A DIVERSITY OF ENZYMES INVOLVED IN THE REGULATION OF REVERSIBLE TYROSINE PHOSPHORYLATION IN SEA-URCHIN EGGS AND EMBRYOS

Reversible tyrosine phosphorylation is involved in the fertilization r eaction and early embryogenesis of the sea urchin (Foltz and Shilling, 1993; Ramachandran et al., 1993). To determine the enzymes present th at may be involved in this regulation, we used a PCR screen to identif y sequences that encode protein tyrosine kinases (PTK) and protein tyr osine phosphatases (PTP). We identified five PTKs and eight PTPs using cDNA libraries from two sea urchin species at two different stages of development, and the similarities to known PTK and PTP amino acid seq uences ranged from 70 to 95%. The cognate proteins represented both '' receptor''-class and cytoplasmic enzymes. Using RNAse protection assay s we found that the respective mRNAs showed many accumulation profiles that we have grouped into three basic patterns: (1) mRNA levels that do not vary by more than two to three times throughout development; (2 ) mRNA levels highest in eggs or ovaries; and (3) mRNA levels highest in gastrula or pluteus stages, mRNAs specific to adult somatic cells o f the ovary were not found, nor were mRNAs that accumulated selectivel y at the blastula stage. The results show that a diversity of enzymes involved in the regulation of reversible tyrosine phosphorylation is p resent in eggs and embryos of the sea urchin and that the differential accumulation in development of each mRNA suggests specific functional responsibilities by members of these enzyme families.