XlHbox 8: a novel Xenopus homeo protein restricted to a narrow band of endoderm

Development ◽  
1989 ◽  
Vol 105 (4) ◽  
pp. 787-794 ◽  
Author(s):  
C.V. Wright ◽  
P. Schnegelsberg ◽  
E.M. De Robertis
Keyword(s):  
Nuclear Protein ◽  
Narrow Band ◽  
Homeobox Gene ◽  
Positional Information ◽  
Temporal Expression ◽  
Factors Affecting ◽  
New Class ◽  
Homeodomain Sequence ◽  
Pancreatic Epithelium ◽  
Endodermal Differentiation

We report the isolation of a new homeobox gene from Xenopus laevis genomic DNA. The homeodomain sequence is highly diverged from the prototype Antennapedia sequence, and contains a unique histidine residue in the helix that binds to DNA. The homeodomain is followed by a 65 amino acid carboxyterminal domain, the longest found to date in any vertebrate homeobox gene. We have raised specific antibodies against an XlHbox 8-beta-gal fusion protein to determine the spatial and temporal expression of this gene. The nuclear protein first appears in a narrow band of the endoderm at stage 33 and develops into expression within the epithelial cells of the pancreatic anlagen and duodenum. Expression within the pancreatic epithelium persists into the adult frog. This unprecedented restriction to an anteroposterior band of the endoderm suggests that vertebrate homeobox genes might be involved in specifying positional information not only in the neuroectoderm and mesoderm, but also in the endoderm. Our data suggest that XlHbox 8 may therefore represent the first member of a new class of position-dependent transcription factors affecting endodermal differentiation.

scholarly journals Motoneuron fate specification revealed by patterned LIM homeobox gene expression in embryonic zebrafish

Development ◽  
1995 ◽  
Vol 121 (12) ◽  
pp. 4117-4125 ◽  
Author(s):  
B. Appel ◽  
V. Korzh ◽  
E. Glasgow ◽  
S. Thor ◽  
T. Edlund ◽  
...  
Keyword(s):  
Gene Expression ◽  
Spinal Cord ◽  
Gene Transcription ◽  
Cell Body ◽  
Homeobox Genes ◽  
Homeobox Gene ◽  
Positional Information ◽  
Axonal Projection ◽  
Fate Specification ◽  
Genes Expression

In zebrafish, individual primary motoneurons can be uniquely identified by their characteristic cell body positions and axonal projection patterns. The fate of individual primary motoneurons remains plastic until just prior to axogenesis when they become committed to particular identities. We find that distinct primary motoneurons express particular combinations of LIM homeobox genes. Expression precedes axogenesis as well as commitment, suggesting that LIM homeobox genes may contribute to the specification of motoneuronal fates. By transplanting them to new spinal cord positions, we demonstrate that primary motoneurons can initiate a new program of LIM homeobox gene expression, as well as the morphological features appropriate for the new position. We conclude that the patterned distribution of different primary motoneuronal types within the zebrafish spinal cord follows the patterned expression of LIM homeobox genes, and that this reflects a highly resolved system of positional information controlling gene transcription.

scholarly journals Specification of cell fate in the developing eye of Drosophila

Development ◽  
1991 ◽  
Vol 113 (Supplement_1) ◽  
pp. 123-130 ◽  
Author(s):  
Ernst Hafen ◽  
Konrad Basler
Keyword(s):  
Tyrosine Kinase ◽  
Cell Fate ◽  
Photoreceptor Cell ◽  
Nuclear Protein ◽  
Single Cells ◽  
Photoreceptor Cells ◽  
Positional Information ◽  
Cellular Interactions ◽  
Eye Imaginal Disc

