Pectoral Fin Development Research Articles

Exogenous retinoic acid induces a stage-specific, transient and progressive extension of Sonic hedgehog expression across the pectoral fin bud of zebrafish.

We have performed a time course analysis of the expression of Sonichedgehog (shh) and patched1 (ptc1) in response to exogenous retinoic acid (RA) application to get some insight into the mechanism(s) underlying the formation of a mirror-image duplication of shh and ptc1 domains of expression in the pectoral fin buds of zebrafish. We have shown that RA exposure during the early stages of pectoral fin development first results in a rapid decrease or complete loss of shh/ptc1 expression. This is followed by reappearance of transcripts in the normal posterior domain, then by a stage-dependent and progressive expansion of the shh domain from the ZPA towards the anterior margin of the bud. Shh transcripts are induced in mesenchymal cells underlying the ventral ectoderm at the base of the bud. Once shh expression is activated in the most anterior cells, the number of shh-expressing cells increases in this region, possibly through an amplification mechanism involving signals from the apical ectodermal ridge. At this time, shh expression disappears from cells centrally located in the bud, resulting in the formation of the two distinct domains. An anterior extension of shh expression is also obtained in syu mutants with impaired shh function, suggesting that shh induction across the fin bud is independent of shh signaling. This study suggests the existence of complex mechanisms controlling the spatial and temporal expression of shh in the developing fin bud.

The bHLH transcription factor hand2 plays parallel roles in zebrafish heart and pectoral fin development.

The precursors of several organs reside within the lateral plate mesoderm of vertebrate embryos. Here, we demonstrate that the zebrafish hands off locus is essential for the development of two structures derived from the lateral plate mesoderm - the heart and the pectoral fin. hands off mutant embryos have defects in myocardial development from an early stage: they produce a reduced number of myocardial precursors, and the myocardial tissue that does form is improperly patterned and fails to maintain tbx5 expression. A similar array of defects is observed in the differentiation of the pectoral fin mesenchyme: small fin buds form in a delayed fashion, anteroposterior patterning of the fin mesenchyme is absent and tbx5 expression is poorly maintained. Defects in these mesodermal structures are preceded by the aberrant morphogenesis of both the cardiogenic and forelimb-forming regions of the lateral plate mesoderm. Molecular analysis of two hands off alleles indicates that the hands off locus encodes the bHLH transcription factor Hand2, which is expressed in the lateral plate mesoderm starting at the completion of gastrulation. Thus, these studies reveal early functions for Hand2 in several cellular processes and highlight a genetic parallel between heart and forelimb development.

Experimental induction of jaw, gill and pectoral fin malformations in Japanese flounder, Paralichthys olivaceus, larvae

The phenotypes of skeletal malformations induced in pharyngeal arches and pectoral fins of Japanese flounder larvae by retinoic acid (RA), disulfiram, 2,2′-dipyridyl and azetidine-2-carboxylic acid were characterized, RA controls gene expression essential for pharyngeal and pectoral fin development; disulfiram is an inhibitor of RA synthase, 2,2′-dipyridyl and azetidine-2-carboxylic acid are inhibitors of collagen synthesis. In larvae exposed to RA at shield stage for 1 h, the Meckel's cartilage did not form in mandible arch. Exposure to RA from hatching period shifted the growth direction of the pharyngeal cartilages posteriorly. Disulfiram did not affect the cartilage formation when given before hatching, even though it shortened the trunk. However, disulfiram exerted teratogenic effects when given after hatching time, inducing bending pharyngeal cartilages and S-shaped pectoral fin plate. 2,2′-Dipyridyl given from hatching also caused bending of pharyngeal cartilages and S-shaped pectoral fin plates. Azetidine-2-carboxylic acid reduced the size of cartilages, without causing remarkable malformation. Thus, it was demonstrated that both RA and inhibitor of its synthesis, and inhibitors of collagen synthesis exert specific teratogenic effects on both pharyngeal and pectoral skeletons of flounder larvae.

