scholarly journals Anterior Hox Genes and the Process of Cephalization

2021 ◽  
Vol 9 ◽  
Author(s):  
James C.-G. Hombría ◽  
Mar García-Ferrés ◽  
Carlos Sánchez-Higueras
Keyword(s):  
Nervous Tissue ◽  
Hox Genes ◽  
The Body ◽  
Sensory Organs ◽  
Hox Gene ◽  
Anterior Segments

During evolution, bilateral animals have experienced a progressive process of cephalization with the anterior concentration of nervous tissue, sensory organs and the appearance of dedicated feeding structures surrounding the mouth. Cephalization has been achieved by the specialization of the unsegmented anterior end of the body (the acron) and the sequential recruitment to the head of adjacent anterior segments. Here we review the key developmental contribution of Hox1–5 genes to the formation of cephalic structures in vertebrates and arthropods and discuss how this evolved. The appearance of Hox cephalic genes preceded the evolution of a highly specialized head in both groups, indicating that Hox gene involvement in the control of cephalic structures was acquired independently during the evolution of vertebrates and invertebrates to regulate the genes required for head innovation.

Homeobox genes and models for patterning the hindbrain and branchial arches

Development ◽  
1991 ◽  
Vol 113 (Supplement_1) ◽  
pp. 187-196 ◽  
Author(s):  
Paul Hunt ◽  
Jenny Whiting ◽  
Ian Muchamore ◽  
Heather Marshall ◽  
Robb Krumlauf
Keyword(s):  
Gene Expression ◽  
Neural Crest ◽  
Expression Pattern ◽  
Hox Genes ◽  
Homeobox Genes ◽  
Neural Plate ◽  
The Body ◽  
Hox Gene ◽  
Hox Code ◽  
Branchial Region

Antennapedia class homeobox genes, which in insects are involved in regional specification of the segmented central regions of the body, have been implicated in a similar role in the vertebrate hindbrain. The development of the hindbrain involves the establishment of compartments which are subsequently made distinct from each other by Hox gene expression, implying that the lineage of neural cells may be an important factor in their development. The hindbrain produces the neural crest that gives rise to the cartilages of the branchial skeleton. Lineage also seems to be important in the neural crest, as experiments have shown that the crest will form cartilages appropriate to its level of origin when grafted to a heterotopic location. We show how the Hox genes could also be involved in patterning the mesenchymal structures of the branchial skeleton. Recently it has been proposed that the rhombomererestricted expression pattern of Hox 2 genes is the result of a tight spatially localised induction from underlying head mesoderm, in which a prepattern of Hox expression is visible. We find no evidence for this model, our data being consistent with the idea that the spatially localised expression pattern is a result of segmentation processes whose final stages are intrinsic to the neural plate. We suggest the following model for patterning in the branchial region. At first a segment-restricted code of Hox gene expression becomes established in the neuroepithelium and adjacent presumptive neural crest. This expression is then maintained in the neural crest during migration, resulting in a Hox code in the cranial ganglia and branchial mesenchyme that reflects the crest's rhombomere of origin. The final stage is the establishment of Hox 2 expression in the surface ectoderm which is brought into contact with neural crest-derived branchial mesenchyme. The Hox code of the branchial ectoderm is established later in development than that of the neural plate and crest, and involves the same combination of genes as the underlying crest. Experimental observations suggest the idea of an instructive interaction between branchial crest and its overlying ectoderm, which would be consistent with our observations. The distribution of clusters of Antennapedia class genes within the animal kingdom suggests that the primitive chordates ancestral to vertebrates had at least one Hox cluster. The origin of the vertebrates is thought to have been intimately linked to the appearance of the neural crest, initially in the branchial region. Our data are consistent with the idea that the branchial region of the head arose in evolution before the more anterior parts, the development of the branchial region employing the Hox genes in a more determinate patterning system. In this scenario, the anterior parts of the head arose subsequently, which may explain the greater importance of interactions in their development, and the fact that Antennapedia class Hox genes are not expressed there.

Hox genes and the evolution of diverse body plans

1995 ◽  
Vol 349 (1329) ◽  
pp. 313-319 ◽  
Keyword(s):  
Transcription Factors ◽  
Hox Genes ◽  
Body Plan ◽  
The Body ◽  
Chromosomal Organization ◽  
Hox Gene ◽  
Body Regions ◽  
Taxonomic Groups ◽  
Novel Model ◽  
Sequence Characteristics

Homeobox genes encode transcription factors that carry out diverse roles during development. They are widely distributed among eukaryotes, but appear to have undergone an extensive radiation in the earliest metazoa, to generate a range of homeobox subclasses now shared between diverse metazoan phyla. The Hox genes comprise one of these subfamilies, defined as much by conserved chromosomal organization and expression as by sequence characteristics. These Hox genes act as markers of position along the antero—posterior axis of the body in nematodes, arthropods, chordates, and by implication, most other triploblastic phyla. In the arthropods this role is visualized most clearly in the control of segment identity. Exactly how Hox genes control the structure of segments is not yet understood, but their differential deployment between segments provides a model for the basis of segment diversity. Within the arthropods, distantly related taxonomic groups with very different body plans (insects, crustaceans) may share the same set of Hox genes. The expression of these Hox genes provides a new character to define the homology of different body regions. Comparisons of Hox gene deployment between insects and a branchiopod crustacean suggest a novel model for the derivation of the insect body plan.

