdoch
- Centre for Biomedical Sciences, School of Biological Sciences, Royal Holloway University of London, Egham, Surrey, UK.
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91
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Li L, Walker TL, Zhang Y, Mackay EW, Bartlett PF. Endogenous interferon gamma directly regulates neural precursors in the non-inflammatory brain. J Neurosci 2010; 30:9038-50. [PMID: 20610738 PMCID: PMC6632462 DOI: 10.1523/jneurosci.5691-09.2010] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2009] [Revised: 03/25/2010] [Accepted: 05/13/2010] [Indexed: 12/23/2022] Open
Abstract
Although a number of growth factors have been shown to be involved in neurogenesis, the role of inflammatory cytokines remains relatively unexplored in the normal brain. Here we investigated the effect of interferon gamma (IFNgamma) in the regulation of neural precursor (NP) activity in both the developing and the adult mouse brain. Exogenous IFNgamma inhibited neurosphere formation from the wild-type neonatal and adult subventricular zone (SVZ). More importantly, however, these effects were mirrored in vivo, with mutant mice lacking endogenous IFNgamma displaying enhanced neurogenesis, as demonstrated by an increase in proliferative bromodeoxyuridine-labeled cells in the SVZ and an increased percentage of newborn neurons in the olfactory bulb. Furthermore, NPs isolated from IFNgamma null mice exhibited an increase in self-renewal ability and in the capacity to produce differentiated neurons and oligodendrocytes. These effects resulted from the direct action of IFNgamma on the NPs, as determined by single-cell assays and the fact that nearly all the neurospheres were derived from cells positive for major histocompatibility complex class I antigen, a downstream marker of IFNgamma-mediated activation. Moreover, the inhibitory effect was ameliorated in the presence of SVZ-derived microglia, with their removal resulting in almost complete inhibition of NP proliferation. Interestingly, in contrast to the results obtained in the adult, exogenous IFNgamma treatment stimulated neurosphere formation from the embryonic brain, an effect that was mediated by sonic hedgehog. Together these findings provide the first direct evidence that IFNgamma acts as a regulator of the active NP pool in the non-inflammatory brain.
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MESH Headings
- Animals
- Animals, Newborn
- Brain/cytology
- Brain/embryology
- Brain/metabolism
- Cell Differentiation/drug effects
- Cell Differentiation/physiology
- Cell Proliferation/drug effects
- Cells, Cultured
- Dose-Response Relationship, Drug
- Embryo, Mammalian
- Flow Cytometry/methods
- Gene Expression Regulation, Developmental/drug effects
- Gene Expression Regulation, Developmental/genetics
- Green Fluorescent Proteins/genetics
- Histocompatibility Antigens Class I/genetics
- Histocompatibility Antigens Class I/metabolism
- Interferon-gamma/deficiency
- Interferon-gamma/drug effects
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microglia/drug effects
- Microglia/metabolism
- Nerve Tissue Proteins/genetics
- Nerve Tissue Proteins/metabolism
- Neurons/drug effects
- Neurons/physiology
- RNA, Messenger/metabolism
- Receptors, Interferon/genetics
- Receptors, Interferon/metabolism
- Stem Cells/drug effects
- Stem Cells/physiology
- Time Factors
- bcl-2-Associated X Protein/deficiency
- Interferon gamma Receptor
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Affiliation(s)
- Li Li
- Queensland Brain Institute, The University of Queensland, Brisbane, Queensland, Australia
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92
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Wilson CW, Chuang PT. Mechanism and evolution of cytosolic Hedgehog signal transduction. Development 2010; 137:2079-94. [PMID: 20530542 DOI: 10.1242/dev.045021] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Hedgehog (Hh) signaling is required for embryonic patterning and postnatal physiology in invertebrates and vertebrates. With the revelation that the primary cilium is crucial for mammalian Hh signaling, the prevailing view that Hh signal transduction mechanisms are conserved across species has been challenged. However, more recent progress on elucidating the function of core Hh pathway cytosolic regulators in Drosophila, zebrafish and mice has confirmed that the essential logic of Hh transduction is similar between species. Here, we review Hh signaling events at the membrane and in the cytosol, and focus on parallel and divergent functions of cytosolic Hh regulators in Drosophila and mammals.
