Chromosomal Polymorphisms in Male Infertility

Chromosomal polymorphisms are structural variations in chromosome morphology or heterochromatin content that occur in the general population. While often considered benign, certain polymorphisms may disrupt meiotic pairing, alter gene expression in germ cells and compromise spermatogenesis. Variants most frequently involve heterochromatic blocks, satellite regions or pericentric inversions, with chromosome 9 standing out as exceptionally heteromorphic. Men carrying these alterations can exhibit reduced sperm concentration (oligozoospermia), abnormal morphology (teratozoospermia) and elevated rates of sperm DNA fragmentation or aneuploidy. The prevalence of specific polymorphisms varies geographically, complicating interpretation of cytogenetic findings. As assisted reproduction becomes more widespread, understanding the impact of these subtle chromosomal changes on natural fertility and treatment outcomes has gained urgency. This summary outlines current insights into the mechanisms by which chromosomal polymorphisms contribute to male infertility, their clinical significance and emerging approaches for genetic counselling and diagnostic evaluation.

Research from Nature Portfolio

A comprehensive analysis assessed whether carriers of chromosomal polymorphic variants experienced altered outcomes in intracytoplasmic sperm injection (ICSI) cycles. Over nine hundred fresh and frozen embryo transfer cycles underwent pre-treatment karyotyping to detect classic heterochromatic variants and structural rearrangements. The study found no significant differences in fertilisation rates, clinical pregnancy or live birth outcomes between carriers and non-carriers of any specific chromosomal polymorphism. These findings challenge earlier suggestions of deleterious effects and underscore the need for large, multi-ethnic cohorts and standardised cytogenetic protocols to resolve conflicting reports on the prognostic value of routine karyotype screening in assisted conception.

Chromosomal Polymorphisms in Male Infertility publication trend

The graph below shows the total number of articles in chromosomal polymorphisms in male infertility across all publications each year (not limited to Nature Index journals).

Technical terms

Chromosomal polymorphism: A structural variation in chromosome morphology or heterochromatin content commonly found in healthy individuals.

Pericentric inversion: A chromosomal rearrangement in which a segment that includes the centromere is reversed.

Heterochromatin variant: An alteration in the size or organisation of tightly packed, non-coding chromosome regions, often near centromeres.

Aneuploidy: The presence of an abnormal number of chromosomes in a cell, which can impair development or fertility.

Intracytoplasmic sperm injection (ICSI): An assisted reproduction technique in which a single sperm is injected directly into an oocyte.

References

1. Polymorphic Rearrangements of Human Chromosome 9 and Male Infertility: New Evidence and Impact on Spermatogenesis. Biomolecules (2023).
2. A comprehensive analysis of chromosomal polymorphic variants on reproductive outcomes after intracytoplasmic sperm injection treatment. Scientific Reports (2023).