Crustacean (malacostracan) Hox genes and the evolution of the arthropod trunk

Development ◽  
2000 ◽  
Vol 127 (11) ◽  
pp. 2239-2249 ◽  
Author(s):  
A. Abzhanov ◽  
T.C. Kaufman
Keyword(s):  
Gene Expression ◽  
Hox Genes ◽  
Expression Patterns ◽  
Gene Expression Pattern ◽  
The Body ◽  
Ancestral State ◽  
Porcellio Scaber ◽  
Hox Gene ◽  
Overlapping Domains ◽  
Discrete Domains

Representatives of the Insecta and the Malacostraca (higher crustaceans) have highly derived body plans subdivided into several tagma, groups of segments united by a common function and/or morphology. The tagmatization of segments in the trunk, the part of the body between head and telson, in both lineages is thought to have evolved independently from ancestors with a distinct head but a homonomous, undifferentiated trunk. In the branchiopod crustacean, Artemia franciscana, the trunk Hox genes are expressed in broad overlapping domains suggesting a conserved ancestral state (Averof, M. and Akam, M. (1995) Nature 376, 420–423). In comparison, in insects, the Antennapedia-class genes of the homeotic clusters are more regionally deployed into distinct domains where they serve to control the morphology of the different trunk segments. Thus an originally Artemia-like pattern of homeotic gene expression has apparently been modified in the insect lineage associated with and perhaps facilitating the observed pattern of tagmatization. Since insects are the only arthropods with a derived trunk tagmosis tested to date, we examined the expression patterns of the Hox genes Antp, Ubx and abd-A in the malacostracan crustacean Porcellio scaber (Oniscidae, Isopoda). We found that, unlike the pattern seen in Artemia, these genes are expressed in well-defined discrete domains coinciding with tagmatic boundaries which are distinct from those of the insects. Our observations suggest that, during the independent tagmatization in insects and malacostracan crustaceans, the homologous ‘trunk’ genes evolved to perform different developmental functions. We also propose that, in each lineage, the changes in Hox gene expression pattern may have been important in trunk tagmatization.

A C. elegans Hox gene switches on, off, on and off again to regulate proliferation, differentiation and morphogenesis

Development ◽  
1996 ◽  
Vol 122 (5) ◽  
pp. 1651-1661 ◽  
Author(s):  
S.J. Salser ◽  
C. Kenyon
Keyword(s):  
Cellular Response ◽  
Hox Genes ◽  
Sense Organ ◽  
Cellular Level ◽  
The Body ◽  
Body Region ◽  
Hox Gene ◽  
C Elegans ◽  
Independent Events ◽  
Gene Switches

Hox genes establish body pattern throughout the animal kingdom, but the role these genes play at the cellular level to modify and shape parts of the body remains a mystery. We find that the C. elegans Antennapedia homolog, mab-5, sequentially programs many independent events within individual cell lineages. In one body region, mab-5 first switches ON in a lineage to stimulate proliferation, then OFF to specify epidermal structures, then ON in just one branch of the lineage to promote neuroblast formation, and finally OFF to permit proper sense organ morphology. In a neighboring lineage, continuous mab-5 expression leads to a different pattern of development. Thus, this Hox gene achieves much of its power to diversify the anteroposterior axis through fine spatiotemporal differences in expression coupled with a changing pattern of cellular response.

scholarly journals Timed collinear activation of Hox genes during gastrulation controls the avian forelimb position

2018 ◽  
Author(s):  
Chloe Moreau ◽  
Paolo Caldarelli ◽  
Didier Rocancourt ◽  
Julian Roussel ◽  
Nicolas Denans ◽  
...  
Keyword(s):  
Natural Variation ◽  
Molecular Mechanisms ◽  
Hox Genes ◽  
Gene Activation ◽  
The Body ◽  
Three Dimensions ◽  
Limb Patterning ◽  
Hox Gene ◽  
Limb Position ◽  
Control Limb

