Requirement of fatty acid transport protein 4 for development, maturation, and function of sebaceous glands in a mouse model of ichthyosis prematurity syndrome

Fatty acid transport protein 4 (FATP4) is one of a family of six transmembrane proteins that facilitate long- and very long-chain fatty acid uptake. FATP4 is expressed in several tissues, including skin. Mutations in human SLC27A4, which encodes FATP4, cause ichthyosis prematurity syndrome, characterized by a thick desquamating epidermis and premature birth. Mice lacking FATP4, which genetically model the human disease, are born with tight, thick skin and a defective skin barrier; they die neonatally due to dehydration and restricted movements. Both the skin phenotype and the lethality are rescued by transgene expression of FATP4 in suprabasal keratinocytes. Sebaceous glands in Fatp4 null skin grafted onto nude mice were found to be dystrophic and enwrapped by thick layers of epithelial cells. Consistent with these results, transgene-rescued Fatp4 null mice showed a subnormal level of FATP4 expression in sebo-cytes and exhibited abnormal development of both sebaceous glands and meibomian glands, specialized sebaceous glands of the eyelids. Sebum from these mice contained a reduced level of type II diester wax, a major mouse sebum lipid species, and showed perturbations in mass spectrometric profiles of diester wax and cholesteryl ester species. In addition, these mice showed an impaired ability to repel water and regulate body temperature after water immersion. Taken together, our results suggest that FATP4 plays crucial roles in the development and maturation of both sebaceous and meibomian glands, as well as in the formation and composition of sebum, likely by regulating the trafficking of fatty acids necessary for proper synthesis of sebum lipids.