Hope is Hopping Toward Us: Fox Squirrels and the Answer to Gunther’s Disease

The Beginning

[Photo by Staff Illustrator]
[Photo by Staff Illustrator]
People say that the chances of becoming a professional sports player or Broadway star are “one in a million”. Jane wanted to make it to the White Way, to be that one, and she was, but for an entirely different reason.

With her dream of being a star on the stage beginning to materialize and her life running according to plan, Jane was surprised when she started developing a severe sensitivity to the stage lights, forcing her to take breaks during rehearsals and causing her to leave performances with splitting headaches. As time passed, her skin acquired a reddish hue even heavy stage makeup couldn’t hide. Wounds caused by the sun disfigured her body, but she ignored them knowing her dream was so close. On the opening night of her leading role in “South Pacific,” Jane collapsed and had her first seizure. She was rushed to the hospital and the show went on without her.

Repeatedly admitted with acute vomiting and abdominal pain following a seizure and photosensitivity, Jane became accustomed to the inside of a hospital. Doctors came and went, all puzzled by her mysterious attacks. Suffering seizures and pain the would-be actress was forced to abandon her histrionic ambitions.

At age 43, Jane went through a particularly torturous seizure followed by threateningly low blood pressure. Several minutes later, the nurse morbidly documented: “Cause of Death: circulatory shock.”

Photosensitivity, reddish urine and skin, hemolytic anemia, an enlarged spleen, and abdominal pain are among the symptoms seen in the unlucky few born with Congenital Erythropoietic Porphyria (CEP), also known as Gunther’s disease, after Hans Günther, the first to describe this condition (Lin, 2013).

Gunther’s disease is a homozygous recessive metabolic disorder that affects heme, an essential compound that gives blood its red pigmentation and aids in oxygen transport. The cause of Gunther’s disease is attributed to a mutation on chromosome 10 that encodes for enzymes necessary for heme production. The mutation causes a deficiency of these enzymes and a consequent abundance of other enzymes called isomer I porphyrins, which accumulate in the skin and tissues. Porphyrins are photosynthesizers, and when the skin is exposed to light, they react to form uroporphyrin I which damages the tissues (Lin, 2013).

Gunther’s disease is rare. Treatments exist, but are demanding of the patient and indefinitely effective. Scientists were essentially in the dark until a common critter shed light on the topic: the fox squirrel.

[Photo: “Fox Squirrel (Sciurus niger)” by Franco Folini, License: CC BY-SA 2.0]
Hope Hops Forward…

Fox squirrels are renowned for their gregarious, playful nature and wispy tails, but in the scientific community, they are more famous for their enzyme imbalance.

In 1937, William J. Turner turned to the Carnegie Museum for access to its extensive bone collection. Turner knew that porphyrins fluoresce under ultraviolet light, so any porphyrin culminations would appear red or pink. Upon examining thousands of animals’ skeletons, he identified that the largest appearance of glowing red bones occurred in Sciurus niger, the fox squirrel, indicating a parallel between Gunther’s disease in humans and squirrels (Turner, 1937).

Scientists Ephraim Levin and Vagn Flyger further investigated this finding in 1971. They took tissue samples from grey squirrels, which do not exhibit signs of Gunther’s disease, and fox squirrels. They found that the presence of uroporphyrinogen III in tissue extracted from fox squirrels is significantly smaller than in grey squirrels. Thus, as in humans, the deficiency of this enzyme explained the surplus of uroporphyrin I (Flyger & Levin, 1971).

Two years later, the two scientists followed up in a second study which revealed more similarities: staining of the teeth and bones with uroporphyrin I, accumulation of the enzyme in soft tissues and in excrements, and fluorescence of red blood cells. In addition, they found that the concentration of porphyrin in the spleen, blood, and urine of fox squirrels fell within the ranges seen in humans affected by Gunther’s disease. However, the most remarkable finding was that although fox squirrels exhibit indicators of Gunther’s disease, they do not suffer from the adverse effects as humans do (Flyger & Levin, 1973).

Fox squirrel skull under visible light (left) and UV light (right)
[Photo: “S. niger skull” by VMNH Paleontology Lab, License: CC BY-NC-SA 3.0 US]
More recently, Alton Dooley Jr. and Nancy Moncrief of the Virginia Museum of Natural History have drawn attention to the relationship between the fox squirrel and Gunther’s disease for paleontological use, which will hopefully give fruit to more research in a medical context and, eventually, a cure (Dooley & Moncrief, 2012).

Next Up

Scientists and patients hope that, with this relatively new animal model, the cure for Gunther’s disease is not too far away. Already, Turner, Levin, and Flyger’s findings, have led to experimental bone marrow transplants which were successful in a few cases. Additionally, blood transfusions to suppress heme production as well as spleen removal have helped some patients (American Porphyria Foundation, 2010).

Realistically, a cure for Gunther’s disease is still many years off. For now, patients can only look out their windows and hope that the fox squirrel, leaping from branch to branch, will soon share its secret for beating the symptoms of Gunther’s disease.

In Brief:

Works Cited

This article was written by cYw20. As always, before leaving a response to this article please view our Rules of Conduct. Thanks! -cYw Editorial Staff