Parental origin of the two additional haploid sets of chromosomes in an embryo with tetraploidy

Abstract

We report on the molecular investigations performed on an embryo with tetraploidy, karyotype 92,XXXY. The embryo was spontaneously aborted after eight weeks of gestation. Molecular analyses were performed in order to determine the parental origin and mode of formation of the two additional haploid sets of chromosomes. Microsatellite markers mapping to pericentromeric chromosome regions were used. Our results show a maternal origin of one additional set of chromosomes most likely due to the incorporation of the polar body of meiosis I and a paternal origin of the second additional set of chromosomes most likely due to dispermy. The karyotype 92,XXXY is rather unusual, indeed the vast majority of cases with tetraploidy have the karyotypes 92,XXXX or 92,XXYY. To the best of our knowledge this is the first case with 92,XXXY for which molecular investigations have been performed.

A brief look at the origin of tetraploidy

“…Unfortunately, investigations of tetraploid spontaneous abortions or newborns are facing the same dilemma. In agreement with Baumer et al (2003), it can only be stated that more data from both sources are needed to determine, in particular, the role of haploid or diploid oocytes combined with three or two paternal contributions, respectively.…”

“…Of note, the constitution XYYY that has never been reported in spontaneous abortions can be found at the zygote level. As discussed by Baumer et al (2003), the karyotype 92,XYYY may be particularly unfavourable and may predispose to very early embryonic loss.…”

“…Also, the spontaneously aborted embryo examined by Baumer et al (2003) has been attributed to dispermy and a meiosis I error in the oocyte. Among the different mechanisms leading to a double maternal contribution, re-incorporation of an already extruded PB is occasionally mentioned.…”

“…A tetraploid embryo with the rare karyotype 92,XXXY that most probably received an additional maternal set of chromosomes due to incorporation of the first polar body and an additional paternal set due to dispermy has recently been described by Baumer et al (2003). Their report contains two remarkable comments: (a) the mode of formation of only six tetraploidies has been elucidated as yet and (b) there is little direct evidence for the assumption that the majority of tetraploidies arise through mitotic failures during the first (in non-mosaic cases) or later divisions (in mosaics).…”

A 92,XXXY Miscarriage Consecutive to a Digynic Triploid Pregnancy

“…Another possibility could be the fusion of 2 normally fertilized eggs [Baumer et al, 2003]. Among tetraploids, 92,XXXY karyotypes are extremely rare.…”