Axial skeletal defects caused by mutation in the spondylocostal dysplasia/pudgy geneDll3are associated with disruption of the segmentation clock within the presomitic mesoderm

A loss-of-function mutation in the mouse delta-like3 (Dll3) gene has been generated following gene targeting, and results in severe axial skeletal defects. These defects, which consist of highly disorganised vertebrae and costal defects, are similar to those associated with the Dll3-dependent pudgy mutant in mouse and with spondylocostal dysplasia (MIM 277300) in humans. This study demonstrates that Dll3neo and Dll3pu are functionally equivalent alleles with respect to the skeletal dysplasia, and we suggest that the three human DLL3 mutations associated with spondylocostal dysplasia are also functionally equivalent to the Dll3neo null allele. Our phenotypic analysis of Dll3neo/Dll3neo mutants shows that the developmental origins of the skeletal defects lie in delayed and irregular somite formation, which results in the perturbation of anteroposterior somite polarity. As the expression of Lfng, Hes1, Hes5 and Hey1 is disrupted in the presomitic mesoderm, we suggest that the somitic aberrations are founded in the disruption of the segmentation clock that intrinsically oscillates within presomitic mesoderm.

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Geminin Orchestrates Somite Formation by Regulating Fgf8 and Notch Signaling

BioMed Research International ◽

10.1155/2018/6543196 ◽

2018 ◽

Vol 2018 ◽

pp. 1-13

Author(s):

Wei Huang ◽

Yu Zhang ◽

Kang Cao ◽

Lingfei Luo ◽

Sizhou Huang

Keyword(s):

Notch Signaling ◽

Signaling Pathways ◽

Critical Factor ◽

Loss Of Function ◽

Presomitic Mesoderm ◽

Tail Bud ◽

Notch Activity ◽

Somite Formation ◽

First Time

During somitogenesis, Fgf8 maintains the predifferentiation stage of presomitic mesoderm (PSM) cells and its retraction gives a cue for somite formation. Delta/Notch initiates the expression of oscillation genes in the tail bud and subsequently contributes to somite formation in a periodic way. Whether there exists a critical factor coordinating Fgf8 and Notch signaling pathways is largely unknown. Here, we demonstrate that the loss of function of geminin gave rise to narrower somites as a result of derepressed Fgf8 gradient in the PSM and tail bud. Furthermore, in geminin morphants, the somite boundary could not form properly but the oscillation of cyclic genes was normal, displaying the blurry somitic boundary and disturbed somite polarity along the AP axis. In mechanism, these manifestations were mediated by the disrupted association of the geminin/Brg1 complex with intron 3 of mib1. The latter interaction was found to positively regulate mib1 transcription, Notch activity, and sequential somite segmentation during somitogenesis. In addition, geminin was also shown to regulate the expression of deltaD in mib1-independent way. Collectively, our data for the first time demonstrate that geminin regulates Fgf8 and Notch signaling to regulate somite segmentation during somitogenesis.

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PAPC couples the Segmentation Clock to somite morphogenesis by regulating N-cadherin dependent adhesion

10.1101/071084 ◽

2016 ◽

Cited By ~ 1

Author(s):

Jerome Chal ◽

Charlene Guillot ◽

Olivier Pourquie

Keyword(s):

Mouse Embryos ◽

Loss Of Function ◽

Presomitic Mesoderm ◽

Segmentation Clock ◽

Anterior Compartment ◽

Chicken Embryos ◽

Differential Adhesion ◽

Complementary Pattern ◽

The Future

Vertebrate segmentation is characterized by the periodic formation of epithelial somites from the mesenchymal presomitic mesoderm (PSM). How the rhythmic signaling pulse delivered by the Segmentation Clock is translated into the periodic morphogenesis of somites remains poorly understood. Here, we focused on the role of Paraxial protocadherin (PAPC/Pcdh8) in this process. We show that in chicken and mouse embryos, PAPC expression is tightly regulated by the Clock and Wavefront system in the posterior PSM. We observed that PAPC exhibits a striking complementary pattern to N-Cadherin (CDH2), marking the interface of the future somite boundary in the anterior PSM. Gain and loss of function of PAPC in chicken embryos disrupt somite segmentation by altering the CDH2-dependent epithelialization of PSM cells. Our data suggest that clathrin-mediated endocytosis is increased in PAPC expressing cells, subsequently affecting CDH2 internalization in the anterior compartment of the future somite. This in turn generates a differential adhesion interface, allowing formation of the acellular fissure that defines the somite boundary. Thus periodic expression of PAPC downstream of the Segmentation Clock triggers rhythmic endocytosis of CDH2, allowing for segmental de-adhesion and individualization of somites.

