scholarly journals The zebrafish presomitic mesoderm elongates through compression-extension

2021 ◽  
Author(s):  
Lewis Thomson ◽  
Leila Muresan ◽  
Benjamin Steventon
Keyword(s):  
Morphometric Analysis ◽  
Cell Tracking ◽  
Paraxial Mesoderm ◽  
Presomitic Mesoderm ◽  
Volume Increase ◽  
Extension Mechanism ◽  
Adopted Model ◽  
Vertebrate Embryos ◽  
Anterior Posterior

AbstractIn vertebrate embryos the presomitic mesoderm become progressively segmented into somites at the anterior end while extending along the anterior-posterior axis. A commonly adopted model to explain how this tissue elongates is that of posterior growth, driven in part by the addition of new cells from uncommitted progenitor populations in the tailbud. However, in zebrafish, much of somitogenesis is associated with an absence of overall volume increase and posterior progenitors do not contribute new cells until the final stages of somitogenesis. Here, we perform a comprehensive 3D morphometric analysis of the paraxial mesoderm and reveal that extension is linked to a volumetric decrease, compression in both dorsal-ventral and medio-lateral axes, and an increase in cell density. We also find that individual cells decrease in their cell volume over successive somite stages. Live cell tracking confirms that much of this tissue deformation occurs within the presomitic mesoderm progenitor zone and is associated with non-directional rearrangement. Furthermore, unlike the trunk somites that are laid down during gastrulation, tail somites develop from a tissue that can continue to elongate in the absence of functional PCP signalling. Taken together, we propose a compression-extension mechanism of tissue elongation that highlights the need to better understand the role of tissue intrinsic and extrinsic forces play in regulating morphogenesis.

Pax3 functions in cell survival and in pax7 regulation

Development ◽  
1999 ◽  
Vol 126 (8) ◽  
pp. 1665-1674 ◽  
Author(s):  
A.G. Borycki ◽  
J. Li ◽  
F. Jin ◽  
C.P. Emerson ◽  
J.A. Epstein
Keyword(s):  
Cell Survival ◽  
Neural Tube ◽  
Muscle Development ◽  
Paraxial Mesoderm ◽  
Wild Type ◽  
Presomitic Mesoderm ◽  
Surface Ectoderm ◽  
Dorsal Neural Tube ◽  
Vertebrate Embryos ◽  
Somitic Mesoderm

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.

The role of presenilin 1 during somite segmentation

Development ◽  
2001 ◽  
Vol 128 (8) ◽  
pp. 1391-1402 ◽  
Author(s):  
K.i. Koizumi ◽  
M. Nakajima ◽  
S. Yuasa ◽  
Y. Saga ◽  
T. Sakai ◽  
...  
Keyword(s):  
Notch Pathway ◽  
Notch Signalling ◽  
Signalling Pathway ◽  
Paraxial Mesoderm ◽  
Presenilin 1 ◽  
Wild Type ◽  
Presomitic Mesoderm ◽  
Notch Signalling Pathway ◽  
Deficient Mice

The Notch signalling pathway plays essential roles during the specification of the rostral and caudal somite halves and subsequent segmentation of the paraxial mesoderm. We have re-investigated the role of presenilin 1 (Ps1; encoded by Psen1) during segmentation using newly generated alleles of the Psen1 mutation. In Psen1-deficient mice, proteolytic activation of Notch1 was significantly affected and the expression of several genes involved in the Notch signalling pathway was altered, including Δ-like3, Hes5, lunatic fringe (Lfng) and Mesp2. Thus, Ps1-dependent activation of the Notch pathway is essential for caudal half somite development. We observed defects in Notch signalling in both the caudal and rostral region of the presomitic mesoderm. In the caudal presomitic mesoderm, Ps1 was involved in maintaining the amplitude of cyclic activation of the Notch pathway, as represented by significant reduction of Lfng expression in Psen1-deficient mice. In the rostral presomitic mesoderm, rapid downregulation of the Mesp2 expression in the presumptive caudal half somite depends on Ps1 and is a prerequisite for caudal somite half specification. Chimaera analysis between Psen1-deficient and wild-type cells revealed that condensation of the wild-type cells in the caudal half somite was concordant with the formation of segment boundaries, while mutant and wild-type cells intermingled in the presomitic mesoderm. This implies that periodic activation of the Notch pathway in the presomitic mesoderm is still latent to segregate the presumptive rostral and caudal somite. A transient episode of Mesp2 expression might be needed for Notch activation by Ps1 to confer rostral or caudal properties. In summary, we propose that Ps1 is involved in the functional manifestation of the segmentation clock in the presomitic mesoderm.

