[5] The TN-X protein is expressed in many parts of the human body, including the skin, muscles, kidneys, blood vessels, and digestive tract.

[6][7] Deficiencies in the TN-X protein due to mutations or not enough of it being produced (haploinsufficiency) can lead to a rare condition called classical-like Ehlers-Danlos syndrome (EDS).

[8] TN-X possesses a modular structure composed, from the N- to the C-terminal part by a Tenascin assembly domain (TAD), a series of 18.5 repeats of epidermal growth factor (EGF)-like motif, a high number of Fibronectin type III (FNIII) module, and a fibrinogen (FBG)-like globular domain.

TN-X is constitutively expressed in adult tissues such as skin, ligaments, tendons, lungs, kidneys, optic nerves, mammary and adrenal glands, blood vessels, testis, and ovaries.

[18] It also interacts with Transforming Growth Factor (TGF)-β[19] which is a pro-fibrotic cytokine and Decorin, a small 100 kDa dermatan sulfate proteoglycan that plays a crucial role in collagen fibrillogenesis.

[20] In vivo, transmission electron microscopy coupled with immuno-labelling confirms the very close location of TN-X with collagen fibbers in dermis, tendons and kidney glomeruli.