A leading cause of male infertility is genetic variation in genes required for sperm formation or function. Considerable evidence suggests PACRG is involved in spermiogeneis. The loss of Pacrg function causes infertility in mice (Lorenzetti et al. 2004) and we have shown an association between variability in the 5′ untranslated region of PACRG and human male infertility (Wilson et al. in preparation). Evidence from studies in C.reinhardtii and T.brucei indicate Pacrg is crucial for axonome formation and microtubule stability. To assess this possibility in mammals, we generated and characterised Pacrg knockout (Quaking viable, Qkv), wildtype and Pacrg transgenic mice (Qkv-Tg). Using confocal and immunoelectron microscopy we showed that Pacrg was localised to the axonemal microtubule doublets of sperm, tracheal and ependymal cilia. The absence of Pacrg was associated with compromised sperm flagella formation and MRI analyses revealed the occurrence of hydrocephalus. Specifically, Qkv mice showed an inward expansion of the lateral ventricles, resulting in a significant reduction in distance between ventricles (1.0 ± 0.6 mm, mean ± s.d., n = 5) and a ~250% increase in ventricle area (70 ± 13 arbitrary units, mean ± s.d., n = 5) compared with wildtype littermates (1.38 ± 0.09 mm; area 26 ± 12, n = 3). Transgenic expression of Pacrg was necessary and sufficient to correct the hydrocephalus (1.45 ± 0.05 mm; area 26 ± 9, n = 2) and infertility phenotypes (evidenced by daily sperm counts and litter sizes). In conclusion, we have shown Pacrg is a novel axoneme associated protein in a subset of motile cilia/flagella and loss of Pacrg function results in spermiogenic defects and hydrocephalus in mice. Further, we have shown that variations in the human PACRG promoter are a risk factor in human male infertility. Collectively these data suggest PACRG is a candidate gene in the human syndrome of primary ciliary dyskinesia.
(1) Lorenzetti D, Bishop CE, Justice MJ. 2004. Deletion of the Parkin coregulated gene causes male sterility in the quaking (viable) mouse mutant. Proc Natl Acad Sci U S A 101(22):8402–8407
Novel DNAAF6 variants identified by whole-exome sequencing cause male infertility and primary ciliary dyskinesia
