Mechanism of anteroposterior axis specification in vertebrates. Lessons from the amphibians

Development ◽  
1992 ◽  
Vol 114 (2) ◽  
pp. 285-302 ◽  
Author(s):  
J.M. Slack ◽  
D. Tannahill
Keyword(s):  
Molecular Markers ◽  
Expression Patterns ◽  
Signal Transduction Pathway ◽  
Homeobox Gene ◽  
Neural Induction ◽  
High Sensitivity ◽  
Neural Plate ◽  
Mesoderm Induction ◽  
Inducing Factors ◽  
Almost All

Interest in the problem of anteroposterior specification has quickened because of our near understanding of the mechanism in Drosophila and because of the homology of Antennapedia-like homeobox gene expression patterns in Drosophila and vertebrates. But vertebrates differ from Drosophila because of morphogenetic movements and interactions between tissue layers, both intimately associated with anteroposterior specification. The purpose of this article is to review classical findings and to enquire how far these have been confirmed, refuted or extended by modern work. The “pre-molecular” work suggests that there are several steps to the process: (i) Formation of anteroposterior pattern in mesoderm during gastrulation with posterior dominance. (ii) Regional specific induction of ectoderm to form neural plate. (iii) Reciprocal interactions from neural plate to mesoderm. (iv) Interactions within neural plate with posterior dominance. Unfortunately, almost all the observable markers are in the CNS rather than in the mesoderm where the initial specification is thought to occur. This has meant that the specification of the mesoderm has been assayed indirectly by transplantation methods such as the Einsteckung. New molecular markers now supplement morphological ones but they are still mainly in the CNS and not the mesoderm. A particular interest attaches to the genes of the Antp-like HOX clusters since these may not only be markers but actual coding factors for anteroposterior levels. We have a new understanding of mesoderm induction based on the discovery of activins and fibroblast growth factors (FGFs) as candidate inducing factors. These factors have later consequences for anteroposterior pattern with activin tending to induce anterior, and FGF posterior structures. Recent work on neural induction has implicated cAMP and protein kinase C (PKC) as elements of the signal transduction pathway and has provided new evidence for the importance of tangential neural induction. The regional specificity of neural induction has been reinvestigated using molecular markers and provides conclusions rather similar to the classical work. Defects in the axial pattern may be produced by retinoic acid but it remains unclear whether its effects are truly coordinate ones or are concentrated in certain regions of high sensitivity. In general the molecular studies have supported and reinforced the “pre-molecular ones”. Important questions still remain: (i) How much pattern is there in the mesoderm (how many states?) (ii) How is this pattern generated by the invaginating organizer? (iii) Is there one-to-one transmission of codings to the neural plate? (iv) What is the nature of the interactions within the neural plate? (v) Are the HOX cluster genes really the anteroposterior codings?

Lim1-related homeobox gene (HpLim1) expressed in sea urchin embryo

Zygote ◽  
1999 ◽  
Vol 8 (S1) ◽  
pp. S71-S72
Author(s):  
Keiko Mitsunaga-Nakatsubo ◽  
Takahiko Kawasaki ◽  
Koichi Takeda ◽  
Koji Akasaka ◽  
Hiraku Shimada
Keyword(s):  
Sea Urchin ◽  
Expression Patterns ◽  
Homeobox Gene ◽  
Mesoderm Induction ◽  
Over Expression ◽  
Lim Domains ◽  
Sea Urchin Embryo ◽  
Cell Type Specific ◽  
Islet 1

A characteristic cysteine-rich motif, LIM domain, was first detected in three different transcription factors: lin-11, Islet-1 and mec-3. A feature shared by these genes is the presence of two LIM domains linked to a DNA-binding homeodomain (Sánchez-García et al., 1994). LIM homeodomain (LHX) proteins have been reported to be implicated in a variety of developmental processes (Dawid et al., 1998).Expression patterns of LHX genes have been analysed in a wide variety of organisms and reported to be cell-type specific (Dawid et al., 1998). In vertebrates, they are expressed in organiser equivalent regions at the gastrula stage, suggesting their involvement in mesoderm induction (Taira et al., 1992; Barnes et al., 1994; Toyama et al., 1995). Hrlim, an ascidian Lim3, zygotically expresses in the endoderm lineage before gastrulation, suggesting that it is involved in the endoderm determination (Wada et al., 1995).Here, cDNA cloning of the Lim1-related homeobox gene (HpLim1) of the sea urchin, Hemicentrotus pulcherrimus, is described together with the spatially as well as temporally regulated expression of HpLim1 during sea urchin development. A possible role of HpLiml in sea urchin development is also discussed based on its spatial pattern of expression and on the result of an over-expression study.

