A family case of fertile human 45,X,psu dic(15;Y) males

Preimplantation genetic testing results of blastocysts from 12 non-Robertsonian translocation carriers with chromosome fusion and comparison with Robertsonian translocation carriers

OBJECTIVE

To investigate the effects of non-Robertsonian translocation with chromosome fusion (N-RBCF) on preimplantation embryos.

DESIGN

Case series.

SETTING

University-affiliated center.

PATIENT(S)

Twelve couples with N-RBCF.

INTERVENTION(S)

Assisted reproduction with preimplantation genetic testing in chromosomal structural rearrangement (PGT-SR).

MAIN OUTCOME MEASURE(S)

Normal embryo rate, unbalanced translocation rate.

RESULT(S)

PGT was performed in 12 N-RBCF carriers, of whom 4 carried Y-autosome fusions and 8 autosomal fusions. A total of 12 (63.2%) of 19 blastocysts exhibited normal/balanced embryos, and only one (5.3%) embryo exhibited unbalanced translocations among Y-autosome fusion cases. In contrast to these findings, the percentage of normal/balanced blastocysts in 8 autosomal N-RBCF cases was 28.2% (11/39), whereas the unbalanced translocation rate was 53.8%. Furthermore, the percentage of normal/balanced embryos in the Robertsonian translocation group was significantly higher than that of the 8 autosomal N-RBCF (48.7% vs. 28.2%) cases. The rates of abnormality from chromosomal fusion in the 8 autosomal N-RBCF cases were significantly higher than those noted in the Robertsonian translocation (53.8% vs. 31.4%) subjects. The results of the stratified analysis according to the carrier's sex demonstrated that the rates of unbalanced translocation were significantly higher in the male autosomal N-RBCF subjects than those from the corresponding Robertsonian translocation (55% vs. 19.7%) cases.

CONCLUSION(S)

A low number of unbalanced translocations was identified in blastocysts from N-RBCF subjects who carried the Y fusion. The risk of unbalanced translocation in autosomal N-RBCF was higher than that of the Robertsonian translocation, notably in male carriers.

Loss of the Y chromosome PAR2 region and additional rearrangements in two familial cases of satellited Y chromosomes: cytogenetic and molecular analysis

Two cases of rare structural aberrations of the Y chromosome were detected: a del(Y) (q12) chromosome in a child with mild dysmorphic features, obesity and psychomotor delay, and two identical satellited Y chromosomes (Yqs) in a normal twin, which were originally observed during routine prenatal diagnosis. In both cases a Yqs chromosome was detected in the father which had arisen from a reciprocal translocation involving the short arm of chromosome 15 and the heterochromatin of the long arm of the Y chromosome (Yqh). Cytogenetic and molecular studies demonstrated that in the reciprocal product of chromosomes 15 and Y PAR2 could not be detected, showing that PAR2 had been deleted. It is discussed whether the translocation of the short arm of an acrocentric chromosome to the heterochromatin of the long arm of the Y chromosome causes instability of this region which results either in loss of genetic material or interference with the normal mechanism of disjunction.

Pseudodicentric 22;Y translocation transmitted through four generations of a large family without phenotypic repercussion

The most frequent Y-autosome translocations involve an acrocentric autosome and they are frequently familial with neither phenotypic nor reproductive repercussion. However, different Y-autosome translocations have been related to infertility, due to abnormal pairing of the X and Y chromosomes at meiosis and an abnormal XY-body formation or by the disruption of the AZFs (Azoospermic Factor). Rare forms of Y-autosome translocations are those resulting in an unbalanced 45-chromosome karyotype that includes a dicentric Y+autosome chromosome. We describe a new case of a familial pseudodicentric 22;Y that is carried by 19 male members of a large family without phenotypic repercussion. Cytogenetic analysis, fluorescence in situ hybridisation (FISH) and subtelomeric Multiplex Ligation-dependent Probe Amplification (MLPA) assay have been performed. All male members of the family showed the karyotype 45,X,psu dic(22;Y)(p11.2;qter).ish psu dic(22;Y) (SRY+,DYZ3+,D14/D22Z1+). In conclusion, the presence of the dicentric chromosome in the male members of the family reported does not seem to interfere with the correct progression of spermatogenesis.