The interaction between human spermatozoa and its homologous zona pellucida : scientific advances and clinical significance

Thesis (PhD)--Stellenbosch University, 2002.ENGLISH ABSTRACT: Infertility is a very common problem worldwide. Recent data have shown that disorders of the male represent the most common single defined cause of infertility. This proposal examines the clinical significance and fundamental physiological aspects of human gamete interaction. These studies are focused on the assessment of the cellular-molecular mechanisms involved in human sperm binding to its homologous zona pellucida resulting in the physiologic induction of the acrosome reaction. We have developed and validated in vitro bioassays that assess specific steps of the fertilization process that are critical for early embryo development. The results of our translational research have already had a significant impact on the overall evaluation of male infertility and on the clinical management of the infertile man in the assisted reproduction arena. Furthermore, the unveiling of the basic mechanisms involved in human gamete interaction will ultimately allow for both (i) the development of new male reproductive diagnostic capabilities and (ii) the design of improved and safer therapies aiding conception in childless couples suffering from male infertility.AFRIKAANSE OPSOMMING: Menslike onvrugbaarheid is 'n algemene wêreldwye probleem en onlangse data toon aan dat die manlike factor die grootste enkel bydraende factor tot hierdie toestand is. Die werk loods 'n intensiewe ondersoek na die kliniese betekenis en basiese fisiologiese aspekte wat 'n rol tydens spermsel en eisel interaksie speel. Hoofstuk 3 fokus op die sellulêre en molekulêre meganismes wat betrokke is tydens spermsel en eisel binding wat gevolglik lei tot akrosoomreaksie van die spermsel. Die werk verteenwoordig die resultate van 10 jaar se navorsing tussen die kandidaat en die promoter. Dit gee oorsprong aan 'n reeks bio-toetse wat die bevrugtingsproses koriografiese ontleed en verskaf dus 'n stap-vir-stap uiteenseting van menslike bevrugting en gevolglike embrio ontwikkeling. Die resultate in Hoostuk 4 bring vernuwing in die begrippe van die manlike faktor en die rol in die kinderlose huwelik. Die resulate soos in Hoofstuk 3 en 4 uiteengesit, vorm nie net die basis vir die moontlike ontwikkeling van nuwe diagnostiese benaderings tot die hantering van die man nies maar speel oojk 'n rol die daarstelling van verbeterde terapeutiese hantering van die kinderlose egpaar. Hoofstuk 5 gee kortliks riglyne en aanbevelings tot opsigte van die gebruik van die spermsel-zona pellucida bindingstoets en akrosomreaksie. Die kandidaat bevel aan dat die genoemde twee bio-toetse deel van die laboratorium ondersoeke van die man gebruik moet word

Globozoospermia is mainly due to DPY19L2 deletion via non-allelic homologous recombination involving two recombination hotspots

To date, mutations in two genes, SPATA16 and DPY19L2, have been identified as responsible for a severe teratozoospermia, namely globozoospermia. The two initial descriptions of the DPY19L2 deletion lead to a very different rate of occurrence of this mutation among globospermic patients. In order to better estimate the contribution of DPY19L2 in globozoospermia, we screened a larger cohort including 64 globozoospermic patients. Twenty of the new patients were homozygous for the DPY19L2 deletion, and 7 were compound heterozygous for both this deletion and a point mutation. We also identified four additional mutated patients. The final mutation load in our cohort is 66.7 (36 out of 54). Out of 36 mutated patients, 69.4 are homozygous deleted, 19.4 heterozygous composite and 11.1 showed a homozygous point mutation. The mechanism underlying the deletion is a non-allelic homologous recombination (NAHR) between the flanking low-copy repeats. Here, we characterized a total of nine breakpoints for the DPY19L2 NAHR-driven deletion that clustered in two recombination hotspots, both containing direct repeat elements (AluSq2 in hotspot 1, THE1B in hotspot 2). Globozoospermia can be considered as a new genomic disorder. This study confirms that DPY19L2 is the major gene responsible for globozoospermia and enlarges the spectrum of possible mutations in the gene. This is a major finding and should contribute to the development of an efficient molecular diagnosis strategy for globozoospermia