scholarly journals Interactions between the WEE-1.3 kinase and the PAM-1 aminopeptidase in oocyte maturation and the early C. elegans embryo

2021 ◽  
Author(s):  
Dorothy Benton ◽  
Eva C Jaeger ◽  
Arielle Kilner ◽  
Ashley Kimble ◽  
Josh Lowry ◽  
...  
Keyword(s):  
Missense Mutation ◽  
Oocyte Maturation ◽  
Protective Role ◽  
C Elegans ◽  
Direct Target ◽  
The One ◽  
Actomyosin Cytoskeleton ◽  
Embryonic Viability ◽  
Anterior Posterior

Abstract Puromycin-sensitive aminopeptidases are found across phyla and are known to regulate the cell-cycle and play a protective role in neurodegenerative disease. PAM-1 is a puromycin-sensitive aminopeptidase important for meiotic exit and polarity establishment in the one-cell Caenorhabditis elegans embryo. Despite conservation of this aminopeptidase, little is known about its targets during development. In order to identify novel interactors, we conducted a suppressor screen and isolated four suppressing mutations in three genes that partially rescued the maternal-effect lethality of pam-1 mutants. Suppressed strains show improved embryonic viability and polarization of the anterior-posterior axis. We identified a missense mutation in wee-1.3 in one of these suppressed strains. WEE-1.3 is an inhibitory kinase that regulates maturation promoting factor. While the missense mutation suppressed polarity phenotypes in pam-1, it does so without restoring centrosome-cortical contact or altering the cortical actomyosin cytoskeleton. To see if PAM-1 and WEE-1.3 interact in other processes, we examined oocyte maturation. While depletion of wee-1.3 causes sterility due to precocious oocyte maturation, this effect was lessened in pam-1 worms, suggesting that PAM-1 and WEE-1.3 interact in this process. Levels of WEE-1.3 were comparable between wild-type and pam-1 strains, suggesting that WEE-1.3 is not a direct target of the aminopeptidase. Thus, we have established an interaction between PAM-1 and WEE-1.3 in multiple developmental processes and have identified suppressors that are likely to further our understanding of the role of puromycin-sensitive aminopeptidases during development.

scholarly journals The Role of White Matter Disconnection in the Symptoms Relating to the Anarchic Hand Syndrome: A Single Case Study

2021 ◽  
Vol 11 (5) ◽  
pp. 632
Author(s):  
Valentina Pacella ◽  
Giuseppe Kenneth Ricciardi ◽  
Silvia Bonadiman ◽  
Elisabetta Verzini ◽  
Federica Faraoni ◽  
...  
Keyword(s):  
White Matter ◽  
Single Case ◽  
Brain Lesion ◽  
Structural Connectivity ◽  
Disconnection Syndrome ◽  
Neuroimaging Data ◽  
Neuropsychological Investigation ◽  
Anterior Posterior

The anarchic hand syndrome refers to an inability to control the movements of one’s own hand, which acts as if it has a will of its own. The symptoms may differ depending on whether the brain lesion is anterior, posterior, callosal or subcortical, but the relative classifications are not conclusive. This study investigates the role of white matter disconnections in a patient whose symptoms are inconsistent with the mapping of the lesion site. A repeated neuropsychological investigation was associated with a review of the literature on the topic to identify the frequency of various different symptoms relating to this syndrome. Furthermore, an analysis of the neuroimaging regarding structural connectivity allowed us to investigate the grey matter lesions and white matter disconnections. The results indicated that some of the patient’s symptoms were associated with structures that, although not directly damaged, were dysfunctional due to a disconnection in their networks. This suggests that the anarchic hand may be considered as a disconnection syndrome involving the integration of multiple antero-posterior, insular and interhemispheric networks. In order to comprehend this rare syndrome better, the clinical and neuroimaging data need to be integrated with the clinical reports available in the literature on this topic.

