TELOMERE DYNAMICS IN DOGS: PRELIMINARY STUDY

Telomeres are protective regions of repetitive DNA at the ends of chromosomes that maintain fidelity of genetic information during replication and are critical for genomic stability. Telomeres shorten each time a cell divides, this loss is owing to the incomplete replication of linear chromosomes by the DNA polymerases also called the ‘endreplication problem’. Steady shortening imposes a finite lifespan of cells and establishes the “molecular clock” of biological aging. Oxidative stress, inflammation, and environmental pollution accelerate the telomere shortening process. Telomeres can be restored by the telomerase, a ribonucleic enzyme that maintains telomere length (TL) and is active during early gestation but is repressed during extra-uterine life in somatic cells [1]. In contrast to the telomeres of somatic cells, those in sperm do not shorten with age because of upregulated telomerase, ensuring the transmission of intact chromosomes over generations. A preliminary study was carried out on blood and semen of male dogs (collected as part of routine clinical checks to which animals were subjected) to assess the telomere dynamics and some semen parameters in this species. The samples were collected from six male dogs (1 Akita, 1 Boxer, 1 English bulldog, 3 Neapolitan Mastiffs). DNA extraction was performed on white blood (WB) cells and semen, and TL was measured in the laboratory of Dana Farber/Harvard Cancer Center Genotyping and Genetics for Population Sciences, a modified qPCR method, as previously described [3]. Semen quality and fertility test were assessed. Semen and WB TL ranges were 0.8147 to 1.2357 and 0.6820 to 1.1491 Exp ddCT respectively, considering that anything over 1.00 is long compared to under 1, that results short. Results of semen parameters ranged as follows: Seminal volume: 8 to 35.5 ml; pH: 6.4 to 6.8; semen concentration: 168 to 940 x 106 spz/ml; total motility: 30 to 90%; progressive motility: 20 to 80%; viability: 60 to 90%; morphological anomalies: 3 to 10%. Data showed a parallelism with human telomere biomass. Analogies have been found between humans and dogs, such as telomere lengths, telomere shortening, absence of telomerase activity of somatic cells, which make the canine species an interesting model to understand the dynamics affecting TL during the course of the life of individuals and of the animal itself in relation also with the lifespan of the dog breed. In addition to understanding the dynamics, the results can extend to reproduction, specifically to infertility, as the shortening of spermatozoa TL has been associated with infertility in men [3]. [1] O’Sullivan R.J., Karlseder J. Telomeres: protecting chromosomes against genome instability, Nat Rev. Mol. Cell Biol. 11:171-181, 2010. [2] Vyas et al. Pilot study of DNA methylation, molecular aging markers and measures of health and well-being in aging, Transl Psychiatry, 9:118, 2019. [3] Cariati et al. Investigation of sperm telomere length as a potential marker of paternal genome integrity and semen quality, Reprod Biomed Online, 33:404-411