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Affiliation(s)
- Christopher W Wilson
- Cardiovascular Research Institute, University of California, San Francisco, CA 94158, USA
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93
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Maun HR, Wen X, Lingel A, de Sauvage FJ, Lazarus RA, Scales SJ, Hymowitz SG. Hedgehog pathway antagonist 5E1 binds hedgehog at the pseudo-active site. J Biol Chem 2010; 285:26570-80. [PMID: 20504762 DOI: 10.1074/jbc.m110.112284] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Proper hedgehog (Hh) signaling is crucial for embryogenesis and tissue regeneration. Dysregulation of this pathway is associated with several types of cancer. The monoclonal antibody 5E1 is a Hh pathway inhibitor that has been extensively used to elucidate vertebrate Hh biology due to its ability to block binding of the three mammalian Hh homologs to the receptor, Patched1 (Ptc1). Here, we engineered a murine:human chimeric 5E1 (ch5E1) with similar Hh-binding properties to the original murine antibody. Using biochemical, biophysical, and x-ray crystallographic studies, we show that, like the regulatory receptors Cdon and Hedgehog-interacting protein (Hhip), ch5E1 binding to Sonic hedgehog (Shh) is enhanced by calcium ions. In the presence of calcium and zinc ions, the ch5E1 binding affinity increases 10-20-fold to tighter than 1 nm primarily because of a decrease in the dissociation rate. The co-crystal structure of Shh bound to the Fab fragment of ch5E1 reveals that 5E1 binds at the pseudo-active site groove of Shh with an epitope that largely overlaps with the binding site of its natural receptor antagonist Hhip. Unlike Hhip, the side chains of 5E1 do not directly coordinate the Zn(2+) cation in the pseudo-active site, despite the modest zinc-dependent increase in 5E1 affinity for Shh. Furthermore, to our knowledge, the ch5E1 Fab-Shh complex represents the first structure of an inhibitor antibody bound to a metalloprotease fold.
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Affiliation(s)
- Henry R Maun
- Department of Protein Engineering, Genentech, Inc., South San Francisco, California 94080, USA
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94
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Liu B, Feng D, Lin G, Cao M, Kan YW, Cunha GR, Baskin LS. Signalling molecules involved in mouse bladder smooth muscle cellular differentiation. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2010; 54:175-80. [PMID: 20013655 DOI: 10.1387/ijdb.082610bl] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
Mouse bladder mesenchyme differentiates into smooth muscle under the influence of urothelium at gestational day 13.5 (E13.5). Sonic hedgehog (Shh) is considered to be the upstream gene arising from the urothelium, which induces smooth muscle in the peripheral bladder mesenchyme. We hypothesize differential gene expression across the full thickness of bladder mesenchyme as a function of proximity to the inducing bladder urothelium and the peripheral location of the smooth muscle. Embryonic bladders from FVB mice were collected at E12.5, 13.5, 15 and 16 and cryosectioned followed by microdissection with a PixCell II laser capture microscope. RNA extraction was performed at the laser captured sites and mRNA expression profiles were measured using SYBR Green quantitative RT-PCR. Smooth muscle a-actin (SMAA) and smooth muscle myosin heavy chain (SM-MHC) were expressed in the E13.5, E15 and E16 bladders in the peripheral layer of mesenchyme, but not in the prospective submucosa. Patched 1 (Ptc1), Gli1 and bone morphogenetic protein (Bmp) 4 expression was consistently elevated in the mesenchymal layer immediately adjacent to the urothelium compared to the peripheral location at E12.5. After E12.5, Ptc1 expression decreased to an undetectable level throughout the bladder mesenchyme. The level of TGF-beta1 was highest in the mesenchymal layer adjacent to the serosa at E13.5. The level of expression of serum response factor (SRF) was also highest at E15 in the peripheral mesenchyme. Genes downstream of Shh are differentially expressed in the prospective submucosa vs. the peripheral bladder mesenchyme as a function gestation age and smooth muscle differentiation.
