title: Isolation, characterization, and expression of Le-msx, a maternally expressed member of the msx gene family from the glossiphoniid leech, Helobdella.
abstract: The msx gene family is one of the most highly conserved of the nonclustered homeobox-containing genes. We have isolated an msx homolog (Le-msx) from the glossiphoniid leech, Helobdella robusta, and characterized its pattern of expression by whole mount in situ hybridization. In situ expression and reverse transcription polymerase chain reaction (RT-PCR) data results show that Le-msx is a maternal transcript initially uniformly distributed in the cortex of immature oocytes that becomes asymmetrically localized to the polar regions of the uncleaved zygote. This is the earliest reported expression for the msx gene family and the first maternally expressed homeodomain-containing transcription factor reported in annelids. During embryonic development, Le-msx is expressed in all 10 embryonic stem cells and their segmental founder cell descendants. At midembryonic stages, Le-msx is expressed in the expanding germinal plate. Le-msx is confined to the central nervous system and nephridia at late (stage 9) stages and subsequently disappears from nephridia. In addition, we present a phylogenetic hypothesis for the evolution of the msx gene family, including the identification of a putative C. elegans msx homolog and the realignment of the sponge msx homolog to the NK class of homeodomain genes.
authors.affiliation: Department of Pharmacological and Physiological Sciences, University of Chicago, Illinois 60637, USA.
authors.forename: V A
authors.initials: VA
authors.lastname: Master
authors.forename: M J
authors.initials: MJ
authors.lastname: Kourakis
authors.forename: M Q
authors.initials: MQ
authors.lastname: Martindale
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003609:Dactinomycin / Q000494:pharmacology; D004475:Ectoderm / Q000737:chemistry; D005801:Genes, Homeobox / Q000187:drug effects / Q000235:genetics*; D018398:Homeodomain Proteins / Q000235:genetics*; D017403:In Situ Hybridization; D007865:Leeches / Q000235:genetics*; D008648:Mesoderm / Q000737:chemistry; D008969:Molecular Sequence Data; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D014018:Tissue Distribution; D014157:Transcription Factors
chemical_list: D018398:Homeodomain Proteins; C106009:Le-msx protein, Helobdella; D014157:Transcription Factors; D003609:Dactinomycin