By Dr. Becker
What small mammal lives underground, excavates with his teeth, has eyes completely covered with skin, and lives for over 20 years? The answer? Why, the blind mole rat of course.
And now scientists have sequenced the genome of this unassuming little fellow because, like his slightly less adorable distant relative the naked mole rat, the blind mole rat is also resistant to cancer. The genome study appears in the June 2014 issue of the journal Nature Communications.1
According to the researchers, the results of genome sequencing have revealed information about the mole rat's lack of eyesight, as well as its high tolerance for low oxygen (hypoxia). They also believe they've discovered important secrets about the little creature's special cancer-fighting powers.
How Blind Mole Rats Defeat Cancer
Lead study author Eviatar Nevo of the University of Haifa in Israel has been studying blind mole rats for a half-century, and has never encountered any evidence of spontaneous tumor development in the little mammals. Even when directly exposed to cancer-causing chemicals, the mole rats remain remarkably resistant.
In most animals, cells that detect the presence of cancer shut themselves down in a phenomenon known as apoptosis, or programmed cell death. But when a blind mole rat's cells identify a problem, the immune system mounts an attack on the tumor instead and causes necrosis (death). According to the results of genome sequencing, the genes involved in the moles' impressive immune system response have been selected through evolution to be expanded or replicated.
The researchers speculate that the mole rat's unusual immune response is because one of the key facilitators of apoptosis, a protein called p53, is altered in the rodents as part of their adaptation to a low oxygen environment.
In the underground world that blind mole rats inhabit, oxygen is scarce -- a situation that would send the p53 protein of other animals into overdrive. That's because low oxygen environments cause programmed cell death in other species. Obviously, if this were also the case with blind mole rats, there would be no more blind mole rats. So they have evolved with a relatively weak p53 response, but a turbocharged immune system necrotic defense that "cancer doesn't know how to deal with," according to study co-author Dr. Denis Larkin of the Royal Veterinary College in London, in an interview with BBC News.
The blind mole rat genome study was conducted by a large team of scientists from all over the world. According to Dr. Larkin, their research puts the rodent in a whole new category for future research. "When you have the whole genome… you can more efficiently use the species as a model – for cancer resistance, or adaptation to hypoxia, or other medical challenges," he told the BBC.
Facts About the Blind Mole Rat
Blind mole rats are furry, with cylindrical bodies, short limbs, and surprisingly small feet and claws, given that they are burrowers. Their eyes are tiny and hidden beneath skin, their ears appear as slight folds, and their minute tails are not externally visible. Sensory whiskers sprout from a flat nose and extend backward.
The mole rats weigh from 3.5 ounces to a little over a pound and range in length from 5 to 14 inches. Their fur is soft and thick, and may be pale to reddish brown or gray. The front of the head is usually lighter in color than the back, and there may be white or yellow stripes that run along the sides of the head or down the middle from nose to forehead.
These little creatures are territorial and solitary. They dig burrows with their incisors, push the loose dirt under their tummies with their front feet, and kick it behind them with their hind feet. When a nice sized pile of soil has collected behind him, the mole rat turns around and uses his nose to pack some of the dirt against the burrow wall. Then he finishes by using his head to push any leftover debris back through the tunnel and up onto the surface.
Blind mole rat burrows can be anywhere from 4 to 10 inches below ground, and they use them to search for food. Their diet consists primarily of roots, tubers, and bulbs, to which they add seeds and green plant parts from occasional nighttime trips to the surface to forage.
The tunnels contain vertical passageways that lead to deeper "hallways" off which the mole rats build separate rooms for food storage, nesting, and elimination. During wet seasons, females construct large mounds that contain chambers for mating and child-rearing. Gestation takes about a month, and there can be from one to five babies in a litter.
Despite their somewhat similar appearance, interestingly, the blind mole rat (Spalax galili) is not closely related to the naked mole rat (Heterocephalus glaber). According to the results of the genome sequencing study, the two mole rats set off on different evolutionary paths some 70 million years ago, and have adapted completely separately to life underground.
Believe it or not, the blind mole rat is actually more closely related to the common house mouse than the naked mole rat!