Spatial specificity of mesodermal even-skipped expression relies on multiple repressor sites.
Individual cardiac progenitors emerge at defined positions within each segment in the trunk mesoderm. Their specification depends on segmental information from the pre-patterned ectoderm, which provides positional information to the underlying cardiac mesoderm via inductive signals. This pattern is further reinforced by repressive interactions between transcription factors that are expressed in neighboring sets of cardiac progenitors. For example, even-skipped (eve) and ladybird early (lbe) gene products mark adjacent cardiac cell clusters within a segment, and their antagonistic interaction results in mutually exclusive expression domains. Lbe acts directly on the eve mesodermal enhancer (eme) to participate in restricting its expression anteriorly. We hypothesized that additional repressive activities must regulate the precise pattern of eve expression in the cardiac mesoderm via this enhancer. In this study, we identified two additional repressor motifs: 4 copies of an "AT"-rich motif (M1a-d) and 2 copies of an "GC"-rich motif (M2 a,b), which when mutated cause expansion of eme-dependent reporter gene expression. We have also examined potential negative regulators of eve and found that their overexpression is sufficient to repress eve as well as the eme enhancer via these sites. Our data suggest that a combination of factors is likely to interact with multiple essential repressor sites to confer precise spatial specificity of eve expression in the cardiac mesoderm.
Liu
Jiandong
J
Development and Aging Program, Center for Neuroscienes, Aging and Stem Cell Research, Burnham Institute for Medical Research, 10901 North Torrey Pines Road, La Jolla, CA 92037, USA.
Qian
Li
L
Han
Zhe
Z
Wu
Xiushan
X
Bodmer
Rolf
R
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D004330:Drosophila / Q000196:embryology / Q000235:genetics; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D004625:Embryo, Nonmammalian; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D017930:Genes, Reporter; D006321:Heart / Q000196:embryology; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008648:Mesoderm / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D010496:Pericardium / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D019076:Transgenes; D020798:Two-Hybrid System Techniques
D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C052837:eve protein, Drosophila