THE PROTEIN-TYROSINE KINASES OF THE SEA-URCHIN ANTHOCIDARIS-CRASSISPINA

In order to know the function of protein tyrosine kinases (PTKs) in th e development of sea urchin embryos, we performed reverse transcriptio n-polymerase chain reaction (RT-PCR) to obtain partial cDNA fragments for PTK genes using primers to highly conserved regions of the PTK fam ily. A total of seven PTK sequences were identified, two of which repr esented receptor PTK (RTK1 and RTK2), and five of which were non-recep tor PTKs (NRTK1-5). RTK1 was highly similar to FGF receptor and Pet ki nase, while RTK2 showed features of the insulin receptor family. NRTK1 and 2 belonged to the Src family and could be involved in egg activat ion at fertilization. NRTK3 showed the features of the Btk family kina ses, while NRTK4 seemed to be a member of the Syk/ZAP70 family. NRTK5 is the Csk-type kinase of the sea urchin, which is known to negatively regulate the Src family kinases. RTK1 was not detected in unfertilize d eggs and was activated after blastula stage. All the other PTK genes were expressed both maternally in unfertilized eggs and zygotically a fter fertilization, though each gene showed distinct temporal patterns .