U21E4

U21E4 is a fictional gene designation used in educational and illustrative contexts to demonstrate gene nomenclature and protein annotation. It does not correspond to a confirmed gene in the human genome and is not associated with any verified biological function outside of teaching materials. The name is commonly used in textbooks, software tutorials, and classroom simulations to model hypothetical gene structure, regulatory relationships, and protein interactions.

In these simulations, U21E4 is described as a protein-coding gene situated on a fictional locus on chromosome 21. The simplified model typically presents a single exon and a coding sequence that would produce a hypothetical U21E4 protein.

Molecular characteristics: The fictional U21E4 protein is described as approximately 32 to 40 kilodaltons, consisting of roughly 280 to 340 amino acids. In common teaching examples, the protein contains a predicted coiled-coil domain and a C-terminal motif that could mediate protein–protein interactions.

Functional context: Within the educational model, U21E4 participates in intracellular transport and vesicle trafficking, acting as a scaffold that helps organize cytoskeletal elements and interactions with Rab GTPases. The exact partners and effects are not observed in real data and are meant to illustrate how researchers annotate function.

Expression and regulation: The simulations often assign broad, ubiquitous expression with a bias toward neural tissues in developmental contexts. Regulatory elements such as hypothetical transcription factor binding sites and promoter methylation are used to teach gene regulation concepts.

Clinical significance and use: There are no real disease associations with U21E4 because it is a fictional construct. It is used to demonstrate loss-of-function phenotypes, knockout models, and genotype–phenotype inference in teaching materials.

History: The designation U21E4 has appeared in educational resources since the early 2010s as a standard placeholder for gene annotation.