Non-random chromosome positioning in mammalian sperm nuclei, with migration of the sex chromosomes during late spermatogenesis

Abstract

Chromosomes are highly organized and\ud compartmentalized in cell nuclei. The analysis of their\ud position is a powerful way to monitor genome organization\ud in different cell types and states. Evidence suggests that the\ud organization of the genome could be functionally important\ud for influencing different cellular and developmental\ud processes, particularly at early stages of development (i.e.\ud fertilization and the consequent entry of the sperm nucleus\ud into the egg). The position of chromosomes in the sperm\ud nucleus might be crucial, because their location could\ud determine the time at which particular chromatin domains\ud are decondensed and remodelled, allowing some epigenetic\ud level of control or influence over subsequent paternal gene\ud expression in the embryo. Here, we analyse genome\ud organization by chromosome position in mammalian\ud sperm nuclei from three breeds of pig, as a model species.\ud We have mapped the preferential position of all\ud chromosomes (bar one) in sperm nuclei in two dimensions\ud and have established that the sex chromosomes are the\ud most internally localized chromosomes in mature sperm.\ud The distribution of two autosomes and chromosomes X and\ud Y in sperm heads was compared in primary and secondary\ud spermatocytes and spermatids in porcine testes. The sex\ud chromosomes were found at the nuclear edge in primary\ud spermatocytes, which correlates with the known position of\ud the XY body and their position in somatic cells, whereas,\ud in spermatids, the sex chromosomes were much more\ud centrally located, mirroring the position of these\ud chromosomes in ejaculated spermatozoa. This study\ud reveals the temporal repositioning of chromosome\ud territories in spermatogenesis

Intrachromosomal rearrangements in avian genome evolution: evidence for regions prone to breakpoints

“…It may however imply that there is a selective advantage to birds in keeping certain blocks of synteny together in the interphase nuclei. Our studies on interphase nuclei in birds (Skinner et al, 2009b) and pigs (Quilter et al, 2002;Foster et al, 2005) provide proof of principle about how future studies in this area might proceed. Our data show that the median breakpoint sizes are lowest in the chicken (70 kb) and highest in the turkey (125 kb).…”

Impact of a selfish B chromosome on chromatin dynamics and nuclear organization in Nasonia

“…Alternatively, it is possible that placement at the tip of the sperm nucleus may confer some epigenetic advantage to the PSR chromosome. Such a hypothesis has been proposed for the sex chromosomes, which localize invariably to discrete regions within the sperm of several mammals (Greaves et al, 2003;Foster et al, 2005).…”

Chromosome architecture in the decondensing human sperm nucleus

“…Although there are only few relevant experimental data, we propose the principles of chromosome organization are similar. The existence of CTs and their preferred nuclear positioning were demonstrated in sperms of boar (Foster et al, 2005), rodents (Haaf and Ward, 1995;Meyer-Ficca et al, 1998) and evolutionary distant non-eutherian mammals (Greaves et al, 2003;Grutzner et al, 2004). Probably, sperm chromosomes in other mammals are also in hairpin (looped) conformation because TEL dimers exists in mouse, rat, boar and bull (Zalensky et al, 1997;Meyer-Ficca et al, 1998).…”