Before further investigation took place, it was thought that Nkx2.2 and Pax4 genes promote cell differentiation of β-cells, but in their absence they instead form ε-cells.
These islet cells are also being studied in pancreatic cancer, where it is hoped that they can act as markers to previously silent tumors.
In human fetal pancreases, single ε-cells scatter in primitive exocrine tissue and are observed to start aggregating into clusters after gestational week 13.
[6] These results in mice pancreas were discovered and confirmed with the use of confocal microscopy, which is able to collect images of thick specimens and exclude fluorescent areas outside of the focal plane.
A total of 36 genes are significantly enriched in ε-cells that aid in proteinase inhibition, processing of hormones, cell migration, and immune activity that differentiates them from α-, β-, δ- and PP-cells.
Examples of specific genes that influence ε-cells are acyl-coenzyme A synthetase long chain family member 1 (ACSL1) and defensin beta 1.
[7] ACSL1 is thought to play a role in the processing of ghrelin while defensin beta 1 produces a protein that can kill bacteria, viruses, and yeast to regulate immunity.
Studies in mice, desert gerbil, and African ice rats have all yielded closely related results on this topic.
[5] In adult pancreas samples, they are observed to be round or oval shaped and remain localized on the mantle of the islets in different amounts, both in clusters and or single cells.
Because of the scarcity of ε-cells in an adult pancreas, it is predicted that they do not continue to produce large amounts of ghrelin that circulates throughout the body.
ACSL1 is an enzyme involved in the first step of fatty acid oxidation, and this pathway functions in this islet cell specifically to modify ghrelin acyl modification.