Ectopic expression
Ectopic is a word used with a prefix ecto-, meaning "out of", and the suffix -topic, meaning "place." Ectopic expression is an abnormal gene expression in a cell type, tissue type, or developmental stage in which the gene is not usually expressed. The term ectopic expression is predominantly used in studies using metazoans, especially in Drosophila melanogaster for research purposes.
How is it used
Although ectopic expression can be caused by a natural condition, it is uncommonly seen in nature because it is a product of defects in gene regulation. In fact, ectopic expression is more commonly used for research purposes. Artificially induced gene expression helps to determine the function of a gene of interest. Common techniques such as overexpressing or misexpressing the genes by UAS- system in D. melanogaster are used. In model organisms, such techniques are used to perform genetic screens to identify a function of the gene involved in specific cellular or developmental processes.Ectopic expression using these techniques is a useful tool because phenotypes induced in a tissue or cell type where they are not normally expressed are easily distinguishable compared to a tissue or cell type where the gene is normally expressed. By comparison with its basal expression, the function of a gene of interest can be identified.
Although the understanding of ectopic expression deals with endogenous genes in an organism, it can be expanded to a similar concept like transgenesis, where an exogenous gene is introduced to a cell or tissue type in which the gene is not usually expressed. The use of ectopic expression in biological science is not only limited to identifying functions of a gene in a known cell or tissue type but also used to discover unknown or additional functions of the gene.