Acute Exercise Regulates hTERT Gene Expression and Alternative Splicing in the hTERT-BAC Transgenic Mouse Model

Abstract

Introduction: Aerobic exercise maintains telomere length through increased human telomerase reverse transcriptase (hTERT) expression and telomerase enzyme activity. The impact of acute exercise on hTERT alternative splicing (AS) is unknown. Purpose: This study aimed to examine hTERT AS in response to acute treadmill running. Methods: A bacterial artificial chromosome mouse model containing the 54-kilobase hTERT gene locus inserted into its genome (hTERT-BAC) was utilized. The gastrocnemius, left ventricle, and brain were excised before (Pre), upon cessation (Post), and during recovery (1, 24, 48, and 72 h; n = 5/time point) from treadmill running (30 min at 60% maximum speed). Full-length (FL) hTERT and the "minus beta" (−β) AS variant (skips exons 7 and 8 and does not code for active telomerase) were measured by gel-based and droplet digital reverse transcription-polymerase chain reaction methods. SF3B4 and SRSF2 protein expression were measured by Western blotting. Results: Compared with Pre, FL hTERT increased at Post before decreasing during recovery in the gastrocnemius (48 and 72 h; P ≤ 0.001) and left ventricle (24 h; P = 0.004). The percentage of FL hTERT in the gastrocnemius also increased during recovery (1 and 72 h; P ≤ 0.017), whereas a decrease was observed in the left ventricle (1, 24, and 48 h; P ≤ 0.041). hTERT decreased in the brain (48 h), whereas FL hTERT percentage remained unaltered. SF3B4 protein expression decreased throughout recovery in the gastrocnemius and tended to be associated with FL hTERT (r = −0.348, P = 0.075) and -β in opposite directions (r = 0.345, P = 0.067). Conclusions: Endurance exercise increased hTERT gene expression, and altered FL hTERT splicing in contractile tissues and may maintain telomere length necessary to improve the function and health of the organism.

Exercise as a Therapy to Maintain Telomere Function and Prevent Cellular Senescence

“…This mouse model, commonly referred to as the hTERT bacterial artificial chromosome (hTERT BAC) mouse, served as an in vivo model to study the gene expression regulation of hTERT in tissues after environmental exposures. Importantly, this mouse model recapitulated the expression pattern of hTERT as observed in human tissues (i.e., repression of hTERT in somatic cells besides the testis and thymus) (85,86). In addition, the splicing patterns of hTERT were preserved, indicating that the mouse splicing machinery recognized the human gene-splicing elements like the human splicing machinery does.…”

“…Importantly, this mouse model recapitulated the expression pattern of hTERT as observed in human tissues ( i.e. , repression of hTERT in somatic cells besides the testis and thymus) (85,86). In addition, the splicing patterns of hTERT were preserved, indicating that the mouse splicing machinery recognized the human gene-splicing elements like the human splicing machinery does.…”

“…No human studies have investigated AS of TERT after exercise. My laboratory has extensively studied TERT mRNA AS regulation in cancer cells (29,65,72), and we have recently published the first report describing how an acute aerobic exercise bout impacts TERT AS and transcriptional-level changes (85), which may have important function implications for how telomere biology impacts cellular senescence as described in the next section.…”

“…Recently, my group used the hTERT BAC mouse model and performed an aerobic (treadmill running) exercise bout to begin understanding how exercise impacts AS of hTERT mRNAs. The mice ran on a treadmill for 30 min at 60% maximum speed, and tissues were collected immediately, as well as 1, 24, 48, and 72 h after the exercise bout (i.e., in recovery) and compared with control animals that were exposed to a motionless treadmill for 30 min and their tissues were immediately harvested (85). We measured FL hTERT (exons 7/8 included) and minus beta TERT (skipping of exons 7/8 indicated by 6/9 junction primers) by RT-PCR in skeletal muscle, cardiac muscle, and the brain.…”

Canonical and extra‐telomeric functions of telomerase: Implications for healthy ageing conferred by endurance training

“…It appears mTOR signalling directly inhibits TERT shuttling into the mitochondria reducing protection against ROS (Miwa et al, 2016), which could account for the link with telomere maintenance and improved health span after endurance exercise, rather than resistance training . However, other evidence indicates mTOR signalling can up-regulate telomerase activity (Sundin & Hentosh, 2012) Considering the recent discovery that exercise may control alternative splicing in transgenic mice (Slusher et al, 2022), the role of Tert splice variants should be verified. These findings may ultimately lead to the development of novel therapeutic strategies to promote healthy biological ageing, particularly for those individuals unable to engage in or who are averse to endurance exercise.…”