The organization of the gene for Drosophila lamin C: limited homology with vertebrate lamin genes and lack of homology versus the Drosophila lamin Dmo gene.

Drosophila melanogaster has, in addition to the well characterized lamin Dmo, a second nuclear lamin called lamin C, which was recently defined by cDNA cloning. Here we characterize the gene encoding Drosophila lamin C. It is composed of 4 exons and 3 introns, which all interrupt the coding sequence. No intron position of the Drosophila lamin C gene has a counterpart in the Drosophila lamin Dmo gene, which has a structure unrelated to the highly conserved structures of vertebrate lamin genes. Surprisingly, however, two of the three intron positions of the Drosophila lamin C gene are also found in all currently known vertebrate lamin genes, which have an additional 8 to 9 introns. Thus, lamin genes from vertebrates and invertebrates can be more closely related in organization than earlier thought on the basis of only two invertebrate genes. The striking difference in structure of the two Drosophila lamin genes indicates that their ancestral genes separated earlier in metazoan evolution and that more than one lamin gene may also be expected in other invertebrates.