Determination of cell fate in the developing eye of Drosophila depends on cellular interactions. In the eye imaginal disc, an initially unpatterned epithelial sheath of cells, single cells are specified in regular intervals to become the R8 photoreceptor cells. Genes such as Notch and scabrous participate in this process suggesting that specification of ommatidial founder cells and the formation of bristles in the adult epidermis involve a similar mechanism known as lateral inhibition. The subsequent steps of ommatidial assembly involve a different mechanism: undetermined cells read their position based on the contacts they make with neighbors that have already begun to differentiate. The development of the R7 photoreceptor cell is best understood. The key role seems to be played by sevenless, a receptor tyrosine kinase on the surface of the R7 precursor. It transmits the positional information – most likely encoded by boss on the neighboring R8 cell membrane – into the cell via its tyrosine kinase that activates a signal transduction cascade. Two components of this cascade – Sos and sina – have been identified genetically, sina encodes a nuclear protein whose expression is not limited to R7. Constitutive activation of the sevenless kinase by overexpression results in the diversion of other ommatidial cells into the R7 pathway, suggesting that activation of the sevenless signalling pathway is sufficient to specify R7 development.

scholarly journals PDX-1 is required for pancreatic outgrowth and differentiation of the rostral duodenum

Development ◽  
1996 ◽  
Vol 122 (3) ◽  
pp. 983-995 ◽  
Author(s):  
M.F. Offield ◽  
T.L. Jetton ◽  
P.A. Labosky ◽  
M. Ray ◽  
R.W. Stein ◽  
...  
Keyword(s):  
Homeobox Gene ◽  
Lacz Reporter ◽  
Additional Insight ◽  
Pancreatic Progenitors ◽  
Proliferation And Differentiation ◽  
Endodermal Differentiation ◽  
Neomycin Resistance ◽  
Beta Galactosidase ◽  
Insight Into

It has been proposed that the Xenopus homeobox gene, XlHbox8, is involved in endodermal differentiation during pancreatic and duodenal development (Wright, C.V.E., Schnegelsberg, P. and De Robertis, E.M. (1988). Development 105, 787–794). To test this hypothesis directly, gene targeting was used to make two different null mutations in the mouse XlHbox8 homolog, pdx-1. In the first, the second pdx-1 exon, including the homeobox, was replaced by a neomycin resistance cassette. In the second, a lacZ reporter was fused in-frame with the N terminus of PDX-1, replacing most of the homeodomain. Neonatal pdx-1 −/− mice are apancreatic, in confirmation of previous reports (Jonsson, J., Carlsson, L., Edlund, T. and Edlund, H. (1994). Nature 371, 606–609). However, the pancreatic buds do form in homozygous mutants, and the dorsal bud undergoes limited proliferation and outgrowth to form a small, irregularly branched, ductular tree. This outgrowth does not contain insulin or amylase-positive cells, but glucagon-expressing cells are found. The rostral duodenum shows a local absence of the normal columnar epithelial lining, villi, and Brunner's glands, which are replaced by a GLUT2-positive cuboidal epithelium resembling the bile duct lining. Just distal of the abnormal epithelium, the numbers of enteroendocrine cells in the villi are greatly reduced. The PDX-1/beta-galactosidase fusion allele is expressed in pancreatic and duodenal cells in the absence of functional PDX-1, with expression continuing into perinatal stages with similar boundaries and expression levels. These results offer additional insight into the role of pdx-1 in the determination and differentiation of the posterior foregut, particularly regarding the proliferation and differentiation of the pancreatic progenitors.

Mouse homeobox gene transcripts occupy different but overlapping domains in embryonic germ layers and organs: a comparison of Hox-3.1 and Hox-1.5

Development ◽  
1988 ◽  
Vol 103 (1) ◽  
pp. 135-144 ◽  
Author(s):  
S.J. Gaunt
Keyword(s):  
Nervous System ◽  
Homeobox Gene ◽  
Positional Information ◽  
Germ Layers ◽  
Temporal And Spatial Patterns ◽  
Small Delay ◽  
Gene Transcripts ◽  
Overlapping Domains ◽  
Temporal And Spatial

By use of in situ hybridization experiments, the mouse homeobox genes Hox-3.1 and Hox-1.5 are compared in the temporal and spatial patterns of their embryonic transcripts. Transcripts of both genes are first detected at about 7 1/2 days, although the appearance of Hox-3.1 transcripts apparently follows Hox-1.5 after a small delay. Hox-3.1 and Hox-1.5 transcripts occupy domains which are different, although overlapping, along the anteroposterior axis of the embryo. The domains are first established within the ectoderm and mesoderm germ layers at 7 1/2–8 days, but subsequently they persist within the nervous system, the prevertebral column and within at least some of the organs (the thyroid, lung, stomach, mesonephric and metanephric kidneys) at 12 1/2 days. In discussion, two different mechanisms are considered by which positional information might first be generated within the germ layers.

