Ectopic expression of a genomic fragment containing a homeobox causes neural defects in the axolotl

1991 ◽  
Vol 69 (5-6) ◽  
pp. 366-374 ◽  
Author(s):  
Mary Whiteley ◽  
John B. Armstrong
Keyword(s):  
Pattern Formation ◽  
Dna Recognition ◽  
Ectopic Expression ◽  
Neural Plate ◽  
Ambystoma Mexicanum ◽  
Genomic Fragment ◽  
Severe Reduction ◽  
Recognition Helix ◽  
The Brain ◽  
Anterior Neural Plate

An axolotl (Ambystoma mexicanum) genomic fragment containing the Ahoxl homeobox was placed under the control of the mouse hsp68 promoter, which seems to function constitutively in the axolotl. The resulting construct was injected into fertilized axolotl eggs to see if it would perturb development. Of the injected embryos, 20% showed severe reduction of the anterior neural plate. Later in development, these embryos had small heads, no eyes, and appeared to lack the normal regionalization of the brain. An additional 35% of the embryos were less severely affected, but had reduced or missing eyes. Control embryos, including ones injected with a construct missing the DNA recognition helix of the homeobox, developed normally.Key words: axolotl, homeobox, neural defects, pattern formation.

The zebrafish buttonhead-like factor Bts1 is an early regulator of pax2.1 expression during mid-hindbrain development

Development ◽  
2001 ◽  
Vol 128 (20) ◽  
pp. 4021-4034 ◽  
Author(s):  
Alexandra Tallafuß ◽  
Thomas P. Wilm ◽  
Michèle Crozatier ◽  
Peter Pfeffer ◽  
Marion Wassef ◽  
...  
Keyword(s):  
Zinc Finger ◽  
Ectopic Expression ◽  
Neural Plate ◽  
Drosophila Embryo ◽  
Knock Down ◽  
Gap Gene ◽  
Similar Strategy ◽  
Necessary And Sufficient ◽  
Embryonic Region ◽  
Anterior Neural Plate

Little is known about the factors that control the specification of the mid-hindbrain domain (MHD) within the vertebrate embryonic neural plate. Because the head-trunk junction of the Drosophila embryo and the MHD have patterning similarities, we have searched for vertebrate genes related to the Drosophila head gap gene buttonhead (btd), which in the fly specifies the head-trunk junction. We report here the identification of a zebrafish gene which, like btd, encodes a zinc-finger transcriptional activator of the Sp-1 family (hence its name, bts1 for btd/Sp-related-1) and shows a restricted expression in the head. During zebrafish gastrulation, bts1 is transcribed in the posterior epiblast including the presumptive MHD, and precedes in this area the expression of other MHD markers such as her5, pax2.1 and wnt1. Ectopic expression of bts1 combined to knock-down experiments demonstrate that Bts1 is both necessary and sufficient for the induction of pax2.1 within the anterior neural plate, but is not involved in regulating her5, wnt1 or fgf8 expression. Our results confirm that early MHD development involves several genetic cascades that independently lead to the induction of MHD markers, and identify Bts1 as a crucial upstream component of the pathway selectively leading to pax2.1 induction. In addition, they imply that flies and vertebrates, to control the development of a boundary embryonic region, have probably co-opted a similar strategy: the restriction to this territory of the expression of a Btd/Sp-like factor.

Examining pattern formation in mouse, chicken and frog embryos with an En-specific antiserum

Development ◽  
1991 ◽  
Vol 111 (2) ◽  
pp. 287-298 ◽  
Author(s):  
C.A. Davis ◽  
D.P. Holmyard ◽  
K.J. Millen ◽  
A.L. Joyner
Keyword(s):  
Electron Microscopy ◽  
Pattern Formation ◽  
Experimental Studies ◽  
Neural Plate ◽  
Limb Bud ◽  
Good Marker ◽  
Early Embryos ◽  
Whole Mount ◽  
Anterior Neural Plate ◽  
Scanning Electron

We have raised an antiserum, designated alpha Enhb-1, to a portion of the mouse En-2 protein containing the homeodomain. The antiserum detects both the En-1 and En-2 proteins in mouse, chick and Xenopus embryos by Western blot analysis. Using whole-mount immunohistochemistry, combined in some cases with scanning electron microscopy, we have examined the distribution of the proteins in the early embryos of these species. The major features of expression were similar. The initial production of En protein occurred, just before or during the formation of the first somites, in a band of the anterior neural plate in the prospective mid/hindbrain region. Later in development En-1 protein accumulated in the ventral ectoderm of the developing mouse and chick limb buds, indicating that a dorsal-ventral polarity is present as soon as any limb bud swelling is apparent and that, at least in the mouse, this polarity is established independently of the apical ectodermal ridge. In all three species, alpha Enhb-1 bound to a subset of ventro-lateral differentiating neurons in the spinal cord and hindbrain and their pattern of birth in the mouse reflected the division of the hindbrain into rhombomeres. En-1 protein also accumulated in a lateral stripe of dermatome in the mouse and chick, indicating a dorsal-ventral subdivision of this tissue. The results show that En expression is a good marker for pattern formation in a variety of tissues and will be useful in experimental studies designed to characterize further these processes.