Anterior neurectoderm is progressively induced during gastrulation: the role of the Xenopus homeobox gene orthodenticle

Development ◽  
1995 ◽  
Vol 121 (4) ◽  
pp. 993-1004 ◽  
Author(s):  
I.L. Blitz ◽  
K.W. Cho
Keyword(s):  
Expression Patterns ◽  
Functional Characterization ◽  
Ectopic Expression ◽  
Homeobox Gene ◽  
Neural Induction ◽  
Cement Gland ◽  
Spemann's Organizer ◽  
Vertical Contact

In order to study the regional specification of neural tissue we isolated Xotx2, a Xenopus homolog of the Drosophila orthodenticle gene. Xotx2 is initially expressed in Spemann's organizer and its expression is absent in the ectoderm of early gastrulae. As gastrulation proceeds, Xotx2 expression is induced in the overlying ectoderm and this domain of expression moves anteriorly in register with underlying anterior mesoderm throughout the remainder of gastrulation. The expression pattern of Xotx2 suggests that a wave of Xotx2 expression (marking anterior neurectoderm) travels through the ectoderm of the gastrula with the movement of underlying anterior (prechordal plate) mesoderm. This expression of Xotx2 is reminiscent of the Eyal-Giladi model for neural induction. According to this model, anterior neural-inducing signals emanating from underlying anterior mesoderm transiently induce anterior neural tissues after vertical contact with the overlying ectoderm. Further patterning is achieved when the ectoderm receives caudalizing signals as it comes in contact with more posterior mesoderm during subsequent gastrulation movements. Functional characterization of the Xotx2 protein has revealed its involvement in differentiation of the anterior-most tissue, the cement gland. Ectopic expression of Xotx2 in embryos induces extra cement glands in the skin as well as inducing a cement gland marker (XAG1) in isolated animal cap ectoderm. Microinjection of RNA encoding the organizer-specific homeo-domain protein goosecoid into the ventral marginal zone results in induction of the Xotx2 gene. This result, taken in combination with the indistinguishable expression patterns of Xotx2 and goosecoid in the anterior mesoderm suggests that Xotx2 is a target of goosecoid regulation.

Distinct elements of the xsna promoter are required for mesodermal and ectodermal expression

Development ◽  
1993 ◽  
Vol 119 (3) ◽  
pp. 661-671 ◽  
Author(s):  
R. Mayor ◽  
L.J. Essex ◽  
M.F. Bennett ◽  
M.G. Sargent
Keyword(s):  
Neural Crest ◽  
Expression Patterns ◽  
In Situ Hybridisation ◽  
Gc Content ◽  
Neural Plate ◽  
Upstream Sequence ◽  
Endogenous Gene ◽  
Inducing Factors ◽  
Translational Start ◽  
Mesoderm Inducing Factors

