Male fertility is in significant decline across the western world. Consequently, the proportion of men requiring fertility treatment has risen from 12.4% in 2004 to 21.3% in 2017. The largest “diagnosed” cause of impaired male fertility is attributed to a combination of low sperm count, poor motility and abnormal morphology and is clinically known as Oligoasthenoteratozoospermia (OAT). The testis typically run at 3-4oC lower than core body temperature. Remarkably, testicular hyperthermia is known to be a major cause of OAT, with a 1°C increase median scrotal temperature enough to cause a 40% reduction in sperm concentration in men. Testicular hyperthermia does not affect all cell but rather appears to be specific to pachytene spermatocytes and round spermatids.
Integral to the formation of functional spermatozoa is the widespread occurrence of ‘alternative splicing’, a process wherein a single pre-mRNA transcript is spliced into multiple distinct mRNA products. Evidence in other model systems demonstrates hypothermia can lead to sever disruption of alternative splicing [87].
To determine if testicular hyperthermia cause aberrant alternative splicing, Next Generation RNA sequencing was performed on round spermatids isolated from male C57 mice (N=5) subject to testicular heat stress (42°C, 30min) versus controls (30°C, 30min). Using MAJIQ and Voila software packages, 395 differential LSV (Local Splice Variation) events were identified (Δψ ≥0.1, 0.9 confidence). Notably, many of the changes were found in long-non coding RNA species. Work is continuing to identify which splicing factors are involved.