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.

Posterior stripe expression of hunchback is driven from two promoters by a common enhancer element

Development ◽  
1995 ◽  
Vol 121 (9) ◽  
pp. 3067-3077 ◽  
Author(s):  
J.S. Margolis ◽  
M.L. Borowsky ◽  
E. Steingrimsson ◽  
C.W. Shim ◽  
J.A. Lengyel ◽  
...  
Keyword(s):  
Transcription Initiation ◽  
Initiation Site ◽  
Drosophila Embryo ◽  
Upstream Region ◽  
Enhancer Element ◽  
Gap Gene ◽  
Gap Genes ◽  
Two Phases ◽  
Necessary And Sufficient

The gap gene hunchback (hb) is required for the formation and segmentation of two regions of the Drosophila embryo, a broad anterior domain and a narrow posterior domain. Accumulation of hb transcript in the posterior of the embryo occurs in two phases, an initial cap covering the terminal 15% of the embryo followed by a stripe at the anterior edge of this region. By in situ hybridization with transcript-specific probes, we show that the cap is composed only of mRNA from the distal transcription initiation site (P1), while the later posterior stripe is composed of mRNA from both the distal and proximal (P2) transcription initiation sites. Using a series of genomic rescue constructs and promoter-lacZ fusion genes, we define a 1.4 kb fragment of the hb upstream region that is both necessary and sufficient for posterior expression. Sequences within this fragment mediate regulation by the terminal gap genes tailless (tll) and a huckebein, which direct the formation of the posterior hb stripe. We show that the tll protein binds in vitro to specific sites within the 1.4 kb posterior enhancer region, providing the first direct evidence for activation of gene expression by tll. We propose a model in which the anterior border of the posterior hb stripe is determined by tll concentration in a manner analogous to the activation of anterior hb expression by bicoid.

Concentration-dependent patterning by an ectopic expression domain of the Drosophila gap gene knirps

Development ◽  
1997 ◽  
Vol 124 (7) ◽  
pp. 1343-1354 ◽  
Author(s):  
D. Kosman ◽  
S. Small
Keyword(s):  
Target Genes ◽  
Ectopic Expression ◽  
Drosophila Embryo ◽  
Asymmetric Distribution ◽  
Protein Diffusion ◽  
Expression Domain ◽  
Gap Gene ◽  
Pair Rule Gene ◽  
Transgenic Lines ◽  
Pair Rule

The asymmetric distribution of the gap gene knirps (kni) in discrete expression domains is critical for striped patterns of pair-rule gene expression in the Drosophila embryo. To test whether these domains function as sources of morphogenetic activity, the stripe 2 enhancer of the pair-rule gene even-skipped (eve) was used to express kni in an ectopic position. Manipulating the stripe 2-kni expression constructs and examining transgenic lines with different insertion sites led to the establishment of a series of independent lines that displayed consistently different levels and developmental profiles of expression. Individual lines showed specific disruptions in pair-rule patterning that were correlated with the level and timing of ectopic expression. These results suggest that the ectopic domain acts as a source for morphogenetic activity that specifies regions in the embryo where pair-rule genes can be activated or repressed. Evidence is presented that the level and timing of expression, as well as protein diffusion, are important for determining the specific responses of target genes.

scholarly journals Gap gene properties of the pair-rule gene runt during Drosophila segmentation

Development ◽  
1994 ◽  
Vol 120 (6) ◽  
pp. 1671-1683 ◽  
Author(s):  
C. Tsai ◽  
J.P. Gergen
Keyword(s):  
Transcriptional Activation ◽  
Expression Patterns ◽  
Normal Component ◽  
Ectopic Expression ◽  
Antagonistic Effect ◽  
Drosophila Embryo ◽  
Gap Gene ◽  
New Family ◽  
Pair Rule Gene ◽  
Pair Rule

The Drosophila Runt protein is a member of a new family of transcriptional regulators that have important roles in processes extending from pattern formation in insect embryos to leukemogenesis in humans. We used ectopic expression to investigate runt's function in the pathway of Drosophila segmentation. Transient over-expression of runt under the control of a Drosophila heat-shock promoter caused stripe-specific defects in the expression patterns of the pair-rule genes hairy and even-skipped but had a more uniform effect on the secondary pair-rule gene fushi tarazu. Surprisingly, the expression of the gap segmentation genes, which are upstream of runt in the segmentation hierarchy was also altered in hs/runt embryos. A subset of these effects were interpreted as due to an antagonistic effect of runt on transcriptional activation by the maternal morphogen bicoid. In support of this, expression of synthetic reporter gene constructs containing oligomerized binding sites for the Bicoid protein was reduced in hs/runt embryos. Finally, genetic experiments demonstrated that regulation of gap gene expression by runt is a normal component of the regulatory program that generates the segmented body pattern of the Drosophila embryo.

