Paracentrotus lividus sea urchin nectin (Pl-nectin) is an extracellular matrix (ECM) protein of the sea urchin embryo on the apical surface of the ectoderm and has been shown to be an adhesive substrate for embryonic cells. A monoclonal antibody (McAb) to Pl-nectin was generated that inhibits the adhesion of blastula cells to Pl-nectin-coated substrates in an in vitro functional assay. To examine for possible in vivo functions of Pl-nectin, Fab fragments (Fabs) of Pl-nectin McAb were added to early blastulae. Ingression of primary mesenchyme cells was not affected by Fabs. As control embryos reached the pluteus stage, treated embryos showed a severe inhibition of skeletal elongation and patterning. When the Fabs were injected directly into the blastocoel, even at higher concentration than was applied externally, skeletogenesis was normal. Therefore, the effect of the antibody on spiculogenesis was indirect. The treatment was partially reversible as embryos eventually seemed to recover and elongate spicules, although with an incorrect patterning. Migration of pigment cells was also affected by the Fabs, since they did not disperse throughout the ectoderm but remained clustered in ectopic areas. In contrast, the development of endoderm structures was not affected. Our results indicate that in the sea urchin embryo the appropriate contact of ectodermal cells with outer ECM components is essential for the correct morphogenesis of inner mesodermal structures.
A new embryonic extracellular matrix protein has been purified from eggs of the sea urchin Paracentrotus lividus. The molecule is a 210 kD dimer consisting of two 105 kD subunits that are held together by S-S bridges. In the unfertilized egg, the protein is found within granules uniformly distributed throughout the cytoplasm. After the egg is fertilized, the antigen is polarized to the apical surface of ectodermal and endodermal cells during all of the developmental stages examined, until the pluteus larva is formed. The protein promotes the adhesion of blastula cells to the substrate and is antigenically distinct from echinonectin, a well characterized substrate adhesion molecule. This report adds a new candidate to the list of known extracellular matrix molecules for the regulation of differentiation and morphogenesis in the sea urchin embryo.
In the fish egg, little attention has hitherto been paid to the changes taking place in the egg membrane at the time of fertilization. This may be due to the fact that the egg membrane is already present on the unfertilized egg and is merely elevated upon fertilization.According to the evidence presented by YAMAMOTO (1939)(1940)(1941)(1942)(1943)(1944)(1945)(1946)(1947)(1948)(1949)(1950)(1951)(1952)(1953)(1954), the cortical alveoli embedded in the cortical layer break down upon fertilization and this change is subsequently followed by the elevation of the egg membrane. Experiments on the Oryzias egg have indicated that a water soluble colloid is released from the cortical alveoli and that the egg membrane is elevated from the surface by the colloidal osmotic pressure of the alveolar colloid. As to the changes in the egg membrane, it has merely been stated that shortly after fertilization the egg membrane is very soft and gradually becomes hard. Kusa (1949 a, b ) has suggested in the salmon egg that the egg membrane hardens as the result of water absorption by the egg and the equilibrium state of the water absorption alters in accordance with the state of hardening. He has also found that the hardening of the egg membrane is chiefly caused by ionic calcium which originates from the body fluid.The importance of changes in the egg membrane of marine invertebrates at the time of fertilization has been recognized by many workers. MOTOMURA (1941) and RUNNSTROM (1947) have shown in the sea urchin egg that the vitelline membrane is transformed into the tough fertilization membrane by the addition of the cortical granule substance. It has also been shown that disulfide bridges and calcium are necessary for the hardening of the membrane (RUNNSTROM et aE. 1943, MONROY and RUNNSTROM 1948, HOBSON 1932and SUGIYAMA 1938.The present paper deals with some experiments on the changes 89
Fibronectin, with a subunit molecular weight of 220,000 daltons, was isolated from the ovary of the sea urchin,Pseudocentrotus depressus, using affinity chromatography on heat-denatured mammalian collagen coupled to Sepharose 4B. The distribution of fibronectin in the sea urchin ovary was examined by indirect immunofluorescence using antifibronectin serum. The basement membrane and the connective tissues exhibited strong fluorescence. The fibronectin was localized closely together with collagen bundles in the sea urchin ovary. Biochemical and immunological examinations indicate that sea urchin fibronectin has similar properties as those of mammalian fibronectin.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.