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  • The Company of Biologists  (20)
  • English  (20)
  • 1
    In: Development, The Company of Biologists, Vol. 128, No. 16 ( 2001-08-15), p. 3061-3070
    Abstract: Semaphorin 3C is a secreted member of the semaphorin gene family. To investigate its function in vivo, we have disrupted the semaphorin 3Clocus in mice by targeted mutagenesis. semaphorin 3C mutant mice die within hours after birth from congenital cardiovascular defects consisting of interruption of the aortic arch and improper septation of the cardiac outflow tract. This phenotype is similar to that reported following ablation of the cardiac neural crest in chick embryos and resembles congenital heart defects seen in humans. Semaphorin 3C is expressed in the cardiac outflow tract as neural crest cells migrate into it. Their entry is disrupted in semaphorin 3C mutant mice. These data suggest that semaphorin 3C promotes crest cell migration into the proximal cardiac outflow tract.
    Type of Medium: Online Resource
    ISSN: 1477-9129 , 0950-1991
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2001
    detail.hit.zdb_id: 2007916-3
    SSG: 12
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  • 2
    Online Resource
    Online Resource
    The Company of Biologists ; 2001
    In:  Development Vol. 128, No. 16 ( 2001-08-15), p. 3071-3080
    In: Development, The Company of Biologists, Vol. 128, No. 16 ( 2001-08-15), p. 3071-3080
    Abstract: Classic studies using avian model systems have demonstrated that cardiac neural crest cells are required for proper development of the cardiovascular system. Environmental influences that perturb neural crest development cause congenital heart defects in laboratory animals and in man. However, little progress has been made in determining molecular programs specifically regulating cardiac neural crest migration and function. Only recently have complex transgenic tools become available that confirm the presence of cardiac neural crest cells in the mammalian heart. These studies have relied upon the use of transgenic mouse lines and fate-mapping studies using Cre recombinase and neural crest-specific promoters. In this study, we use these techniques to demonstrate that PlexinA2 is expressed by migrating and postmigratory cardiac neural crest cells in the mouse. Plexins function as co-receptors for semaphorin signaling molecules and mediate axon pathfinding in the central nervous system. We demonstrate that PlexinA2-expressing cardiac neural crest cells are patterned abnormally in several mutant mouse lines with congenital heart disease including those lacking the secreted signaling molecule Semaphorin 3C. These data suggest a parallel between the function of semaphorin signaling in the central nervous system and in the patterning of cardiac neural crest in the periphery.
    Type of Medium: Online Resource
    ISSN: 1477-9129 , 0950-1991
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2001
    detail.hit.zdb_id: 2007916-3
    SSG: 12
    Location Call Number Limitation Availability
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  • 3
    In: Development, The Company of Biologists, Vol. 138, No. 20 ( 2011-10-15), p. 4555-4564
    Abstract: Zinc-finger nucleases (ZFNs) allow targeted gene inactivation in a wide range of model organisms. However, construction of target-specific ZFNs is technically challenging. Here, we evaluate a straightforward modular assembly-based approach for ZFN construction and gene inactivation in zebrafish. From an archive of 27 different zinc-finger modules, we assembled more than 70 different zinc-finger cassettes and evaluated their specificity using a bacterial one-hybrid assay. In parallel, we constructed ZFNs from these cassettes and tested their ability to induce lesions in zebrafish embryos. We found that the majority of zinc-finger proteins assembled from these modules have favorable specificities and nearly one-third of modular ZFNs generated lesions at their targets in the zebrafish genome. To facilitate the application of ZFNs within the zebrafish community we constructed a public database of sites in the zebrafish genome that can be targeted using this archive. Importantly, we generated new germline mutations in eight different genes, confirming that this is a viable platform for heritable gene inactivation in vertebrates. Characterization of one of these mutants, gata2a, revealed an unexpected role for this transcription factor in vascular development. This work provides a resource to allow targeted germline gene inactivation in zebrafish and highlights the benefit of a definitive reverse genetic strategy to reveal gene function.
