Posts tagged ‘genetics’
Last year Jemima Harrison’s controversial BBC documentary Pedigree Dogs Exposed gave British dog lovers a shocking look into the ugly side of the dog breding industry. Inbreeding, exaggeration of maladaptive traits, a maniacal focus on eugenic purity and an obsession with fashion over function have wreaked havoc in far too many breeds. While the expose hasn’t yet provoked the kinds of wide-spread changes in breeding that many of us would like to see; it certainly opened a lot of eyes.
This week ABC’s Nightline aired an eye-opening episode called Best in Show? exposing the countless, needless problems caused by closed registries. As my friend Gina posted over at PetConnection:
It’s time to open these registries and get some fresh genetic material into the business of purebred dogs. And into the dogs as well. Open the registries to well-planned, scientifically sound outcrosses. You will still have your breeds as you like them, just healthier.
I couldn’t agree more. Pat the Terrierman posted some great information here — he was involved in preparing the episode. Please watch both documentaries and share them with your dog-loving friends. We owe our dogs the best health we can give them. To do that we need to provide them with a genetic heritage based on health, temperament and working ability rather than outdated ideas of exaggerated type and racial purity.
I”m getting ready for rotator cuff surgery next week and too busy to blog so here are some links to some other goodies on the web.
First, an excellent piece on the importance of restraining your dog in the car from our friends over at PetConnection.
Terrierman has a link to a full-length version of Pedigree Dogs Exposed. If you haven’t already seen it MAKE THE TIME!
My good friend Caveat provides a link to an interesting piece from the Opinion Mill on the pointlessness of debating with a closed mind.
Last, but not least, VetOnTheEdge has a ‘beverage warning’ post on pet anatomy and human squeamishness.
OKay… this isn’t really a newsflash since the story I’m writing about was published almost two weeks ago, still — I’m still going to post it as one since it appears that pretty much everyone in the mainstream media missed the key point in this story.
Back on New Years Day the New York Times reported:
THE most difficult thing about the cloned puppies is not telling them apart, but explaining why they don’t look exactly alike. This was the problem Lou Hawthorne faced on a recent afternoon hike with Mira and MissyToo, two dogs whose embryos were created from the preserved, recycled and repurposed nuclear DNA of the original Missy, a border collie-husky mix who died in 2002.
Mr. Hawthorne, who is 48, is highly invested in the notion of likeness. With clones, after all, what good does similar do? It is Mr. Hawthorne’s biotech company, BioArts, which is based here in the Bay Area but has arrangements with a laboratory in South Korea, that performed the actual cloning.
He also has particular reason to be sensitive to questions that touch on the authenticity of the clones, given the history of his chief geneticist, Dr. Hwang Woo Suk of the Sooam Biotech Research Foundation in South Korea. Dr. Hwang is perhaps best known for fraudulently reporting in 2004 that a team he led had successfully cloned human embryos and stem cells. After the false claims were unearthed, he was fired by Seoul National University, where he did his research as a professor. But he is also widely acknowledged for having been involved in successfully cloning an Afghan hound in 2005.
A clone is defined as a genetically identical organism, cell, virus or DNA molucule derived from the reproduction of a singleprogenitor through asexual means. Plants are regularly cloned through leaf cuttings but cloning animals is a lot more difficult. We can’t cut the leg off, say, a slamander and then coax that leg to sprout a new creature (though in some cases the salamander can at least grow a new leg to replace the amputated one). No, cloning animals is a lot of work. To clone an animal you need to start with an unfertilized egg cell. You must then replace that cell’s nucleus with the nucleus of a diploid cell (i.e., one that has two homologous copies of each chromosome) of the animal to be cloned. Then you implant that that egg cell, which has – in effect, been ‘fertilized by two identical copies of the donor’s DNA and implant it in the womb of the surrogate. The important issue here is that while all of the nuclear DNA for the new organism will be identical to that of the donor — the mitochondrial DNA of the cloned individual will come from the egg cell donor.
While it may not govern traits like height, hair color or an innate fondness for polka music, mitochondrial DNA are believed to be important in the transmission and expression of many genetic disorder. Acquired mutations in mitochondrial DNA are also believed to play a key role in aging. And this may be a vital factor in cloning. Dolly, the famous cloned sheep died an early death. She was euthanized at the age of six (most sheep live 10 to 12 years) because of early onset arthritis and lung disease.
