The cellular eye lens and crystallins of cubomedusan jellyfish

Summary The ultrastructure and major soluble proteins of the transparent eye lens of two cubomedusan jellyfish,Tripedalia cystophora andCarybdea marsupialis, have been examined. Each species has two complex eyes (one large and one small) on four sensory structures called rhopalia. The lenses consist of closely spaced cells with few organelles. The lens is situated next to the retina, with only an acellular layer separating it from the photoreceptors. SDS-PAGE showed that the large lens ofC. marsupialis has only two crystallin polypeptide bands (with molecular masses of approximately 20000 and 35000 daltons), while that ofT. cystophora has three bands (two with a molecular mass near 20000 daltons and one with a molecular mass near 35000 daltons). Interestingly, the small lens ofT. cystophora appears to be markedly deficient in or lack the lower molecular weight proteins. The crystallins behaved as monomeric proteins by FPLC and showed no immunological reaction with antisera of the major squid crystallin, chicken-crystallin or mouse-crystallin in western immunoblots. Very weak reactions were found with antimouse- and-crystallin sera. The 35000 dalton crystallin ofT. cystophora was purified and called J1-crystallin. It contained relatively high leucine (13%) and tyrosine (9%) and low methionine (2%). Several tryptic peptides were sequenced. Weak sequence similarities were found with- and-crystallins, which may account for some of the apparent weak immunological crossreactivity with these vertebrate crystallins. A polyclonal antiserum made in rabbits from a synthetic peptide of J1-crystallin reacted strongly with J1-crystallin ofT. cystophora andC. marsupialis in immunoblots; by contrast, no reaction was obtained with the lower molecular weight crystallins from these jellyfish, with the squid crystallin, or with any crystallins from the frog or human lens. Thus, despite the structural similarities between the cubomedusan, squid and vertebrate lenses, their crystallins appear very different.Abbreviations SDS-PAGE sodium dodecylsulfate-polyacrylamide gel electrophoresis - bp base pairs - PTC phenylisothiocyanate - FPLC fast phase liquid chromatography - NBRF National Biomedical Research Foundation A portion of this work was presented by Joram Piatigorsky at the First Hans Bloemendal Lecture in June 1988 in Nijmegen, The Netherlands