    Type of Medium: Online Resource
    ISSN: 1477-9129 , 0950-1991
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2011
    detail.hit.zdb_id: 2007916-3
    SSG: 12
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  • 4
    Online Resource
    Online Resource
    The Company of Biologists ; 2019
    In:  Development Vol. 146, No. 3 ( 2019-02-01)
    In: Development, The Company of Biologists, Vol. 146, No. 3 ( 2019-02-01)
    Abstract: Dynamic organization of chromatin within the three-dimensional nuclear space has been postulated to regulate gene expression and cell fate. Here, we define the genome-wide distribution of nuclear peripheral heterochromatin as a multipotent P19 cell adopts either a neural or a cardiac fate. We demonstrate that H3K9me2-marked nuclear peripheral heterochromatin undergoes lineage-specific reorganization during cell-fate determination. This is associated with spatial repositioning of genomic loci away from the nuclear periphery as shown by 3D immuno-FISH. Locus repositioning is not always associated with transcriptional changes, but a subset of genes is upregulated. Mef2c is specifically repositioned away from the nuclear periphery during early neurogenic differentiation, but not during early cardiogenic differentiation, with associated transcript upregulation. Myocd is specifically repositioned during early cardiogenic differentiation, but not during early neurogenic differentiation, and is transcriptionally upregulated at later stages of cardiac differentiation. We provide experimental evidence for lineage-specific regulation of nuclear architecture during cell-fate determination in a mouse cell line.
    Type of Medium: Online Resource
    ISSN: 1477-9129 , 0950-1991
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2019
    detail.hit.zdb_id: 2007916-3
    SSG: 12
    Location Call Number Limitation Availability
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  • 5
    Online Resource
    Online Resource
    The Company of Biologists ; 2006
    In:  Development Vol. 133, No. 8 ( 2006-04-15), p. 1565-1573
    In: Development, The Company of Biologists, Vol. 133, No. 8 ( 2006-04-15), p. 1565-1573
    Abstract: Individuals with 22q11 deletion syndrome (22q11DS;DiGeorge/velo-cardio-facial syndrome) have multiple congenital malformations,including cardiovascular defects. Most individuals with this syndrome possess 1.5-3.0 Mb hemizygous 22q11.2 deletions. The T-box transcription factor TBX1, lies within the nested 1.5 Mb interval and is a strong candidate for its etiology. Inactivation of Tbx1 in the mouse results in neonatal lethality owing to the presence of a single cardiac outflow tract. One important goal is to understand the molecular pathogenesis of cardiovascular defects in this syndrome. However, the molecular pathways of Tbx1 are still largely unexplored. Here, we show that Tbx1is co-expressed with the bicoid-like homeodomain transcription factor Pitx2 in secondary heart field cells in the pharyngeal mesenchyme. In situ hybridization studies in Tbx1-/- mouse embryos revealed downregulation of Pitx2 in these cells. To test for a possible genetic interaction, we intercrossed Tbx1+/- and Pitx2+/- mice. Tbx1+/-;Pitx2+/- mice died perinatally with cardiac defects, including double outlet right ventricle, and atrial and ventricular septal defects, all occurring with variable penetrance. An enhancer located between exons 4 and 5 in which a putative T-half site was identified near an Nkx2.5-binding site regulates asymmetric expression of Pitx2. We show using in vitro studies that Tbx1 binds to this site and activates the Pitx2 enhancer with the synergistic action of Nkx2.5. The results presented in this study unravel a novel Tbx1-Pitx2 pathway linking Tbx1 to asymmetric cardiac morphogenesis.