SummaryLimb position along the body is highly consistent within one species but very variable among vertebrates. Despite major advances in our understanding of limb patterning in three dimensions, how limbs reproducibly form along the anteroposterior axis remains largely unknown. Hox genes have long been suspected to control limb position, however supporting evidences are mostly correlative and their role in this process remains unclear. Here we show that Hox genes determine the avian forelimb position in a two-step process: first, their sequential collinear activation during gastrulation controls the relative position of their own successive expression domains along the body axis. Then, within these collinear domains, Hox genes differentially activate or repress the genetic cascade responsible for forelimb initiation. Furthermore, we provide evidences that changes in the timing of collinear Hox gene activation might underlie natural variation in forelimb position between different birds. Altogether our results which characterize the cellular and molecular mechanisms underlying the regulation and natural variation of forelimb position in avians, show a direct and early role for Hox genes in this process.

scholarly journals Hox genes and morphological identity: axial versus lateral patterning in the vertebrate mesoderm

Development ◽  
2000 ◽  
Vol 127 (19) ◽  
pp. 4265-4275 ◽  
Author(s):  
J.L. Nowicki ◽  
A.C. Burke
Keyword(s):  
Gene Expression ◽  
Hox Genes ◽  
Expression Profiles ◽  
The Body ◽  
Lateral Plate ◽  
Global Pattern ◽  
Hox Gene ◽  
Embryonic Origin ◽  
Morphological Identity ◽  
Derivatives Of

The successful organization of the vertebrate body requires that local information in the embryo be translated into a functional, global pattern. Somite cells form the bulk of the musculoskeletal system. Heterotopic transplants of segmental plate along the axis from quail to chick were performed to test the correlation between autonomous morphological patterning and Hox gene expression in somite subpopulations. The data presented strengthen the correlation of Hox gene expression with axial specification and focus on the significance of Hox genes in specific derivatives of the somites. We have defined two anatomical compartments of the body based on the embryonic origin of the cells making up contributing structures: the dorsal compartment, formed from purely somitic cell populations; and the ventral compartment comprising cells from somites and lateral plate. The boundary between these anatomical compartments is termed the somitic frontier. Somitic tissue transplanted between axial levels retains both original Hox expression and morphological identity in the dorsal compartment. In contrast, migrating lateral somitic cells crossing the somitic frontier do not maintain donor Hox expression but apparently adopt the Hox expression of the lateral plate and participate in the morphology appropriate to the host level. Dorsal and ventral compartments, as defined here, have relevance for experimental manipulations that influence somite cell behavior. The correlation of Hox expression profiles and patterning behavior of cells in these two compartments supports the hypothesis of independent Hox codes in paraxial and lateral plate mesoderm.

scholarly journals The unusual gene order in the Echinoderm Hox cluster is related to the embryo and larva symmetries

2015 ◽  
Author(s):  
Spyros Papageorgiou
Keyword(s):  
Sea Urchin ◽  
Gene Sequence ◽  
Hox Genes ◽  
Developmental Stages ◽  
Rotational Symmetry ◽  
The Body ◽  
Gene Location ◽  
Linear Arrangement ◽  
Hox Gene ◽  
Hox Cluster

Background: Hox gene collinearity relates the sequential location of Hox genes in the 3´ to 5´ direction on the chromosome with the linear arrangement of the body elements along the anterior-posterior (A/P) axis of bilaterian embryos. This spatial Hox gene collinearity has been almost universally respected in diverse organisms like worms, insects or vertebrates. It is therefore surprising that the above well established collinearity rule is violated in the case of Echinoderms. No explanation of this violation is apparent. Here a hypothesis is put forward which provides a cue to understand the abnormal serial gene location in the sea urchin disorganized Hox cluster. Results: Bilateral symmetry along the A/P embryo axis is established at the very early stages of ontogeny of the sea urchin. For the subsequent developmental stages, rotational symmetry emerges in the vestibula larva. In analogy to the linear A/P case, the circular topology of modules might be a reflection of the architectural restructuring of the Hox loci where the 3´ and 5´ ends of the Hox cluster approach each other so that a closed contour of the chromatin fiber is formed. At a later stage, the break and opening of the cluster contour at the level of Hox4 combined with the rotational symmetry leads to the observed Hox gene sequence that violates the standard 3´ to 5´ collinearity. Conclusion: The unusual gene series manifests the congruence of Hox gene sequence in the cluster with the circular arrangement of the sea urchin primary podia. Accordingly, the Hox sequence after the break at Hox4 is not a violation but an extension of Hox gene collinearity to animals with rotational symmetry.

scholarly journals Contributions of HOX genes to cancer hallmarks: Enrichment pathway analysis and review

