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The physiological impact of the serum and glucocorticoid-inducible kinase SGK1. Curr Opin Nephrol Hypertens 2009; 18:439-48. [PMID: 19584721 DOI: 10.1097/mnh.0b013e32832f125e] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
PURPOSE OF REVIEW The role of serum and glucocorticoid-inducible kinase 1 (SGK1) in renal physiology and pathophysiology is reviewed with particular emphasis on recent advances. RECENT FINDINGS The mammalian target of rapamycin complex 2 has been shown to phosphorylate SGK1 at Ser422 (the so-called hydrophobic motif). Ser397 and Ser401 are two additional SGK1-phosphorylation sites required for maximal SGK1 activity. A 5' variant alternate transcript of human Sgk1 has been identified that is widely expressed and shows improved stability, enhanced membrane association, and greater stimulation of epithelial Na+ transport. SGK1 is essential for optimal processing of the epithelial sodium channel and also regulates the expression of the Na+-Cl- cotransporter. With regard to pathophysiology, SGK1 participates in the stimulation of renal tubular glucose transport in diabetes, the renal profibrotic effect of both angiotensin II and aldosterone, and in fetal programing of arterial hypertension. SUMMARY The outlined recent findings advanced our understanding of the molecular regulation of SGK1 as well as the role of the kinase in renal physiology and the pathophysiology of renal disease and hypertension. Future studies using pharmacological inhibitors of SGK1 will reveal the utility of the kinase as a new therapeutic target.
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52
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New horizons at the caudal embryos: coordinated urogenital/reproductive organ formation by growth factor signaling. Curr Opin Genet Dev 2009; 19:491-6. [PMID: 19765973 DOI: 10.1016/j.gde.2009.08.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2009] [Revised: 07/29/2009] [Accepted: 08/21/2009] [Indexed: 11/23/2022]
Abstract
The cloaca/urogenital sinus and its adjacent region differentiate into the urogenital/reproductive organs. Caudal regression syndrome (CRS; including mermaid syndrome), a type of severe cloacal malformation displays hindlimb fusion and urogenital organ defects, thus suggesting that such defects are caused by several morphogenetic alterations during early development. The attenuation of bone morphogenetic protein (Bmp) signaling at the posterior primitive streak of embryos leads to the caudal dysmorphogenesis including the cloaca and fusion of both hindlimbs. Genetic tissue lineage studies indicate the presence of coordinated organogenesis. Hedgehog (HH)-responding cells derived from peri-cloacal mesenchyme (PCM) contribute to the urogenital/reproductive organs. These findings indicate the existence of developmental programs for the coordinated organogenesis of urogenital/reproductive tissues based on growth factor function and crosstalk.
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Non-homeodomain regions of Hox proteins mediate activation versus repression of Six2 via a single enhancer site in vivo. Dev Biol 2009; 335:156-65. [PMID: 19716816 DOI: 10.1016/j.ydbio.2009.08.020] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2009] [Revised: 08/19/2009] [Accepted: 08/21/2009] [Indexed: 10/20/2022]
Abstract
Hox genes control many developmental events along the AP axis, but few target genes have been identified. Whether target genes are activated or repressed, what enhancer elements are required for regulation, and how different domains of the Hox proteins contribute to regulatory specificity are poorly understood. Six2 is genetically downstream of both the Hox11 paralogous genes in the developing mammalian kidney and Hoxa2 in branchial arch and facial mesenchyme. Loss-of-function of Hox11 leads to loss of Six2 expression and loss-of-function of Hoxa2 leads to expanded Six2 expression. Herein we demonstrate that a single enhancer site upstream of the Six2 coding sequence is responsible for both activation by Hox11 proteins in the kidney and repression by Hoxa2 in the branchial arch and facial mesenchyme in vivo. DNA-binding activity is required for both activation and repression, but differential activity is not controlled by differences in the homeodomains. Rather, protein domains N- and C-terminal to the homeodomain confer activation versus repression activity. These data support a model in which the DNA-binding specificity of Hox proteins in vivo may be similar, consistent with accumulated in vitro data, and that unique functions result mainly from differential interactions mediated by non-homeodomain regions of Hox proteins.
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54
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HOXD13 binds DNA replication origins to promote origin licensing and is inhibited by geminin. Mol Cell Biol 2009; 29:5775-88. [PMID: 19703996 DOI: 10.1128/mcb.00509-09] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
HOX DNA-binding proteins control patterning during development by regulating processes such as cell aggregation and proliferation. Recently, a possible involvement of HOX proteins in replication origin activity was suggested by results showing that a number of HOX proteins interact with the DNA replication licensing regulator geminin and bind a characterized human origin of replication. The functional significance of these observations, however, remained unclear. We show that HOXD13, HOXD11, and HOXA13 bind in vivo all characterized human replication origins tested. We furthermore show that HOXD13 interacts with the CDC6 loading factor, promotes pre-replication complex (pre-RC) proteins assembly at origins, and stimulates DNA synthesis in an in vivo replication assay. HOXD13 expression in cultured cells accelerates DNA synthesis initiation in correlation with the earlier pre-RC recruitment onto origins during G(1) phase. Geminin, which interacts with HOXD13 as well, blocks HOXD13-mediated assembly of pre-RC proteins and inhibits HOXD13-induced DNA replication. Our results uncover a function for Hox proteins in the regulation of replication origin activity and reveal an unforeseen role for the inhibition of HOX protein activity by geminin in the context of replication origin licensing.