    Type of Medium: Online Resource
    ISSN: 1477-9129 , 0950-1991
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2006
    detail.hit.zdb_id: 2007916-3
    SSG: 12
    Location Call Number Limitation Availability
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  • 6
    Online Resource
    Online Resource
    The Company of Biologists ; 2004
    In:  Development Vol. 131, No. 14 ( 2004-07-15), p. 3481-3490
    In: Development, The Company of Biologists, Vol. 131, No. 14 ( 2004-07-15), p. 3481-3490
    Abstract: Cardiac neural crest cells are multipotent migratory cells that contribute to the formation of the cardiac outflow tract and pharyngeal arch arteries. Neural crest-related developmental defects account for a large proportion of congenital heart disorders. Recently, the genetic bases for some of these disorders have been elucidated, and signaling pathways required for induction,migration and differentiation of cardiac neural crest have emerged. Bone morphogenetic proteins comprise a family of secreted ligands implicated in numerous aspects of organogenesis, including heart and neural crest development. However, it has remained generally unclear whether BMP ligands act directly on neural crest or cardiac myocytes during cardiac morphogenesis,or function indirectly by activating other cell types. Studies on BMP receptor signaling during organogenesis have been hampered by the fact that receptor knockouts often lead to early embryonic lethality. We have used a Cre/loxP system for neural crest-specific deletion of the type I receptor, ALK2, in mouse embryos. Mutant mice display cardiovascular defects, including persistent truncus arteriosus, and abnormal maturation of the aortic arch reminiscent of common forms of human congenital heart disease. Migration of mutant neural crest cells to the outflow tract is impaired, and differentiation to smooth muscle around aortic arch arteries is deficient. Moreover, in Alk2 mutants, the distal outflow tract fails to express Msx1, one of the major effectors of BMP signaling. Thus, the type I BMP receptor ALK2 plays an essential cell-autonomous role in the development of the cardiac outflow tract and aortic arch derivatives.
    Type of Medium: Online Resource
    ISSN: 1477-9129 , 0950-1991
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2004
    detail.hit.zdb_id: 2007916-3
    SSG: 12
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  • 7
    In: Disease Models & Mechanisms, The Company of Biologists
    Abstract: Neurofibromatosis type 1 (NF1) is a common, dominantly inherited genetic disorder that results from mutations in the neurofibromin 1 (NF1) gene. Affected individuals demonstrate abnormalities in neural crest-derived tissues that include hyperpigmented skin lesions and benign peripheral nerve sheath tumors. NF1 patients also have a predisposition to malignancies including juvenile myelomonocytic leukemia (JMML), optic glioma, glioblastoma, schwannoma, and malignant peripheral nerve sheath tumors (MPNSTs). In an effort to better define the molecular and cellular determinants of NF1 disease pathogenesis in vivo, we employed targeted mutagenesis strategies to generate zebrafish harboring stable germline mutations in nf1a and nf1b, orthologues of NF1. Animals homozygous for loss-of-function alleles of nf1a or nf1b alone are phenotypically normal and viable. Homozygous loss of both alleles in combination generates larval phenotypes that resemble aspects of the human disease and results in larval lethality between 7 and 10 days post fertilization. nf1-null larvae demonstrate significant central and peripheral nervous system defects. These include aberrant proliferation and differentiation of oligodendrocyte progenitor cells (OPCs), dysmorphic myelin sheaths, and hyperplasia of Schwann cells. Loss of nf1 contributes to tumorigenesis as demonstrated by an accelerated onset and increased penetrance of high-grade gliomas and MPNSTs in adult nf1a+/-; nf1b-/-; p53e7/e7 animals. nf1-null larvae also demonstrate significant motor and learning defects. Importantly, we identify and quantitatively analyze a novel melanophore phenotype in nf1-null larvae, providing the first animal model of the pathognomonic pigmentation lesions of NF1. Together, these findings support a role for nf1a and nf1b as potent tumor suppressor genes that also function in the development of both central and peripheral glial cells as well as melanophores in zebrafish.
    Type of Medium: Online Resource
    ISSN: 1754-8411 , 1754-8403
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2012
    detail.hit.zdb_id: 2451104-3
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  • 8
    In: Development, The Company of Biologists, Vol. 133, No. 10 ( 2006-05-15), p. 2063-2073
    Abstract: Connexin 43 (Cx43) is expressed in the embryonic heart, cardiac neural crest (CNC) and neural tube, and germline knockout (KO) of Cx43 results in aberrant cardiac outflow tract (OFT) formation and abnormal coronary deployment. Prior studies suggest a vital role for CNC expression of Cx43 in heart development. Surprisingly, we found that conditional knockout (CKO) of Cx43 in the dorsal neural tube and CNC mediated by Wnt1-Cre failed to recapitulate the Cx43-null OFT phenotype, although coronary vasculature was abnormal in this mutant line. A broader CKO mediated by P3pro (Pax3)-Cre,involving both ventral and dorsal aspects of the thoracic neural tube and CNC,resulted in infundibular bulging and coronary anomalies similar to those seen in germline Cx43-null hearts. P3pro-Cre-mediated loss of Cx43 in the neural tube was characterized by a late phase of cellular delamination from the dorsal and lateral neural tube, a markedly increased abundance of neuroepithelium-derived cells outside of the neural tube and an excess of such cells infiltrating the heart and infundibulum. Thus, expression of Cx43 in the CNC is crucial for normal coronary deployment, but Cx43 is not required in the CNC for normal OFT morphogenesis. Rather, this study suggests a novel function for Cx43 in which Cx43 acts through non-crest neuroepithelial cells to suppress cellular delamination from the neural tube and thereby preserve normal OFT development.
