P Marin

Y chromosome microdeletions in infertile men with varicocele

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.

Different insulin-like 3 (INSL3) gene mutations not associated with human cryptorchidism.

Cryptorchidism is the most frequent congenital anomaly of the urogenital tract in the male, but its etiology is for the most part unknown. Evidence suggests that a possible genetic cause may be involved. Animal models support this hypothesis, and in particular INSL3 (Leydig insulin-like 3 hormone) has been proposed as putative gene for cryptorchidism, since male mice mutant for Insl3 exhibit bilateral abdominal cryptorchidism due to alteration of gubernaculum development. In this study, we analyzed whether mutations in INSL3 could be associated with human cryptorchidism. Heteroduplex analysis and sequencing of both exons of INSL3 in 65 ex-cryptorchid patients and a group of control subjects allowed us to find four nucleotide changes in the sequence of exon 1. These mutations are all single base substitutions from G to A at position 27, 96, 126 and 178. Only the 178G→A substitution changes codon 60 from alanine to threonine (A60T). All mutations were found in comparable distribution in ex-cryptorchid patients and non-cryptorchid men. Therefore, all mutations represent neutral polymorphisms not associated with phenotype. This study confirms previous observations and demonstrates a novel polymorphism in the INSL3 gene. In contrast to that described for the mutant mouse, these data indicate that mutations of INSL3 do not seem to represent a frequent cause of cryptorchidism.

A novel gene (PD1) with a potential role on rat spermatogenesis

PD1 is a novel protein particularly expressed at the testicular level. The relative cDNA sequences were cloned from human and rat testis libraries revealing an open reading frame for a protein of 520 and 511 amino acids respectively. The human PD1 amino acid sequence shows 85% identity with rat sequence suggesting that PD1 gene has been highly conserved during mammalian evolution. Immunohistochemical analysis showed that this protein is detected in the tubular compartment of the testis and, in particular, in the cytoplasm of the Sertoli cells. PD1 expression is not constitutive but seems to be under the influence of neighboring spermatogenic cells as demonstrated by its reduction in hypospermatogenesis with respect to normal spermatogenesis and a further reduction in Sertoli cell-only syndrome. During testicular development in the rat (from 2 to 45 days of age) the PD1 mRNA level became detectable at 14 days and then increased steadly with an advancement of age. These findings suggest that PD1 may play a role in the regulation of spermatogenesis and may be a potential candidate gene for defects of male fertility.