Sequential roles for Otx2 in visceral endoderm and neuroectoderm for forebrain and midbrain induction and specification

Development ◽  
1998 ◽  
Vol 125 (5) ◽  
pp. 845-856 ◽  
Author(s):  
M. Rhinn ◽  
A. Dierich ◽  
W. Shawlot ◽  
R.R. Behringer ◽  
M. Le Meur ◽  
...  
Keyword(s):  
Es Cells ◽  
Homeobox Gene ◽  
Neural Plate ◽  
Regulatory Genes ◽  
Neural Function ◽  
Visceral Endoderm ◽  
Essential Function ◽  
The Brain ◽  
Anterior Neural Plate ◽  
Recombination Assay

The homeobox gene Otx2 is a mouse cognate of the Drosophila orthodenticle gene, which is required for development of the brain, rostral to rhombomere three. We have investigated the mechanisms involved in this neural function and specifically the requirement for Otx2 in the visceral endoderm and the neuroectoderm using chimeric analysis in mice and explant recombination assay. Analyses of chimeric embryos composed of more than 90% of Otx2−/− ES cells identified an essential function for Otx2 in the visceral endoderm for induction of the forebrain and midbrain. The chimeric studies also demonstrated that an anterior neural plate can form without expressing Otx2. However, in the absence of Otx2, expression of important regulatory genes, such as Hesx1/Rpx, Six3, Pax2, Wnt1 and En, fail to be initiated or maintained in the neural plate. Using explant-recombination assay, we could further demonstrate that Otx2 is required in the neuroectodem for expression of En. Altogether, these results demonstrate that Otx2 is first required in the visceral endoderm for the induction, and subsequently in the neuroectoderm for the specification of forebrain and midbrain territories.

A Xenopus homebox gene defines dorsal-ventral domains in the developing brain

Development ◽  
1993 ◽  
Vol 118 (1) ◽  
pp. 193-202 ◽  
Author(s):  
M.S. Saha ◽  
R.B. Michel ◽  
K.M. Gulding ◽  
R.M. Grainger
Keyword(s):  
Initial Step ◽  
Neural Plate ◽  
Developing Brain ◽  
Vertebrate Development ◽  
Tissue Interactions ◽  
Temporal Localization ◽  
Distinguishing Features ◽  
The Brain ◽  
Anterior Neural Plate ◽  
Anterior Posterior

One of the distinguishing features of vertebrate development is the elaboration of the anterior neural plate into forebrain and midbrain, yet little is known about the early tissue interactions that regulate pattern formation in this region or the genes that mediate these interactions. As an initial step toward analyzing the process of regionalization in the anterior-most region of the brain, we have screened an anterior neural cDNA library for homeobox clones and have identified one which we have called XeNK-2 (Xenopus NK-2) because of its homology to the NK-2 family of homeobox genes. From neurula stages, when XeNK-2 is first detectable, through hatching stages, XeNK-2 mRNA is expressed primarily in the anterior region of the brain. By swimming tadpole stages, XeNK-2 expression resolves into a set of bands positioned at the forebrain-midbrain and the midbrain-hindbrain boundaries, after which XeNK-2 transcripts are no longer detectable. In addition to localized expression along the anterior-posterior axis, XeNK-2 may also play a role in the process of regionalization along the dorsal-ventral axis of the developing brain. At all stages examined, XeNK-2 mRNA is restricted to a pair of stripes that are bilaterally symmetrical in the ventral-lateral region of the brain. To begin to identify the tissue interactions that are required for the proper spatial and temporal localization of XeNK-2, we have performed a series of explant experiments. Consistent with earlier work showing that the A/P axis is not fixed at mid-gastrula stages, we show that XeNK-2 expression is activated when assayed in gastrula stage explants taken from any region along the entire A/P axis and that the tissue interactions necessary to localize XeNK-2 along the A/P axis are not completed until later neurula stages.

scholarly journals Hallmarks of primary neurulation are conserved in the zebrafish forebrain

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Jonathan M. Werner ◽  
Maraki Y. Negesse ◽  
Dominique L. Brooks ◽  
Allyson R. Caldwell ◽  
Jafira M. Johnson ◽  
...  
Keyword(s):  
Neural Tube ◽  
Time Lapse ◽  
Neural Plate ◽  
Neural Tube Closure ◽  
Developmental Studies ◽  
Underlying Causes ◽  
The Central Nervous System ◽  
Resolution Imaging ◽  
Fold Formation ◽  
Anterior Neural Plate

