Exon 2 was replaced with one in which murine nucleotides 459-698 were replaced by the corresponding human sequence (amino acids 79-160) containing a 24 bp duplication in the polyalanine tract (c.428_451dup24) generating a partially humanized exon 2. A loxP-flanked neomycin resistance cassette follows the modified exon 2 and was removed via cre-mediated recombination. Western blot analysis confirmed reduced protein expression.