ISSN:
1573-6849
Keywords:
meiosis
;
spatial organization
;
XY chromosomes
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract We have used multicolour fluorescencein situ hybridization to study the behaviour of the X and Y chromosomes in relation to a representative autosome, chromosome 1, on air-dried testicular preparations from normal fertile human males. In a proportion of Sertoli cells at interphase as well as spermatogonial metaphases there is an apparent selective undercondensation of the heterochromatic block of the long arm of the Y, which may be of functional significance with respect to Y-specific gene activity, initiating and maintaining spermatogenesis; we suggest that this may involve a mechanism similar to heterochromatin position-effect variegation inDrosophila. In the supporting Sertoli as well as pre-meiotic and leptotene cells the X and Y occupy relatively restricted domains at opposite poles of the nuclear membrane, while the chromosome 1 centromere regions are located interstitially and appear prealigned. The XY pairing and ‘sex vesicle’ formation comprises a complex series of spatial movement and differential condensation patterns. On the basis of these observations we propose that: the XIST/Xist gene, known to be involved in somatic X inactivation, imposes a chromatin reorganization leading to bending at the X-inactivation centre both at first meiotic prophase in males and in the soma in females; and the differential X and Y segments are protected from potentially deleterious meiotic exchanges by their separate spatial orientation. In addition, there is an indication that the timing of pairing and first meiotic segregation of the sex chromosomes is different, and precocious in comparison to the pairing and segregation of the autosomes, which may explain the high incidence of sex chromosome aneuploidy in sperm.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01552867
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