Hunchback gene

Cell types at the posterior end of the fly embryo are controlled by a different mechanism—one in which control is at the translational level rather than the transcriptional level. As just discussed, transcription of the embryo s hunchback gene, which promotes anterior cell fates, produces an anteriorly located band of hunchback mRNA and Hunchback protein because of the anterior posterior gradient of maternally derived Bicoid protein. In addition, however, hunch-... 

Gap genes—define four broad regions in the egg hunchback (hb)... 

Early anterioposterior patterning in Drosophila produces an anterior posterior gradient of Hunchback (Hb), a transcription factor that promotes anterior cell fates. Transcription of the embryonic hb gene is activated by maternally derived Bicoid protein, which is localized to the anterior (see Figure 15-20). 

In Section 15.3, we saw that maternally derived Bicoid plays a key role in initiating the transcription of gap genes (e.g., hunchback) in the anterior region of the early fly embryo other maternal factors prevent the translation of hunchback mRNA in the posterior. Further specification of cell fates in Drosophila is controlled by transcription cascades in which... 

Figure 3.10 Concentration gradient of bicoid in the developing fruitfly. Concentration of bicoid protein has been measured in developing embryos as a function of location on the anterior-posterior axis. When present at high levels, biocoid protein activates the gene tailless at intermediate levels, inhibits the gene KruppeC, and activates hunchback. Spatial localization of gene expression is thereby achieved with a simple mechanism for protein-gradient formation.

Tautz, D. and Pfeifle, C., Non-radioactive in situ hybridisation methods for the localization of specific RNAs in Drosophila embryos reveals translational control of the segmentation gene hunchback. Chromosoma, 98, 81-85, 1989. 

Kriippel acts as a gap gene regulating expression of hunchback and even-skipped in the intermediate germ cricket Gryllus bimaculatus. Dev Biol. 2006 Jun 15 294(2) 471-81. Epub 2006 Apr 17. 

Tautz, D. and Pfeifle, C. (1989) A non-radioactive in situ hybridization method for the localization of specific RNAs in Drosophila embryos reveals translational control of the segmentation gene hunchback. Chromosoma 98,81-85. Hemmati-Brivanlou, A., Frank, D., Bolce, M. B., Sive, H. L., and Harland, R. M. (1990) Localization of specific mRNAs in Xenopus embryos by whole mount in situ hybridization. Development 110,325-330. 

Driever W, Nusslein-Volhard C (1989) The bicdd protein is a positive regulator of hunchback transcription in the early drosophUa embryo. Nature 337 138-143 Driever W, Thoma G, Nusslein-Volhard C (1989) Determination of spatid domains of zygotic gene expression in the drosophila embryo by the affinity of binding sites for the bicoid morphogen. 

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