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The major yolk protein is synthesized in the digestive tract and secreted into the body cavities in sea urchin larvae
Author(s) -
Unuma Tatsuya,
Konishi Kooichi,
Kiyomoto Masato,
Matranga Valeria,
Yamano Keisuke,
Ohta Hiromi,
Yokota Yukio
Publication year - 2009
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.20939
Subject(s) - biology , sea urchin , metamorphosis , yolk , coelom , annelid , echinoderm , anatomy , larva , medicine , microbiology and biotechnology , fishery , ecology
Major yolk protein (MYP), a transferrin superfamily protein contained in yolk granules of sea urchin eggs, also occurs in the coelomic fluid of male and female adult sea urchins regardless of their reproductive cycle. MYP in the coelomic fluid (CFMYP; 180 kDa) has a zinc‐binding capacity and has a higher molecular mass than MYP in eggs (EGMYP; 170 kDa). CFMYP is thought to be synthesized in the digestive tract and secreted into the coelomic fluid where it is involved in the transport of zinc derived from food. To clarify when and where MYP synthesis starts, we investigated the expression of MYP during larval development and growth in Pseudocentrotus depressus . MYP mRNA was detected using RT‐PCR in the early 8‐arm pluteus stage and its expression persisted until after metamorphosis. Real‐time RT‐PCR revealed that MYP mRNA increased exponentially from the early 8‐arm stage to metamorphosis. Western blotting showed that maternal EGMYP disappeared by the 4‐arm stage and that newly synthesized CFMYP was present at and after the mid 8‐arm stage. In the late 8‐arm larvae, MYP mRNA was detected in the digestive tract using in situ hybridization, and the protein was found in the somatocoel and the blastocoel‐derived space between the somatocoel and epidermis using immunohistochemistry. These results suggest that CFMYP is synthesized in the digestive tract and secreted into the body cavities at and after the early 8‐arm stage. We assume that in larvae, CFMYP transports zinc derived from food via the body cavities to various tissues, as suggested for adults. Mol. Reprod. Dev. 76: 142–150, 2009. © 2008 Wiley‐Liss, Inc.