Bicoid gene

The anterior-posterior axis in Drosophila is defined at least in part by the products of the bicoid and nanos genes. The bicoid gene product is a major anterior morphogen, and the nanos gene product is a major posterior morphogen. The mRNA from the bicoid gene is synthesized by nurse cells and deposited in the unfertilized egg near its anterior pole. 

Translational repression of cad in the anterior region of the Drosophila embryo is affected by the bicoid gene product (Rivera-Pomar and Jackie, 1996 Rivera-Pomar et al., 1996), and this repression is necessary for proper development of anterior structures. Ubiquitous expression of cad early in embryogenesis leads to defects in head formation and segmentation (Mlodzik et al., 1990). Conversely, loss of... 

Deleting the 3 UTR of the bicoid gene would yield what phenotype in a mutant fly Why ... 

Finkelstein, R., and Perrimon, N. (1990) The orthodenticle gene is regulated by bicoid and torso and specifies Drosophila head development [see comments]. Nature 346 485—488. 

An interesting case of regulation at the translation level was discovered on the example of the homeodomain protein bicoid (bed), which is important in Drosophila differentiation (Dubnau and Struhl, 1996). The bicoid protein is a transcriptional activator that binds a cognate DNA element and stimulates the transcription of the neighboring genes. Apart from its specific DNA-binding capabUity, the bicoid protein binds to 3 -, non-translating sequences of the mRNA of another homeodomain protein (caudal protein) to inhibit its translation. 

FIGURE 28-36 Distribution of a maternal gene product in a Drosophila egg. (a) Micrograph of an immunologically stained egg, showing distribution of the bicoid (bed) gene product. The graph measures stain intensity. This distribution is essential for normal develop-... 

Lamonerie, T., Tremblay, J.J., Lanctot, C., Therrien, M., Gauthier, Y., Drouin, J. 1996. Ptxl, a bicoid-related homeobox transcription factor involved in transcription of the pro-opiomelanocortin gene. Genes Dev. 10, 1284-1294. 

Simeone, A., Acampora, D., Mallamaci, A., Stornaiuolo, A., D apice, M.R., Nigro, V., Boncinelli, E. 1993. A vertebrate gene related to orthodenticle contains a homeodomain of the bicoid class and demarcates anterior neuroectoderm in the gastrulating mouse embryo. EMBO J. 12, 2735-2747. 

Bicoid protein, a homeodomain-type transcription factor, activates expression of certain anterior-specific genes discussed later. In the syncytial fly embryo. Bicoid protein spreads through the common cytoplasm away from the an-... 

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-... 

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