[From spermatid to spermatozoa : what changes are necessary for development?].
The male gamete modifications during spermiogenesis were summarized in view to answer the question : "Is it a risk for a baby conceived by fertilization with a spermatid to be different of a baby conceived with a spermatozoon?" Cytoplasmic changes in spermiogenesis mainly concern the Golgi apparatus (acrosome vesicle), centrosomal material (flagelium), mitochondria (periaxonemal ring) and ooplasm volume (drastic reduction). These changes are not necessary in case of microfertilization (ICSI) and their absence could be without consequences on post fertilization development. Nuclear changes affect chromatin with the substitution of histones by protamines to insure sperm ADN stability across male and female genital tracts. Spermatid gene transduction brings new proteins which are related to fertilization (acrosomal enzymes, flagellum proteins, protamines...) and seem no longer useful after gametes fusion. There is no report of genomic imprinting occurring during spermiogenesis in mammals. Moreover, the important sperm changes during epididymal maturation (formation of disulfure bonds, acquisition of motility and of molecules for oocyte recognition, methylation of certain genes...) were found not necessary for embryo development in case of ICSI with epididymal or testicular spermatozoa. Normal and fertile animals (mice and rabbits) were born from ICSI with spermatids originated from normal males; an animal model with sterile males delivering apparently normal spermatids is lacking. Although the risk for defectuous babies from fertilization with spermatids is highly subjective, caution is needed and requires team competence, complete informed consent by the patients and exhaustive analysis of the methods used and results obtained. Moreover the evident risk to "reproduce" the father infertility must be compared with the psychosocial injury induced by using the alternative option of donor insemination.
Testart
J
J
INSERM U 355-32, Clamart.
D000818:Animals; D004195:Disease Models, Animal; D005314:Embryonic and Fetal Development; D005260:Female; D005307:Fertilization in Vitro; D006801:Humans; D008297:Male; D051379:Mice; D011817:Rabbits; D013087:Spermatids / Q000254:growth & development*; D013091:Spermatogenesis; D013094:Spermatozoa / Q000254:growth & development