Lox10, a member of the NK-2 homeobox gene class, is expressed in a segmental pattern in the endoderm and in the cephalic nervous system of the leech Helobdella

Development ◽  
1993 ◽  
Vol 118 (3) ◽  
pp. 877-892 ◽  
Author(s):  
D. Nardelli-Haefliger ◽  
M. Shankland
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
In Situ Hybridization ◽  
Animal Species ◽  
Homeobox Gene ◽  
Endoderm Differentiation ◽  
Homeodomain Sequence ◽  
Supraesophageal Ganglion ◽  
The Central Nervous System

A novel leech homeobox gene, Lox10, is shown to encode a homeodomain sequence characteristic of a phyletically widespread NK-2 homeobox gene class. Lox10 expression was examined in leech embryos of various ages by in situ hybridization. In the unsegmented cephalic region, Lox10 RNA is expressed in a subset of the cells descended from the a' and b' micromeres, including a small cluster of cells, believed to be postmitotic neurons, within the supraesophageal ganglion of the central nervous system. Hybridization signal was not detected in either the mesoderm or ectoderm of the trunk segments, and the apparent restriction of Lox10 ectodermal expression to the nonsegmented cephalic domain resembles the restricted forebrain expression pattern of its mammalian homologues. Lox10 is also expressed within the endodermal tissues of the leech midgut, which arises by cellularization from a polynucleate syncytium. Endodermal expression is organized into a pattern of transverse stripes and spots which are aligned with the intersegmental septa, and which prefigure the pattern of gut wall constrictions observed at later stages of development. Lox10 is the first molecular marker of segmentally periodic endoderm differentiation reported for any animal species.

Xenopus Hox-2 genes are expressed sequentially after the onset of gastrulation and are differentially inducible by retinoic acid

Development ◽  
1992 ◽  
Vol 116 (Supplement) ◽  
pp. 195-202 ◽  
Author(s):  
Erik-Jan Dekker ◽  
Maria Pannese ◽  
Erwin Houtzager ◽  
Ans Timmermans ◽  
Edoardo Boncinelli ◽  
...  
Keyword(s):  
Retinoic Acid ◽  
Expression Patterns ◽  
Positional Information ◽  
Developmental Expression ◽  
Temporal Expression ◽  
Mammalian Cell Lines ◽  
All Trans Retinoic Acid ◽  
Temporal Expression Pattern ◽  
Six Genes ◽  
Chromosomal Sequence

In this paper, we review experiments to characterise the developmental expression and the responses to all-trans retinoic acid (RA) of six members of the Hox-2 complex of homeobox-containing genes, during the early development of Xenopus laevis. We showed that the six genes are expressed in a spatial sequence which is colinear with their putative 3′ to 5′ chromosomal sequence and that five of them are also expressed rapidly after the beginning of gastrulation, in a 3′ to 5′ colinear temporal sequence. The sixth gene (Xhox2.9) has an exceptional spatial and temporal expression pattern. The six genes all respond to RA by showing altered spatiotemporal expression patterns, and are also RA-inducible, the sequence of the magnitudes of their RA responses being colinear with their 3′ to 5′ chromosomal sequence, and with their spatial and temporal expression sequences. Our data also reveal that there is a pre-existing anteroposterior polarity in the embryo's competence for a response to RA. These results complement and extend previous findings made using murine and avian embryos and mammalian cell lines. They suggest that an endogenous retinoid could contribute to positional information in the early Xenopus embryo.

