Sex-chromosome pairing and male fertility

Abstract

In this paper a hypothesis is presented which relates chromosome pairing and sterility in males. This hypothesis has been formulated on the basis of data from numerous meiotic systems in the male of Drosophila melanogaster, where the sex chromosomes have heterochromatic pairing sites, sites which must interact in order for postmeiotic development to be normal. The predictions of this theory have been tested in three principal situations: (1) in various sex chromosome systems of man, the mouse, voles, and beetles; (2) in the B chromosome system of the grasshopper Myrmeleotettix maculatus; and (3) in univalent autosomal cases in man and in translocation heterozygotes of the mouse. In all three situations a striking correlation has been obtained between reduction or absence of pairing, on the one hand, and gametogenic breakdown, on the other. It is concluded that a saturation of pairing sites between homologous chromosomes, whether sex chromosomes or autosomes, is essential for regular meiotic or postmeiotic development.

Meiosis in haploid rye: extensive synapsis and low chiasma frequency

“…Miklos (1974) suggested that a saturation of pairing sites is necessary to permit a regular maturation of germ cells. In this context, the extensive synapsis observed in this haploid rye is considered to be nonhomologous and it takes place in order to satisfy pairing requirements.…”

Son-sire regression based heritability estimates of chiasma frequency, using T70H mouse translocation heterozygotes, and the relation between univalence, chiasma frequency and sperm production

“…It is impossible to tell whether the relationship between the two is causative or whether both are influenced by the same genes. If one likes to apply Miklos' (1974) hypothesis regarding spermiogenic arrest one could state that a high chiasma frequency results from enough meiotic pairing sites being occupied. Unoccupied sites, according to the hypothesis, would lead to decondensation of chromatin sometime afterwards.…”

“…A relation between univalence and a breakdown of meiosis has been suggested both for the mouse and for man (Miklos, 1974;Searle, 1974;Chandley et al, 1975). We have investigated this point further by comparing the epididymal sperm count with the counts for translocation-caused univalence and the chiasma counts, using the son-sire pairs of this experiment.…”

Sex chromosome silencing in the marsupial male germ line

“…One idea is that MSCI and meiotic silencing by unpaired chromatin exist only as an evolutionary relic of meiotic silencing of unpaired DNA, a host defense mechanism first described in Neurospora crassa (21) with analogies in metazoans such as Caenorhabditis elegans (22). Other ideas suggest that silencing is obligatory for the suppression of recombination between nonhomologous regions of the X and Y (23), or for preventing asynapsed XY regions from triggering the meiotic checkpoint (24).…”