LRRC56 deletion causes primary ciliary dyskinesia in mice characterized by dynein arms defects

Leucine Rich Repeat Containing protein 56 (LRRC56), also known as DNAAF12, is a member of the LRRC superfamily, whose dysfunction is associated with mucociliary clearance and laterality defects in humans. Here, we generated LRRC56-knockout mice using the CRISPR/Cas9 nuclease system to specifically target exons 4-5 of the LRRC56 gene. We observed that homozygous LRRC56 gene deletion is definitely deleterious, as 27.8% of LRRC56-/- mice died before adulthood. Among the surviving LRRC56-/- mice, the most prominent phenotypes included hydrocephalus, situs inversus, male infertility, and bronchiectasis. Transmission electron microscopy revealed defects in dynein arms of cilia and disorganized axonemal structure in flagella. Immunofluorescence analysis similarly revealed the absence of inner and outer dynein arm markers DNALI1 and DNAI2 in the cilia. Heterozygous LRRC56+/- mice developed normally, without exhibiting any symptoms of primary ciliary dyskinesia. In conclusion, the knockout of the LRRC56 gene in mice leads to a range of conditions consistent with primary ciliary dyskinesia. The absence of DNALI1 and DNAI2 signaling in knockout mouse cilia supports the critical role of the LRRC56 gene in dynein arm assembly.