Identification of the egg-surface substance of sea urchin, Hemicentrotus pulcherrimus, by monoclonal antibodies

Two monoclonal antibodies (mAbs ES-1 and ES-2) were screened by binding to the entire region of egg-surface membrane and a part of surface region of blastomeres of sea urchin, Hemicentrotus pulcherrimus. The mAb ES-1 immunoprecipitated a single band at 175KD when 2-ß-mercaptoethanol (ME) was included in sample buffer, and at 150KD in absence of ME. MAb ES-2 formed multiple bands (mainly 140KD–300KD) including a band at 175KD (+ME). By indirect fluorescent antibody staining of cryosectioned gonads, embryos or larvae just before metamorphosis and some adult tissues, it was found that mAb ES-1 recognized one egg-surface substance which was specific for the apical surface membrane of embryonic ectodermal cells, and mAb ES-2 which was supposed to recognize a carbohydrate epitope was specifc to embryonic surface substance(s).