Localisation of the Y chromosome stature gene to a 700 kb interval in close proximity to the centromere.
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Adult↗
Biomedical subjects
A Ferlin
Publications and source records attributed to A Ferlin.
[Alteration of spermatogenesis and Y chromosome microdelations. Analysis of the DAZ gene family].
The Y chromosome has a fundamental role in sex determination and regulation of spermatogenesis. Three regions (designated as AZFa, b, and c) on the long arm of this chromosome exist, deletions of which result in severe damage to spermatogenesis with azoospermia or severe oligozoospermia. Recent progresses in molecular biology and extraordinary development of assisted reproduction techniques contributed to the research on this chromosome and the genes involved in spermatogenesis. About 10-15% of subjects affected by azoospermia or severe oligozoospermia carry a deletion in one or more AZF regions, 60% of which involves AZFc. The genes responsible for the testicular phenotype observed in these subjects are DBY and USP9Y for AZFa, RBMY1 for AZFb, and DAZ for AZFc. In this article, the current knowledge on biology and genetics of the Y chromosome are reported with particular interest to deletions found in infertile subjects. Furthermore, the more recent advances on DAZ gene and its role in spermatogenesis and male infertility are discussed.
Animals↗
Novel insulin-like 3 (INSL3) gene mutation associated with human cryptorchidism.
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Cryptorchidism↗
Offspring conceived by intracytoplasmic sperm injection.
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Congenital Abnormalities↗
CDY1 analysis in infertile patients with DAZ deletions.
The DAZ (deleted in azoospermia) gene family is considered the major AZFc ("azoospermia factor" c) candidate responsible for male infertility. However, other genes have been recently mapped to this region and they could contribute to the AZFc phenotype. In particular, the testis-specific CDY1 (chromadomain protein 1) gene has one copy within the DAZ cluster and another one at its distal end. Therefore, this gene could be associated with the spermatogenic damage observed in DAZ-deleted patients since at least one CDY1 copy is invariably absent in these patients. In this study, we investigated whether selected infertile patients affected by different testiculopathies caused by DAZ deletions retained CDY1 and if a genotype-phenotype relation could be demonstrated. We found 3 out of 17 patients with absence of both CDY1 copies, while 14 patients have only one CDY1 copy absent. Two out of the 3 patients with deletion of both copies of CDY1 were affected by severe hypospermatogenesis while one patient presented Sertoli cell-only syndrome. Therefore, there was no clear relation between genotype and phenotype, and the loss of the distal copy of CDY1 does not seem to worsen the phenotype of infertile patients with deletion of the DAZ gene cluster. However, a possible contribution of CDY1 in determining the spermatogenic alteration could not be excluded.
Deleted in Azoospermia 1 Protein↗
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 I. 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.
Adult↗
Prognostic value of Y deletion analysis. The role of current methods.
Y chromosome microdeletions represent the most frequent genetic alteration in azoospermic and severely oligozoospermic men, and screening for microdeletions in AZFa, b and c are routinely performed in the major andrology and infertility centres. Since patients with Y microdeletions often require intracytoplasmic sperm injection (ICSI), the question of whether the type of the microdeletion present could have prognostic value for the presence of spermatozoa in the ejaculate or in the testes [by testicular sperm extraction (TESE)] is an interesting one. The review of the literature on this topic showed that there is still no clear genotype--phenotype relationship, i.e. similar testicular alterations may be caused by different types of microdeletions, and apparently identical microdeletions may be associated with diverse tubular damage. Even in azoospermic men, the localization of the microdeletion cannot be used as a valid prognostic parameter before TESE--ICSI to identify patients with spermatozoa in their testes. The only finding with absolute negative prognostic value is the presence of complete AZFa--c deletions, which are invariably associated with an absence of spermatozoa. Microdeletions in AZFa or AZFb seem to have promising prognostic value, but more data and gene-specific deletions have to be provided to draw clear conclusions. The absence of a clear genotype--phenotype relationship, and therefore of a prognostic value of Y deletion analysis, is probably due to the current methods used for the screening of the microdeletions. In fact, to date most centres do not use gene-specific markers but instead use anonymous primers that contribute little information to the pathogenic role of the microdeletions.
Gene Deletion↗
Y chromosome microdeletions and alterations of spermatogenesis.
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.
Chromosome Aberrations↗
Store-operated calcium influx and stimulation of steroidogenesis in rat Leydig cells: role of Ca(2+)-activated K(+) channels.
