Conserved expression of a B-type nuclear lamin in different tissues of the sea urchin

To study patterns of lamin expression in sea urchins, monoclonal and polyclonal antibodies were used to probe 2-D immunoblots of Strongylocentrotus purpuratus and Lytechinus pictus embryos and adult tissues. Three major charge isoforms of a single M(r) 70,000 lamin are common to different tissues of S. purpuratus, and are accompanied by two-to-four more variable minor charge variants. L. pictus expresses and M(r) 70,000 lamin that is distinct from that of S. purpuratus in pI, yet displays essentially the same pattern of major and minor charge isoforms. The results demonstrate that the single lamin gene product so far identified in sea urchin embryos appears to be constitutively expressed in most cells, and that three major charge isoforms are common to these different cell types.