Mutations in dynein genes in patients affected by isolated non-syndromic asthenozoospermia

BACKGROUND: Asthenozoospermia (AZS) is a common cause of male infertility characterized by reduced forward motility (WHO grade A+B sperm motility < 50% or A < 25%) or absent sperm motility in fresh ejaculate. AZS may exist as an isolated disorder, in combination with other sperm anomalies or as part of a syndromic association. Up to date, only a few genes, constituting the cilia/flagella structure, have been associated with isolated AZS in humans, whereas several other genes are known to be involved in syndromic form of AZS, including primary ciliary dyskinesia (PCD) and Kartagener syndrome (KS). Axonemal ultrastructural defects, including absent or shortened arms of dyneins, can be found in > 50% of PCD/KS patients. Approximately 90% of KS male patients are affected by AZS. The majority of KS patients can be ascribed to dynein genes mutations. METHODS: Mutation screening of DNAI1, DNAH5 and DNAH11 genes was performed in 90 patients with isolated non-syndromic AZS and 200 controls. RESULTS: We found three mutations (one in each gene) specifically associated with AZS in seven patients (7.8%). Mutations are inherited from the mothers and may be found in familial clusters. No ultrastructural axonemal anomaly was detected in sperm. CONCLUSIONS: We report for the first time a possible association between mutations in dynein genes and isolated AZS. Male carriers of the mutations always exhibit AZS, whereas female carriers manifest no alterations in either fertility or pulmonary clearance.