Karyotyping and localization of genes on the chromosomes of the sea urchins, Strongylocentrotus drobachiensis and Strongylocentrotus purpuratus.

摘要

The purple sea urchin, Strongylocentrotus purpuratus , is an important model for probing gene interactions during animal development and is the only non-chordate deuterostome for which a complete genome sequence is available. None of the genes cloned in this project have been localized on chromosomes, and maps of gene loci for S. purpuratus and for all sea urchin species do not exist. Here I provide a description of the first successful methods for karyotyping and localizing of specific gene loci on chromosomes of the purple sea urchin, Strongylocentrotus purpuratus and also of the related green sea urchin, Strongylocentrotus droebachiensis.;Both species have 42 chromosomes in their diploid genomes. Most of their chromosomal pairs are acrocentric or submetacentric with one telocentric pair. There are two large, eight medium and ten small pairs plus one putative sex specific pair. In both species, bindin genes were localized on two chromosomal pairs fluorescent in situ hybridization (FISH). Fluorescently labeled bacterial artificial chromosome (BAC) clones from the S. purpuratus genome were prepared for the developmentally important genes, brachyury, foxA, and foxB, and they were localized on chromosomes with both single and dual labeling. All three genes reside on different chromosomes. The protocols provide an important proof of concept for researchers in developmental and molecular biology as gene maps for the many interesting genes in the sea urchin genome are developed.