Immunoglobulin from Antarctic fish species of Rajidae family.
Immunoglobulins (Ig) of Chondroichthyes have been extensively studied in sharks; in contrast, in skates investigations on Ig remain scarce and fragmentary despite the high occurrence of skates in all of the major oceans of the world. To focus on Rajidae Igμ, the most abundant heavy chain isotype, we have chosen the Antarctic species Bathyraja eatonii, Bathyraja albomaculata, Bathyraja brachyurops, and Amblyraja georgiana which live at high latitudes in the Southern Ocean, and at very low temperatures. We prepared mRNA from the spleen of individuals of each species and performed RT-PCR experiments using two oligonucleotides designed on the alignment of various elasmobranch Igμ heavy chain sequences available in GenBank. The PCR products, about 1400-nt long, were cloned and sequenced. Nucleotide sequence identities calculated for the constant region domains ranged from 88.5% to 97.5% between species, and from 91.1% to 99.7% within species. In a distance tree, including also Raja erinacea sequences, two major branches were obtained, one containing Arhynchobatinae sequences, the other one Rajinae sequences. Four presumptive D gene segments were identified in the region of the VH/D/JH recombination; two different D segments were often found in the same sequence. Moreover, 5-15 genomic fragments of different lengths, carrying the gene locus encoding Igμ chain were revealed by Southern blotting analysis. B. eatonii amino acid sequences were analyzed for the positional diversity by Shannon entropy analysis, showing CH4 as the most conserved domain, and CH3 as the most variable one. B. eatonii CDR3 region length varied between 11 and 15 amino acid residues; the mean length (13.4 aa) was greater than that of Leucoraja eglanteria sequences (7.7 aa). An alignment of representative sequences of Antarctic species and R. erinacea showed that more cysteine residues not involved in the intradomain disulfide bridges were present in Antarctic species.
Institute of Protein Biochemistry, CNR, Via P. Castellino 111, Naples, Italy. mr.coscia@ibp.cnr.it
Maria Rosaria
MR
Coscia
Ennio
E
Cocca
Stefano
S
Giacomelli
Fausta
F
Cuccaro
Umberto
U
Oreste
D000595:Amino Acid Sequence; D000818:Animals; D000864:Antarctic Regions; D001483:Base Sequence; D003001:Cloning, Molecular; D003545:Cysteine / Q000235:genetics; D029941:Fish Proteins / Q000235:genetics* / Q000276:immunology; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D020539:Sequence Analysis, Protein; D012860:Skates, Fish / Q000235:genetics* / Q000276:immunology
D029941:Fish Proteins; D007143:Immunoglobulin Heavy Chains; D003545:Cysteine