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Affiliation(s)
- Benchun Liu
- Department of Urology, University of California, San Francisco, San Francisco, CA, USA
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95
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Gribble SL, Nikolaus OB, Carver MS, Hoshijima K, Dorsky RI. Chromosomal position mediates spinal cord expression of a dbx1a enhancer. Dev Dyn 2010; 238:2929-35. [PMID: 19842185 DOI: 10.1002/dvdy.22122] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Dbx homeodomain proteins are important for the production of multiple spinal cord cell types. To examine the regulation of Dbx genes in more detail, we have generated transgenic zebrafish in which fluorescent protein expression is driven by predicted dbx1a enhancers. We identified three areas of sequence conservation upstream of the dbx1a coding sequence and generated fluorescent reporter constructs driven by these predicted enhancer elements and the endogenous dbx1a promoter. In multiple stable insertions of a 3.5-kb enhancer fragment, we observed that there was additional reporter expression in the dorsal spinal cord not normally observed by dbx1a in situ hybridization. In addition, these lines exhibited only transient reporter expression, unlike the endogenous gene. Surprisingly, a single insertion line expressed the reporter in the endogenous pattern, indicating that other local regulatory elements modulate gene expression through the 3.5-kb enhancer.
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Affiliation(s)
- Suzanna L Gribble
- Department of Neurobiology and Anatomy, University of Utah School of Medicine, Salt Lake City, Utah 84132-3401, USA
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96
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Manuel M, Martynoga B, Yu T, West JD, Mason JO, Price DJ. The transcription factor Foxg1 regulates the competence of telencephalic cells to adopt subpallial fates in mice. Development 2010; 137:487-97. [PMID: 20081193 PMCID: PMC2858907 DOI: 10.1242/dev.039800] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/26/2099] [Indexed: 12/17/2022]
Abstract
Foxg1 is required for development of the ventral telencephalon in the embryonic mammalian forebrain. Although one existing hypothesis suggests that failed ventral telencephalic development in the absence of Foxg1 is due to reduced production of the morphogens sonic hedgehog (Shh) and fibroblast growth factor 8 (Fgf8), the possibility that telencephalic cells lacking Foxg1 are intrinsically incompetent to generate the ventral telencephalon has remained untested. We examined the ability of Foxg1(-/-) telencephalic cells to respond to Shh and Fgf8 by examining the expression of genes whose activation requires Shh or Fgf8 in vivo and by testing their responses to Shh and Fgf8 in culture. We found that many elements of the Shh and Fgf8 signalling pathways continue to function in the absence of Foxg1 but, nevertheless, we were unable to elicit normal responses of key ventral telencephalic marker genes in Foxg1(-/-) telencephalic tissue following a range of in vivo and in vitro manipulations. We explored the development of Foxg1(-/-) cells in Foxg1(-/-) Foxg1(+/+) chimeric embryos that contained ventral telencephalon created by normally patterned wild-type cells. We found that Foxg1(-/-) cells contributed to the chimeric ventral telencephalon, but that they retained abnormal specification, expressing dorsal rather than ventral telencephalic markers. These findings indicate that, in addition to regulating the production of ventralising signals, Foxg1 acts cell-autonomously in the telencephalon to ensure that cells develop the competence to adopt ventral identities.
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Affiliation(s)
- Martine Manuel
- Genes and Development Group, University of Edinburgh, Hugh Robson Building, George Square, Edinburgh EH8 9XD, UK.
