Misexpression

It seems reasonable to hope that misexpression analysis of murine homeobox genes might also provide clues to their function. The first such... 

Two subsequent studies by Kauret al. (1992) and McLain et al. (1992) used the same p-actin promoter to drive misexpression of the Hox-2.2... 

Lufkin et al. (1992) also used a homeobox gene promoter exchange to drive misexpression of the Hox-4.2 gene. The Hox-1.6 promoter was observed to extend the anterior transcription boundary, and this region of ectopic expression gave a number of abnormalities, including absence... 

The most dramatic illustration of the evolutionary conservation of homeobox genes comes from experiments that swap Drosophila and mammalian cognates and test for functional equivalence. McGinnis and co-workers have reported remarkable phenotypic similarities in flies that misexpress Drosophila homeobox genes or their mammalian counterparts. Indeed, this ectopic expression assay in Drosophila indicates that the Drosophila and cognate mammalian homeobox proteins are essentially functionally identical. 

Morgan, B. A., Izipisua-Belmonte, J-C., Duboule, D., and Tabin, C. (1992). Targeted misexpression of Hox-4.6 in the avian limb bud causes apparent homeotic transformations. Nature 358 236-239. 

A mbros Less is known about how cki-1 is shut off in VPCs than about how cki-1 is turned on in these cells. However, when we misexpress lin-14 late in development, it will maintain cki-1 expression later than in the normal vulval lineage. Therefore, extinction of cki-1 expression in VPCs is influenced by some activity that is in turn dependent on lin-14 down-regulation. All our cki-1 expression constructs retain the 3hUTR of cki-1 (Hong et al 1998), and so the dynamic cki-1 expression we observe could reflect post-transcriptional regulation in addition to transcription regulation. 

Reverse genetic approaches start with a sequence and attempt to identify a function for the gene. This can be done by using PCR-based screens on DNA from insertionally mutagenized populations, ectopic misexpression of the gene, and expression studies, e.g., with RT-PCR or microarray analyses. 

Rorth P (1996) A modular misexpression screen in Drosophila detecting tissue-specific phenotypes. Proc Natl Acad Sci USA 93 12418-12422... 

Kosbash T o put it more generally, if you do a misexpression experiment and get a behavioural consequence with this vector, it is impossible to distinguish whether it is because of up-regulation in the usual locations or because of ectopic expression in the new locations. This is due to the fact that the construct also expresses more heavily in the traditional clock cells. Therefore it could be the up-regulation in the traditional clock cells that leads to the behavioural consequences. 

Chiappetta, A., Michelotti, V., Fambrini, M., Bruno, L., Salvini, M., Petrarulo, M., Azmi, A., Van Onckelen, H., Pugliesi, C., and Bitonti, M.B., Zeatin accumulation and misexpression of a class I knox gene are intimately linked in the epiphyllous response of the interspecific hybrid EMB-2 (Helianthus annuus X H. tuberosus), Planta, 223, 917-931, 2006. 

Keller, C., Erickson, M., and Abmayr, S. (1997). Misexpression of nautilus induces myogenesis in cardioblasts and alters the pattern of somatic muscle fibers. Dev. Biol. 787 197-212. 

Bell, E., Wingate, R., Lumsden, A. 1999. Homeotic transformation of rhombomere identity after localized Hoxbl misexpression. Science 284, 2168-2171. 

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