ARL13B-Cerulean rescues Arl13b-null mouse from embryonic lethality and reveals a role for ARL13B in spermatogenesis.

ARL13B is a regulatory GTPase enriched in cilia, making it a popular marker for this organelle. Arl13bhnn/hnn mice lack ARL13B expression, die during mid-gestation, and exhibit defects in ciliogenesis. The R26Arl13b-Fucci2aR biosensor mouse line directs the expression of fluorescently tagged full-length Arl13b cDNA upon Cre recombination. To determine whether constitutive, ubiquitous expression of Cerulean-tagged ARL13B (ARL13B-Cerulean) can replace endogenous gene expression, we generated Arl13bhnn/hnn animals expressing ARL13B-Cerulean. We show that Arl13bhnn/hnn;Arl13b-Cerulean mice survive to adulthood with no obvious physical or behavioral defects, indicating that the fluorescently tagged protein can functionally replace the endogenous protein during development. However, we observed that rescued males failed to sire offspring, revealing a role for ARL13B in spermatogenesis. This work shows that the R26Arl13b-Fucci2aR mouse contains an inducible allele of Arl13b capable of functioning in most tissues and biological processes.