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55
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Kawakami Y, Uchiyama Y, Rodriguez Esteban C, Inenaga T, Koyano-Nakagawa N, Kawakami H, Marti M, Kmita M, Monaghan-Nichols P, Nishinakamura R, Izpisua Belmonte JC. Sall genes regulate region-specific morphogenesis in the mouse limb by modulating Hox activities. Development 2009; 136:585-94. [PMID: 19168674 DOI: 10.1242/dev.027748] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The genetic mechanisms that regulate the complex morphogenesis of generating cartilage elements in correct positions with precise shapes during organogenesis, fundamental issues in developmental biology, are still not well understood. By focusing on the developing mouse limb, we confirm the importance of transcription factors encoded by the Sall gene family in proper limb morphogenesis, and further show that they have overlapping activities in regulating regional morphogenesis in the autopod. Sall1/Sall3 double null mutants exhibit a loss of digit1 as well as a loss or fusion of digit2 and digit3, metacarpals and carpals in the autopod. We show that Sall activity affects different pathways, including the Shh signaling pathway, as well as the Hox network. Shh signaling in the mesenchyme is partially impaired in the Sall mutant limbs. Additionally, our data suggest an antagonism between Sall1-Sall3 and Hoxa13-Hoxd13. We demonstrate that expression of Epha3 and Epha4 is downregulated in the Sall1/Sall3 double null mutants, and, conversely, is upregulated in Hoxa13 and Hoxd13 mutants. Moreover, the expression of Sall1 and Sall3 is upregulated in Hoxa13 and Hoxd13 mutants. Furthermore, by using DNA-binding assays, we show that Sall and Hox compete for a target sequence in the Epha4 upstream region. In conjunction with the Shh pathway, the antagonistic interaction between Hoxa13-Hoxd13 and Sall1-Sall3 in the developing limb may contribute to the fine-tuning of local Hox activity that leads to proper morphogenesis of each cartilage element of the vertebrate autopod.
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Affiliation(s)
- Yasuhiko Kawakami
- Gene Expression Laboratory, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA
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Chambers D, Wilson LJ, Alfonsi F, Hunter E, Saxena U, Blanc E, Lumsden A. Rhombomere-specific analysis reveals the repertoire of genetic cues expressed across the developing hindbrain. Neural Dev 2009; 4:6. [PMID: 19208226 PMCID: PMC2649922 DOI: 10.1186/1749-8104-4-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2008] [Accepted: 02/10/2009] [Indexed: 11/24/2022] Open
Abstract
Background The Hox family of homeodomain transcription factors comprises pivotal regulators of cell specification and identity during animal development. However, despite their well-defined roles in the establishment of anteroposterior pattern and considerable research into their mechanism of action, relatively few target genes have been identified in the downstream regulatory network. We have sought to investigate this issue, focussing on the developing hindbrain and the cranial motor neurons that arise from this region. The reiterated anteroposterior compartments of the developing hindbrain (rhombomeres (r)) are normally patterned by the combinatorial action of distinct Hox genes. Alteration in the normal pattern of Hox cues in this region results in a transformation of cellular identity to match the remaining Hox profile, similar to that observed in Drosophila homeotic transformations. Results To define the repertoire of genes regulated in each rhombomere, we have analysed the transcriptome of each rhombomere from wild-type mouse embryos and not those where pattern is perturbed by gain or loss of Hox gene function. Using microarray and bioinformatic methodologies in conjunction with other confirmatory techniques, we report here a detailed and comprehensive set of potential Hox target genes in r2, r3, r4 and r5. We have demonstrated that the data produced are both fully reflective and predictive of rhombomere identity and, thus, may represent some the of Hox targets. These data have been interrogated to generate a list of candidate genes whose function may contribute to the generation of neuronal subtypes characteristic of each rhombomere. Interestingly, the data can also be classified into genetic motifs that are predicted by the specific combinations of Hox genes and other regulators of hindbrain anteroposterior identity. The sets of genes described in each or combinations of rhombomeres span a wide functional range and suggest that the Hox genes, as well as other regulatory inputs, exert their influence across the full spectrum of molecular machinery. Conclusion We have performed a systematic survey of the transcriptional status of individual segments of the developing mouse hindbrain and identified hundreds of previously undescribed genes expressed in this region. The functional range of the potential candidate effectors or upstream modulators of Hox activity suggest multiple unexplored mechanisms. In particular, we present evidence of a potential new retinoic acid signalling system in ventral r4 and propose a model for the refinement of identity in this region. Furthermore, the rhombomeres demonstrate a molecular relationship to each other that is consistent with known observations about neurogenesis in the hindbrain. These findings give the first genome-wide insight into the complexity of gene expression during patterning of the developing hindbrain.
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Affiliation(s)
- David Chambers
- MRC Centre for Developmental Neurobiology, King's College London, UK.
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Abstract
A joint meeting of the Japanese and French societies for Developmental Biology, entitled `Frontiers in Developmental Biology', was recently held in Giens, France. The organizers, Patrick Lemaire and Shinichi Aizawa, showcased some of the rapid progress in the field that has been made possible through the use of modern large-scale network analyses, and of an increasingly sophisticated array of tools and ideas from microscopy, mathematics and computer science.
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Affiliation(s)
| | - Edwin Munro
- Center for Cell Dynamics, Friday Harbor Labs, University of Washington, 620 University Road, Friday Harbor, WA 98250, USA
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58
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Wang Z, Yuan L, Rossiter SJ, Zuo X, Ru B, Zhong H, Han N, Jones G, Jepson PD, Zhang S. Adaptive evolution of 5'HoxD genes in the origin and diversification of the cetacean flipper. Mol Biol Evol 2008; 26:613-22. [PMID: 19074008 DOI: 10.1093/molbev/msn282] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The homeobox (Hox) genes Hoxd12 and Hoxd13 control digit patterning and limb formation in tetrapods. Both show strong expression in the limb bud during embryonic development, are highly conserved across vertebrates, and show mutations that are associated with carpal, metacarpal, and phalangeal deformities. The most dramatic evolutionary reorganization of the mammalian limb has occurred in cetaceans (whales, dolphins, and porpoises), in which the hind limbs have been lost and the forelimbs have evolved into paddle-shaped flippers. We reconstructed the phylogeny of digit patterning in mammals and inferred that digit number has changed twice in the evolution of the cetacean forelimb. First, the divergence of the early cetaceans from their even-toed relatives coincided with the reacquisition of the pentadactyl forelimb, whereas the ancestors of tetradactyl baleen whales (Mysticeti) later lost a digit again. To test whether the evolution of the cetacean forelimb is associated with positive selection or relaxation of Hoxd12 and Hoxd13, we sequenced these genes in a wide range of mammals. In Hoxd12, we found evidence of Darwinian selection associated with both episodes of cetacean forelimb reorganization. In Hoxd13, we found a novel expansion of a polyalanine tract in cetaceans compared with other mammals (17/18 residues vs. 14/15 residues, respectively), lengthening of which has previously been shown to be linked to synpolydactyly in humans and mice. Both genes also show much greater sequence variation among cetaceans than across other mammalian lineages. Our results strongly implicate 5'HoxD genes in the modulation of digit number, web forming, and the high morphological diversity of the cetacean manus.