This study evaluates the role of internal calcium store depletion in the activation of ionic fluxes and steroidogenesis in adult rat Leydig cells. Thapsigargin and cyclopiazonic acid, two inhibitors of Ca(2+)-adenosine triphosphatase of internal Ca(2+) stores induced a dose-dependent rise in intracellular Ca(2+) concentrations following kinetics that would not be expected if the calcium rise was dependent only on internal calcium store depletion, but it was in keeping with the presence of calcium influx from the external medium. In fact, chelation of external calcium with EGTA during the plateau phase reduced the intracellular calcium concentration to basal levels. When added in calcium-free medium, thapsigargin and cyclopiazonic acid still induced a rise in the intracellular calcium concentration that was transient, and when calcium was added back to the medium, a rapid and sustained intracellular calcium increase was observed. Thapsigargin and cyclopiazonic acid induced a dose-dependent rise in testosterone secretion in the presence and absence of calcium in the external medium, although in calcium-free medium this stimulatory effect was lower. Leydig cell plasma membrane potential monitoring demonstrated that thapsigargin and cyclopiazonic acid induced first a rapid hyperpolarization, followed by a sustained depolarization phase that was reversed by the addition of the calcium-chelating agent EGTA. In the absence of calcium in the external medium the first phase of hyperpolarization was still present, but it was not followed by plasma membrane depolarization but by the slow return of plasma membrane potential to resting levels. The readdition of calcium to the external medium induced the rapid plasma membrane depolarization. Plasma membrane hyperpolarization was completely abolished by Leydig cell preincubation with the K(+) channel blockers tetraethylammonium and charybdotoxin. Leydig cell preincubation with K(+) channel inhibitors reduced the thapsigargin-stimulated Ca(2+) influx from the external medium and testosterone secretion. These results suggest that internal Ca(2+) stores depletion in rat Leydig cells induces a rise in intracellular Ca(2+), determining important plasma membrane potential variations that influence testosterone secretion.
Animals↗
Sertoli cell function in infertile patients with and without microdeletions of the azoospermia factors on the Y chromosome long arm.
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.
Chromosome Mapping↗
Deletion and expression analysis of AZFa genes on the human Y chromosome revealed a major role for DBY in male infertility.
Three distinct regions, designated AZFa, b and c from proximal to distal Yq, are required for normal spermato-genesis in humans. Deletions involving AZFa (deletion interval 5C/D) seem to occur less frequently in infertile men and to be associated with a more severe testicular phenotype, with almost complete absence of germ cells. AZFa contains three genes, named USP9Y, DBY and UTY, and presents high homology with the mouse Delta Sxr (b) interval, deletion of which causes a severe spermatogenic impairment. However, the specific role of these genes in human spermatogenesis is still unknown and it is not clear which of them is responsible for the AZFa phenotype. Here we describe a complete sequence map of the AZFa region, the genomic structure of AZFa genes and their deletion analysis in a large number of infertile men characterized by well-defined spermatogenic alterations. Both USP9Y and DBY may cause severe testiculopathies, but DBY appears to be the major AZFa candidate. DBY is frequently deleted in infertile patients and its absence produces severe spermatogenic damage leading to a significant reduction of germ cells or even to their complete absence. Expression analysis of AZFa genes and their X-homologues revealed ubiquitous expression for all of them except DBY; this gene produces a long transcript which is ubiquitously expressed in addition to a shorter transcript which is only expressed in the testis, suggesting a specific role for DBY in the spermatogenic process. This hypothesis is further supported by the high similarity of DBY to other DEAD box proteins belonging to the PL10 subclass.
Animals↗
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.
Biopsy, Needle↗
FSH in the treatment of oligozoospermia.
