While the levels of filaggrin in the epidermis of E18.5 Abca12el12/el12 mice were slightly increased, its processing into a functional 27 kDa monomer was ablated (Figure 3E) as has previously been observed in HI patients [18], indicating that normal LB and Abca12 function is required for this process. This evidence concerns the gene FLG and Harlequin ichthyosis.