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Affiliation(s)
- Zhe Wang
- School of Life Science, East China Normal University, Shanghai, China
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59
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Kiefer SM, Robbins L, Barina A, Zhang Z, Rauchman M. SALL1 truncated protein expression in Townes-Brocks syndrome leads to ectopic expression of downstream genes. Hum Mutat 2008; 29:1133-40. [PMID: 18470945 DOI: 10.1002/humu.20759] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Mutations in SALL1 lead to the dominant multiorgan congenital anomalies that define Townes-Brocks syndrome (TBS). The majority of these mutations result in premature termination codons that would be predicted to trigger nonsense-mediated decay (NMD) of mutant mRNA and cause haploinsufficiency. Our previous studies using a gene targeted mouse model (Sall1-DeltaZn) suggested that TBS phenotypes are due to expression of a truncated mutant protein, not haploinsufficiency. In this report, we strengthen this hypothesis by showing that expression of the mutant protein alone in transgenic mice is sufficient to cause limb phenotypes that are characteristic of TBS patients. We prove that the same pathogenetic mechanism elucidated in mice is occurring in humans by demonstrating that truncated SALL1 protein is expressed in cells derived from a TBS patient. TBS mutant protein is capable of dominant negative activity that results in ectopic activation of two downstream genes, Nppa and Shox2, in the developing heart and limb. We propose a model for the pathogenesis of TBS in which truncated Sall1 protein causes derepression of Sall-responsive target genes.
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Affiliation(s)
- Susan M Kiefer
- Research and Education Service Line, St. Louis Veterans Administration Medical Center, U.S. Department of Veterans Affairs, St. Louis, Missouri 63106, USA
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60
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Abstract
Despite decades of research, morphogenesis along the various body axes remains one of the major mysteries in developmental biology. A milestone in the field was the realisation that a set of closely related regulators, called Hox genes, specifies the identity of body segments along the anterior-posterior (AP) axis in most animals. Hox genes have been highly conserved throughout metazoan evolution and code for homeodomain-containing transcription factors. Thus, they exert their function mainly through activation or repression of downstream genes. However, while much is known about Hox gene structure and molecular function, only a few target genes have been identified and studied in detail. Our knowledge of Hox downstream genes is therefore far from complete and consequently Hox-controlled morphogenesis is still poorly understood. Genome-wide approaches have facilitated the identification of large numbers of Hox downstream genes both in Drosophila and vertebrates, and represent a crucial step towards a comprehensive understanding of how Hox proteins drive morphological diversification. In this review, we focus on the role of Hox genes in shaping segmental morphologies along the AP axis in Drosophila, discuss some of the conclusions drawn from analyses of large target gene sets and highlight methods that could be used to gain a more thorough understanding of Hox molecular function. In addition, the mechanisms of Hox target gene regulation are considered with special emphasis on recent findings and their implications for Hox protein specificity in the context of the whole organism.
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Affiliation(s)
- Stefanie D Hueber
- Department of Molecular Biology, AG I. Lohmann, MPI for Developmental Biology, Tübingen, Germany
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61
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Huang K, Rabold R, Abston E, Schofield B, Misra V, Galdzicka E, Lee H, Biswal S, Mitzner W, Tankersley CG. Effects of leptin deficiency on postnatal lung development in mice. J Appl Physiol (1985) 2008; 105:249-59. [PMID: 18467551 DOI: 10.1152/japplphysiol.00052.2007] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Leptin modulates energy metabolism and lung development. We hypothesize that the effects of leptin on postnatal lung development are volume dependent from 2 to 10 wk of age and are independent of hypometabolism associated with leptin deficiency. To test the hypotheses, effects of leptin deficiency on lung maturation were characterized in age groups of C57BL/6J mice with varying Lep(ob) genotypes. Quasi-static pressure-volume curves and respiratory impedance measurements were performed to profile differences in respiratory system mechanics. Morphometric analysis was conducted to estimate alveolar size and number. Oxygen consumption was measured to assess metabolic rate. Lung volume at 40-cmH(2)O airway pressure (V(40)) increased with age in each genotypic group, and V(40) was significantly (P < 0.05) lower in leptin-deficient (ob/ob) mice beginning at 2 wk. Differences were amplified through 7 wk of age relative to wild-type (+/+) mice. Morphometric analysis showed that alveolar surface area was lower in ob/ob compared with +/+ and heterozygote (ob/+) mice beginning at 2 wk. Unlike the other genotypic groups, alveolar size did not increase with age in ob/ob mice. In another experiment, ob/ob at 4 wk received leptin replacement (5 microg.g(-1) x day(-1)) for 8 days, and expression levels of the Col1a1, Col3a1, Col6a3, Mmp2, Tieg1, and Stat1 genes were significantly increased concomitantly with elevated V(40). Leptin-induced increases in V(40) corresponded with enlarged alveolar size and surface area. Gene expression suggested a remodeling event of lung parenchyma after exogenous leptin replacement. These data support the hypothesis that leptin is critical to postnatal lung remodeling, particularly related to increased V(40) and enlarged alveolar surface area.
