[1][2] The term ectopic expression is predominantly used in studies using metazoans, especially in Drosophila melanogaster for research purposes.
[2] 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.
Paired box protein Pax-6 in humans is a transcription factor, which is a main regulatory gene of eye and brain development.
In a study, researchers identified ectopic expression of OR genes in non-olfactory tissues in the mouse model by measuring transcript levels.
They found important phenotypes of ectopic SSX2 expression that is involved in tumorigenesis: 1) immediate induction of genomic instability, 2) long-term support of tumor cell growth.