The aim of this study was to individuate parameters able to distinguish oligozoospermic subjects who will respond to follicle-stimulating hormone (FSH) therapy. A group of 135 oligozoospermic subjects was divided in three groups considering basal FSH and inhibin B concentrations: group A (normal FSH and inhibin B) characterized by moderate hypospermatogenesis sometimes associated to partial spermatidic arrest; group B (high FSH and normal inhibin B) characterized by hypospermatogenesis associated or not to spermatogonial/spermatocytic arrest; group C (high FSH and low inhibin B) characterized by severe hypospermatogenesis. Seventy-eight patients were treated with FSH at the dose of 75 IU on alternate days while 57 were treated with the same dose every day for 3 months. After FSH treatment a significant increase in ejaculated sperm concentration was observed only in oligozoospermic subjects with normal basal FSH and inhibin B plasma levels (group A) showing a testicular cytological picture of moderate hypospermatogenesis. In these subjects no differences in sperm production were observed between the two protocols of therapy. In the remaining patients of group A, characterized by hypospermatogenesis associated with maturation arrest at spermatidic level and in group B and C, no increase in sperm concentration was observed after therapy. These data suggest that FSH treatment may have a role in oligozoospermic subjects only when the spermatogenetic alterations consist in germ cell depopulation without maturative disturbances and with normal FSH concentrations.
Adult↗
Role of the AZFa candidate genes in male infertility.
The AZFa region on the Y-chromosome long arm has been recently assembled in a complete sequence map contained in a contig and shown to span more than 1 Mb. It contains three genes, USP9Y, DBY and UTY, but only the former two can be at present considered candidate genes for the infertile phenotype associated with deletion of this interval. These genes have X-homologues and are expressed in many tissues, even if DBY has a shorter transcript expressed in the testis only, strengthening its role in spermatogenesis. Only few patients with gene-specific deletion have been reported and a clear genotype-phenotype relation is still lacking. While deletions or even smaller mutations in USP9Y seem to be associated with a testicular phenotype of severe hypospermatogenesis, patients with deletions of DBY may present both Sertoli cell-only syndrome and severe hypospermatogenesis. On the contrary, the phenotype of patients with deletion of both USP9Y and DBY seem to be invariably azoospermia with a testicular histology of Sertoli cell-only.
Chromosome Mapping↗
Effects of cryopreservation on progesterone-induced ion fluxes and acrosome reaction in human spermatozoa.
The present study evaluated the effects of cryopreservation on progesterone-induced variations of calcium ion concentration [Ca(2+)](i), plasma membrane potential and acrosome reaction in human spermatozoa. Spermatozoa from 10 fertile donors were divided in two equivalent aliquots, one used as control (fresh spermatozoa) and the other used after freezing-thawing. Measurement of spermatozoa [Ca(2+)](i) before and after freezing-thawing showed a significant reduction of basal [Ca(2+)](i) in thawed spermatozoa (P < 0.01). Progesterone induced a rise of [Ca(2+)](i) both in fresh and thawed spermatozoa with a significant reduction after freezing-thawing (P < 0.01). The monitoring of sperm plasma membrane potential demonstrated that progesterone induced plasma membrane depolarization in fresh spermatozoa that was absent in thawed spermatozoa. The inhibitory effects of freezing-thawing on progesterone induced [Ca(2+)](i) and plasma membrane potential variations in human spermatozoa were closely related to the inhibition of the acrosome reaction. In conclusion the present study demonstrates that freezing-thawing procedures reduce the responsiveness of human spermatozoa to progesterone in terms of [Ca(2+)](i) rise and completely inhibit its effects on plasma membrane potential variations, thus supporting the hypothesis that freezing-thawing procedures may differently modify the plasma membrane receptors for progesterone in human spermatozoa which are known to express at least two receptors for this steroid in their plasma membrane.
Acrosome Reaction↗
Male infertility caused by a de novo partial deletion of the DAZ cluster on the Y chromosome.
Deletions in distal Yq interval 6 represent the cause of 10-15% of idiopathic severe male infertility and map to a region defined AZFc (azoospermia factor c). The testis-specific gene DAZ is considered a major AZFc candidate, and its deletion has been associated with a severe disruption in spermatogenesis. However, DAZ is actually a multicopy gene family consisting of seven clustered copies spanning about 1 megabase. Only deletions removing the entire DAZ gene cluster together with other genes have been reported in infertile males. Because no case of spermatogenic failure has been traced to intragenic deletions, point mutations, or even deletions not involving all the DAZ copies, the definitive proof for a requirement of DAZ for spermatogenesis is still debatable. Here we report the first case of a partial deletion of the DAZ cluster removing all but one of the copies. This deletion is present in a patient affected with severe oligozoospermia who had a testicular phenotype characterized by a great quantitative reduction of germ cells (severe hypospermatogenesis). The absence of this deletion in the fertile brother of the patient suggests that this de novo mutation indeed caused the spermatogenic failure.
Adult↗
In-vitro spermatogenesis.
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Biopsy, Needle↗