Immuno-genomics studies realized in Echinodermata (Invertebrates) were surprising. 3 classes out of 5 Echinodermata presented an IGKappa gene and an Fc receptor gene. It was, first demonstrated, in Asterids and Ophuirids. It was, secondly clearly shown, in the ancestral Crinoïd: Antedon bifida.

Keywords: Invertebrates; Echinodermata; Crinoids; Igkappa Gene; Fc Gene; A. Bifida;

The general idea that emerged from the experiments, made in our laboratory, was that Echinodermata, as exemplified, by sea star Asterias rubens (Asterids)and by Ophiocomina nigra (Ophuirids), possessed an immune system, able to mount cellular and humoral-specific responses,

After stimulation with a foreign antigen: the horse-radish peroxides (HRP) [1, 2]. Then, these echinodermata produced a primitive antibody, correlated to an Igkappa gene [3,4] to a Fab gene [5], an Fc receptor gene [6].But a question deserves to be put: did the ancestral Echinodermata, Antedon bifida, (Crinoïd) possess such genes? It is why, in a first time, we look for IgKappa gene, Fab gene, Fc receptor gene in these crinoids by the mean of genomic studies.

Antedon bifida was obtained at the station « Of Biologie Marine of Roscoff » France.

Digestive coeca were excised from the A. bifida body.

Bifida mRNA was obtained from Uptizol (Interchim). Quality control was operated.

Sequencing was made on Illumina Next Seq 500 with paired-end: 2. 75 bp Transcriptome was assembled from RNASeq fastq files using Trinity v2.1.1 [7] with default parameters. A BLAST database was created with the assembled transcripts using makeblastdb application from ncbi-blast+ (v2.2.31+). The sequences of transcripts of interest were then blasted against this database using blastn application from ncbi-blast+ [8] with parameter word size 7.

The (Table 1) which is following summarizes the found Antedon bifida transcriptomes of Igkappa gene and Fc receptor gene of IgA (FCAR) of IgE (Fcer2a) we met in Homo sapiens and in Mus musculus:

>TRINITY_DN9178_c0_g1_i2(Igk):

5'AGCGAATGAAAAAGAAGAACCGGCCAAAAAAAGTACTTCTACCAAAGAAGCGAATGAAAAAGAAGAACC GGCCAAAAAAAGTACTTCTACCAAAGAAGAAACTGAAATAGAAGAACTAACCGAAACAAGTATTTCTACAA AATCAGTTTCTGCCAGTGATATATTCCTTGGTACAACTTTCACACTGGAGATGGGATTCTGCGTAGGACCT GAACACAAACCGTTTACAGGAGATTTCGACGGTGACGGTAATGAAGATCTTCTGTTTCACAATTCAAAGAC AGGCTCGAAAAAGATATACTATGCAAGTTGTGACGGCTCTTTTAATGGTGATAGGTCGTGGAGAAGAGAGA TGAATTTTTGCTACGTAAGTGGATATGATCTATACATTGGTGATTTCAACGGCGATGGTCGATCCGATATG CTGTGTCATCGTCCTCAGTATGGTCAGATTTGGGTTGTGTTGGCGCAACCTGGGGGTGTATTCACTGCTAA CCCGTGGTCGTATAGTCCCAATTGGTGCAAGGCCACCACTGATAAAGTATATATTGGAGACTTCAACGCAG ACGGTCGGGATGATATTCTTTGCCACACACAAAGTTCGGGTTACATTGCAATATATTATGCATTATACACT GGTTATTTTTCTACCTCTACAACATATCGCTTTACACGAAGTATGAGTTGGTGCAGAGGTACATATCAAAG AGTGTATACTGGAGATTTCAACGGAGACCGAAGGGTTGATATGCTCTGCCACGACTACTCATCTGGCTACA TATATGTAGCAGTAGCCACAGCGACTGGTGGATTCACCTCTGCCACATGGAGCAGAAGTATGGGCTGGTGC AAGCATTCGAACTCTAAGCTCAGCATTGGAGATTTCAATAAAGATAACCGCGACGACATCATGTGCAGCGA CACAAATGGTCCTTACTGGATAGCATTCTCTCTGTACAACGGTTCGTTTTCATCTAAAAGCTGGACCCGTA AACAAAACTGGTGTACATCTGGCAATGATGTGTTAGTTTCGGATGTGAATGGAGATGGTGGGGATGATTTG ATGTGCCATAATGAAGCCGACGGCATCAAGTACATATCGATCAACCATAAGGCCTAAAGCAAGTTCCTCTC AATATTACAGAAAACTATTCACCACAAATGATTCATTTTGTACTGAACCTCAATTCAAATTCAATTAAAAT TTACATAAACGTTAACGGAAGGATACAATCAACTAAAATAATGTTCATTCATTATTTTTCGTCGATAACCT AAACAAAAATCAGATAAGAAATTATACAATAATATACTGTAAACGTATTATACAAAATAATTAAATGTATA TTAAGCTACTGTACTTAGAAATGTACTTGTACGCTTATTAATATTAATAAGCCTAATGCCCGGGTTGATAA TAATAAAATACATTTTTGCAAGTTCAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA AAAAAAACTCAAAAGTCCCAGGCCCCACCCCGACCTACTGAACCAGAAAG3'

>TRINITY_DN13535_c0_g1_i1(FCAR)

5'ACTCTACGAACCAAATTTAAATATAACCCGAGAATGTATGTACAACCGATCCAGTAAAATGGTAACATTCAAG ACTACGATTATGTACCTTGTTAAATTAAAATAAAATAAAGTACCGGTAGATACACCATCATAAATATCAGCCTTT CATCAAGCAAAACAGTCATTTGTTTACAGTTCTGTCTTGAGTAGATGTTCTCAGCAAATTTTTCTAATATAACA ATTATAAACTTCTTGTGAAGATGAAATTTATTGATTTAATTGGATGCCAGTTAATTTTATTTAGAATTATTTTT AATTTTGATCTGAGAAACAGAATTAAGAACTGGAAAAGAAATGAACAAAAGTTTCCATAAAACTATCGTTATT CAATTTAGTTTGTTTCTATACAATGGCAAATTAACACTTTCAAGAGAGGTGCATATTTTTATTTTTGGTCAACT ATGCTTACAATAGGTAAAATAAAATATTAACATCCCCCTACCCTACTTACATCCCAACTTATCACGTAATAAACCT TATTTCTCTGTCGGGAAAATTTCAGATTTGAGCAAGTATAATTTTATTTATTATTTCAGAATGTTCTCTATTTTA ACTGGGTGCTTGATACAATTAACATTGTAGAAGTTTATTTGTTTATTTGTTTATTTGTTTGTTTGTTTGTTTGTT TAGATGGAGTTTCTCTCTTGTTGTCCAGGCTGGAGTGCAATGGCA3'

Fortunaly, we find again in another Echinodermata, the IgKappa gene, the Fc receptor gene, we found in the Asterid: Asterias Rubens and in the Ophuirid: Ophiocomina nigra. Fab gene was found also in A.bifida, but the e-value was not significant. A considerable role may be assigned to crinoids IgKappa gene and Fc receptor gene: it is the one of Antedon bifida primitive antibody, but further research is needed in order, to examine and characterize the “immunocytochemical aspects of immunizations” to HRP (Horse-radish peroxides) or other antigen in Antedon bifida.

Nevertheless, for the third time, we find an invertebrate primitive antibody in an Echinodermata: it’s a great novelty!

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