Generation of a conditional Adamts6 mouse allele reveals roles in lung maturation in addition to cardiac and musculoskeletal development.

Prior analysis of mouse embryos homozygous for a point mutation (p.Ser149Arg) that abrogated secretion of the protease, ADAMTS6, showed that it is essential for cardiovascular and limb development. Because Adamts6 S149R/S149R mice do not survive past birth, it is currently not feasible to investigate ADAMTS6 in specific cellular lineages postnatally. Therefore, we generated a conditional allele using CRISPR-Cas9-mediated genome editing to insert unidirectional loxP sites flanking the first coding exon in Adamts6, resulting in a frameshift mutation after loxP recombination. Mice homozygous for the unrecombined floxed allele (Adamts6 fl/fl) are viable, fertile, and without overt phenotype. Adamts6 del/del embryos, generated upon constitutive recombination induced by a CMV-Cre transgene, also do not survive past birth and have identical defects in the heart and limbs as Adamts6 S149R/S149R embryos, demonstrating efficient transgene recombination. In addition to previous defects in cardiovascular and limb development, Adamts6 del/del embryos have reduced airway branching, thereby identifying a role for ADAMTS6 in lung maturation. This newly generated Adamts6 fl allele makes feasible analysis of ADAMTS6 secreted by cells of different lineages and during specified temporal windows during developmental processes as well as in disease models.