Telomeres, species differences, and unusual telomeres in vertebrates: presenting challenges and opportunities to understanding telomere dynamics

Abstract

There has been increasing interest in the use of telomeres as biomarkers of stress, cellular ageing and life-histories. However, the telomere landscape is a diverse feature, with noticeable differences between species, a fact which is highlighted by the unusual telomeres of various vertebrate organisms. We broadly review differences in telomere dynamics among vertebrates, and emphasize the need to understand more about telomere processes and trends across species. As part of these species differences, we review unusual telomeres in vertebrates. This includes mega-telomeres, which are present across a diverse set of organisms, but also focusing on the unusual telomeres traits of marsupials and monotremes, which have seen little to no prior discussion, yet uniquely stand out from other unusual telomere features discovered thus far. Due to the presence of at least two unique telomere features in the marsupial family Dasyuridae, as well as to the presence of physiological strategies semelparity and torpor, which have implications for telomere life-histories in these species, we suggest that this family has a very large potential to uncover novel information on telomere evolution and dynamics.

Chromosome Evolution in Marsupials

“…The maternally-derived chromosomes, therefore, have short telomeres. This parental control of telomere length model suggests resetting of telomere length in the germline, with elongation of telomeres taking place in the male germ line and trimming of telomeres in the female germline [ 63 , 64 ].…”

Ectothermic telomeres: it's time they came in from the cold

“…Most research on telomere length, its regulation by telomerase and telomerase somatic expression (and repression) has been performed on endotherms (mostly humans, e.g. reviews in [ 8 – 10 ] and references therein). In endotherms, as opposed to ectotherms, telomerase repression in somatic tissue, and telomere length distributions, have been suggested to be an evolutionary response to the risk of tumour development because of endotherms' higher metabolic rate and cellular replication.…”

Oncogenesis as a Selective Force: Adaptive Evolution in the Face of a Transmissible Cancer

“…In addition to the emergence of a novel transmissible cancer, molecular studies of DFTD (including analyses of karyotypes, methylomes and telomeres) have shown high cancer evolutionary plasticity and adaptability . The combination of the DFTD's ability to evolve novel traits (e.g.…”

“…Parallel to the host, DFTD may also show signs of adaptation. Although no direct evidence for co‐evolution between host and DFTD has yet been found, chromosomal, genomic and epigenetic studies demonstrate that DFTD is not a static, but rather an evolving clonal cell line . Notably, different tumour variants have been found to have differing epidemic patterns; tetraploid tumours showed reduced force of infection and no demographic effects at a particular population (West Pencil Pine) in north‐western Tasmania .…”