Huckebein is part of a combinatorial repression code in the anterior blastoderm.
The hierarchy of the segmentation cascade responsible for establishing the Drosophila body plan is composed by gap, pair-rule and segment polarity genes. However, no pair-rule stripes are formed in the anterior regions of the embryo. This lack of stripe formation, as well as other evidence from the literature that is further investigated here, led us to the hypothesis that anterior gap genes might be involved in a combinatorial mechanism responsible for repressing the cis-regulatory modules (CRMs) of hairy (h), even-skipped (eve), runt (run), and fushi-tarazu (ftz) anterior-most stripes. In this study, we investigated huckebein (hkb), which has a gap expression domain at the anterior tip of the embryo. Using genetic methods we were able to detect deviations from the wild-type patterns of the anterior-most pair-rule stripes in different genetic backgrounds, which were consistent with Hkb-mediated repression. Moreover, we developed an image processing tool that, for the most part, confirmed our assumptions. Using an hkb misexpression system, we further detected specific repression on anterior stripes. Furthermore, bioinformatics analysis predicted an increased significance of binding site clusters in the CRMs of h 1, eve 1, run 1 and ftz 1when Hkb was incorporated in the analysis, indicating that Hkb plays a direct role in these CRMs. We further discuss that Hkb and Slp1, which is the other previously identified common repressor of anterior stripes, might participate in a combinatorial repression mechanism controlling stripe CRMs in the anterior parts of the embryo and define the borders of these anterior stripes.
Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade São Paulo, R. do Matão, 277, Cidade Universitária, 05508-000, São Paulo, SP, Brazil. lpma@usp.br
Luiz Paulo
LP
Andrioli
Luciano Antonio
LA
Digiampietri
Lilian Ponce
LP
de Barros
Ariane
A
Machado-Lima
D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D001756:Blastoderm / Q000196:embryology / Q000378:metabolism*; D019521:Body Patterning / Q000502:physiology*; D019295:Computational Biology; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004330:Drosophila / Q000196:embryology*; D029721:Drosophila Proteins / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000033:anatomy & histology / Q000196:embryology / Q000378:metabolism; D051717:Fushi Tarazu Transcription Factors / Q000378:metabolism; D018398:Homeodomain Proteins / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D017403:In Situ Hybridization; D009687:Nuclear Proteins / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism
D051792:Basic Helix-Loop-Helix Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D051717:Fushi Tarazu Transcription Factors; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; C087725:Hkb protein, Drosophila; C052837:eve protein, Drosophila; C497169:ftz protein, Drosophila; C489235:hairy protein, Drosophila; C080833:run protein, Drosophila