Phenotyping analysis of homozygous Ccdc151Snbl mutant animals showed a spectrum of features with three distinct laterality phenotypes, as detailed in Table S6. Mutants displayed either situs solitus with normal visceral organ situs (Figure 3E, panel I), situs inversus totalis with mirror-image symmetric organ situs (Figure 3E, panel II), or heterotaxy with discordant or randomized organ situs (Figure 3E, panel III). In the latter case of more complex heterotaxy, a typical mutant exhibited normal heart orientation (levocardia) and lung lobation, but inverted liver lobation with dextrogastria (Figure 3E, panel III). Among mutants surviving to term, 33% exhibited heterotaxy and 66% had either situs inversus or situs solitus. These findings are consistent with observations from other mouse models of PCD such as Dnah5, Armc4, and Dyx1c1 mutants.21,27,48 Consistent with other PCD mouse models, congenital heart defects observed in Ccdc151Snbl mutants included dextrocardia with a duplicated inferior vena cava (Figure 3E, panel V). This was confirmed by histopathology examination of intracardiac anatomy with 3D reconstruction using episcopic confocal microscopy, which also revealed a muscular ventricular septal defect (VSD) akin to that seen in the affected individual OP-675 carrying CCDC151 mutations (Figure 3E, panel VIII). In another heterotaxic mutant, a coronary fistula was detected by videomicroscopy of the contracting heart (Figure 3E, panel VI and Movie S9) and confirmed by episcopic confocal microscopy 3D reconstruction (Figure 3E, panel IX). As documented in detail in Table S6, in addition to abdominal inversion and abnormal lung lobation and bronchial branching, other heart defects were noted including inverted outflow tract. Together, these findings confirm Snowball to be an informative PCD mouse model.