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97
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Ching S, Vilain E. Targeted disruption of Sonic Hedgehog in the mouse adrenal leads to adrenocortical hypoplasia. Genesis 2010; 47:628-37. [PMID: 19536807 DOI: 10.1002/dvg.20532] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Development of the mammalian adrenal gland is regulated by a diverse network of growth and transcription factors. Disruptions in these pathways often result in adrenal insufficiency because of adrenal hypoplasia. Several lines of evidence have suggested that the Hedgehog signaling pathway, which controls many aspects of tissue and organ patterning, may play a direct role in adrenal morphogenesis as well. Therefore, we examined the role of Sonic Hedgehog (Shh), a member of the Hedgehog family, in mouse adrenal development. We show that Shh and its downstream effectors Gli1, Gli2, and Gli3 are expressed in the adrenal cortex throughout development, and that Shh is required for normal adrenal organogenesis. Conditional inactivation of Shh in the adrenal cortex using a Cre-loxP system resulted in severe hypoplasia and disorganization of the cortex. In mice carrying the targeted mutation (Shh(fl/fl;SF-1/Cre+)), adrenal mass was significantly reduced and the cortex failed to encapsulate the adrenal medulla. Taken together, these results establish a direct role for Shh signaling in normal adrenal development.
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Affiliation(s)
- Saunders Ching
- Department of Human Genetics, University of California, Los Angeles, California, USA
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98
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Merchant JL, Saqui-Salces M, El-Zaatari M. Hedgehog signaling in gastric physiology and cancer. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2010; 96:133-56. [PMID: 21075343 DOI: 10.1016/b978-0-12-381280-3.00006-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The Hedgehog family of ligands was originally identified in mutagenesis screens of Drosophila embryos. Hedgehog signaling in multiple tissues is important during embryonic development. A common theme regarding Hedgehog expression in adult tissues is that tissue injury reactivates the developmental pattern of expression. In most instances, this appears to be important to initiate tissue repair. In the gastrointestinal (GI) tract, where epithelial cells are constantly replenished from progenitor populations, Hedgehog signaling also appears to be essential for regeneration. By contrast, reactivated Hedgehog signaling in adult tissues does not automatically predispose the tissue to transformation, but instead requires sustained tissue injury in the form of chronic inflammation. In this chapter, we review what is known about Hedgehog ligands and signaling during development of relevant organs, and discuss how the patterns of Hedgehog regulation are recapitulated in the GI tract during embryogenesis, adult homeostasis, and neoplastic transformation.
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Affiliation(s)
- Juanita L Merchant
- Department of Internal Medicine, University of Michigan, Ann Arbor, Michigan, USA
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99
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Goetz SC, Ocbina PJR, Anderson KV. The primary cilium as a Hedgehog signal transduction machine. Methods Cell Biol 2009; 94:199-222. [PMID: 20362092 DOI: 10.1016/s0091-679x(08)94010-3] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The Hedgehog (Hh) signal transduction pathway is essential for the development and patterning of numerous organ systems, and has important roles in a variety of human cancers. Genetic screens for mouse embryonic patterning mutants first showed a connection between mammalian Hh signaling and intraflagellar transport (IFT), a process required for construction of the primary cilium, a small cellular projection found on most vertebrate cells. Additional genetic and cell biological studies have provided very strong evidence that mammalian Hh signaling depends on the primary cilium. Here, we review the evidence that defines the integral roles that IFT proteins and cilia play in the regulation of the Hh signal transduction pathway in vertebrates. We discuss the mechanisms that control localization of Hh pathway proteins to the cilium, focusing on the transmembrane protein Smoothened (Smo), which moves into the cilium in response to Hh ligand. The phenotypes caused by loss of cilia-associated proteins are complex, which suggests that cilia and IFT play active roles in mediating Hh signaling rather than serving simply as a compartment in which pathway components are concentrated. Hh signaling in Drosophila does not depend on cilia, but there appear to be ancient links between cilia and components of the Hh pathway that may reveal how this fundamental difference between the Drosophila and mammalian Hh pathways arose in evolution.