Xsna, the Xenopus homologue of Drosophila snail, is expressed in both mesoderm and ectoderm. Expression occurs in all mesoderm initially but is down regulated in a tissue-specific fashion at the end of gastrulation in a way that reveals the subdivision of the mesoderm before its derivatives are overtly differentiated. Xsna is also expressed in the ectoderm of the prospective neural fold from stage 11, in a distinct band of cells surrounding the prospective neural plate, which we designate the neural plate border. The deep and superficial ectoderm compartments labelled by Xsna represent the prospective neural crest and the prospective roof of the neural tube, respectively. Xsna expression persists in neural crest cells during their subsequent migration. The role of the Xsna promoter in creating this pattern of expression has been investigated by injecting fertilised eggs with constructs containing the 5′ upstream sequence of the gene fused to a reporter. An element of 115 base pairs (−160 to −45 relative to the transcriptional start) is sufficient to drive appropriate reporter gene expression. The promoter does not contain a TATA or CAAT box and does not have a high GC content, but RNA synthesis starts precisely at 33 bases upstream to the translational start. The start sequence can be deleted so that transcription is initiated elsewhere without affecting the expression pattern. The distribution of Xsna promoter activity within the embryo, examined using beta-galactosidase (beta-gal) fusions, is similar to that of the endogenous mRNA seen by in situ hybridisation. The contribution of elements within the 5′ sequence have been assessed by comparing the expression patterns of constructs that have deletions in this region. Sequences from −112 to −97 are required for mesodermal expression and sequences from −96 to −44 are required for ectodermal expression. The behaviour of the injected promoter constructs differ in one important respect from the endogenous gene in that expression in an animal cap assay is not inducible by mesoderm-inducing factors but is inducible by cells of the vegetal pole.

scholarly journals Spatial expression pattern of serine proteases in the blood fluke Schistosoma mansoni determined by fluorescence RNA in situ hybridization

2021 ◽  
Vol 14 (1) ◽  
Author(s):  
Lenka Ulrychová ◽  
Pavel Ostašov ◽  
Marta Chanová ◽  
Michael Mareš ◽  
Martin Horn ◽  
...  
Keyword(s):  
In Situ Hybridization ◽  
Schistosoma Mansoni ◽  
Rna Sequencing ◽  
Serine Proteases ◽  
Expression Patterns ◽  
High Sensitivity ◽  
Host Parasite Interactions ◽  
Highly Sensitive ◽  
Host Parasite

Abstract Background The blood flukes of genus Schistosoma are the causative agent of schistosomiasis, a parasitic disease that infects more than 200 million people worldwide. Proteases of schistosomes are involved in critical steps of host–parasite interactions and are promising therapeutic targets. We recently identified and characterized a group of S1 family Schistosoma mansoni serine proteases, including SmSP1 to SmSP5. Expression levels of some SmSPs in S. mansoni are low, and by standard genome sequencing technologies they are marginally detectable at the method threshold levels. Here, we report their spatial gene expression patterns in adult S. mansoni by the high-sensitivity localization assay. Methodology Highly sensitive fluorescence in situ RNA hybridization (FISH) was modified and used for the localization of mRNAs encoding individual SmSP proteases (including low-expressed SmSPs) in tissues of adult worms. High sensitivity was obtained due to specifically prepared tissue and probes in combination with the employment of a signal amplification approach. The assay method was validated by detecting the expression patterns of a set of relevant reference genes including SmCB1, SmPOP, SmTSP-2, and Sm29 with localization formerly determined by other techniques. Results FISH analysis revealed interesting expression patterns of SmSPs distributed in multiple tissues of S. mansoni adults. The expression patterns of individual SmSPs were distinct but in part overlapping and were consistent with existing transcriptome sequencing data. The exception were genes with significantly low expression, which were also localized in tissues where they had not previously been detected by RNA sequencing methods. In general, SmSPs were found in various tissues including reproductive organs, parenchymal cells, esophagus, and the tegumental surface. Conclusions The FISH-based assay provided spatial information about the expression of five SmSPs in adult S. mansoni females and males. This highly sensitive method allowed visualization of low-abundantly expressed genes that are below the detection limits of standard in situ hybridization or by RNA sequencing. Thus, this technical approach turned out to be suitable for sensitive localization studies and may also be applicable for other trematodes. The results suggest that SmSPs may play roles in diverse processes of the parasite. Certain SmSPs expressed at the surface may be involved in host–parasite interactions. Graphic abstract

scholarly journals A novel method for visualizing and tracking endogenous mRNA in a specific cell population in pathological neovascularization

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Md Imam Uddin ◽  
Tyler C. Kilburn ◽  
Sara Z. Jamal ◽  
Craig L. Duvall ◽  
John S. Penn
Keyword(s):  
Real Time ◽  
Disease Burden ◽  
Ex Vivo ◽  
Expression Patterns ◽  
Fluorescence Emission ◽  
High Sensitivity ◽  
Living Systems ◽  
Specific Cell ◽  
Potential Marker

