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.

Molecular studies in three patients with isodicentric Y chromosome.

Three patients carrying an isodicentric (idic) Y chromosome associated with a mosaic 45,X cell line were studied using molecular techniques. Genotype-phenotype correlations suggested an effect of the 45,X cell line on sexual differentiation. A relationship was established between instability of the idic(Y) chromosome and localization of the breakpoint on Yq, and between azoospermia and deletion of interval 6 on Yq.

FISH detection of mixed chimerism in 33 patients submitted to bone marrow transplantation.

Fluorescence in situ hybridization (FISH) and cytogenetic analysis were carried out in 33 transplanted patients suffering from different hematologic disease using probes for X and Y chromosomes and ABL and BCR genes. FISH showed that recipient cells were invariably present during post-transplant follow-up. Stable minimal residual disease was associated with clinical and hematologic remission, while a progressive increase of host cells was strictly related with disease relapse. Cytogenetic investigation on the same samples showed recipient cells only in few cases. It was concluded that FISH analysis is useful for: (1) characterizing cases in which standard cytogenetic analysis has failed; (2) detecting host cells in sex-mismatched transplanted patients; and (3) evaluating Ph-negative CML with the BCR/ABL rearrangement. The possibility of detecting chromosome rearrangements in interphase nuclei using FISH analysis improves diagnosis and prediction of disease evolution and prompts earlier therapeutic approaches.

Retrospective investigation of hematopoietic chimerism after BMT by PCR amplification of hypervariable DNA regions.

We report on nine patients submitted to BMT with sex-matched donors and investigated by means of PCR amplification of the VNTRs ApoB, D1S80, DXS52, and D17S5. In all cases it was possible to detect a polymorphism able to distinguish between donor and patient cells, thus allowing us to recognize the presence of complete or mixed chimerism. In eight patients PCR analysis showed a complete chimerism during the entire follow-up. Only one of these patients relapsed, while the others are alive and without any sign of relapse 56.2 months (mean) after BMT. Mixed chimerism was detected in only one patient, who relapsed 3 months after this finding. These results confirm the usefulness of the study of PCR-amplified VNTRs in the assessment of marrow engraftment after BMT, mostly in sex-matched transplants where, in the absence of specific chromosome rearrangements, cytogenetic or FISH analysis cannot be used.

Complex translocations of the Ph chromosome and Ph negative CML arise from similar mechanisms, as evidenced by FISH analysis.

The authors report on 13 patients with chronic myeloid leukemia (CML) studied by serial karyotyping and fluorescence in situ hybridization (FISH) of their bone marrow cells. Ten patients had complex translocations of the Ph chromosome while the remaining three were Ph negative. FISH analysis revealed in all 13 patients the translocation of the ABL protooncogene into chromosome 22 at band q11. Moreover, in all complex translocations but one, FISH with a chromosome 22 painting probe demonstrated on one chromosome 9 at band q34 the presence of material from chromosome 22, in addition to signals on the third chromosome involved in complex changes. Therefore, in this study complex translocations appeared as secondary changes resulting from two consecutive translocations with a total of at least four breaks. The first translocation gave rise to the standard t(9;22)(q34;q11). The second one included a break distal to the original breakpoint at band 9q34 and another one on a third chromosome. Furthermore FISH using S1 and S15 probes, mapped at band 22q11.2 or 22q12, gave evidence that in complex translocations the secondary breakpoint on der(9) was in the translocated segment 22q11-qter between bands q11 and q12. FISH analysis also disclosed the presence of material from chromosome 22 on one chromosome 9 in the three patients with Ph negative CML, demonstrating that in these cases a retranslocation between chromosomes 9q+ and 22q- had occurred. Consequently, the four-break mechanism could also be invoked for the three Ph negative CML patients.

A newborn with ring chromosome 10, aganglionic megacolon, and renal hypoplasia.

A newborn infant is reported who had aganglionic megacolon, renal hypoplasia, severe growth retardation, generalised hypotonia, and various dysmorphic features. Chromosome analysis of lymphocytes and fibroblasts showed a ring chromosome 10 with breakpoints at p13-15 and q26. AluI digestion showed that the ring chromosome was monocentric. FISH with an alpha satellite probe specific for chromosome 10 showed one signal only in about 20% of interphase nuclei. It is suggested that aganglionic megacolon could result from dynamic somatic mosaicism owing to loss of the ring chromosome.