Meeting Abstract

P2.74  Saturday, Jan. 5  Gene loss, gene duplication and Hox cluster fragmentation in the leech Helobdella CHO, S.-J.*; TIMBANG, L.; AHN, A.; REGALADO, S.G.; WEISBLAT, D.A.; Univ. of California, Berkeley; Univ. of California, Berkeley; Univ. of California, Berkeley; Univ. of California, Berkeley; Univ. of California, Berkeley sjcho71_cns@calmail.berkeley.edu

Studies in vertebrates (superphylum Deuterostomia) and insects (superphylum Ecdysozoa) have led to the generalizations that: 1) Hox genes usually occur as an ordered cluster along the chromosome; 2) the spatiotemporal order of their expression corresponds to their order within the cluster, with genes at the 3’ end of the cluster expressed more anteriorly in the embryo; 3) they function to provide regional or segment-specific identities to tissues along the anteroposterior (AP) axis. Previous studies have shown that Hox genes in annelids show these general patterns of expression as well. Genomic analyses have shown that the eleven Hox genes in the polychaete annelid Capitella telata and the mollusc Lottia gigantea (superphylum Lophotrochozoa) occur as ordered clusters, too. However, compared to Lottia and Capitella, the Hox gene cluster in the leech Helobdella (a clitellate annelid) is highly disrupted. A total of nineteen Hox genes have been identified; some Hox genes have been duplicated and others have been lost. The leech Hox genes occur in incomplete clusters or as isolated genes. Understanding the reorganization of Hox genes in the leech presents us with a good opportunity to examine the connection between gene order and expression.