AbstractPrimary neurulation is the process by which the neural tube, the central nervous system precursor, is formed from the neural plate. Incomplete neural tube closure occurs frequently, yet underlying causes remain poorly understood. Developmental studies in amniotes and amphibians have identified hingepoint and neural fold formation as key morphogenetic events and hallmarks of primary neurulation, the disruption of which causes neural tube defects. In contrast, the mode of neurulation in teleosts has remained highly debated. Teleosts are thought to have evolved a unique mode of neurulation, whereby the neural plate infolds in absence of hingepoints and neural folds, at least in the hindbrain/trunk where it has been studied. Using high-resolution imaging and time-lapse microscopy, we show here the presence of these morphological landmarks in the zebrafish anterior neural plate. These results reveal similarities between neurulation in teleosts and other vertebrates and hence the suitability of zebrafish to understand human neurulation.

scholarly journals A gene regulatory network that underlies the derivation of the anterior neural plate from the epiblast

2010 ◽  
Vol 344 (1) ◽  
pp. 495
Author(s):  
Makiko Iwafuchi-Doi ◽  
Tatsuya Takemoto ◽  
Yuzo Yoshida ◽  
Isao Matsuo ◽  
Jun Aruga ◽  
...  
Keyword(s):  
Gene Regulatory Network ◽  
Regulatory Network ◽  
Neural Plate ◽  
Gene Regulatory ◽  
Anterior Neural Plate

Citral, an inhibitor of retinoic acid synthesis, modifies pattern formation during limb regeneration in the axolotl Ambystoma mexicanum

1999 ◽  
Vol 77 (11) ◽  
pp. 1835-1837 ◽  
Author(s):  
Steven R Scadding
Keyword(s):  
Retinoic Acid ◽  
Pattern Formation ◽  
Limb Regeneration ◽  
Acid Synthesis ◽  
Ambystoma Mexicanum

While the effects of exogenous retinoids on amphibian limb regeneration have been studied extensively, the role of endogenous retinoids is not clear. Hence, I wished to investigate the role of endogenous retinoic acid during axolotl limb regeneration. Citral is a known inhibitor of retinoic acid synthesis. Thus, I treated regenerating limbs of the larval axolotl Ambystoma mexicanum with citral. The result of this inhibition of retinoic acid synthesis was that limb regeneration became extremely irregular and hypomorphic, with serious pattern defects, or was inhibited altogether. I conclude that endogenous retinoic acid plays an important role in pattern formation during limb regeneration.

Symmetrical vascularization patterns in normal and retinoic acid treated limb regenerates of the axolotl, Ambystoma mexicanum

1998 ◽  
Vol 76 (9) ◽  
pp. 1795-1796 ◽  
Author(s):  
Steven R Scadding ◽  
Andrew Burns
Keyword(s):  
Retinoic Acid ◽  
Pattern Formation ◽  
Vascular System ◽  
Limb Regeneration ◽  
Ambystoma Mexicanum ◽  
Limb Pattern ◽  
Regeneration Blastema

The purpose of this investigation was to determine whether there were any asymmetries in the vascularization of the limb-regeneration blastema in the axolotl, Ambystoma mexicanum, that might be related to pattern formation, and to determine if retinoic acid could modify the vascular patterns of the blastema. We used acrylic casts of the vascular system of the limbs to assess the pattern of vascularization. We observed a very regular symmetrical arrangement of capillaries in the limb-regeneration blastema that did not appear to be modified by doses of retinoic acid sufficient to modify the limb pattern.

Overexpression of the forebrain-specific homeobox gene six3 induces rostral forebrain enlargement in zebrafish

Development ◽  
1998 ◽  
Vol 125 (15) ◽  
pp. 2973-2982 ◽  
Author(s):  
M. Kobayashi ◽  
R. Toyama ◽  
H. Takeda ◽  
I.B. Dawid ◽  
K. Kawakami
Keyword(s):  
Homeobox Gene ◽  
Cloning And Expression ◽  
Optic Stalk ◽  
Sine Oculis ◽  
Murine Homolog ◽  
Enhanced Expression ◽  
Rostral Region ◽  
The Brain ◽  
Early Gastrula ◽  
Anterior Neural Plate

The Drosophila homeobox gene sine oculis is expressed in the rostral region of the embryo in early development and is essential for eye and brain formation. Its murine homolog, Six3, is expressed in the anterior neural plate and eye anlage, and may have crucial functions in eye and brain development. In this study, we describe the cloning and expression of zebrafish six3, the apparent ortholog of the mouse Six3 gene. Zebrafish six3 transcripts are first seen in hypoblast cells in early gastrula embryos and are found in the anterior axial mesendoderm through gastrulation. six3 expression in the head ectoderm begins at late gastrula. Throughout the segmentation period, six3 is expressed in the rostral region of the prospective forebrain. Overexpression of six3 in zebrafish embryos induced enlargement of the rostral forebrain, enhanced expression of pax2 in the optic stalk and led to a general disorganization of the brain. Disruption of either the Six domain or the homeodomain abolish these effects, implying that these domains are essential for six3 gene function. Our results suggest that the vertebrate Six3 genes are involved in the formation of the rostral forebrain.

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