Meiosis and fertility in XYY mice

Abstract

Four XYY male mice that showed no evidence of somatic-cell mosaicism are described. All had much reduced testis weights and considerable impairment of spermatogenesis, so that few spermatocytes survived to the second division of meiosis. In each mouse the primary spermatocytes observed were predominantly XYY, although, in two of the males, small populations of XY spermatocytes and spermatogonia were seen. However, unlike the situation in man, these XY components had failed to become dominant at the expense of the XYY cells. At diakinesis/first metaphase in the XYY spermatocytes the observed frequencies of the four possible kinds of sex-chromosome associations showed highly significant differences between males. These differences may be real or may in part be artifactual. It is suggested that conclusions drawn concerning pairing preferences of the three sex chromosomes and of their consequences as well should be treated with caution. In view of the small testis size and the few germ cells of all kinds seen in our males, we consider that in most mice the detrimental effect of the XYY constitution starts early and progresses through the seminiferous cycle rather than having a sudden effect at first anaphase, as has been previously suggested. The four males all produced some sperm, but only one gave an above-zero epididymal sperm count, and this was only 1 % of normal. This male, unlike all the previously tested XYY males, proved fertile early in life but soon became sterile. When the observations from all seven XYY males that have now been described are considered together, it is concluded that there is usually a severe impairment of spermatogenesis leading to sterility at an early age. However, the condition may have degrees of manifestation, as in man, and some XYY mice may be subfertile for a limited period rather than completely sterile.

A phenotypically normal cattle with 60, XY/61, XYY karyotype.

“…The cat was phenotypically normal , but germinal cell stages were absent. Some impairment of spermatogenesis was also observed in the majority of the cases reported in man (Zeuthen et al 1973;Skakkebaek et al 1973) and mice (Cattanach 1961;Russel and Chu 1961;Evans et al 1978) with the XYY karyotype. The extra Y chromosome which appears to have no significant erect on the phenotype, is frequently associated with a reduction in reproductive performance.…”

“…The XY/XYY individuals had a normal male conformation and no physical abnormalities, but histopathologic examination of the testicular tissue revealed the absence of germinal cell stages in the cat. Also, the XYY condition in man (Zeuthen et al 1973;Skakkebaek et al 1973) and mice (Cattanach 1961;Russel and Chu 1961;Evans et al 1978) is frequently associated with reduced fertility. This paper presents additional evidence on a 60, XY/61, XYY karyotype detected in a Japanese Black cattle.…”

Evidence that sex chromosome asynapsis, rather than excess Y gene dosage, is responsible for the meiotic impairment of XYY mice

“…XYY mice suffer severe spermatogenic impairment (Cattanach and Pollard, 1969;Rathenberg and Müller, 1973;Evans et al, 1978;Das and Kar, 1981;Tease, 1990;Mahadevaiah et al, 2000), although some sperm are produced. Consequently, they are almost always sterile unless there is germinal mosaicism for an XY cell line (our unpublished data).…”

An analysis of meiotic impairment and of sex chromosome associations throughout meiosis in XYY mice

“…The relative frequencies of the various sex chromosome associations at diakinesis and the first meiotic metaphase (MI) are very heterogeneous and have been taken to suggest either random synapsis of the three sex chromosomes (resulting in twice as many XY bivalent/Y univalent as X univalent/YY bivalent associations) or a synaptic advantage of the X over either Y chromosome (Cattanach and Pollard, 1969;Evans et al, 1969Evans et al, , 1978Rathenberg and Müller, 1973;Manna and Roy, 1980;Das and Kar, 1981;Das and Behera, 1984). However, as is evident from the study of Rodriguez and Burgoyne (2000), the frequencies of the various sex chromosome associations at diakinesis/MI bear little resemblance to those at pachytene, when synapsis is first completed.…”