Male Infertility Associated with a Supernumerary Marker Chromosome

Update on genetic screening and treatment for infertile men with genetic disorders in the era of assisted reproductive technology

A genetic etiology of male infertility is identified in fewer than 25% of infertile men, while 30% of infertile men lack a clear etiology, resulting in a diagnosis of idiopathic male infertility. Advances in reproductive genetics have provided insights into the mechanisms of male infertility, and a characterization of the genetic basis of male infertility may have broad implications for understanding the causes of infertility and determining the prognosis, optimal treatment, and management of couples. In a substantial proportion of patients with azoospermia, known genetic factors contribute to male infertility. Additionally, the number of identified genetic anomalies in other etiologies of male infertility is growing through advances in whole-genome amplification and next-generation sequencing. In this review, we present an up-to-date overview of the indications for appropriate genetic tests, summarize the characteristics of chromosomal and genetic diseases, and discuss the treatment of couples with genetic infertility by microdissection-testicular sperm extraction, personalized hormone therapy, and in vitro fertilization with pre-implantation genetic testing.

Small supernumerary marker chromosomes (sSMC) and male infertility: characterization of five new cases, review of the literature, and perspectives

PURPOSE

To characterize small supernumerary marker chromosomes (sSMC) in infertile males RESEARCH QUESTION: Are molecular cytogenetic methods still relevant for the identification and characterization of sSMC in the era of next-generation sequencing?

METHODS

In this paper, we report five males with oligoasthenozoospermia or azoospermia with a history of recurrent pregnancy loss in partnership in four cases. R-banding karyotyping and fluorescence in situ hybridization (FISH) analysis were performed and showed sSMC in all five cases. Microdissection and reverse-FISH were performed in one case.

RESULTS

One sSMC, each, was derived from chromosome 15 and an X-chromosome; two sSMC were derivatives of chromosome 22. The fifth sSMC was a ring chromosome 4 complemented by a deletion of the same region 4p14 to 4p16.1 in one of the normal chromosomes 4. All markers were mosaics except one of sSMC(22).

CONCLUSION

Through this study, we emphasize the necessity of a proper combination of high-throughput techniques with conventional cytogenetic and FISH methods. This could provide a personalized diagnostic and accurate results for the patients suffering from infertility or RPL. We also highlight FISH analyses, which are essential tools for detecting sSMC in infertile patients. In fact, despite its entire composition of heterochromatin, sSMC can have effects on spermatogenesis by producing mechanical perturbations during meiosis and increasing meiotic nondisjunction rate. This would contribute to understand the exact chromosomal mechanism disrupting the natural and the assisted reproduction leading to offer a personalized support.