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Affiliation(s)
- Kewu Huang
- Johns Hopkins Bloomberg School of Public Health, Department of Environmental Health Sciences, Baltimore, MD 21205, USA
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62
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Montavon T, Le Garrec JF, Kerszberg M, Duboule D. Modeling Hox gene regulation in digits: reverse collinearity and the molecular origin of thumbness. Genes Dev 2008; 22:346-59. [PMID: 18245448 DOI: 10.1101/gad.1631708] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
During the development of mammalian digits, clustered Hoxd genes are expressed following a collinear regulatory strategy, leading to both the growth of digits and their morphological identities. Because gene dosage is a key parameter in this system, we used a quantitative approach, associated with a collection of mutant stocks, to investigate the nature of the underlying regulatory mechanism(s). In parallel, we elaborated a mathematical model of quantitative collinearity, which was progressively challenged and validated by the experimental approach. This combined effort suggested a two-step mechanism, which involves initially the looping and recognition of the cluster by a complex including two enhancer sequences, followed by a second step of microscanning of genes located nearby. In this scenario, the respective rank of the genes, with respect to the 5' extremity of the cluster, is primordial, as well as different gene-specific affinities. This model accounts for the quantitative variations observed in our many mutant strains, and reveals the molecular constraint leading to thumbness; i.e., why a morphological difference must occur between the most anterior digit and the others. We also show that the same model applies to the collinear regulation of Hox genes during the emergence of external genitalia, though with some differences likely illustrating the distinct functionalities of these structures in adults.
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Affiliation(s)
- Thomas Montavon
- National Research Centre Frontiers in Genetics, School of Life Sciences, Ecole Polytechnique Fédérale, CH-1015 Lausanne, Switzerland
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63
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Affiliation(s)
- Jacqueline Deschamps
- Hubrecht Institute, Developmental Biology and Stem Cell Research, Utrecht 3584 CT, The Netherlands.
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64
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Hoxd13 binds in vivo and regulates the expression of genes acting in key pathways for early limb and skeletal patterning. Dev Biol 2008; 317:497-507. [PMID: 18407260 DOI: 10.1016/j.ydbio.2008.02.048] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Revised: 02/21/2008] [Accepted: 02/22/2008] [Indexed: 11/24/2022]
Abstract
5' HoxD genes are required for the correct formation of limb skeletal elements. Hoxd13, the most 5'-located HoxD gene, is important for patterning the most distal limb region, and its mutation causes human limb malformation syndromes. The mechanisms underlying the control of developmental processes by Hoxd13, and by Hox genes in general, are still elusive, due to the limited knowledge on their direct downstream target genes. We identified by ChIP-on-chip 248 known gene loci bound invivo by Hoxd13. Genes relevant to limb patterning and skeletogenesis were further analysed. We found that Hoxd13 binds invivo, in developing limbs, the loci of Hand2, a gene crucial to limb AP axis patterning, of Meis1 and Meis2, involved in PD patterning, of the Sfrp1, Barx1, and Fbn1 genes, involved in skeletogenesis, and of the Dach1, Bmp2, Bmp4, andEmx2 genes. We show that Hoxd13 misexpression in developing chick limbs alters the expression of the majority of these genes, supporting the conclusion that Hoxd13 directly regulates their transcription. Our results indicate that 5' Hox proteins regulate directly both key genes for early limb AP and PD axis patterning and genes involved, at later stages, in skeletal patterning.
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65
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Matis C, Oury F, Remacle S, Lampe X, Gofflot F, Picard JJ, Rijli FM, Rezsohazy R. Identification of Lmo1 as part of a Hox-dependent regulatory network for hindbrain patterning. Dev Dyn 2007; 236:2675-84. [PMID: 17676642 DOI: 10.1002/dvdy.21266] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The embryonic functions of Hox proteins have been extensively investigated in several animal phyla. These transcription factors act as selectors of developmental programmes, to govern the morphogenesis of multiple structures and organs. However, despite the variety of morphogenetic processes Hox proteins are involved in, only a limited set of their target genes has been identified so far. To find additional targets, we used a strategy based upon the simultaneous overexpression of Hoxa2 and its cofactors Pbx1 and Prep in a cellular model. Among genes whose expression was upregulated, we identified LMO1, which codes for an intertwining LIM-only factor involved in protein-DNA oligomeric complexes. By analysing its expression in Hox knockout mice, we show that Lmo1 is differentially regulated by Hoxa2 and Hoxb2, in specific columns of hindbrain neuronal progenitors. These results suggest that Lmo1 takes part in a Hox paralogue 2-dependent network regulating anteroposterior and dorsoventral hindbrain patterning.
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Affiliation(s)
- Christelle Matis
- Unit of Developmental Genetics, Université Catholique de Louvain, Brussels, Belgium
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66
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Misra V, Lee H, Singh A, Huang K, Thimmulappa RK, Mitzner W, Biswal S, Tankersley CG. Global expression profiles from C57BL/6J and DBA/2J mouse lungs to determine aging-related genes. Physiol Genomics 2007; 31:429-40. [PMID: 17726092 DOI: 10.1152/physiolgenomics.00060.2007] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
This study identified gene expression profiles that provided evidence for genomic mechanisms underlying the pathophysiology of aging lung. Aging lungs from C57BL/6 (B6) and DBA/2 (D2) mouse strains differ in physiology and morphometry. Lungs were harvested from B6 mice at 2, 18, and 26 mo and from D2 mice at 2 and 18 mo of age. Purified RNA was subjected to oligonucleotide microarray analyses, and differential expression analyses were performed for comparison of various data sets. A significant majority of differentially expressed genes were upregulated with aging in both strains. Aging D2 lungs uniquely exhibited upregulation in stress-response genes including xenobiotic detoxification cascades. In contrast, aging B6 lungs showed downregulation of heat shock-response genes. Age-dependent downregulation of genes common to both B6 and D2 strains included several collagen genes (e.g., Col1a1 and Col3a1). There was a greater elastin gene (Eln) expression in D2 mice at 2 mo, and Eln was uniquely downregulated with age in this strain. The matrix metalloproteinase 14 gene (Mmp14), critical to alveolar structural integrity, was also downregulated with aging in D2 mice only. Several polymorphisms in the regulatory and untranslated regions of Mmp14 were identified between strains, suggesting that variation in Mmp14 gene regulation contributes to accelerated aging of lungs in D2 mice. In summary, lungs of B6 and D2 mice age with variable rates at the gene expression level, and these quantifiable genomic differences provide a template for understanding the variability in age-dependent changes in lung structure and function.
