The naked mole-rat is also of interest because it is extraordinarily long-lived for a rodent of its size (up to 32 years ) and holds the record for the longest living rodent. The mortality rate of the species does not increase with age, and thus does not conform to that of most mammals (as frequently defined by the Gompertz-Makeham law of mortality). Naked mole-rats are highly resistant to cancer and maintain healthy vascular function longer in their lifespan than shorter-living rats. The reason for their longevity is debated, but is thought to be related to their ability to substantially reduce their metabolism during hard times, and so prevent aging-induced damage from oxidative stress. This has been referred to as "living their life in pulses". Their longevity has also been attributed to "protein stability". Because of their extraordinary longevity, an international effort was put into place to sequence the genome of the naked mole-rat. A draft genome was made available in 2011 with an improved version released in 2014. Its somatic number is 2n = 60. Further transcriptome sequencing revealed genes related to mitochondria and oxidation reduction processes to have high expression levels in the naked mole-rat when compared to mice, which may contribute to their longevity.