High rate of premature chromosome condensation in human oocytes following microinjection with round-headed sperm: Case report

Apport de l’exploration cytogénétique et ultrastructurale dans le pronostic de fertilité des sujets globozoospermiques

La globozoospermie est une forme sévère de tératozoospermie caractérisée par des spermatozoïdes à tête ronde avec absence ou présence d’un acrosome rudimentaire. L’objectif de cette étude est d’analyser les spermatozoïdes de six patients présentant un syndrome de globozoospermie et de rendre compte de l’inefficacité de plusieurs tentatives de fécondation in vitro avec ICSI. L’exploration de ces sujets a été réalisée par l’étude du taux d’aneuploïdies spermatiques par hybridation in situ fluorescente (sperm-FISH) pour les chromosomes X, Y et 18, du taux de fragmentation d’ADN par la technique TUNEL ainsi que par l’étude ultrastructurale détaillée de la morphologie spermatique en utilisant la microscopie électronique à transmission (MET). Onze tentatives d’ICSI ont été réalisées chez ces patients, avec un taux de fécondation faible (9,37 %), et aucune grossesse n’a été obtenue. Cette étude a permis de confirmer la variabilité des phénotypes spermatiques observés dans ce syndrome et de faible taux de fécondation après FIV-ICSI, et ce, quel que soit le phénotype.

Fertilisation failure after intracytoplasmic sperm injection is not associated with sperm aneuploidy of a globozoospermic patient

The objective of this study was to determine the aneuploidy rate in spermatozoa from a globozoospermic patient who underwent three unsuccessful intracytoplasmic sperm injection (ICSI) treatment cycles together with his wife. The aneuploidy rates of chromosomes 13, 18, 21, X and Y as well as the diploidy rate in the spermatozoa of this man were evaluated by fluorescence in situ hybridisation to clarify if chromosomal aneuploidy could be a cause for the low fertilisation rate observed in this case. In the spermatozoa of our patient no increase in aneuploidy rates was found for the tested chromosomes (0.0% disomies of chromosomes 13, 18 and 21 with a diploidy rate of 0.6%; X/Y missegregation: 0.6%) indicating that the ICSI outcome of the couple was not impaired by sperm aneuploidy of the globozoospermic man.

Mutation of beta-glucosidase 2 causes glycolipid storage disease and impaired male fertility

beta-Glucosidase 2 (GBA2) is a resident enzyme of the endoplasmic reticulum thought to play a role in the metabolism of bile acid-glucose conjugates. To gain insight into the biological function of this enzyme and its substrates, we generated mice deficient in GBA2 and found that these animals had normal bile acid metabolism. Knockout males exhibited impaired fertility. Microscopic examination of sperm revealed large round heads (globozoospermia), abnormal acrosomes, and defective mobility. Glycolipids, identified as glucosylceramides by mass spectrometry, accumulated in the testes, brains, and livers of the knockout mice but did not cause obvious neurological symptoms, organomegaly, or a reduction in lifespan. Recombinant GBA2 hydrolyzed glucosylceramide to glucose and ceramide; the same reaction catalyzed by the beta-glucosidase acid 1 (GBA1) defective in subjects with the Gaucher's form of lysosomal storage disease. We conclude that GBA2 is a glucosylceramidase whose loss causes accumulation of glycolipids and an endoplasmic reticulum storage disease.

Globozoospermia revisited

Globozoospermia is a rare (incidence <0.1%) but severe disorder in male infertility. Total globozoospermia is diagnosed by the presence of 100% round-headed spermatozoa lacking an acrosome. It is still unclear whether patients whose ejaculate contains both normal and globozoospermic cells (partial globozoospermia) suffer from a variation of the same syndrome. Apart from the fact that affected males suffer from reduced fertility or even infertility, no other physical characteristics can be associated with the syndrome. ICSI is a treatment option for these patients, although low fertilization rates after ICSI show a reduced ability to activate the oocyte. In globozoospermic cells, the use of acrosome markers has demonstrated an absent or severely malformed acrosome. Chromatin compaction appears to be disturbed but is not consistently over- or undercondensed. In some cases, an increased number of cells with DNA fragmentation have been observed. The analysis of the cytogenetic composition revealed an increased aneuploidy rate in some cases. Nonetheless, no increased number of spontaneous abortions or congenital defects has been reported in pregnancies conceived after ICSI. The pathogenesis of globozoospermia most probably originates in spermiogenesis, more specifically in acrosome formation and sperm head elongation. In several knockout mouse models, a phenotype similar to that in humans was found. Together with the occurrence of affected siblings, these findings indicate a genetic origin, which makes globozoospermia a good candidate for genetic analysis. More research is needed to elucidate the pathogenesis of human globozoospermia to further understand globozoospermia as well as (abnormalities in) spermiogenesis and spermatogenesis in general.