The expression of pannier and achaete-scute homologues in a mosquito suggests an ancient role of pannier as a selector gene in the regulation of the dorsal body pattern

Development ◽  
2002 ◽  
Vol 129 (16) ◽  
pp. 3861-3871 ◽  
Author(s):  
Corinna Wülbeck ◽  
Pat Simpson
Keyword(s):  
Expression Patterns ◽  
Ectopic Expression ◽  
Positional Information ◽  
New Class ◽  
Medial Dorsal ◽  
Duplication Events ◽  
Selector Genes ◽  
Bristle Pattern ◽  
Body Pattern

The Drosophila gene pannier (pnr) has recently been assigned to a new class of selector genes (Calleja, M., Herranz, H., Estella, C., Casal, J., Lawrence, P., Simpson, P. and Morata, G. (2000). Development 127, 3971-3980; (Mann, R. S. and Morata, G. (2000). Annu. Rev. Cell Dev. Biol. 16, 243-271). It specifies pattern in the dorsal body. On the dorsal notum it is expressed in a broad medial domain and directly regulates transcription of the achaete-scute (ac-sc) genes driving their expression in small discrete clusters within this domain at the sites of each future bristle. This spatial resolution is achieved through modulation of Pnr activity by specific co-factors and by a number of discrete cis-regulatory enhancers in the ac-sc gene complex. We have isolated homologues of pnr and ac-sc in Anopheles gambiae, a basal species of Diptera that diverged from Drosophila melanogaster (Dm) about 200 million years ago, and examined their expression patterns. We found that an ac-sc homologue of Anopheles, Ag-ASH, is expressed on the dorsal medial notum at the sites where sensory organs emerge in several domains that are identical to those of the pnr homologue, Ag-pnr. This suggests that activation of Ag-ASH by Ag-Pnr has been conserved. Indeed, when expressed in Drosophila, Ag-pnr is able to mimic the effects of ectopic expression of Dm-pnr and induce ectopic bristles. These results are discussed in the context of the gene duplication events and the acquisition of a modular promoter, that may have occurred at different times in the lineage leading to derived species such as Drosophila. The bristle pattern of Anopheles correlates in a novel fashion with the expression domains of Ag-pnr/Ag-ASH. While precursors for the sensory scales can arise anywhere within the expression domains, bristle precursors arise exclusively along the borders. This points to the existence of specific positional information along the borders, and suggests that Ag-pnr specifies pattern in the medial, dorsal notum, as in Drosophila, but via a different mechanism.

Expression of a homeobox gene product in normal and mutant zebrafish embryos: evolution of the tetrapod body plan

Development ◽  
1990 ◽  
Vol 109 (2) ◽  
pp. 279-288 ◽  
Author(s):  
A. Molven ◽  
C.V. Wright ◽  
R. Bremiller ◽  
E.M. De Robertis ◽  
C.B. Kimmel
Keyword(s):  
Gene Product ◽  
Sensory Neurons ◽  
Protein Level ◽  
Homeobox Gene ◽  
Positional Information ◽  
Body Plan ◽  
Mouse Embryos ◽  
Zebrafish Embryos ◽  
Anteroposterior Axis ◽  
Somitic Mesoderm

An antibody was used to detect antigens in zebrafish that appear to be homologous to the frog homeodomain-containing protein XlHbox 1. These antigens show a restricted expression in the anteroposterior axis and an anteroposterior gradient in the pectoral fin bud, consistent with the distribution of XlHbox 1 protein in frog and mouse embryos. In the somitic mesoderm, a sharp anterior limit of expression coincides exactly with the boundary between somites 4 and 5, and the protein level fades out posteriorly. A similar, graded expression of the antigen is seen within the series of Rohon-Beard sensory neurons of the CNS. We also immunostained the mutant spt-1 (‘spadetail’), in which the trunk mesoderm is greatly depleted and disorganized in the region of XlHbox 1 expression. The defects stem from misdirected cell movements during gastrulation, but nervertheless, newly recruited cells that partially refill the trunk mesoderm express the antigen within the normal span of the anteroposterior axis. This finding suggests that the mutation does not delete positional information required for activation of the XlHbox 1 gene.

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