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Affiliation(s)
- Vikas Misra
- Department of Environmental Health Sciences, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland 21205, USA
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67
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Tüzel E, Samli H, Kuru I, Türkmen S, Demir Y, Maralcan G, Güler C. Association of Hypospadias with Hypoplastic Synpolydactyly and Role of HOXD13 Gene Mutations. Urology 2007; 70:161-4. [PMID: 17656229 DOI: 10.1016/j.urology.2007.03.013] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2006] [Revised: 01/29/2007] [Accepted: 03/05/2007] [Indexed: 01/02/2023]
Abstract
OBJECTIVES To present the association of hypospadias with hypoplastic synpolydactyly and discuss the molecular genetic basis of these conditions. METHODS A large synpolydactyly kindred first described in 1995 was reinvestigated. Affected and unaffected subjects were interviewed, and pedigrees of the most recent generations were constructed. The marriages of two affected individuals were identified. The siblings who were homozygous for the deformity were asked to attend our institution and underwent a detailed clinical evaluation. Genetic studies and mutation screening were performed using polymerase chain reaction on genomic DNA extracted from venous blood. RESULTS Of the 245 members of the kindred, 125 individuals were affected. Of these 125 individuals, 12 were homozygotes (6 females and 6 males) with a mean age of 12 years. The remaining 113 individuals (57 females and 56 males) were heterozygotes showing milder limb deformities. No sex-related phenotypic difference was found in the extremity findings, but all the males with a homozygote pattern had hypospadias. Three had distal penile, two had mid-shaft, and one had penoscrotal hypospadias. Of the affected 56 heterozygote males, 22 were also noted to have distal hypospadias in various forms. Neither the heterozygote nor the homozygote females had any genital anomalies. The laboratory tests and karyotype profiles of these individuals were normal. Mutation screening of the homozygote subjects revealed a polyalanine duplication band of nine additional alanine residues at the human HOXD13 gene. CONCLUSIONS These findings strongly suggest that specific mutations in HOXD13 gene may cause both hypoplastic synpolydactyly and hypospadias.
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Affiliation(s)
- Emre Tüzel
- Department of Urology, Afyon Kocatepe University School of Medicine, Afyon, Turkey.
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Haraguchi R, Motoyama J, Sasaki H, Satoh Y, Miyagawa S, Nakagata N, Moon A, Yamada G. Molecular analysis of coordinated bladder and urogenital organ formation by Hedgehog signaling. Development 2007; 134:525-33. [PMID: 17202190 DOI: 10.1242/dev.02736] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The urogenital and reproductive organs, including the external genitalia, bladder and urethra, develop as anatomically aligned organs. Descriptive and experimental embryology suggest that the cloaca, and its derivative, the urogenital sinus, contribute to the formation of these organs. However, it is unknown how the primary tissue lineages in, and adjacent to, the cloaca give rise to the above organs, nor is bladder formation understood. While it is known that sonic hedgehog (Shh) is expressed by the cloacal epithelia, the developmental programs that regulate and coordinate the formation of the urogenital and reproductive organs have not been elucidated. Here we report that Shh mutant embryos display hypoplasia of external genitalia, internal urethra (pelvic urethra) and bladder. The importance of Shh signaling in the development of bladder and external genitalia was confirmed by analyzing a variety of mutant mouse lines with defective hedgehog signaling. By genetically labeling hedgehog-responding tissue lineages adjacent to the cloaca and urogenital sinus, we defined the contribution of these tissues to the bladder and external genitalia. We discovered that development of smooth muscle myosin-positive embryonic bladder mesenchyme requires Shh signaling, and that the bladder mesenchyme and dorsal (upper) external genitalia derive from Shh-responsive peri-cloacal mesenchyme. Thus, the mesenchymal precursors for multiple urogenital structures derive from peri-cloacal mesenchyme and the coordination of urogenital organ formation from these precursors is orchestrated by Shh signals.
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Affiliation(s)
- Ryuma Haraguchi
- Center for Animal Resources and Development, CARD and Pharmaceutical Sciences, Kumamoto University, Honjo 2-2-1, Kumamoto, Japan
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69
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Hueber SD, Bezdan D, Henz SR, Blank M, Wu H, Lohmann I. Comparative analysis of Hox downstream genes in Drosophila. Development 2006; 134:381-92. [PMID: 17166915 DOI: 10.1242/dev.02746] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Functional diversification of body parts is dependent on the formation of specialized structures along the various body axes. In animals, region-specific morphogenesis along the anteroposterior axis is controlled by a group of conserved transcription factors encoded by the Hox genes. Although it has long been assumed that Hox proteins carry out their function by regulating distinct sets of downstream genes, only a small number of such genes have been found, with very few having direct roles in controlling cellular behavior. We have quantitatively identified hundreds of Hox downstream genes in Drosophila by microarray analysis, and validated many of them by in situ hybridizations on loss- and gain-of-function mutants. One important finding is that Hox proteins, despite their similar DNA-binding properties in vitro, have highly specific effects on the transcriptome in vivo, because expression of many downstream genes respond primarily to a single Hox protein. In addition, a large fraction of downstream genes encodes realizator functions, which directly affect morphogenetic processes, such as orientation and rate of cell divisions, cell-cell adhesion and communication, cell shape and migration, or cell death. Focusing on these realizators, we provide a framework for the morphogenesis of the maxillary segment. As the genomic organization of Hox genes and the interaction of Hox proteins with specific co-factors are conserved in vertebrates and invertebrates, and similar classes of downstream genes are regulated by Hox proteins across the metazoan phylogeny, our findings represent a first step toward a mechanistic understanding of morphological diversification within a species as well as between species.
