The origin and phenotype of XO males

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

We report on a familial case including four male probands from three generations with a 45,X,psu dic(15;Y)(p11.2;q12) karyotype. 45,X is usually associated with a female phenotype and only rarely with maleness, due to translocation of small Y chromosomal fragments to autosomes. These male patients are commonly infertile because of missing azoospermia factor regions from the Y long arm. In our familial case we found a pseudodicentric translocation chromosome, that contains almost the entire chromosomes 15 and Y. The translocation took place in an unknown male ancestor of our probands and has no apparent effect on fertility and phenotype of the carrier. FISH analysis demonstrated the deletion of the pseudoautosomal region 2 (PAR2) from the Y chromosome and the loss of the nucleolus organizing region (NOR) from chromosome 15. The formation of the psu dic(15;Y) chromosome is a reciprocal event to the formation of the satellited Y chromosome (Yqs). Statistically, the formation of 45,X,psu dic(15;Y) (p11.2;q12) is as likely as the formation of Yqs. Nevertheless, it has not been described yet. This can be explained by the dicentricity of this translocation chromosome that usually leads to mitotic instability and meiotic imbalances. A second event, a stable inactivation of one of the two centromeres is obligatory to enable the transmission of the translocation chromosome and thus a stably reduced chromosome number from father to every son in this family.

Fetal gender: antenatal discrepancy between phenotype and genotype

Sexual discrepancy is reported in both 46,XY females and 46,XX males, and most diagnoses of sex reversal are made in the postpubertal period. We report three cases of sexual discrepancy, which were revealed by karyotyping following genetic amniocentesis, chorionic villus sampling and fetal blood sampling. The etiologies of 46,XX male, 45,X male and 46,XY female subjects are reviewed. When sexual discrepancy between fetal karyotype and ultrasonographic fetal phenotype is encountered, sample error and placental mosaicism should be excluded. A detailed fetal ultrasound examination should be performed to check for syndromic gender discrepancy. When repeat karyotyping is indicated, localization of the Sox related Y chromosome gene should be carried out.

The phenotype of a 45,X male with a Y/18 translocation

In this report, we describe a male infant with a 45,X karyotype; the entire short arm and the centromere of the Y chromosome were translocated onto the short arm of chromosome 18, resulting in an unbalanced dicentric chromosome. Breakpoints were identified by in situ fluorescence hybridization (FISH) on the proximal Yq11 and 18p11.2. Both Y and 18 centromeric alphoid sequences were identified on the derived 18 chromosome. Clinical features were compatible with 18p- syndrome and no Turner stigmata were present in our propositus. Short stature was likely to be related to the deletion of 18p and/or Yq, where a gene involved in stature determination has been located proximal to a gene involved in spermatogenesis (AZF).

Molecular detection of a translocation (Y;11) (q11.2;q24) in a 45,X male with signs of Jacobsen syndrome

A 45,X karyotype was found in a boy with dysmorphic features, hypoglycaemia and pancytopenia. DNA analysis showed the presence of the Y-chromosomal DNA sequences SRY, ZFY, DYZ4, DYZ3 and DYS1. Using fluorescent in situ hybridization, we located DYZ4 and DYZ3 on chromosome 11qter and concluded that a de novo translocation (Y;11) (q11.2;q24) with a deletion of 11q24----qter and a deletion of Yq11.2----Yqter were present; Jacobsen syndrome and azoospermia are associated with these deletions. Signs of Jacobsen syndrome were observed in the patient.

Azoospermia in XX male

The Authors report a case of azoospermia in a young adult who, though phenotypically a male, was a carrier of karyotype 46 XX. It is a rare case and is due to the precocious migration of fragment Y which produces testis differentiation on chromosome X. These sexual differentiation anomalies produce no genital ambiguity because the process takes place in the very early phase of the sexual differentiation process.

A sterile male with 45,X0 and a Y;22 translocation

Cytogenetic analysis of a 20-year-old sterile male revealed a 45,X0 karyotype with no evidence for Y-chromosomal material on any of the chromosomes analysed by Q-, G- and C-banding. DNA analysis with 17 different Y chromosome-derived probes revealed the presence of Yp DNA sequences in the patient's genome. In situ hybridization with the Yp-derived probe pJA36B disclosed a translocation of Y-chromosomal material onto the short arm of a chromosome 22.

A 45,X male with molecular evidence of a translocation of Y euchromatin onto chromosome 1

A 45,X complement was found in lymphocyte and fibroblast cultures of a male infant with severe growth and mental retardation and mild dysmorphism. Lymphocyte DNA from this patient was found to contain Yp chromosome sequences. In situ hybridization (ISH) with the 50f2 probe led to a clear assignment of euchromatic material on the short arm of chromosome 1. This observation and others from the literature argue in favour of the conclusion that all 45,X males are probably either the result of undetected mosaicism or are carriers of Y translocated material.

Y;autosome translocations and mosaicism in the aetiology of 45,X maleness: assignment of fertility factor to distal Yq11

Three 45,X males have been studied with Y-DNA probes by Southern blotting and in situ hybridization. Southern blotting studies with a panel of mapped Y-DNA probes showed that in all three individuals contiguous portions of the Y chromosome including all of the short arm, the centromere, and part of the euchromatic portion of the long arm were present. The breakpoint was different in each case. The individual with the largest portion (intervals 1-6) is a fertile male belonging to a family in which the translocation is inherited in four generations. The second adult patient, who has intervals 1-5, is an azoospermic, sterile male. These phenotypic findings suggest the existence of a gene involved in spermatogenesis in interval 6 in distal Yq11. The third case, a boy with penoscrotal hypospadias, has intervals 1-4B. In situ hybridization with the pseudoautosomal probe pDP230 and the Y chromosome specific probe pDP105 showed that Y-derived DNA was translocated onto the short arm of a chromosome 15, 14, and 14, respectively. One of the patients was a mosaic for the 14p+ translocation chromosome. Our data and those reported by others suggest the following conclusions based on molecular studies in eight 45,X males: The predominant aetiological factor is Y;autosome translocation observed in seven of the eight cases. As the remaining case was a low-grade mosaic involving a normal Y chromosome, the maleness in all cases was due to the effect of the testis determining factor, TDF. There is preferential involvement of the short arm of an acrocentric chromosome (five out of seven translocations) but other autosomal regions can also be involved. The reason why one of the derivative translocation chromosomes becomes lost may be that it has no centromere.