Developmental regulation of Tbx5 in zebrafish embryogenesis

T-box ( tbx) genes constitute a large family of transcriptional regulators involved in developmental patterning processes. In tetrapods, tbx5 has been implicated in specifying forelimb type identity. Here, we report the cloning of the zebrafish tbx5.1 gene and characterise its expression during zebrafish embryogenesis and early larval development of wild type and mutant embryos that affect pectoral fin patterning. tbx5.1 is expressed during development of the heart, the pectoral fins and the eye. Notably, its expression in the lateral plate mesoderm defines a single and continuous region of heart and pectoral fin precursor cells, and constitutes the earliest specific marker for pectoral fin development in the zebrafish.

Development of the pectoral, pelvic, dorsal and anal fins in cultured sea bream

Development of the pectoral, pelvic, dorsal and anal fins in cultured sea bream

Bone morphogenetic protein-4 expression characterizes inductive boundaries in organs of developing zebrafish.

We have cloned and examined the expression pattern of zebrafish bone morphogenetic protein-4 (BMP4) as a start to evaluating signals which might participate in the fashioning of organ systems in this genetically tractable species. The predicted sequence of the mature zebrafish protein is more than 75% identical to that of other vertebrates and 66% identical to Drosophila decapentaplegic (Dpp). As in other species, BMP4 is expressed ventrally during gastrulation, but the zebrafish is unusual in having an additional dorsal domain of expression. Subsequent BMP4 expression is especially prominent in sensory organs, fin buds, and in the gut, kidney, and heart. In all these sites, it becomes particularly enriched in regions of inductive demarcations. For example, expression initially extends through the entire heart tube but then becomes limited to the boundaries between cardiac chambers (sinus venosus-atrial junction, atrio-ventricular junction, and aortic root) prior to cushion formation. In early pectoral fin development, BMP4 is at first expressed uniformly but then becomes restricted to the mesenchyme subjacent to the apical ectodermal ridge. This suggests that among its roles in development, BMP4 serves as a signal in primordial outgrowth and also as a signal demarcating the borders within organs or structures where subspecializations occur.

Early pectoral fin development and morphogenesis of the apical ectodermal ridge in the killifish, Aphyosemion scheeli.

Using scanning electron microscopy it has been found that in the killifish the distal epithelium of the pectoral fin bud forms a morphologically distinct apical ectodermal ridge along its entire distal margin. This ridge is a relatively more prominent feature than its counterpart in various tetrapod systems. At a later stage the ridge becomes folded internally and elongates distally marking the transformation of the ridge into a fin fold. By continued distal growth the fin fold develops into a semicircular swimming-paddle. Collagenous rays or actinotrichia differentiate in a highly ordered arrangement close to the epithelial basement membrane within the space enclosed by this elongating fin fold and apparently support the early swimming-paddle. During the ridge-to-fold transition the fin bud displays a dorsal deflection of approximately 45 degrees and a caudalward rotation about the axis of the fin itself. This change in orientation results in close apposition of the developing fin structure to the flank.

Identification of Eggs, Larvae, and Juveniles of the Rainbow Smelt, Osmerus mordax, with Comparisons to Larval Alewife, Alosa pseudoharengus, and Gizzard Shad, Dorosoma cepedianum

Abstract Eggs and larvae of the rainbow smelt, Osmerus mordax, were reared in the laboratory to 7.4 mm total length. Larger sizes were collected by plankton net from Lake Erie, Lake Ontario, and Cayuga Lake, New York. Manually stripped eggs were adhesive and demersal with a granular, yellow yolk. Egg diameter after fertilization and water hardening was 1.0 mm. The majority of eggs hatched between 183 and 195 h after fertilization at an average water temperature of 16.5 C. Average length of larvae at 195 h was 5.6 mm. Yolk absorption was complete at 6.4 mm. Pectoral fin development began before hatching. The dorsal, anal, and caudal fin rays began development at approximately 14 mm. The pelvic fins budded between 17 and 20 mm. All fin rays were complete at 36 mm. The adipose fin was complete at 29 mm. Separation of rainbow smelt from alewife (Alosa pseudoharengus) and gizzard shad (Dorosoma cepedianum) was accomplished using yolk sac position, preanal and postanal myomeres, and snout-to-vent length as a pe...