Male Endocrine and Genetic Factors · Genetic Causes of Male Infertility
Moro E et al., 2000 · Molecular and cellular endocrinology
The pathogenic mechanisms by which varicocele disrupt spermatogenesis are not clearly understood and it is possible that when varicocele is associated with a severe bilateral testiculopathy, other causes may represent the actual aetiological factor. Since microdeletions in the Y chromosome long arm (Yq) have become in last years a major cause of male infertility, we perform a Yq microdeletion screening in infertile men with varicocele. We selected 40 patients with severe oligozoospermia (sperm count<5x10(6)/ml, group 1) and 80 with varicocele and mild oligozoospermia (sperm count 10-20x10(6)/ml, group 2). Deletions of Yq was observed in seven out of 40 patients (17.5%) of group 1, while no deletions were found in patients of group 2, suggesting that the bilateral testicular damage observed in patients of group 1 is due to the underlying genetic anomaly, and not to varicocele itself. The finding of a genetic aetiology in infertile men with varicocele suggests that in such patients a Yq microdeletion screening should be performed, both for a proper diagnosis and to avoid unnecessary treatments that will probably not improve the sperm count.
Male Endocrine and Genetic Factors · Genetic Causes of Male Infertility
Foresta C et al., 2001 · Endocrine reviews
Three different spermatogenesis loci have been mapped on the Y chromosome and named "azoospermia factors" (AZFa, b, and c). Deletions in these regions remove one or more of the candidate genes (DAZ, RBMY, USP9Y, and DBY) and cause severe testiculopathy leading to male infertility. We have reviewed the literature and the most recent advances in Y chromosome mapping, focusing our attention on the correlation between Y chromosome microdeletions and alterations of spermatogenesis. More than 4,800 infertile patients were screened for Y microdeletions and published. Such deletions determine azoospermia more frequently than severe oligozoospermia and involve especially the AZFc region including the DAZ gene family. Overall, the prevalence of Y chromosome microdeletions is 4% in oligozoospermic patients, 14% in idiopathic severely oligozoospermic men, 11% in azoospermic men, and 18% in idiopathic azoospermic subjects. Patient selection criteria appear to substantially influence the prevalence of microdeletions. No clear correlation exists between the size and localization of the deletions and the testicular phenotype. However, it is clear that larger deletions are associated with the most severe testicular damage. Patients with Y chromosome deletions frequently have sperm either in the ejaculate or within the testis and are therefore suitable candidates for assisted reproduction techniques. This possibility raises a number of medical and ethical concerns, since the use of spermatozoa carrying Y chromosome deletions may produce pregnancies, but in such cases the genetic anomaly will invariably be passed on to male offspring.
Male Endocrine and Genetic Factors · Genetic Causes of Male Infertility
Foresta C et al., 2001 · The Journal of clinical endocrinology and metabolism
Deletions of the azoospermia factors on the Y chromosome long arm are an important cause of male infertility, and they may involve germ cell-specific genes or ubiquitously expressed genes. To date, no clinical or hormonal parameters have yet been found to distinguish patients with and without Yq microdeletions. In particular, Sertoli cell function, as evaluated by inhibin B, has not yet been described. Our hypothesis was that microdeletions involving genes specifically expressed in germ cells should not alter Sertoli cell function. To do this, we have evaluated the testicular hormonal function in infertile patients affected by severe testiculopathies with and without Yq microdeletions, with particular emphasis on Sertoli cell function. We studied 102 well-characterized infertile patients; 27 had Yq microdeletions, and 75 were classified as idiopathic infertiles. Patients with Yq microdeletions had lower FSH and higher inhibin B plasma concentrations with respect to patients without microdeletions, suggesting that Sertoli cell function in Yq-deleted men is only partially altered. Furthermore, patients with deletions involving germ cell-specific genes had higher concentrations of inhibin B with respect to patients with deletions of ubiquitously expressed genes. These results suggested that a specific alteration of germ cells only partially influences Sertoli cell function. Hormonal status of patients without deletions suggested that in such cases the cause that has determined the spermatogenic defect may have damaged both Sertoli and germ cells. Inhibin B production in patients with Yq deletions was about 70% higher than the nondeleted patients, and the functional relationship between FSH and inhibin B was normally preserved. This study elucidated the multifactorial mechanisms underlying spermatogenic defects, where Sertoli cells may be normally functioning or damaged depending on the primary cause that has determined the testicular damage.
Reproductive Genetics · Chromosomal Abnormalities
Foresta C et al., 1997 · The Journal of clinical endocrinology and metabolism
A genetic etiology has been recently proposed for some severe forms of idiopathic male infertility and a region of the Y chromosome long arm (Yq) defined AZF is thought to be critical for the regulation of spermatogenesis. To date, two genes, YRRM and DAZ, have been identified in AZF, but the actual relationship between genotype and phenotype related to AZF deletions is not well characterized. By means of a PCR strategy we typed Yq microdeletions in 16 azoospermic and 22 severely oligozoospermic subjects whose testicular cytological picture (assessed by fine needle aspiration) was that of Sertoli cell-only syndrome and severe hypospermatogenesis, respectively. Microdeletions in AZF were found in 37.5% of azoospermic men and in 22.7% of severely oligozoospermic men, suggesting that very frequently these genetic abnormalities determine a severe quantitative defect in spermatogenesis. Furthermore, DAZ and YRRM do not seem to be the sole genes regulating spermatogenesis, as deletions in these genes were observed in only 6 of the 11 deleted cases. No correlation between the spermatogenic defect and the type of Yq deletion exists. Intracytoplasmic sperm injection performed using spermatozoa of these Y-deleted patients will invariably pass this defect onto their male offspring. Screening for deletion within AZF or at least an informed consent should, therefore, be obtained in all idiopathic infertile male undergoing a program of intracytoplasmic sperm injection of a spermatozoon into the oocyte.
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