title: Differential expression of caudal and dorsal genes in the teloblast lineages of the oligochaete annelid Tubifex tubifex.
abstract: We have cloned homologues (designated Ttu-cdx and Ttu-dl) of caudal and dorsal genes from the oligochaete annelid Tubifex tubifex. In situ hybridization revealed that Ttu-cdx begins to be expressed around the time of completion of ectodermal teloblastogenesis (i.e., the onset of gastrulation). At this time, Ttu-cdx expression is detected in a few cells that are located in the anteriormost part of the mesodermal germ bands (GBs). As development proceeds and the GBs elongate, the domain of Ttu-cdx-expressing cells in the GBs extends posteriorly. During this process, M teloblasts and primary blast cells remained negative for Ttu-cdx expression. This Ttu-cdx expression pattern is in sharp contrast to the posterior caudal expression in other organisms. Expression of Ttu-dl is detected from the one-cell stage through to the gastrula stage. Although Ttu-dl is expressed in most blastomeres, there are regional differences in Ttu-dl expression levels. During early cleavage, a large amount of Ttu-dl mRNA, which is supplied maternally, is inherited by D-cell line micromeres 2d and 4d; the remaining micromeres and macromeres inherit relatively small amounts of Ttu-dl transcripts. Another regional difference in Ttu-dl expression levels is seen in the ectodermal GB that is comprised of four bast-cell bandlets. The ventralmost bandlet (N lineage) exhibits the highest level of Ttu-dl expression with the lowest level in the two middle bandlets (O and P lineages) and an intermediate level in the dorsalmost bandlet (Q lineage).
authors.affiliation: Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Kei
authors.initials: K
authors.lastname: Matsuo
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Yoshida
authors.forename: Takashi
authors.initials: T
authors.lastname: Shimizu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001757:Blastomeres / Q000166:cytology / Q000378:metabolism; D019521:Body Patterning; D002454:Cell Differentiation; D019070:Cell Lineage / Q000235:genetics; D003001:Cloning, Molecular; D004475:Ectoderm / Q000166:cytology / Q000378:metabolism; D004627:Embryonic Induction; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009835:Oligochaeta / Q000166:cytology / Q000196:embryology*; D010802:Phylogeny; D013045:Species Specificity