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Affiliation(s)
- Stefanie D Hueber
- Max Planck Institute for Developmental Biology, Spemanstrasse 37-39, D-72076 Tübingen, Germany
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70
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Donner AL, Williams T. Frontal nasal prominence expression driven by Tcfap2a relies on a conserved binding site for STAT proteins. Dev Dyn 2006; 235:1358-70. [PMID: 16502414 PMCID: PMC2738421 DOI: 10.1002/dvdy.20722] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The AP-2 transcription factor family is linked with development of the head and limbs in both vertebrate and invertebrate species. Recent evidence has also implicated this gene family in the evolution of the neural crest in chordates, a critical step that allowed the development and elaboration of the vertebrate craniofacial skeleton. In mice, the inappropriate embryonic expression of one particular AP-2 gene, Tcfap2a, encoding AP-2alpha, results in multiple developmental abnormalities, including craniofacial and limb defects. Thus, Tcfap2a provides a valuable genetic resource to analyze the regulatory hierarchy responsible for the evolution and development of the face and limbs. Previous studies have identified a 2-kilobase intronic region of both the mouse and human AP-2alpha locus that directs expression of a linked LacZ transgene to the facial processes and the distal mesenchyme of the limb bud in transgenic mice. Further analysis identified two highly conserved regions of approximately 200-400 bp within this tissue-specific enhancer. We have now initiated a transgenic and biochemical analysis of the most important of these highly conserved regions. Our analysis indicates that although the sequences regulating face and limb expression have been integrated into a single enhancer, different cis-acting sequences ultimately control these two expression domains. Moreover, these studies demonstrate that a conserved STAT binding site provides a major contribution to the expression of Tcfap2a in the facial prominences.
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Affiliation(s)
- Amy L. Donner
- Department of Molecular, Cellular, and Developmental Biology, Yale University, 266 Whitney Ave, New Haven, CT 06511
| | - Trevor Williams
- Department of Molecular, Cellular, and Developmental Biology, Yale University, 266 Whitney Ave, New Haven, CT 06511
- Department of Craniofacial Biology and Dept. of Cell and Developmental Biology UCHSC at Fitzsimons, Mailstop 8120, P.O. Box 6511, Aurora, CO, 80045
- Corresponding author: , phone: (303) 724 4571, FAX: (303) 724 4580 N.B. Alternate corresponding author: , phone: (617) 525-4710 FAX: (617) 525-4751
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71
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Lang F, Böhmer C, Palmada M, Seebohm G, Strutz-Seebohm N, Vallon V. (Patho)physiological significance of the serum- and glucocorticoid-inducible kinase isoforms. Physiol Rev 2006; 86:1151-78. [PMID: 17015487 DOI: 10.1152/physrev.00050.2005] [Citation(s) in RCA: 516] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The serum- and glucocorticoid-inducible kinase-1 (SGK1) is ubiquitously expressed and under genomic control by cell stress (including cell shrinkage) and hormones (including gluco- and mineralocorticoids). Similar to its isoforms SGK2 and SGK3, SGK1 is activated by insulin and growth factors via phosphatidylinositol 3-kinase and the 3-phosphoinositide-dependent kinase PDK1. SGKs activate ion channels (e.g., ENaC, TRPV5, ROMK, Kv1.3, KCNE1/KCNQ1, GluR1, GluR6), carriers (e.g., NHE3, GLUT1, SGLT1, EAAT1-5), and the Na+-K+-ATPase. They regulate the activity of enzymes (e.g., glycogen synthase kinase-3, ubiquitin ligase Nedd4-2, phosphomannose mutase-2) and transcription factors (e.g., forkhead transcription factor FKHRL1, beta-catenin, nuclear factor kappaB). SGKs participate in the regulation of transport, hormone release, neuroexcitability, cell proliferation, and apoptosis. SGK1 contributes to Na+ retention and K+ elimination of the kidney, mineralocorticoid stimulation of salt appetite, glucocorticoid stimulation of intestinal Na+/H+ exchanger and nutrient transport, insulin-dependent salt sensitivity of blood pressure and salt sensitivity of peripheral glucose uptake, memory consolidation, and cardiac repolarization. A common ( approximately 5% prevalence) SGK1 gene variant is associated with increased blood pressure and body weight. SGK1 may thus contribute to metabolic syndrome. SGK1 may further participate in tumor growth, neurodegeneration, fibrosing disease, and the sequelae of ischemia. SGK3 is required for adequate hair growth and maintenance of intestinal nutrient transport and influences locomotive behavior. In conclusion, the SGKs cover a wide variety of physiological functions and may play an active role in a multitude of pathophysiological conditions. There is little doubt that further targets will be identified that are modulated by the SGK isoforms and that further SGK-dependent in vivo physiological functions and pathophysiological conditions will be defined.
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Affiliation(s)
- Florian Lang
- Department of Physiology, University of Tuebingen, Tuebingen, Germany.
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72
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Hersh BM, Nelson CE, Stoll SJ, Norton JE, Albert TJ, Carroll SB. The UBX-regulated network in the haltere imaginal disc of D. melanogaster. Dev Biol 2006; 302:717-27. [PMID: 17174297 PMCID: PMC1892158 DOI: 10.1016/j.ydbio.2006.11.011] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2006] [Revised: 10/20/2006] [Accepted: 11/03/2006] [Indexed: 11/27/2022]
Abstract
Hox proteins have been proposed to act at multiple levels within regulatory hierarchies and to directly control the expression of a plethora of target genes. However, for any specific Hox protein or tissue, very few direct in vivo-regulated target genes have been identified. Here, we have identified target genes of the Hox protein Ultrabithorax (UBX), which modifies the genetic regulatory network of the wing to generate the haltere, a modified hindwing. We used whole-genome microarrays and custom arrays including all predicted transcription factors and signaling molecules in the Drosophila melanogaster genome to identify differentially expressed genes in wing and haltere imaginal discs. To elucidate the regulation of selected genes in more detail, we isolated cis-regulatory elements (CREs) for genes that were specifically expressed in either the wing disc or haltere disc. We demonstrate that UBX binds directly to sites in one element, and these sites are critical for activation in the haltere disc. These results indicate that haltere and metathoracic segment morphology is not achieved merely by turning off the wing and mesothoracic development programs, but rather specific genes must also be activated to form these structures. The evolution of haltere morphology involved changes in UBX-regulated target genes, both positive and negative, throughout the wing genetic regulatory network.
