Abstract
BackgroundRing chromosomes are often associated with spermatogenetic failure. However, the mechanism is poorly understood. We here reported a single man with severe oligospermia and a ring chromosome 4 with a microdeletion at 4p16.3.ResultsSynapsis (as SCP3), recombination (as MLH1) and transcriptional inactivation (as BRCA1) in a testicular biopsy were examined by fluorescence immunostaining. In the oligospermia patient, 35.4% of spermatocytes were in zygotene phase compared with 5.2% in controls. The patient had a significantly reduced recombination frequency with mean of 45.9 MLH1 foci/cell compared with 47.8 in controls. In the patient, chromosome 4 in all pachytene cells displayed loop formation with varying degrees of unpaired regions. BRCA1 localized along asynapsed regions regardless of XY body association.ConclusionsRing chromosome 4 might affect the progression of meiosis I prophase, synapse formation, and transcriptional activation of asynapsed areas, and impair male fertility.
Highlights
Ring chromosomes are often associated with spermatogenetic failure
Multiple short SCP3-positive segments were revealed at leptotene; 46 complete but unpaired SCP3-positive elements with 46 CREST signals were observed at zygotene; synapsis of homologues was completed with 23 CREST, 23 synaptonemal complex (SC) signals and the appearance of MLH1 foci at pachytene
Meiotic prophase I substages were identified in the patient's biopsy sample using immunofluorescence to determine the appearance and chronology of SCP3. 164 primary spermatocytes from the patient and 1828 from five control men were analyzed
Summary
Ring chromosomes are often associated with spermatogenetic failure. We here reported a single man with severe oligospermia and a ring chromosome 4 with a microdeletion at 4p16.3. Chromosomal structural abnormalities such as inversion, translocation and complex chromosome rearrangements can disturb the first meiotic division and result in sterility [1,2,3,4]. Ring chromosomes are rare chromosomal structural abnormalities. The underlying mechanisms of spermatogenetic failure in patients with ring chromosomes are not fully understood. We report a patient with ring chromosome 4 and microdeletion of chromosome region 4p16.3 presenting the core features of Wolf-Hirschhorn syndrome and spermatogenic arrest. To understand the mechanisms of spermatogenic arrest in this patient, this study used fluorescence immunocytogenetic methods to investigate
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