Tumor Biology ◽  
2020 ◽  
Vol 42 (5) ◽  
pp. 101042832091805 ◽  
Author(s):  
Danielle Barbosa Brotto ◽  
Ádamo Davi Diógenes Siena ◽  
Isabela Ichihara de Barros ◽  
Simone da Costa e Silva Carvalho ◽  
Bruna Rodrigues Muys ◽  
...  
Keyword(s):  
Gene Family ◽  
Tumor Progression ◽  
Hox Genes ◽  
Critical Role ◽  
The Body ◽  
Systematic Evaluation ◽  
Hox Gene ◽  
Cancer Hallmarks ◽  
Cancer Phenotype

Homeobox genes function as master regulatory transcription factors during development, and their expression is often altered in cancer. The HOX gene family was initially studied intensively to understand how the expression of each gene was involved in forming axial patterns and shaping the body plan during embryogenesis. More recent investigations have discovered that HOX genes can also play an important role in cancer. The literature has shown that the expression of HOX genes may be increased or decreased in different tumors and that these alterations may differ depending on the specific HOX gene involved and the type of cancer being investigated. New studies are also emerging, showing the critical role of some members of the HOX gene family in tumor progression and variation in clinical response. However, there has been limited systematic evaluation of the various contributions of each member of the HOX gene family in the pathways that drive the common phenotypic changes (or “hallmarks”) and that underlie the transformation of normal cells to cancer cells. In this review, we investigate the context of the engagement of HOX gene targets and their downstream pathways in the acquisition of competence of tumor cells to undergo malignant transformation and tumor progression. We also summarize published findings on the involvement of HOX genes in carcinogenesis and use bioinformatics methods to examine how their downstream targets and pathways are involved in each hallmark of the cancer phenotype.

scholarly journals Hox genes mediate the escalation of sexually antagonistic traits in water striders

2018 ◽  
Author(s):  
Antonin Jean Johan Crumière ◽  
Abderrahman Khila
Keyword(s):  
Sexual Conflict ◽  
Hox Genes ◽  
The Body ◽  
Water Strider ◽  
Fitness Costs ◽  
Sex Combs Reduced ◽  
Hox Gene ◽  
Sex Combs ◽  
Sex Comb ◽  
Resistance Trait

AbstractSexual conflict occurs when traits favoured in one sex impose fitness costs on the other sex. In the case of sexual conflict over mating rate, the sexes often undergo antagonistic coevolution and escalation of traits that enhance female’s resistance to mating and traits that increase male’s persistence. How this escalation in sexually antagonistic traits is established during ontogeny remains unclear. In the water strider Rhagovelia antilleana, male persistence traits consist of sex combs in the forelegs and multiple rows of spines and a thick femur in the rearlegs. Female resistance trait consists of a prominent spike-like projection of the pronotum. RNAi knockdown against the Hox gene Sex Combs Reduced resulted in the reduction of both the sex comb in males and the pronotum projection in females. RNAi against the Hox gene Ultrabithorax resulted in the complete loss or reduction of all persistence traits in male rearlegs. These results demonstrate that Hox genes can mediate sex-specific escalation of antagonistic traits along the body axis of both sexes.

scholarly journals Organ- and Site-Specific HOX Gene Expression in Stromal Cells

2021 ◽  
Author(s):  
Masoumeh Mirrahimi ◽  
Caroline Ospelt
Keyword(s):  
Gene Expression ◽  
Stromal Cells ◽  
Hox Genes ◽  
Specific Pattern ◽  
Body Plan ◽  
The Body ◽  
Site Specific ◽  
Hox Gene ◽  
Conserved Genes

HOX genes are a group of evolutionarily conserved genes that encode a family of transcription factors that regulate early developmental morphogenetic processes and continue to be expressed into adulthood. These highly conserved HOX factors play an unquestioned crucial role as master regulators during embryonic vertebrate development and morphogenesis by controlling the three dimensional body plan organization. HOX genes specify regions of the body plan of an embryo along the head-tail axis. They encode proteins that specify the characteristics of ‘position’, ensuring that the correct structures form in the correct places of the body. Expression of HOX is known to persist in many tissues in the postnatal period suggesting the role of these genes not only during development but also for the functioning of tissues throughout life. The tissue-specific pattern of HOX gene expression is inherent in stromal/stem cells of mesenchymal origin, such as mesenchymal stromal cells, fibroblasts, smooth muscle cells, and preadipocytes, enabling them to memorize their topographic location in the form of their HOX code and to fulfill their location-specific functions. In this chapter, we focus on the expression and potential role of HOX genes in adult tissues. We review evidence that site-specific expression of HOX genes is connected to location-specific disease susceptibility and review studies showing that dysregulated expression of HOX genes can be associated with various diseases. By recognizing the importance of site-specific molecular mechanisms in the organ stroma, we gain new insights into the processes underlying the site-specific manifestation of disease.

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