Neuronal collagen XVII is localized to lipofuscin granules.

We have earlier shown that collagen XVII is expressed by neurons in the human brain, although its exact intracellular location and function have remained unknown. In this study we have localized collagen XVII specifically to neuronal lipofuscin granules using electron microscopy in autopsy samples from the human brainstem. Our results show that collagen XVII expression is mainly confined to an ultrastructurally definable, specific type of lipofuscin granule. The function of neuronal collagen XVII remains unclear. However, as the functional significance of lipofuscin remains debated, the presence of collagen XVII in just some types of lipofuscin may be helpful in the process of exploring the variety of neuronal, age-related lipopigments, which are as yet defined operationally rather than functionally or structurally.