Y/X-Chromosome-Bearing Sperm Shows Elevated Ratio in the Left but Not the Right Testes in Healthy Mice.

ABSTRACT

The sex chromosomes play central roles in determining the sex of almost all of the multicellular organisms. It is well known that meiosis in mammalian spermatogenesis produces ~50% Y- and ~50% X-chromosome-bearing sperm, a 11 ratio. Here we first reveal that the X-chromosome-encoded miRNAs show lower expression levels in the left testis than in the right testis in healthy mice using bioinformatics modeling of miRNA-sequencing data, suggesting that the YX ratio could be unbalanced between the left testis and the right testis. We further reveal that the YX ratio is significantly elevated in the left testis but balanced in the right testis using flow cytometry. This study represents the first time the biased YX ratio in the left testis but not in the right testis is revealed.