AbstractDiabetic retinopathy, retinopathy of prematurity and retinal vein occlusion are potentially blinding conditions largely due to their respective neovascular components. The development of real-time in vivo molecular imaging methods, to assess levels of retinal neovascularization (NV), would greatly benefit patients afflicted with these conditions. mRNA hybridization techniques offer a potential method to image retinal NV. The success of these techniques hinges on the selection of a target mRNA whose tissue levels and spatial expression patterns correlate closely with disease burden. Using a model of oxygen-induced retinopathy (OIR), we previously observed dramatic increases in retinal endoglin that localized to neovascular structures (NV), directly correlating with levels of neovascular pathology. Based on these findings, we have investigated Endoglin mRNA as a potential marker for imaging retinal NV in OIR mice. Also of critical importance, is the application of innovative technologies capable of detecting mRNAs in living systems with high sensitivity and specificity. To detect and visualize endoglin mRNA in OIR mice, we have designed and synthesized a novel imaging probe composed of short-hairpin anti-sense (AS) endoglin RNA coupled to a fluorophore and black hole quencher (AS-Eng shRNA). This assembly allows highly sensitive fluorescence emission upon hybridization of the AS-Eng shRNA to cellular endoglin mRNA. The AS-Eng shRNA is further conjugated to a diacyl-lipid (AS-Eng shRNA–lipid referred to as probe). The lipid moiety binds to serum albumin facilitating enhanced systemic circulation of the probe. OIR mice received intraperitoneal injections of AS-Eng shRNA–lipid. Ex vivo imaging of their retinas revealed specific endoglin mRNA dependent fluorescence superimposed on neovascular structures. Room air mice receiving AS-Eng shRNA–lipid and OIR mice receiving a non-sense control probe showed little fluorescence activity. In addition, we found that cells in neovascular lesions labelled with endoglin mRNA dependent fluorescence, co-labelled with the macrophage/microglia-associated marker IBA1. Others have shown that cells expressing macrophage/microglia markers associate with retinal neovascular structures in proportion to disease burden. Hence we propose that our probe may be used to image and to estimate the levels of retinal neovascular disease in real-time in living systems.

scholarly journals Extended expression of MaKN1 contributes to the leaf morphology in aquatic forms of Myriophyllum aquaticum

Botany ◽  
2015 ◽  
Vol 93 (9) ◽  
pp. 611-621
Author(s):  
M.D. Shafiullah ◽  
Christian R. Lacroix
Keyword(s):  
Apical Meristem ◽  
Leaf Morphology ◽  
Expression Patterns ◽  
Homeobox Gene ◽  
Leaf Primordia ◽  
Leaf Primordium ◽  
Myriophyllum Aquaticum ◽  
Knox Gene ◽  
Leaf Morphogenesis

Myriophyllum aquaticum (Vell.) Verdc. is heterophyllous in nature with highly dissected simple leaves consisting of several lobes. KNOX (KNOTTED1-LIKE HOMEOBOX) genes are believed to have played an important role in the evolution of leaf diversity. Up-regulation of KNOX during leaf primordium initiation can lead to leaf dissection in plants with simple leaves and, if overexpressed, can produce ectopic meristems on leaves. A previous study on KNOX gene expression in the aerial form of this species showed that this gene is expressed in the shoot apical meristem (SAM), as well as in leaf primordia P0 to P8. Based on these results, it was hypothesized that the prolonged expression of the MaKN1 (Myriophyllum aquaticum Knotted1-like homeobox) gene beyond P8, might play an important role in the generation of more lobes, longer lobes, and hydathode formation in the aquatic leaves of M. aquaticum. The technique of in situ hybridization was carried out using a previously sequenced 300 bp fragment of MaKN1 to determine the expression patterns of this gene in the shoot of aquatic forms of the plant. Expression patterns of MaKN1 revealed that the SAM and leaf primordia of aquatic forms of M. aquaticum at levels P0 (youngest) to P4 were distributed throughout these structures. The level of expression of this MaKN1 gene progressively became more localized to lobes in older leaf primordia (levels P5 to P12). Previous studies of aerial forms of this plant showed MaKN1 expression until P8. Our results with aquatic forms show that the highly dissected leaf morphology in aquatic forms was the result of the prolonged expression of MaKN1 beyond P8. This resulted in the formation of elongated and slightly more numerous lobes, and hydathodes in aquatic forms. These findings support the view that KNOX genes are important developmental regulators of leaf morphogenesis and have played an important role in the evolution of leaf forms in the plant kingdom.