Mutually repressive interactions between the gap genes giant and Kruppel define middle body regions of the Drosophila embryo

Development ◽  
1991 ◽  
Vol 111 (2) ◽  
pp. 611-621 ◽  
Author(s):  
R. Kraut ◽  
M. Levine
Keyword(s):  
Gene Expression ◽  
Weak Interactions ◽  
Ectopic Expression ◽  
Early Embryo ◽  
Drosophila Embryo ◽  
Regulatory Interactions ◽  
Gap Gene ◽  
Gap Genes ◽  
Body Regions ◽  
Bona Fide

The gap genes play a key role in establishing pair-rule and homeotic stripes of gene expression in the Drosophila embryo. There is mounting evidence that overlapping gradients of gap gene expression are crucial for this process. Here we present evidence that the segmentation gene giant is a bona fide gap gene that is likely to act in concert with hunchback, Kruppel and knirps to initiate stripes of gene expression. We show that Kruppel and giant are expressed in complementary, non-overlapping sets of cells in the early embryo. These complementary patterns depend on mutually repressive interactions between the two genes. Ectopic expression of giant in early embryos results in the selective repression of Kruppel, and advanced-stage embryos show cuticular defects similar to those observed in Kruppel- mutants. This result and others suggest that the strongest regulatory interactions occur among those gap genes expressed in nonadjacent domains. We propose that the precisely balanced overlapping gradients of gap gene expression depend on these strong regulatory interactions, coupled with weak interactions between neighboring genes.

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.

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

hlh-12, a gene that is necessary and sufficient to promote migration of gonadal regulatory cells in C. elegans, evolved within the Caenorhabditis clade

Genetics ◽  
2021 ◽  
Author(s):  
Hana E Littleford ◽  
Karin Kiontke ◽  
David H A Fitch ◽  
Iva Greenwald
Keyword(s):  
Ectopic Expression ◽  
Morphological Diversity ◽  
Nematode Species ◽  
Bhlh Protein ◽  
Vulval Development ◽  
C Elegans ◽  
Form And Function ◽  
Somatic Gonad ◽  
And Function ◽  
Necessary And Sufficient

Abstract Specialized cells of the somatic gonad primordium of nematodes play important roles in the final form and function of the mature gonad. C. elegans hermaphrodites are somatic females that have a two-armed, U-shaped gonad that connects to the vulva at the midbody. The outgrowth of each gonad arm from the somatic gonad primordium is led by two female Distal Tip Cells (fDTC), while the Anchor Cell (AC) remains stationary and central to coordinate uterine and vulval development. The bHLH protein HLH-2 and its dimerization partners LIN-32 and HLH-12 had previously been shown to be required for fDTC specification. Here, we show that ectopic expression of both HLH-12 and LIN-32 in cells with AC potential transiently transforms them into fDTC-like cells. Furthermore, hlh-12 was known to be required for the fDTCs to sustain gonad arm outgrowth. Here, we show that ectopic expression of HLH-12 in the normally stationary AC causes displacement from its normal position, and that displacement likely results from activation of the leader program of fDTCs because it requires genes necessary for gonad arm outgrowth. Thus, HLH-12 is both necessary and sufficient to promote gonadal regulatory cell migration. As differences in female gonadal morphology of different nematode species reflect differences in the fate or migratory properties of the fDTCs or of the AC, we hypothesized that evolutionary changes in the expression of hlh-12 may underlie evolution of such morphological diversity. However, we were unable to identify an hlh-12 ortholog outside of Caenorhabditis. Instead, by performing a comprehensive phylogenetic analysis of all Class II bHLH proteins in multiple nematode species, we found that HLH-12 evolved within the Caenorhabditis clade, possibly by duplicative transposition of hlh-10. Our analysis suggests that control of gene regulatory hierarchies for gonadogenesis can be remarkably plastic during evolution without adverse phenotypic consequence.

Targeting gene expression to the head: the Drosophila orthodenticle gene is a direct target of the Bicoid morphogen

Development ◽  
1998 ◽  
Vol 125 (21) ◽  
pp. 4185-4193 ◽  
Author(s):  
Q. Gao ◽  
R. Finkelstein
Keyword(s):  
Gene Expression ◽  
Target Genes ◽  
Regulatory Element ◽  
Regulatory Region ◽  
Repeated Sequence ◽  
Drosophila Embryo ◽  
Sequence Motif ◽  
Specific Expression ◽  
Gap Gene

The Bicoid (Bcd) morphogen establishes the head and thorax of the Drosophila embryo. Bcd activates the transcription of identified target genes in the thoracic segments, but its mechanism of action in the head remains poorly understood. It has been proposed that Bcd directly activates the cephalic gap genes, which are the first zygotic genes to be expressed in the head primordium. It has also been suggested that the affinity of Bcd-binding sites in the promoters of Bcd target genes determines the posterior extent of their expression (the Gene X model). However, both these hypotheses remain untested. Here, we show that a small regulatory region upstream of the cephalic gap gene orthodenticle (otd) is sufficient to recapitulate early otd expression in the head primordium. This region contains two control elements, each capable of driving otd-like expression. The first element has consensus Bcd target sites that bind Bcd in vitro and are necessary for head-specific expression. As predicted by the Gene X model, this element has a relatively low affinity for Bcd. Surprisingly, the second regulatory element has no Bcd sites. Instead, it contains a repeated sequence motif similar to a regulatory element found in the promoters of otd-related genes in vertebrates. Our study is the first demonstration that a cephalic gap gene is directly regulated by Bcd. However, it also shows that zygotic gene expression can be targeted to the head primordium without direct Bcd regulation.

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