Array comparative genomic hybridization in male infertility.

BACKGROUND: Male infertility caused by a maturation arrest of spermatogenesis is a condition with an abrupt stop in spermatogenesis, mostly at the level of primary spermatocytes. The etiology remains largely unknown. METHODS: We focused on patients with a complete arrest at the spermatocyte level (n = 9) and used array comparative genomic hybridization to screen for deletions or duplications that might be associated with maturation arrest. Interesting copy number variations (CNVs) were further examined by using quantitative PCR. Where appropriate, the expression pattern was analyzed in multiple human tissues including the testis. RESULTS: A total of 227 CNVs were detected in the patient group. After the elimination of CNVs that were also present in the control group or that were not likely to be involved in male infertility, the remaining 11 regions were investigated more in detail. We first determined the expression pattern of seven genes, for which expression had not been reported to be investigated in testicular tissue, after which one region could be eliminated. Next, all 10 promising candidate regions were analyzed by quantitative PCR in a control population. CONCLUSIONS: Eight deletions/duplications were absent in our control group, and therefore might be linked with the male infertility in our patients. One of these alterations, however, has been detected in a proven fertile father group. Further research is necessary to determine the relationship between the observed genomic alterations and maturation arrest of spermatogenesis. Furthermore, several of the above genes have not been studied at the functional level and consequently, more research is required to determine their role in spermatogenesis.

Mutation analysis of three genes in patients with maturation arrest of spermatogenesis and couples with recurrent miscarriages.

The primary aim of this study was to gain more insight into maturation arrest of spermatogenesis (MA) and its relationship with mutations in genes essential for meiosis. The study also investigated the possibility that mutations in human meiosis genes cause a milder phenotype and that, in such cases, meiosis could potentially be completed with the production of mature germ cells having an abnormal chromosomal constitution causing miscarriage. Among 40 patients with MA, five changes were observed that also predicted alterations at the amino acid level. However, since these changes were also present in men with normozoospermia in equal frequencies, it was assumed that these changes are single nucleotide polymorphisms. Among 46 patients with recurrent miscarriages, two additional changes were detected predicting an alteration at the amino acid level. One change was detected in controls. However, the second heterozygous change, detected in a conserved functional domain of the SYCP3 gene, was absent in >200 controls. These preliminary results stress the need to further investigate the relationship between abnormalities in meiosis genes and the formation of gametes with abnormal chromosomal constitution. More research is also necessary to determine the impact and frequency of such changes before implementing mutation screening in genetic counselling.

[Genetics and male infertility]. / Genetica van de mannelijke onvruchtbaarheid.

Infertility is a problem affecting many couples with a child wish. In about half of these couples a male factor is (co-) responsible for the fertility concern. For part of these patients a genetic factor will be the underlying cause of the problems. This paper gives an overview of the studies performed in the Department of Embryology and Genetics of the Vrije Universiteit Brussel and the Centre for Medical Genetics of UZ Brussel in order to gain more insight into the genetic causes of male infertility. The studies, focusing on men with fertility problems, can be subdivided into three groups: studies on deletions on the long arm of the Y chromosome, studies on X-linked genes and studies on autosomal genes. It is obvious that Yq microdeletions should be considered as a cause of male infertility. Only for patients with a complete AZFc deletion, a small number of spermatozoa can be retrieved. However, even for these patients assisted reproductive technologies are necessary. Complete AZF deletions are found in 4.6% of the patients visiting the centres for Reproductive Medicine and Medical Genetics of the UZ Brussel and for whom no other cause of the fertility problems have been detected. Taken into consideration this low prevalence of Yq microdeletions, it is obvious that also other factors, including genetic factors, must be causing fertility problems. Potentially, gr/gr deletions (partial deletions of the AZFc region) might influence the fertility status of the patients. It remains, however, unclear which of the genes located in the deleted regions are important for the progression of spermatogenesis, in case of partial or complete AZF deletions. In our studies we have also investigated mutations in genes located on the X chromosome. In analogy to the Y chromosome, the X chromosome is interesting in view of studying male infertility since men only have a single copy of the sex chromosomes. As a consequence, mutations in genes crucial for spermatogenesis will have an immediate impact on the sperm production. The genes NXF2, USP26 and TAF7L were investigated for the presence of mutations. All observed single nucleotide changes were also present in control samples, questioning their relationship with male infertility. We also studied five autosomal genes: SYCP3, MSH4, DNMT3L, STRA8 and ETV5. Only for the genes STRA8 and ETV5, changes were detected that were absent in a control population existing of men with normozoospermia. Functional analysis of the changes in ETV5 and the localization of the change observed in STRA8 showed that also these alterations were probably not the cause of the fertility problems in these men. It can be concluded that mutations are rarely detected in men with fertility problems. This low frequency of mutations has also been confirmed in several published studies. Therefore, further research is necessary to determine the impact of genetic causes on male infertility.