The Expression of Sel1L and Tan-1 in Normal and Neoplastic Cells

2000 ◽  
Vol 15 (1) ◽  
pp. 26-32 ◽  
Author(s):  
M. Cattaneo ◽  
R. Orlandi ◽  
C. Ronchini ◽  
P. Granelli ◽  
G. Malferrari ◽  
...  
Keyword(s):  
Cell Function ◽  
Sequence Similarity ◽  
Expression Patterns ◽  
Negative Regulator ◽  
Chromosomal Mapping ◽  
Normal Adult ◽  
Neoplastic Cells ◽  
C Elegans ◽  
Pancreatic Cancers ◽  
Almost All

We have previously reported on the isolation and chromosomal mapping of a novel human gene (SEL1L), which shows sequence similarity to sel-1, an extragenic suppressor of C. elegans. sel-1 functions as a negative regulator of lin-12 activity, the latter being implicated in the control of diverse cellular differentiation events. In the present study we compare the expression patterns of SEL1L and TAN-1, the human ortholog of lin-12 in normal and neoplastic cells. We found that, whereas both genes are expressed in fetal tissues at similar levels, they are differentially expressed in normal adult and neoplastic cells. In normal adult cells SEL1L is generally present at very low levels; only in the cells of the pancreas does it show maximum expression. By contrast, SEL1L is generally well represented in most neoplastic cells but not in those of pancreatic and gastric carcinomas, where transcription is either downregulated or completely repressed. TAN-1 on the other hand is well represented in almost all normal and neoplastic cells, with very few exceptions. Our observations suggest that SEL1L is presumably implicated in pancreatic and gastric carcinogenesis and that, along with TAN-1, it is very important for normal cell function. Alterations in the expression of SEL1L may be used as a prognostic marker for gastric and pancreatic cancers.

Neural induction and regionalisation in the chick embryo

Development ◽  
1992 ◽  
Vol 114 (3) ◽  
pp. 729-741 ◽  
Author(s):  
K.G. Storey ◽  
J.M. Crossley ◽  
E.M. De Robertis ◽  
W.E. Norris ◽  
C.D. Stern
Keyword(s):  
Spinal Cord ◽  
Nervous System ◽  
Molecular Markers ◽  
Chick Embryo ◽  
Normal Development ◽  
Neural Induction ◽  
Stage 4 ◽  
Embryo Chick ◽  
Host Embryo ◽  
Embryonic Region

Induction and regionalisation of the chick nervous system were investigated by transplanting Hensen's node into the extra-embryonic region (area opaca margin) of a host embryo. Chick/quail chimaeras were used to determine the contributions of host and donor tissue to the supernumerary axis, and three molecular markers, Engrailed, neurofilaments (antibody 3A10) and XlHbox1/Hox3.3 were used to aid the identification of particular regions of the ectopic axis. We find that the age of the node determines the regions of the nervous system that form: young nodes (stages 2–4) induced both anterior and posterior nervous system, while older nodes (stages 5–6) have reduced inducing ability and generate only posterior nervous system. By varying the age of the host embryo, we show that the competence of the epiblast to respond to neural induction declines after stage 4. We conclude that during normal development, the initial steps of neural induction take place before stage 4 and that anteroposterior regionalisation of the nervous system may be a later process, perhaps associated with the differentiating notochord. We also speculate that the mechanisms responsible for induction of head CNS differ from those that generate the spinal cord: the trunk CNS could arise by homeogenetic induction by anterior CNS or by elongation of neural primordia that are induced very early.