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16. Physiological effects of IDH1 loss-of-function on Chondrocyte Differentiation through Hedgehog Pathway upregulation

Inquiry@Queen's Undergraduate Research Conference Proceedings ◽

10.24908/iqurcp.9897 ◽

2018 ◽

Author(s):

Cassie Tyson

Keyword(s):

Developmental Stages ◽

Hedgehog Pathway ◽

Chondrocyte Differentiation ◽

Loss Of Function ◽

Wild Type ◽

Phenotypic Analysis ◽

Growth Plate Chondrocytes ◽

Idh Mutations ◽

Cartilage Tumors ◽

Deficient Mice

Cartilage tumors are the most common and terminal primary neoplasms in bone. Physiologically, bones formed through endochondral ossification are regulated by the Hedgehog pathway and Parathyroid hormone-like hormone feedback loop. The upregulation of the infamous Hedgehog pathway has been demonstrated in several non-cartilaginous neoplasms. Recently, frequent mutational events of isocitrate dehydrogenase1 (IDH1) were identified in cartilage tumors. In other neoplasms, IDH mutations produces an oncometabolite that can promote HIF1a activation, contributing to tumorigenesis. Currently, the role of IDH1 mutations in cartilage tumors remain unknown. Investigating the physiological aspect of IDH1proves useful in identifying novel therapeutic targets for cartilage tumors. IDH1 deficient and wild-type littermates, were harvested for forelimbs and hindlimbs at various developmental stages for phenotypic analysis via hematoxylin and eosin staining. Histological analysis demonstrated IDH1 homozygous deficient mice at embryonic stages exhibited dwarfism and an elongated layer of hypertrophic chondrocytes. This was verified via immunohistochemistry Type 10 Collagen staining and Quantitative PCR (qPCR) using the chondrocyte terminal differentiation marker Col10a1. Whole skeletons of IDH1 deficient mice were subjected to skeletal double staining which demonstrated delayed mineralization of underdeveloped IDH1 deficient mice contrasted with wild-type littermates. qPCR was performed to examine the status of chondrocyte differentiation through the Hedgehog pathway in cultured primarymouse growth plate chondrocytes. Interestingly, IDH1 deficient non-neoplastic cells revealed significant upregulation of Hedgehog target molecules in IDH1 deficient chondrocytes. As a result, the loss-offunction of IDH1 was identified as a potential impairment of chondrocyte differentiation and a factor towards chondrocyte tumorgenisis.

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her1, a zebrafish pair-rule like gene, acts downstream of notch signalling to control somite development

Development ◽

10.1242/dev.126.13.3005 ◽

1999 ◽

Vol 126 (13) ◽

pp. 3005-3014 ◽

Cited By ~ 8

Author(s):

C. Takke ◽

J.A. Campos-Ortega

Keyword(s):

Active Form ◽

Notch Signalling ◽

Paraxial Mesoderm ◽

Presomitic Mesoderm ◽

Essentially Normal ◽

Early Embryos ◽

Somite Formation ◽

Genes Encoding ◽

Ectopic Activation ◽

Pair Rule

During vertebrate embryonic development, the paraxial mesoderm becomes subdivided into metameric units known as somites. In the zebrafish embryo, genes encoding homologues of the proteins of the Drosophila Notch signalling pathway are expressed in the presomitic mesoderm and expression is maintained in a segmental pattern during somitogenesis. This expression pattern suggests a role for these genes during somite development. We misexpressed various zebrafish genes of this group by injecting mRNA into early embryos. RNA encoding a constitutively active form of notch1a (notch1a-intra) and a truncated variant of deltaD [deltaD(Pst)], as well as transcripts of deltaC and deltaD, the hairy-E(spl) homologues her1 and her4, and groucho2 were tested for their effects on somite formation, myogenesis and on the pattern of transcription of putative downstream genes. In embryos injected with any of these RNAs, with the exception of groucho2 RNA, the paraxial mesoderm differentiated normally into somitic tissue, but failed to segment correctly. Activation of notch results in ectopic activation of her1 and her4. This misregulation of the expression of her genes might be causally related to the observed mesodermal defects, as her1 and her4 mRNA injections led to effects similar to those seen with notch1a-intra. deltaC and deltaD seem to function after subdivision of the presomitic mesoderm, since the her gene transcription pattern in the presomitic mesoderm remains essentially normal after misexpression of delta genes. Whereas notch signalling alone apparently does not affect myogenesis, zebrafish groucho2 is involved in differentiation of mesodermal derivatives.