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Affiliation(s)
- Bradley M Hersh
- Howard Hughes Medical Institute and University of Wisconsin-Madison, 1525 Linden Drive, Madison, WI 53703, USA.
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73
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Yamada G, Suzuki K, Haraguchi R, Miyagawa S, Satoh Y, Kamimura M, Nakagata N, Kataoka H, Kuroiwa A, Chen Y. Molecular genetic cascades for external genitalia formation: an emerging organogenesis program. Dev Dyn 2006; 235:1738-52. [PMID: 16598715 DOI: 10.1002/dvdy.20807] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
External genitalia are anatomical structures located at the posterior embryonic region as part of several urogenital/reproductive organs. The embryonic anlage of the external genitalia, the genital tubercle (GT) develops as a bud-shaped structure with an initial urethral plate and later urethra. Embryonic external genitalia are considered to be one of the appendages. Recent experiments suggest that essential regulatory genes possess similar functions for the outgrowth regulation of the GT and limb appendages. The transient embryonic epithelia located in the distal GT are called the distal urethral epithelium (DUE) regulating, at least in part, the (distal) GT development. This review covers the available data about early patterning of GT and discusses the molecular developmental similarities and points of divergence between the different appendages. Development of the male and female external genitalia is also reviewed.
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Affiliation(s)
- G Yamada
- Center for Animal Resources and Development (CARD), Graduate School of Medical and Pharmaceutical Sciences, Kumamoto University, Kumamoto, Japan.
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74
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Tucker RP, Kenzelmann D, Trzebiatowska A, Chiquet-Ehrismann R. Teneurins: transmembrane proteins with fundamental roles in development. Int J Biochem Cell Biol 2006; 39:292-7. [PMID: 17095284 DOI: 10.1016/j.biocel.2006.09.012] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2006] [Revised: 09/26/2006] [Accepted: 09/27/2006] [Indexed: 12/11/2022]
Abstract
Teneurins are a novel family of transmembrane proteins expressed during pattern formation and morphogenesis. Originally discovered as ten-m and ten-a in Drosophila, four vertebrate teneurins as well as a Caenorhabditis elegans homologue were identified. The conserved domain architecture of teneurins includes an intracellular domain containing polyproline motifs. The long extracellular domain consists of eight EGF-like repeats, a region of conserved cysteines and unique YD-repeats. Vertebrate teneurins are most prominently expressed in the developing central nervous system, but are also expressed in developing limbs. In C. elegans, RNAi experiments and studies of mutants reveal that teneurins are required during fundamental developmental processes like cell migration and axon pathfinding. Cell culture experiments suggest that the intracellular domain of teneurins translocates to the nucleus following release from the membrane by proteolytic processing. Interestingly, the human teneurin-1 gene is located on the X-chromosome in a region where several families with X-linked mental retardation are mapped.
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Affiliation(s)
- Richard P Tucker
- Department of Cell Biology and Human Anatomy, University of California at Davis, Davis, CA 95616, USA.
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75
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Kurzrock EA, Delair S. Hypospadias and Kallmann's syndrome: distinction between morphogenesis and growth of the male phallus. J Pediatr Urol 2006; 2:515-7. [PMID: 18947671 DOI: 10.1016/j.jpurol.2005.11.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2005] [Accepted: 11/12/2005] [Indexed: 11/16/2022]
Abstract
Although some boys with hypospadias have a small phallus, few actually have micropenis. Boys with Kallmann's syndrome have an endocrinopathy and micropenis, yet the disease is not associated with hypospadias. We present a boy affected by both Kallmann's syndrome and hypospadias. One might assume a closer association of these two diseases, as they both are hormonally dependent and severely affect the genitalia. In actuality, the coexistence of the two disorders has not been previously reported. This rare association provides the opportunity to consider how the morphogenesis and growth of the male phallus are temporally and hormonally distinct.
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Affiliation(s)
- Eric A Kurzrock
- Department of Urology, UC Davis School of Medicine, 4860 Y Street, Suite 3500, Sacramento, CA 95817, USA.
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76
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Wilhelm D, Koopman P. The makings of maleness: towards an integrated view of male sexual development. Nat Rev Genet 2006; 7:620-31. [PMID: 16832429 DOI: 10.1038/nrg1903] [Citation(s) in RCA: 160] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
As the mammalian embryo develops, it must engage one of the two distinct programmes of gene activity, morphogenesis and organogenesis that characterize males and females. In males, sexual development hinges on testis determination and differentiation, but also involves many coordinated transcriptional, signalling and endocrine networks that underpin the masculinization of other organs and tissues, including the brain. Here we bring together current knowledge about these networks, identify gaps in the overall picture, and highlight the known defects that lead to disorders of male sexual development.
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Affiliation(s)
- Dagmar Wilhelm
- Division of Molecular Genetics and Development, Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD 4072, Australia
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77
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Pearson JC, Lemons D, McGinnis W. Modulating Hox gene functions during animal body patterning. Nat Rev Genet 2006; 6:893-904. [PMID: 16341070 DOI: 10.1038/nrg1726] [Citation(s) in RCA: 618] [Impact Index Per Article: 34.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
With their power to shape animal morphology, few genes have captured the imagination of biologists as the evolutionarily conserved members of the Hox clusters have done. Recent research has provided new insight into how Hox proteins cause morphological diversity at the organismal and evolutionary levels. Furthermore, an expanding collection of sequences that are directly regulated by Hox proteins provides information on the specificity of target-gene activation, which might allow the successful prediction of novel Hox-response genes. Finally, the recent discovery of microRNA genes within the Hox gene clusters indicates yet another level of control by Hox genes in development and evolution.