Mouse Hox-3.4: homeobox sequence and embryonic expression patterns compared with other members of the Hox gene network

Development ◽  
1990 ◽  
Vol 109 (2) ◽  
pp. 329-339 ◽  
Author(s):  
S.J. Gaunt ◽  
P.L. Coletta ◽  
D. Pravtcheva ◽  
P.T. Sharpe
Keyword(s):  
Gene Network ◽  
Common Ancestor ◽  
Expression Patterns ◽  
Homeobox Gene ◽  
Predicted Amino Acid Sequence ◽  
Chromosome 15 ◽  
Hox Gene ◽  
The Central Nervous System ◽  
Genomic Organisation

A putative mouse homeobox gene (Hox-3.4) was previously identified 4kb downstream of the Hox-3.3 (Hox-6.1)* gene (Sharpe et al. 1988). We have now sequenced the Hox-3.4 homeobox region. The predicted amino acid sequence shows highest degree of homology in the mouse with Hox-1.3 and -2.1. This, together with similarities in the genomic organisation around these three genes, suggests that they are comembers of a subfamily, derived from a common ancestor. Hox-3.4 appears to be a homologue of the Xenopus Xlhbox5 and human cp11 genes (Fritz and De Robertis, 1988; Simeone et al. 1988). Using a panel of mouse-hamster somatic cell hybrids we have mapped the Hox-3.4 gene to chromosome 15. From the results of in situ hybridization experiments, we describe the distribution of Hox-3.4 transcripts within the 12 1/2 day mouse embryo, and we compare this with the distributions of transcripts shown by seven other members of the Hox gene network. We note three consistencies that underlie the patterns of expression shown by Hox-3.4. First, the anterior limits of Hox-3.4 transcripts in the embryo are related to the position of the Hox-3.4 gene within the Hox-3 locus. Second, the anterior limits of Hox-3.4 expression within the central nervous system are similar to those shown by subfamily homologues Hox-2.1 and Hox-1.3, although the tissue-specific patterns of expression for these three genes show many differences. Third, the patterns of Hox-3.4 expression within the spinal cord and the testis are very similar to those shown by a neighbouring Hox-3 gene (Hox-3.3), but they are quite different from those shown by Hox-1 genes (Hox-1.2, -1.3 and -1.4).

Isolation and characterization of a downstream target of Pax6 in the mammalian retinal primordium

Development ◽  
2001 ◽  
Vol 128 (20) ◽  
pp. 3987-3994 ◽  
Author(s):  
Gilbert Bernier ◽  
Wolfgang Vukovich ◽  
Lorenz Neidhardt ◽  
Bernhard G. Herrmann ◽  
Peter Gruss
Keyword(s):  
Transcription Factor ◽  
Expression Pattern ◽  
Large Scale ◽  
Ectopic Expression ◽  
Signal Transduction Pathway ◽  
Homeobox Gene ◽  
Optic Vesicle ◽  
Altered Expression ◽  
Retina Development ◽  
Isolation And Characterization

The transcription factor Pax6 is required for eye morphogenesis in humans, mice and insects, and can induce ectopic eye formation in vertebrate and invertebrate organisms. Although the role of Pax6 has intensively been studied, only a limited number of genes have been identified that depend on Pax6 activity for their expression in the mammalian visual system. Using a large-scale in situ hybridization screen approach, we have identified a novel gene expressed in the mouse optic vesicle. This gene, Necab, encodes a putative cytoplasmic Ca2+-binding protein and coincides with Pax6 expression pattern in the neural ectoderm of the optic vesicle and in the forebrain pretectum. Remarkably, Necab expression is absent in both structures in Pax6 mutant embryos. By contrast, the optic vesicle-expressed homeobox genes Rx, Six3, Otx2 and Lhx2 do not exhibit an altered expression pattern. Using gain-of-function experiments, we show that Pax6 can induce ectopic expression of Necab, suggesting that Necab is a direct or indirect transcriptional target of Pax6. In addition, we have found that Necab misexpression can induce ectopic expression of the homeobox gene Chx10, a transcription factor implicated in retina development. Taken together, our results provide evidence that Necab is genetically downstream of Pax6 and that it is a part of a signal transduction pathway in retina development.

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