Temporal and spatial expression of EmH-3, a homeobox-containing gene isolated from the freshwater sponge Ephydatia muelleri

Richelle-Maurer, Evelyn; Vyver, Gisèle Van De

doi:10.1016/s0047-6374(99)00037-8

Cited by 20 publications

(5 citation statements)

References 47 publications

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“…Homeobox genes have been identified in demosponges (Coutinho et al 1994;Kruse et al 1994;Seimyia et al 1994;Degnan et al 1995;Richelle-Maurer et al 1998, 1999, and their temporal and spatial expressions have been shown in both adults (Seimyia et al 1997;Larroux and Degnan 1999;Richelle-Maurer et al 1999) and embryos (Leys et al 1999). However, spicule transport by cells across the sponge mesohyl to distances of up to several hundred micrometres has also been recorded in siliceous sponges (Elvin 1971;Bond and Harris 1988;Bond 1992;TokyoCinema Inc. 1996;Custódio et al 2002).…”

Section: Siliceous Frameworkmentioning

confidence: 99%

Mineral skeletogenesis in sponges

Uriz¹

2006

Can. J. Zool.

140

153

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Sponges secrete a variety of mineral skeletons consisting of calcite, aragonite, and (or) amorphous silica that confer strength and protect them from physical perturbations. Calcification takes place in a solution of bicarbonate and calcium ions, which is supersaturated with respect to both calcite and aragonite. In contrast, siliceous spicules are formed from an environment that is undersaturated with respect to silicon. Silification is the predominant process of biomineralization in extant sponges (92% of the species). The number of axes of symmetry in the large skeletal elements (megasclere spicules) is the main skeletal difference between the classes Hexactinellida (monaxons and triaxons) and Demospongiae (monaxons and tetraxons). Hypersilification occurs in both lithistid demosponges and hexactinellids, which are mostly confined to silicon-rich environments. Both siliceous and calcareous sponge skeletons are deposited within a well-defined restricted space by the so-called matrix-mediated mineralization. Both processes require organic molecules, which are secreted by a particular cell type (sclerocytes) and guide spicule formation. In most siliceous sponges, these molecules form a discrete filament, which is mainly triangular or quadrangular in cross section in demosponges and hexactinellids, respectively. No discrete axial filament has been reported for calcareous sponges. Silica polycondensation produces nanospheres to microspheres, which are arranged in concentric layers to form the spicules. The potential number of siliceous spicule types in a sponge species appears to be fixed genetically, but the environmental conditions (specifically the availability of silicon) may determine whether a genetically determined spicule type is finally expressed. In this study I review the current knowledge on sponge skeletogenesis, from molecular, cellular, and structural points of view. The contribution of environment variables, as well as the proliferation and decay of the main skeleton types in the past, are also considered. Résumé :Les éponges sécrètent une variété de squelettes minéraux de calcite, d'aragonite et(ou) de silice amorphe qui les renforcent et les protègent des perturbations physiques. La calcification se produit à partir d'une solution d'ions bicarbonate et calcium qui est sursaturée par rapport à la calcite et l'aragonite. En revanche, les spicules siliceux se forment à partir d'un milieu qui est sous-saturé en silicium. La silification est le processus dominant de biominéralisation chez les éponges actuelles (92 % des espèces). Le nombre d'axes de symétrie des éléments majeurs du squelette (les spicules mégasclères) est la plus grande différence entre les squelettes de la classe des hexactinellides (à un et trois axes) et ceux des desmosponges (à un et quatre axes). L'hypersilification se produit à la fois chez les desmosponges lithistides et les hexactinellides qui sont en majorité confinés dans les milieux riches en silicium. Les squelettes, tant siliceux que calcaires, des éponges se déposent dans...

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Section: Siliceous Frameworkmentioning

confidence: 99%

Mineral skeletogenesis in sponges

Uriz¹

2006

Can. J. Zool.

140

153

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“…Within the last years, a large number of diploblastic Antp-related genes have been isolated (13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31). Among those, cnidarian sequences related to Hox and paraHox genes were found (15, 17-19, 22, 23, 25, 28, 29, 31), but the characterization of diploblastic Hox families, as well as their possible relatedness to triploblastic families, remains unclear in several cases (26,32).…”

mentioning

confidence: 99%

Evolution of Antp-class genes and differential expression ofHydra Hox/paraHoxgenes in anterior patterning

Gauchat

Mazet

Berney

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

176

125

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The conservation of developmental functions exerted by Antpclass homeoproteins in protostomes and deuterostomes suggested that homologs with related functions are present in diploblastic animals. Our phylogenetic analyses showed that Antp-class homeodomains belong either to non-Hox or to Hox͞paraHox families. Among the 13 non-Hox families, 9 have diploblastic homologs, Msx, Emx, Barx, Evx, Tlx, NK-2, and Prh͞Hex, Not, and Dlx, reported here. Among the Hox͞paraHox, poriferan sequences were not found, and the cnidarian sequences formed at least five distinct cnox families. Two are significantly related to the paraHox Gsx (cnox-2) and the mox (cnox-5) sequences, whereas three display some relatedness to the Hox paralog groups 1 (cnox-1), 9͞10 (cnox-3) and the paraHox cdx (cnox-4). Intermediate Hox͞paraHox genes (PG 3 to 8 and lox) did not have clear cnidarian counterparts. In Hydra, cnox-1, cnox-2, and cnox-3 were not found chromosomally linked within a 150-kb range and displayed specific expression patterns in the adult head. During regeneration, cnox-1 was expressed as an early gene whatever the polarity, whereas cnox-2 was up-regulated later during head but not foot regeneration. Finally, cnox-3 expression was reestablished in the adult head once it was fully formed. These results suggest that the Hydra genes related to anterior Hox͞paraHox genes are involved at different stages of apical differentiation. However, the positional information defining the oral͞aboral axis in Hydra cannot be correlated strictly to that characterizing the anterior-posterior axis in vertebrates or arthropods. T he discovery of structural and functional homologies between regulatory genes used by Drosophila and vertebrates during their development led to the hypothesis that animals would share a common set of genes for defining the head, trunk, and posterior regions at early developmental stages (1-6). The proposed genes were homeobox genes belonging either to the Antp class, like empty-spiracle (emx), even-skipped (evx), Hox genes, or to the Prd class, like orthodenticle (Otx), goosecoid. Phylogenetic analyses performed on a vast amount of Hox homeodomain (HD) sequences, including representatives from all classes of homeobox genes from animals, protozoa, fungi, and plants, confirmed the monophyly of the Antp class as well as its position as a sister group to the Paired class (7). Within the Antp class, the Hox gene organization is distinctive and enigmatic: the genes map in clusters, and the order of individual genes within a cluster correlates with their temporospatial expression pattern along the anterior-posterior body axis during development (8). Recently, it was proposed that the common bilaterian ancestor of protostomes and deuterostomes had at least seven Hox genes (9). However, the question of the composition of the ancestral HOX cluster remains open. Analysis of Hox homeobox sequences (10) suggested that the conserved HOX cluster emerged early in the evolution of metazoans from an original cluster harboring three ancestral g...

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“…To date, expression data for these genes are very scarce [POU class genes (Seimyia et al, 1997), and EmH-3 (Richelle-Maurer and Van de Vyver, 1999)]. …”

mentioning

confidence: 99%