A pathology of the sperm centriole responsible for defective sperm aster formation, syngamy and cleavage

Abstract

BACKGROUND: In the present report we analyse the structural and functional features of sperm from a patient with severe asthenoteratozoospermia and failure of cleavage after ICSI. METHODS: Sperm were studied by phase contrast and transmission electron microscopy and microinjected into bovine oocytes to examine aster formation using antibodies against acetylated alpha- and beta-tubulins. RESULTS: Acephalic sperm, headless tails and abnormal alignments of the head-tail junction were observed. Flagella evidenced the features of dysplasia of the fibrous sheath. Bovine oocytes injected with patient's sperm showed male and female pronuclei but a faulty development of microtubules from the sperm-derived centrosome. The first ICSI attempt using conventional sperm selection methods resulted in fertilized two pronuclei zygotes, but no syngamy or cleavage. Three more ICSI attempts were performed, carefully avoiding sperm with obvious anomalies of the connecting piece. Fertilization and cleavage took place in all cycles, and in two of them positive betahCG plasma levels were detected but preclinical abortions ensued. CONCLUSIONS: We propose that the alterations in the head-tail junction and attachment, responsible for the observed sperm phenotype, result from centriolar dysfunctions that cause insufficient sperm aster formation, lack of syngamy and cleavage or defective embryos leading to early abortions.