Abstract
Only a few studies have described sperm chromosome intranuclear positioning changes in men with reproductive failure and an incorrect somatic karyotype. We studied the influence of Robertsonian translocations on the acrocentric chromosome positioning in human sperm cells. The basis of the analysis was the localization of NORs (nucleolar organizing regions) in sperm nuclei from three Robertsonian translocation carriers, namely, rob(13;22), rob(13;15) and rob(13;14), with a known meiotic segregation pattern. All three carriers presented with a similar percentage of genetically normal sperm cells (i.e., approximately 40%). To visualize NORs, we performed 2D-FISH with directly labelled probes. We used the linear and radial topologies of the nucleus to analyse the NORs distribution. We found an affected positioning of NORs in each case of the Robertsonian translocations. Moreover, the NORs tended to group, most often in two clusters. Both in Robertsonian carriers and control sperm cells, NORs mostly colocalized in the medial areas of the nuclei. In the case of the Roberstonian carriers, NORs were mostly concentrated in the peripheral part of the medial area, in contrast to control sperm cells in which the distribution was more dispersed towards the internal area.
Highlights
Robertsonian translocations (ROBs), named after the American biologist W.R.B
The meiotic segregation patterns were examined for the ROB carriers on the basis of ca. 2100–3400 sperm cells counted
There is a generally accepted view that changes in sperm chromosome organization may be critical for pronuclear chromatin remodelling, which in consequence may disturb the transmission of paternal chromosomal information to the zygote31
Summary
Robertsonian translocations (ROBs), named after the American biologist W.R.B. Robertson, were first described in 1916 in grasshoppers. In most carriers of different nonhomologous ROBs, the frequency of genetically balanced segregants is around 80%, and the numbers of offspring with normal or balanced karyotypes are similar which can indicate a homogenous segregation behaviour of Robertsonian translocations independent of the chromosome pairs involved. The topology and organization of chromosomes in human sperm cells is a subject of numerous studies due to suggestions that intranuclear architecture is of considerable importance for the correct decondensation of chromatin in the male pronucleus30–32 In this context, it seems important that changes in the chromosomal topology were detected in men with reproductive failures and correct somatic karyotype. We found altered distribution of NORs in each case of the Robertsonian translocation Such an observation stemmed mostly from the comparison of the localization of NORs in sperm cells from a control donor with normal karyotype vs ROB carriers
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