Same Gene Guides Cheetah and Tabby Cat Coat Patterns

A mutation in one gene produces tabby cats with blotches and cheetahs with stripes

By Sarah Zielinski

smithsonian.com
September 20, 2012

image: http://blogs.smithsonianmag.com/science/files/2012/09/kaelin6HR_470x251_scaled_cropp.jpg

image: http://blogs.smithsonianmag.com/science/files/2012/09/kaelin6HR.jpg

A genetic mutation determines whether a tabby cat is a mackerel (top row) or blotched (bottom row). (Image courtesy of Helmi Flick)

Tabby may be a colloquial term for a female kitty, but it’s more properly the name for the common stripey pattern on a domestic cat’s coat. Those tabby markings come in two main varieties: proper vertical stripes of dark on a light background, known as the mackerel pattern, and a blotched variety consisting of less-organized, dark whorls. Now scientists from Stanford University and elsewhere have identified the gene that determines whether a tabby is mackerel or blotched and found that the same gene also can make a cheetah a king. The study appears in today’s issue of Science.
“We were motivated by a basic question: How do periodic patterns like stripes and spots in mammals arise?” study co-author Gregory Barsh, an investigator at HudsonAlpha and a Stanford geneticist, said in a press release. “Until now, there’s been no obvious biological explanation for cheetah spots or the stripes on tigers, zebras or even the ordinary house cat.”

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Barsh and his colleagues examined DNA taken from feral kitties in Northern California that were captured, sterilized and released (a common practice employed to control the size of feral cat populations) and from tissue samples collected by the City of Huntsville Animal Services group. All the mackerel tabbies they studied had a normal version of a gene the researchers named Transmembrane Aminopeptidase Q (Taqpep) while all the blotched tabbies had a mutated form of the gene.
The Taqpep gene establishes the pattern of a cat’s coat while a kitty is still in the womb, likely by determining the level of expression of another gene–Endothelin3 (Edn3)–that drives the shade produced by a hair cell (lots of Edn3 results in darker hair). The form of the pattern is actually established out of a random interaction of chemicals that ends up producing something that looks non-random–British mathematician Alan Turing first proposed this theory in 1952, and it was later simulated in computer models and earlier this year scientists discovered the chemicals in question.
Still to be determined, though, is why some domestic cats don’t have any pattern at all despite the status of their Taqpep gene. (On a side note, blotched tabbies are sometimes called “classic” tabbies but not because they’re more common. The blotched pattern is a more recent mutation; the original wild ancestors of domestic kitties were mackerels similar to Old World wild cats of today.)
But domestic cats aren’t the only cats that can vary in coat pattern, of course. Most cheetahs, for example, are the common spotted variety, but a few rare cats are known as king cheetahs, and these sub-Saharan kitties have dark stripes running along their backs (see below). When the researchers examined skin and blood samples taken from captive and wild cheetahs from South Africa and Namibia, they found that not only did the cats have the same Taqpep gene as domestic kitties, but also the gene worked in a similar way on the wild cats’ coats. A normal Taqpep gene produced the regular spotted cats but a mutated Taqpep merged the spots into stripes, just as the gene had merged the tabby stripes into blotches.
Though scientists cannot yet explain how the zebra got its stripes, at least now they can explain how the king cheetah got his.

image: http://blogs.smithsonianmag.com/science/files/2012/09/kaelin4HR.jpg

The difference between a normal spotted cheetah (left) and a rare king cheetah (right) is a mutation in a single gene. (Image courtesy of Greg Barsh, from the Ann van Dyk cheetah preserve)

Friday, September 11, 2015

How PetsCanProtect Against Allergies In Children

https://www.yahoo.com/parenting/how-pets-can-protect-against-allergies-in-kids-128844971122.html

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By Kathryn Doyle

In a small, preliminary study, infants in households with furry pets were found to share some of the animals’ gut bacteria - possibly explaining why early animal exposure may protect against some allergies, researchers say.

The infants’ mothers had a history of allergy, so the babies were at increased risk too, and it was once thought that pets might be a trigger for allergies in such children, the authors point out in the Journal of Allergy and Clinical Immunology.

"Earlier it was thought that exposure to pets early in childhood was a risk factor for developing allergic disease,” said Dr. Merja Nermes of the University of Turku in Finland, who coauthored the research letter. “Later epidemiologic studies have given contradictory results and even suggested that early exposure to pets may be protective against allergies, though the mechanisms of this protective effect have remained elusive."Adding pet microbes to the infant intestinal biome may strengthen the immune system, she told Reuters Health by email.

Nermes and her colleagues wanted to see how, exactly, exposure to household pets might influence children’s immune systems.

The researchers used an ongoing probiotic study of pregnant women with a history of allergies. From the participants, they selected 51 infants of families with furry pets (dogs, cats or rabbits) in the home and 64 infants with no pet in the home, as a comparison group.The study team collected fecal samples from diapers when the babies were one month of age and these were tested for the DNA of two types of Bifidobacteria that are found specifically in animal guts: B. the rmophilum and B. pseudolongum.

One third of infants from the pet-exposed group had animal-specific bifidobacteria in their fecal samples, compared to 14 percent of the comparison group. It’s not clear where the infants without furry pets at home acquired their gut bacteria, the authors write.When the babies were six months old they had skin prick tests to assess allergies to cow’s milk, egg white, flours, cod, soybeans, birch, grasses, cat, dog, potato, banana and other allergens.

At six months of age, 19 infants had reactions to at least one of the allergens tested. None of these infants had B. thermophilum bacteria in their fecal samples.

Past research has linked growing up on a farm or exposure to dog dander indoors with protection against airway allergens, the study team writes. Other studies have found increased "richness and diversity” in the gut microbes of kids exposed to household pets.

“When infants and furry pets live in a close contact in the same household, transfer of microbiota between pets and infants occurs,” Nermes said. “For example, when a dog licks the infants face or hand, the pet-derived microbiota can end up via the mouth into the infants intestine.

"Human-specific Bifidobacteria have beneficial health effects, and animal-specific strains may also be beneficial, she said. It is still unclear, however, if exposure to these bacteria protects against allergies later in life, she said.

"Future research is needed to assess if these infants develop less atopic dermatitis, asthma, or allergic rhinitis later,” she said.

Pediatricians should not advise parents to avoid having pets in the home for fear of allergies, she said.

“If a family with a pregnant mother or an infant wants to have a pet, the family can be encouraged to have one, because the development of allergic disease cannot be prevented by avoiding pets,” she said.