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Affiliation(s)
- Sarah C Goetz
- Developmental Biology Program, Sloan-Kettering Institute, 1275 York Avenue, New York, New York 10065, USA
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100
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Krauß S, So J, Hambrock M, Köhler A, Kunath M, Scharff C, Wessling M, Grzeschik KH, Schneider R, Schweiger S. Point mutations in GLI3 lead to misregulation of its subcellular localization. PLoS One 2009; 4:e7471. [PMID: 19829694 PMCID: PMC2758996 DOI: 10.1371/journal.pone.0007471] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2009] [Accepted: 09/22/2009] [Indexed: 11/23/2022] Open
Abstract
Background Mutations in the transcription factor GLI3, a downstream target of Sonic Hedgehog (SHH) signaling, are responsible for the development of malformation syndromes such as Greig-cephalopolysyndactyly-syndrome (GCPS), or Pallister-Hall-syndrome (PHS). Mutations that lead to loss of function of the protein and to haploinsufficiency cause GCPS, while truncating mutations that result in constitutive repressor function of GLI3 lead to PHS. As an exception, some point mutations in the C-terminal part of GLI3 observed in GCPS patients have so far not been linked to loss of function. We have shown recently that protein phosphatase 2A (PP2A) regulates the nuclear localization and transcriptional activity a of GLI3 function. Principal Findings We have shown recently that protein phosphatase 2A (PP2A) and the ubiquitin ligase MID1 regulate the nuclear localization and transcriptional activity of GLI3. Here we show mapping of the functional interaction between the MID1-α4-PP2A complex and GLI3 to a region between amino acid 568-1100 of GLI3. Furthermore we demonstrate that GCPS-associated point mutations, that are located in that region, lead to misregulation of the nuclear GLI3-localization and transcriptional activity. GLI3 phosphorylation itself however appears independent of its localization and remains untouched by either of the point mutations and by PP2A-activity, which suggests involvement of an as yet unknown GLI3 interaction partner, the phosphorylation status of which is regulated by PP2A activity, in the control of GLI3 subcellular localization and activity. Conclusions The present findings provide an explanation for the pathogenesis of GCPS in patients carrying C-terminal point mutations, and close the gap in our understanding of how GLI3-genotypes give rise to particular phenotypes. Furthermore, they provide a molecular explanation for the phenotypic overlap between Opitz syndrome patients with dysregulated PP2A-activity and syndromes caused by GLI3-mutations.
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Affiliation(s)
- Sybille Krauß
- Charité University Hospital, Department of Dermatology, Berlin, Germany
- Max-Planck Institute for Molecular Genetics, Department of Human Molecular Genetics (Ropers), Berlin, Germany
| | - Joyce So
- Max-Planck Institute for Molecular Genetics, Department of Human Molecular Genetics (Ropers), Berlin, Germany
| | - Melanie Hambrock
- Max-Planck Institute for Molecular Genetics, Department of Human Molecular Genetics (Ropers), Berlin, Germany
| | - Andrea Köhler
- Institute of Biochemistry and Center for Molecular Biosciences Innsbruck (CMBI), Innsbruck, Austria
| | - Melanie Kunath
- Max-Planck Institute for Molecular Genetics, Department of Human Molecular Genetics (Ropers), Berlin, Germany
| | - Constance Scharff
- Max-Planck Institute for Molecular Genetics, Department of Human Molecular Genetics (Ropers), Berlin, Germany
| | - Martina Wessling
- Center for Human Genetics, Phillipps University, Marburg, Germany
| | | | - Rainer Schneider
- Max-Planck Institute for Molecular Genetics, Department of Human Molecular Genetics (Ropers), Berlin, Germany
- Institute of Biochemistry and Center for Molecular Biosciences Innsbruck (CMBI), Innsbruck, Austria
- * E-mail:
| | - Susann Schweiger
- Max-Planck Institute for Molecular Genetics, Department of Human Molecular Genetics (Ropers), Berlin, Germany
- Ninewells Hospital, Department of Neuroscience and Pathology, Dundee, United Kingdom
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