    Type of Medium: Online Resource
    ISSN: 1477-9129 , 0950-1991
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 2006
    detail.hit.zdb_id: 2007916-3
    SSG: 12
    Location Call Number Limitation Availability
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  • 9
    Online Resource
    Online Resource
    The Company of Biologists ; 1998
    In:  Development Vol. 125, No. 22 ( 1998-11-15), p. 4359-4367
    In: Development, The Company of Biologists, Vol. 125, No. 22 ( 1998-11-15), p. 4359-4367
    Abstract: Endocardial cushions are the precursors of the cardiac valves and form by a process of epithelial-mesenchymal transformation. Secreted growth factors from myocardium induce endocardial cells to transform into mesenchyme and invade the overlying extracellular matrix. Here, we show that the product of the Nf1 neurofibromatosis gene is required to regulate this event. In the absence of neurofibromin, mouse embryo hearts develop overabundant endocardial cushions due to hyperproliferation and lack of normal apoptosis. Neurofibromin deficiency in explant cultures is reproduced by activation of ras signaling pathways, and the Nf1−/− mutant phenotype is prevented by inhibiting ras in vitro. These results indicate that neurofibromin normally acts to modulate epithelial-mesenchymal transformation and proliferation in the developing heart by down regulating ras activity.
    Type of Medium: Online Resource
    ISSN: 0950-1991 , 1477-9129
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1998
    detail.hit.zdb_id: 2007916-3
    SSG: 12
    Location Call Number Limitation Availability
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  • 10
    Online Resource
    Online Resource
    The Company of Biologists ; 1999
    In:  Development Vol. 126, No. 8 ( 1999-04-15), p. 1665-1674
    In: Development, The Company of Biologists, Vol. 126, No. 8 ( 1999-04-15), p. 1665-1674
    Abstract: In developing vertebrate embryos, Pax3 is expressed in the neural tube and in the paraxial mesoderm that gives rise to skeletal muscles. Pax3 mutants develop muscular and neural tube defects; furthermore, Pax3 is essential for the proper activation of the myogenic determination factor gene, MyoD, during early muscle development and PAX3 chromosomal translocations result in muscle tumors, providing evidence that Pax3 has diverse functions in myogenesis. To investigate the specific functions of Pax3 in development, we have examined cell survival and gene expression in presomitic mesoderm, somites and neural tube of developing wild-type and Pax3 mutant (Splotch) mouse embryos. Disruption of Pax3 expression by antisense oligonucleotides significantly impairs MyoD activation by signals from neural tube/notochord and surface ectoderm in cultured presomitic mesoderm (PSM), and is accompanied by a marked increase in programmed cell death. In Pax3 mutant (Splotch) embryos, MyoD is activated normally in the hypaxial somite, but MyoD-expressing cells are disorganized and apoptosis is prevalent in newly formed somites, but not in the neural tube or mature somites. In neural tube and somite regions where cell survival is maintained, the closely related Pax7 gene is upregulated, and its expression becomes expanded into the dorsal neural tube and somites, where Pax3 would normally be expressed. These results establish that Pax3 has complementary functions in MyoD activation and inhibition of apoptosis in the somitic mesoderm and in repression of Pax7 during neural tube and somite development.
    Type of Medium: Online Resource
    ISSN: 0950-1991 , 1477-9129
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1999
    detail.hit.zdb_id: 2007916-3
    SSG: 12
    Location Call Number Limitation Availability
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