Generation of poly- and mono-clonal antibodies against trout fibronectin (FN) and their use in FN immunodetection in teleost fishes.

Immunization of rats with gelatin-affinity column purified fibronectin (FN) from rainbow trout (Oncorhynchus mykiss) plasma produced a polyclonal antiserum that reacts specifically with FN in immunoblotted protein extracts and cultured cells, not only from trout but also from swordtails (Xiphophorus helleri). Most importantly, this antiserum specifically stains FN-containing structures in sections from embryos, as well as skin and dorsal fin of swordtails and platyfish (Xiphophorus maculatus), allowing, e.g., correlation of the distribution of FN with neural crest cell development in Xiphophorus. The antiserum also cross-reacts with FN in sections from embryos of the Japanese medaka (Oryzias latipes) and coho salmon (Oncorhynchus kisutch). In addition to the polyclonal antibodies, monoclonal anti-trout FN antibodies were produced in rats. These did not exhibit reactivity on sections, but stained the cultured fish cells and FN in immunoblots. Both types of antibodies may be of interest to the fish industry for marking the level of FN as an indicator, not only for infectious diseases, but also for certain developmental stages such as smoltification and spawning.

A putative marker for human melanoma. A monoclonal antibody derived from the melanoma gene in the Xiphophorus melanoma model.

A MoAb was raised against a peptide corresponding to an exposed domain of the putative tyrosine kinase receptor protein encoded by Xmrk, a gene involved in melanoma formation and/or progression in the Xiphophorus fish melanoma model. The antibody reacts specifically with cells from human melanocytic lesions, ie, common acquired nevi, primary and metastatic melanoma biopsies. No reactivity with other cells, including normal melanocytes, was observed in the biopsies or with cells in biopsies from normal tissue (skin, liver, lung, spleen) and from other malignancies including those of neuroectodermal origin. The reactivity was very weak and variable in metastatic melanomas but very strong and characteristic of a receptor-type antigen in primary melanomas, a stage in melanoma progression in which cells have acquired metastasizing potential. It is suggested that the antigen recognized may be involved in growth promotion and represents the human equivalent of the fish melanoma gene product.

Distribution and migration pathways of HNK-1-immunoreactive neural crest cells in teleost fish embryos.

Whole mounts and cross-sections of embryos from three species of teleost fish were immunostained with the HNK-1 monoclonal antibody, which recognizes an epitope on migrating neural crest cells. A similar distribution and migration was found in all three species. The crest cells in the head express the HNK-1 epitope after they have segregated from the neural keel. The truncal neural crest cells begin to express the epitope while they still reside in the dorsal region of the neural keel; this has not been observed in other vertebrates. The cephalic and anterior truncal neural crest cells migrate under the ectoderm; the cephalic cells then enter into the gill arches and the anterior truncal cells into the mesentery of the digestive tract where they cease migration. These cephalic and anterior trunk pathways are similar to those described in Xenopus and chick. The neural crest cells of the trunk, after segregation, accumulate in the dorsal wedges between the somites, however, unlike in chick and rat, they do not migrate in the anterior halves of the somites but predominantly between the neural tube and the somites, the major pathway observed in carp and amphibians; some cells migrate over the somites. The HNK-1 staining of whole-mount embryos revealed a structure resembling the Rohon-Beard and extramedullary cells, the primary sensory system in amphibians. Such a system has not been described in fish.

Neural crest development in the Xenopus laevis embryo, studied by interspecific transplantation and scanning electron microscopy.

The Xenopus borealis quinacrine marker and scanning electron microscopy have been used to study the appearance, migration, and homing of neural crest cells in the embryo of Xenopus. The analysis shows that the primordium of the neural crest develops from the nervous layer of the ectoderm and consists of three segments at early neurula stages. This primordium is located in the lateral halves of the neural folds behind the prospective eye vesicles. The histological and experimental evidence shows that the neural crest cells also originate from the medial portion of the neural folds. The neural crest segments in the cephalic region start to migrate just before the closure of the neural tube. Isotopic and isochronic unilateral grafts of X. borealis neural crest into X. laevis embryos were performed in order to map the fate of the cranial crest segments and the vagal-truncal neural crest. The analysis of the X. laevis host embryos shows that the mandibular crest segment contributes to the lower jaw (Meckel's cartilage), quadrate, and ethmoid-trabecular cartilages, as well as to the ganglionic and Schwann cells of the trigeminus nerve, the connective tissues, the mesenchymal and choroid layers of the eye, and the cornea. The hyoid crest segment is located in the ceratohyal cartilage and in ganglia VII and VIII. The branchial crest segment migrates from the caudal part of the otic vesicle and divides into two portions which contribute to the cartilages of the gills. The vagal-truncal neural crest starts to migrate later at stage 25. It migrates by means of the vagus complex in a ventral direction and penetrates into the splanchnic layer of the digestive tract. The trunk neural crest cells disperse into three different pathways which differ from those of the avian embryo at this level.