What do the FAE-specific genes tell us about FAE and M cell biology?
Our results do provide some interesting insights into FAE and M cell biology. While the transcytosis function of M cells helps distinguish them from conventional enterocytes, less is known about features distinguishing the general FAE cell phenotype from that of other enterocytes. Reports of characteristic glycosylation patterns in the FAE (9) and the FAE expression pattern found for a hybrid transgene (11) suggest that FAE has its own specific program of gene regulation. The studies presented here help define the FAE in molecular detail by identifying for the first time some of the particular proteins associated with FAE and M cells in mammalian Peyer s patch. Some of these proteins have predictably important roles in epithelial development. For example, MMP15 belongs to the family of membrane-type matrix metalloproteinases; family members are known to be involved in tissue inflammation, wound healing, tumor metastasis and regulation of epithelial integrity (20,21). TM4SF3 and TM4SF5
