Abstract
Back groundMen with 47, XYY syndrome are presented with varying physical attributes and degrees of infertility. Little information has been documented regarding the meiotic progression in patients with extra Y chromosome along with the synapses and recombination between the two Y chromosomes.MethodsSpermatocyte spreading and immunostaining were applied to study the behavior of the extra Y chromosome during meiosis I in an azoospermia patient with 47, XYY syndrome and results were compared with five healthy controls with proven fertility.ResultsThe extra Y chromosome was present in all the studied spermatocytes of the patient and preferentially paired and synapsed with the other Y chromosome. Consistently, gamma-H2AX staining completely disappeared from the synapsed regions of Y chromosomes. More interestingly, besides recombination on short arms, recombination on the long arms of Y chromosomes was also observed. No pairing and synapsis defects between homologous autosomes were detected, while significantly reduced recombination frequencies on autosomes were observed in the patient. The meiotic prophase I progression was disturbed with significantly increased proportion of leptotene, zygotene cells and decreased pachytene spermatocytes in the patient when compared with the controls.ConclusionsThese findings highlight the importance of studies on meiotic behaviors in patients with an abnormal chromosomal constitution and provide an important framework for future studies, which may elucidate the impairment caused by extra Y chromosome in mammalian meiosis and fertility.Electronic supplementary materialThe online version of this article (doi:10.1186/s13039-016-0218-z) contains supplementary material, which is available to authorized users.
Highlights
The 47,XYY sex chromosome variation is the most common sex chromosome anomaly after Klinefelter syndrome [1,2,3], occurring in approximately 1 out of 1000 live male births [4]
Considerable attention has been given to the somatic abnormalities associated with 47,XYY conditions but less is known about their meiotic behaviors; that is, how sex chromosome imbalance influence the meiotic progression, and homologous pairing, synapsis and recombination
Fluorescence in situ hybridization (FISH) To identify the Y chromosomes in spermatocytes,FISH was performed as we previously reported on the spermatocyte spreads immunostained for meiotic analyses in previous experiments using a DNA probe specific to the long arm of human Y chromosome(A generous gift from Professor Mingrong Wang, Cancer Institute and Hospital, Chinese Academy of Medical Sciences, Beijing, China)
Summary
Analysis of the semen revealed that the patient was suffering from azoospermia. Karyotyping on G-banded metaphases of peripheral blood lymphocytes revealed a karyotype of 47, XYY in all the 100 studied cells of the patient. Higher frequency of Y-Y synapsis was observed in those spermatocytes where Y chromosomes were found associated with X chromosomes in all the 45 studied spermatocytes (Table 3). Recombination frequency of autosomes in the 47, XYY patient was determined in pachytene spermatocytes and compared to those in 437 spermatocytes from five controls. We immunostained mid-late pachytene spermatocytes of the patient and controls for the meiotic sex chromosome inactivation (MSCI) marker, Fig. 2 Sex chromosome pairing and recombination in the 47, XYY patient. The γ-H2AX signals were only visible only on X chromosome in the spermatocytes where two Y chromosomes were completely paired and synapsed (Fig. 4e-g) These results indicate that synapsis can occur between the two Y chromosomes. Reduced number of germ cells and no mature sperm were observed in testicular sections of the 47,XYY patient (Fig. 6b)
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