Transcriptional Differences in Identical Twins With Different Reproductive Capacities: A Case Report.

Disorders of sperm production can be classified quantitatively as oligospermia (low sperm count) or azoospermia (no sperm during ejaculation). Numerous genes have been implicated in spermatogenesis. We describe a case of two identical twins who presented with different reproductive capabilities. One brother was infertile due to azoospermia, and the other, although oligospermic, previously naturally fathered a child. They were found to have differential gene expression based on RNA sequencing analysis. In the man with azoospermia, we found elevated E2F1 and HOXB9 gene expressions when compared with his brother, suggesting that the increased RNA expression of these genes could influence sperm production.