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Affiliation(s)
- Joseph C Pearson
- Section in Cell & Developmental Biology, University of California, San Diego, La Jolla, California 92093, USA
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78
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Cobb J, Dierich A, Huss-Garcia Y, Duboule D. A mouse model for human short-stature syndromes identifies Shox2 as an upstream regulator of Runx2 during long-bone development. Proc Natl Acad Sci U S A 2006; 103:4511-5. [PMID: 16537395 PMCID: PMC1450202 DOI: 10.1073/pnas.0510544103] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Deficiencies or mutations in the human pseudoautosomal SHOX gene are associated with a series of short-stature conditions, including Turner syndrome, Leri-Weill dyschondrosteosis, and Langer mesomelic dysplasia. Although this gene is absent from the mouse genome, the closely related paralogous gene Shox2 displays a similar expression pattern in developing limbs. Here, we report that the conditional inactivation of Shox2 in developing appendages leads to a strong phenotype, similar to the human conditions, although it affects a different proximodistal limb segment. Furthermore, using this mouse model, we establish the cellular etiology of these defects and show that Shox2 acts upstream the Runx2 gene, a key regulator of chondrogenesis.
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Affiliation(s)
- John Cobb
- *Department of Zoology and Animal Biology and National Research Center “Frontiers in Genetics,” Sciences III, University of Geneva, Quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland; and
| | - Andrée Dierich
- Institut de Génétique et de Biologie Moléculaire et Cellulaire/Institut Clinique de la Souris, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur/Collège de France, BP 10142, 67404 Strasbourg, France
| | - Yolande Huss-Garcia
- Institut de Génétique et de Biologie Moléculaire et Cellulaire/Institut Clinique de la Souris, Centre National de la Recherche Scientifique/Institut National de la Santé et de la Recherche Médicale/Université Louis Pasteur/Collège de France, BP 10142, 67404 Strasbourg, France
| | - Denis Duboule
- *Department of Zoology and Animal Biology and National Research Center “Frontiers in Genetics,” Sciences III, University of Geneva, Quai Ernest Ansermet 30, 1211 Geneva 4, Switzerland; and
- To whom correspondence should be addressed. E-mail:
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79
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Mohit P, Makhijani K, Madhavi MB, Bharathi V, Lal A, Sirdesai G, Reddy VR, Ramesh P, Kannan R, Dhawan J, Shashidhara LS. Modulation of AP and DV signaling pathways by the homeotic gene Ultrabithorax during haltere development in Drosophila. Dev Biol 2006; 291:356-67. [PMID: 16414040 DOI: 10.1016/j.ydbio.2005.12.022] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2005] [Revised: 12/05/2005] [Accepted: 12/06/2005] [Indexed: 11/24/2022]
Abstract
Suppression of wing fate and specification of haltere fate in Drosophila by the homeotic gene Ultrabithorax is a classical example of Hox regulation of serial homology (Lewis, E.B. 1978. Nature 276, 565-570) and has served as a paradigm for understanding homeotic gene function. We have used DNA microarray analyses to identify potential targets of Ultrabithorax function during haltere specification. Expression patterns of 18 validated target genes and functional analyses of a subset of these genes suggest that down-regulation of both anterior-posterior and dorso-ventral signaling is critical for haltere fate specification. This is further confirmed by the observation that combined over-expression of Decapentaplegic and Vestigial is sufficient to override the effect of Ubx and cause dramatic haltere-to-wing transformations. Our results also demonstrate that analysis of the differential development of wing and haltere is a good assay system to identify novel regulators of key signaling pathways.
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Affiliation(s)
- Prasad Mohit
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500 007, India
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80
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Salsi V, Zappavigna V. Hoxd13 and Hoxa13 Directly Control the Expression of the EphA7 Ephrin Tyrosine Kinase Receptor in Developing Limbs. J Biol Chem 2006; 281:1992-9. [PMID: 16314414 DOI: 10.1074/jbc.m510900200] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Hoxa and Hoxd genes, related to the Drosophila Abd-B gene, display regionally restricted expression patterns and are necessary for the formation of the limb skeletal elements. Hox genes encode transcription factors, which are supposed to control the expression of a series of downstream target genes, whose nature has remained largely elusive. Several genes were identified that are differentially expressed in relation to Hox gene activity; few studies, however, explored their direct regulation by Hox proteins. Ephrin tyrosine kinase receptors and ephrins have been proposed as Hox targets, and recently, evidence was gained for their role in limb development. The expression of the EphA7 gene in developing limbs was shown to correlate with the expression of Hoxa13 and Hoxd13; however, its direct regulation by these genes has never been assessed. We have characterized the EphA7 promoter region and show that it contains multiple binding sites for paralog group 13 Hox proteins. We found that one of these sites is bound in vivo by HOXA13 and HOXD13 and by endogenous Hoxd13 in developing mouse limbs. Moreover, we show that HOXD13 and HOXA13 activate transcription from the EphA7 promoter and that a mutation of the HOXA13/HOXD13 binding site was sufficient to abolish activation. Conversely, the HOXD13(147L) mutation, identified in patients displaying a novel brachydactyly-polydactyly syndrome, does not bind to in vivo, and fails to transactivate the EphA7 promoter. These results establish that EphA7 is a direct downstream target of Hoxd13 and Hoxa13 during limb development, thus providing further insight into the regulatory networks that control limb patterning.
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Affiliation(s)
- Valentina Salsi
- Department of Animal Biology, University of Modena and Reggio Emilia, Via G. Campi 213/d, Modena 41100, Italy
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