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PHENOTYPIC ANALYSIS OF OsTPKb LOSS OF FUNCTION MUTANT RICE LINES

Biotechnologia Acta ◽

10.15407/biotech8.04.122 ◽

2015 ◽

Vol 8 (4) ◽

pp. 122-127

Author(s):

Isayenkov S. V. ◽

Keyword(s):

Loss Of Function ◽

Phenotypic Analysis

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The allocation of cells in the presomitic mesoderm during somite segmentation in the mouse embryo

Development ◽

10.1242/dev.103.2.379 ◽

1988 ◽

Vol 103 (2) ◽

pp. 379-390 ◽

Cited By ~ 1

Author(s):

P.P. Tam

Keyword(s):

Mouse Embryo ◽

Colloidal Gold ◽

Wheat Germ ◽

Mouse Embryos ◽

Middle Region ◽

Presomitic Mesoderm ◽

Posterior Displacement ◽

Somite Formation ◽

Gold Conjugate

Orthotopic grafts of wheat germ agglutinin-colloidal gold conjugate (WGA-gold) labelled cells were used to demonstrate differences in the segmental fate of cells in the presomitic mesoderm of the early-somite-stage mouse embryos developing in vitro. Labelled cells in the anterior region of the presomitic mesoderm colonized the first three somites formed after grafting, while those grafted to the middle region of this tissue were found mostly in the 4th-7th newly formed somites. Labelled cells grafted to the posterior region were incorporated into somites whose somitomeres were not yet present in the presomitic mesoderm at the time of grafting. There was therefore an apparent posterior displacement of the grafted cells in the presomitic mesoderm. Colonization of somites by WGA-gold labelled cells was usually limited to two to three consecutive somites in the chimaera. The distribution of cells derived from a single graft to two somites was most likely due to the segregation of the labelled population when cells were allocated to adjacent meristic units during somite formation. Further spreading of the labelled cells to several somites in some cases was probably the result of a more extensive mixing of mesodermal cells among the somitomeres prior to somite segmentation.

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The Notch ligand, X-Delta-2, mediates segmentation of the paraxial mesoderm in Xenopus embryos

Development ◽

10.1242/dev.124.6.1169 ◽

1997 ◽

Vol 124 (6) ◽

pp. 1169-1178 ◽

Cited By ~ 31

Author(s):

W.C. Jen ◽

D. Wettstein ◽

D. Turner ◽

A. Chitnis ◽

C. Kintner

Keyword(s):

Paraxial Mesoderm ◽

Bhlh Gene ◽

Presomitic Mesoderm ◽

Notch 1 ◽

Notch Ligand ◽

Basic Helix Loop Helix ◽

Helix Loop Helix ◽

Vertebrate Embryo ◽

Somite Formation ◽

Segmental Expression

Segmentation of the vertebrate embryo begins when the paraxial mesoderm is subdivided into somites, through a process that remains poorly understood. To study this process, we have characterized X-Delta-2, which encodes the second Xenopus homolog of Drosophila Delta. Strikingly, X-Delta-2 is expressed within the presomitic mesoderm in a set of stripes that corresponds to prospective somitic boundaries, suggesting that Notch signaling within this region establishes a segmental prepattern prior to somitogenesis. To test this idea, we introduced antimorphic forms of X-Delta-2 and Xenopus Suppressor of Hairless (X-Su(H)) into embryos, and assayed the effects of these antimorphs on somite formation. In embryos expressing these antimorphs, the paraxial mesoderm differentiated normally into somitic tissue, but failed to segment properly. Both antimorphs also disrupted the segmental expression of X-Delta-2 and Hairy2A, a basic helix-loop-helix (bHLH) gene, within the presomitic mesoderm. These observations suggest that X-Delta-2, via X-Notch-1, plays a role in segmentation, by mediating cell-cell interactions that underlie the formation of a segmental prepattern prior to somitogenesis.

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AHK3-Mediated Cytokinin Signaling Is Required for the Delayed Leaf Senescence Induced by SSPP

International Journal of Molecular Sciences ◽

10.3390/ijms20082043 ◽

2019 ◽

Vol 20 (8) ◽

pp. 2043

Author(s):

Yanan Wang ◽

Xiyu Zhang ◽

Yanjiao Cui ◽

Lei Li ◽

Dan Wang ◽

...

Keyword(s):

Leaf Senescence ◽

Protein Phosphatase ◽

Developmental Process ◽

Loss Of Function ◽

Cytokinin Signaling ◽

Phenotypic Analysis ◽

Exogenous Cytokinin ◽

Cytokinin Treatment ◽

Encoding Gene ◽

Multiple Signaling

Leaf senescence is a highly-programmed developmental process regulated by an array of multiple signaling pathways. Our group previously reported that overexpression of the protein phosphatase-encoding gene SSPP led to delayed leaf senescence and significantly enhanced cytokinin responses. However, it is still unclear how the delayed leaf senescence phenotype is associated with the enhanced cytokinin responses. In this study, we introduced a cytokinin receptor AHK3 knockout into the 35S:SSPP background. The phenotypic analysis of double mutant revealed that AHK3 loss-of-function reversed the delayed leaf senescence induced by SSPP. Moreover, we found the hypersensitivity of 35S:SSPP to exogenous cytokinin treatment disappeared due to the introduction of AHK3 knockout. Collectively, our results demonstrated that AHK3-mediated cytokinin signaling is required for the delayed leaf senescence caused by SSPP overexpression and the detailed mechanism remains to be further elucidated.

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