Molecular Human Reproduction, Vol. 7, No. 7, 691-693,
July 2001
© 2001 European Society of Human Reproduction and Embryology
Letter to the editor |
The role of USP9Y and DBY in infertile patients with severely impaired spermatogenesis
1 Centre for Reproductive Medicine and 2 Centre for Medical Genetics, University Hospital, Dutch-speaking Brussels Free University (Vrije Universiteit Brussel), Laarbeeklaan 101, B-1090 Brussels, Belgium Laboratoire de Génétique, Biologie du Développement et de la Reproduction, EA 3185, Genetique et Reproduction, Faculte de Medecine et de Pharmacie. Place Saint-Jacques, 25030, Besancion Cedex, France
Dear Sir,
Our attention was drawn to the article by Blagosklonova et al. (2000) in which Yq microdeletions were investigated retrospectively by performing PCR on DNA extracted from archival sections of testicular biopsies. We were very surprised at the high number of USP9Y (formerly known as DFFRY) deletions found in patients with Sertoli cell-only syndrome (SCOS) (4/22) and we thought it would be worthwhile to check this in our own population of azoospermic patients with primary testicular dysfunction.
We therefore analysed 69 subjects with complete SCOS (SCO type I, complete absence of germ cells) and 17 patients with incomplete SCOS (SCO type II, some tubules still show a focal presence of immature germ cells). The classification of the patients according to their clinical diagnosis and testis histology is shown in Table I
. The DNA of these subjects had already been analysed in our routine Yq deletion screening programme (Van Landuyt et al., 2000) in which the markers sY84, sY132, sY254 and sY158 were used to study the three AZF regions. The 69 men with SCO type I included three patients carrying a Yq deletion: one with an AZFa deletion, one with an AZFc deletion and another patient with a contiguous deletion of AZFa, b and c. In the patients with SCO type II, one man presented with a deletion of AZFb and AZFc. All Yq deleted patients were diagnosed as idiopathic infertile.
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To assess the presence of isolated deletions of the USP9Y gene, we performed PCR on the genomic DNA of peripheral blood of these 86 patients with the same internal USP9Y primers used by the authors, thus bypassing their cumbersome technique of DNA extraction from archival testis tissue. Female negative and fertile male positive PCR controls were included in each PCR experiment.
However, screening the USP9Y gene in this large and well-defined group of patients did not lead to the remarkable results obtained by Blagosklonova et al. (2000) since no USP9Y deletions were found. We demonstrated that only the two patients with the previously detected AZFa deletions (one isolated deletion of AZFa and one contiguous deletion of AZFa, b and c, both deleted for the marker sY84) were also lacking the USP9Y locus.
According to the article by Foresta et al. (2000), deletions of DBY outnumber USP9Y deletions. When we analysed the same patient group with both DBY1 and DBY2 markers, used by this group, we found two patients with a partial deletion in DBY, both presenting complete SCOS. One patient was deleted for DBY1 (5' side of the gene) (Figure 1) and was positive for DBY2 (more distal to the 3' side). The other patient was lacking the sequence normally amplified by DBY2 (Figure 2) but was positive for DBY1. Our two patients with the known AZFa deletion were probably deleted for the whole DBY gene as both markers showed negative results. Both patients were positive for the sY84 locus (Figure 3).
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Summarising our results obtained with the marker sY84 of the Yq deletion screening programme and the results obtained with this study of the USP9Y and DBY genes, we now have an AZFa deletion frequency of 7.8% (4/51) in idiopathic infertile patients with complete SCOS: two patients with a combined deletion of marker sY84, DBY and USP9Y and two patients with a partial deletion of the DBY gene.
We can conclude that our data do not support the data from the retrospective study by Blagosklonova et al. (2000), who found a high percentage (18%) of USP9Y deletions. How can it be that the authors find four USP9Y deletions in a small group of 22 SCOS patients and we found only two (combined deletions with sY84 and DBY) in a larger and more strictly selected group of 51 patients? It is noteworthy that the authors do not mention anything about the clinical features of these patients, assuming that selection of the subjects was merely done on the basis of their testicular phenotype, (which makes our patient group even larger in comparison).
Do we have to consider these findings accidental or are there other factors involved such as ethnic background of the patients and environmental factors? Or do we have to question the complex technique of extracting DNA from archival Bouin fixed material? In order to evaluate the methodology of the study by Blagosklonova et al. and thus to make the right conclusions, a comparative analysis should be performed on DNA extracted from peripheral blood versus DNA from Bouin fixed testis tissue.
We can also conclude that the prevalence of AZFa deletions that we obtained (7.8%) is lower but more comparable to the data reported by Foresta et al. (2000). This group described a prevalence of 9.7% (4/41) of AZFa deletions in idiopathic SCOS. In three cases, an isolated deletion of the DBY gene was found, while the remaining patient was carrying a larger deletion of DBY together with USP9Y. An isolated deletion of the USP9Y gene was detected only in 1/92 idiopathic severe oligozoospermic patients with severe hypospermatogenesis. Sun and co-workers observed an even lower prevalence (1/576) of USP9Y deletions (Sun et al., 1999). Taking our results together with those of Foresta et al. (2000), we can agree with the latter authors on the important role of the DBY gene, rather than USP9Y, as a candidate for the full AZFa testicular phenotype.
Notes
3 To whom correspondence should be addressed 
References
Blagosklonova, O., Fellmann, F., Clavequin, M.-C. et al. (2000) AZFa deletions in Sertoli cell-only syndrome: a retrospective study. Mol. Hum. Reprod., 6, 795–799.
Foresta, C., Ferlin, A. and Moro, E. (2000) Deletion and expression analysis of AZFa genes on the human Y chromosome revealed a major role for DBY in male infertility. Hum. Mol. Genet., 9, 1161–1169.
Sun, C., Skaletsky, H., Birren, B. et al. (1999) An azoospermic man with a de novo point mutation in the Y-chromosomal gene USP9Y. Nature Genet., 23, 429–432.[ISI][Medline]
Van Landuyt, L., Lissens, W., Stouffs, K. et al. (2000) Validation of a simple Yq deletion screening programme in an ICSI candidate population. Mol. Hum. Reprod., 6, 291–297.
World Health Organization (2000) WHO Manual for the Standardized Investigation, Diagnosis and Management of the Infertile Male. Cambridge University Press, Cambridge, UK.
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