Anterior mesendoderm induces mouse Engrailed genes in explant cultures

Development ◽  
1993 ◽  
Vol 118 (1) ◽  
pp. 139-149 ◽  
Author(s):  
S.L. Ang ◽  
J. Rossant
Keyword(s):  
Direct Evidence ◽  
Neural Tissue ◽  
Explant Culture ◽  
Neural Plate ◽  
Explant Cultures ◽  
Neural Marker ◽  
Engrailed Genes ◽  
Anterior Posterior

We have developed germ layer explant culture assays to study the role of mesoderm in anterior-posterior (A-P) patterning of the mouse neural plate. Using isolated explants of ectodermal tissue alone, we have demonstrated that the expression of Engrailed-1 (En-1) and En-2 genes in ectoderm is independent of mesoderm by the mid- to late streak stage, at least 12 hours before their onset of expression in the neural tube in vivo at the early somite stage. In recombination explants, anterior mesendoderm from headfold stage embryos induces the expression of En-1 and En-2 in pre- to early streak ectoderm and in posterior ectoderm from headfold stage embryos. In contrast, posterior mesendoderm from embryos of the same stage does not induce En genes in pre- to early streak ectoderm but is able to induce expression of a general neural marker, neurofilament 160 × 10(3) M(r). These results provide the first direct evidence for a role of mesendoderm in induction and regionalization of neural tissue in mouse.

Hox genes and the evolution of vertebrate axial morphology

Development ◽  
1995 ◽  
Vol 121 (2) ◽  
pp. 333-346 ◽  
Author(s):  
A.C. Burke ◽  
C.E. Nelson ◽  
B.A. Morgan ◽  
C. Tabin
Keyword(s):  
Hox Genes ◽  
Cervical Vertebrae ◽  
Homeobox Gene ◽  
Paraxial Mesoderm ◽  
Thoracic Vertebrae ◽  
Homeotic Genes ◽  
Evolutionary Variation ◽  
Axial Morphology ◽  
Anterior Posterior ◽  
Anterior Posterior Axis

A common form of evolutionary variation between vertebrate taxa is the different numbers of segments that contribute to various regions of the anterior-posterior axis; cervical vertebrae, thoracic vertebrae, etc. The term ‘transposition’ is used to describe this phenomenon. Genetic experiments with homeotic genes in mice have demonstrated that Hox genes are in part responsible for the specification of segmental identity along the anterior-posterior axis, and it has been proposed that an axial Hox code determines the morphology of individual vertebrae (Kessel, M. and Gruss, P. (1990) Science 249, 347–379). This paper presents a comparative study of the developmental patterns of homeobox gene expression and developmental morphology between animals that have homologous regulatory genes but different morphologies. The axial expression boundaries of 23 Hox genes were examined in the paraxial mesoderm of chick, and 16 in mouse embryos by in situ hybridization and immunolocalization techniques. Hox gene anterior expression boundaries were found to be transposed in concert with morphological boundaries. This data contributes a mechanistic level to the assumed homology of these regions in vertebrates. The recognition of mechanistic homology supports the historical homology of basic patterning mechanisms between all organisms that share these genes.

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

Development ◽  
1999 ◽  
Vol 126 (13) ◽  
pp. 3005-3014 ◽  
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.

Myogenesis in paraxial mesoderm: preferential induction by dorsal neural tube and by cells expressing Wnt-1

Development ◽  
1995 ◽  
Vol 121 (11) ◽  
pp. 3675-3686 ◽  
Author(s):  
H.M. Stern ◽  
A.M. Brown ◽  
S.D. Hauschka
Keyword(s):  
Neural Tube ◽  
Muscle Development ◽  
Paraxial Mesoderm ◽  
Myogenic Response ◽  
Dorsal Neural Tube ◽  
Ventral Neural Tube ◽  
Myogenic Induction ◽  
Inductive Activity

Previous studies have demonstrated that the neural tube/notochord complex is required for skeletal muscle development within somites. In order to explore the localization of myogenic inducing signals within the neural tube, dorsal or ventral neural tube halves were cultured in contact with single somites or pieces of segmental plate mesoderm. Somites and segmental plates cultured with the dorsal half of the neural tube exhibited 70% and 85% myogenic response rates, as determined by immunostaining for myosin heavy chain. This response was slightly lower than the 100% response to whole neural tube/notochord, but was much greater than the 30% and 10% myogenic response to ventral neural tube with and without notochord. These results demonstrate that the dorsal neural tube emits a potent myogenic inducing signal which accounts for most of the inductive activity of whole neural tube/notochord. However, a role for ventral neural tube/notochord in somite myogenic induction was clearly evident from the larger number of myogenic cells induced when both dorsal neural tube and ventral neural tube/notochord were present. To address the role of a specific dorsal neural tube factor in somite myogenic induction, we tested the ability of Wnt-1-expressing fibroblasts to promote paraxial mesoderm myogenesis in vitro. We found that cells expressing Wnt-1 induced a small number of somite and segmental plate cells to undergo myogenesis. This finding is consistent with the localized dorsal neural tube inductive activity described above, but since the ventral neural tube/notochord also possesses myogenic inductive capacity yet does not express Wnt-1, additional inductive factors are likely involved.

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