Exon 7 was replaced with modified exons 7 to 11 lacking amino acids 248 to 337 followed by a Flag-HA tag, a transcriptional stop, and a FRT-flanked neomycin resistance cassette followed by a single loxP site. Flpe-mediated recombination removed the neomycin cassette. Both collagen repeat domains are deleted. (J:249238)