The mitochondrial DNA issue isn’t news to Hawthorne, the Times reports:
Elizabeth Wictum, associate director of the Veterinary Genetics Laboratory at the University of California, Davis, said that earlier this year, she and her staff had taken sets of DNA extracts from Mr. Hawthorne’s puppies and compared them with stored samples of Missy’s DNA, and concluded that the results were “consistent with clones.”
“The puppies had the same nuclear DNA as Missy, and different mitochondrial DNA, which is what you get from a cloned animal,” Ms. Wictum said. “If somebody were trying to, say, sneak in two samples from the same dog or an identical twin and claim that one was a clone’s, there would be no differentiation between the nuclear and mitochondrial DNA.”
Add in the develomental differences that can occur due to in vitro conditions and the fact that you can never even come close to replicating the environmental conditions that the original pet was raised in and it seems obvious that a clone can’t possibly be identical to its parent. There can be many differences between a clone and its single parent — and some of these differences may be vitally important. Cloning is still very much in its infancy and it’s difficult to say how it will be used in the future. Today much research is focused on tissue cloning. Possibly safer and certainly a lot less controversial than the cloning of entire animals, research on things like hair transplants, donor organs and meat is moving forward as is related work on genetically modifying animals to produce drugs and antibodies in their milk or eggs.
At a price tag of $170,000 each, I don’t see a big future for cloned dogs. And I’m’ thankful for that.
From GenomeWeb news:
NEW YORK (GenomeWeb News) – A new mutation detected in dachshunds is providing insights into the genetics behind a group of devastating eye diseases.
In a paper appearing online in Genome Research last night, investigators from Norway, Sweden, and the US used genome-wide studies of just over a dozen dachshund sibling pairs to identify a new mutation linked to eye diseases called cone-rod dystrophy. The mutation, in a gene called NPHP4, is helping researchers pinpoint the molecular changes underlying some forms of the eye disease and, they say, may ultimately lead to new therapies.
“This gene has been associated with a combination of kidney and eye disease in human patients,” co-senior author Frode Lingaas, a researcher at the Norwegian School of Veterinary Science, said in a statement. “Here, we found a mutation that affects only the eyes, suggesting that this gene might be a candidate for human patients with eye disease only.”
Cone-rod dystrophy refers to a set of degenerative eye disorders in which the retina loses photoreceptor cells over time. Because these cells help the eye detect bright light, photoreceptor degeneration eventually leads to a condition known as “dayblindness.” It can also result in total blindness in the long run. So far, though, just a handful of cone-rod dystrophy genes have been discovered in humans.
Scientists test specially designed sunglasses
to aid the vision of a dachshund suffering
from dayblindness caused by inherited cone
-rod dystrophy. (Credit: Photo courtesy of
Frode Lingaas, Norwegian School of Veterinary
Sciency Daily reports:
In this study, scientists led by Dr. Frode Lingaas of the Norwegian School of Veterinary Science and Dr. Kerstin Lindblad-Toh of the Broad Institute of MIT and Harvard have identified a mutation in a novel gene for early-onset CRD in standard wire-haired dachshund by genome-wide association mapping of a dachshund family.
Eye disorders are one of the most frequently inherited disorders in dogs, however canine CRD is limited to only a few breeds. A gene mutation had previously been associated with CRD in the miniature long-haired dachshund, while a genetic basis for CRD in the standard wire-haired dachshund and the pit bull terrier remained unknown.
Lingaas noted that identification of causal mutations for diseases has practical implications for dogs, as genetic tests could be implemented to avoid new cases of the disorder and reduce the frequency of the mutation in the population. Furthermore, this investigation of the genetic basis for CRD in dogs could facilitate the development of treatments for humans
The number of studies finding parallels between human and canine genetic disease – and modes to screen for and treat these disorders in both species – seems to be snowballing lately – and the happy results often prove to be a benefit to us and to our canine companions.
Kudos to Dr. Lindblad-Toh and others who are conducting these studies. We had the opportunity to correspond with Dr. L-T earlier this year when our Zorro’s end was near. The old man was afflicted with several different genetic disorders and when she contacted us we were glad to provide the laboratory data and blood samples she needed for her research. It was devastating to lose the old fellow – participating in her research gave us a small ray of hope that his passing might help other dogs, or humans, in the future.
More news in comparative medicine. This time the story involves humans helping other primates. EurekAlert reports that:
A medical test developed to detect an overload of iron in humans has recently been adapted to screen for the condition in some distant relatives: diminutive monkeys from South America, according to veterinarians at the Wildlife Conservation Society.
The test—which is now used to screen for elevated iron levels in marmosets and tamarins (callitrichidae) —is a recent example of how advances in human health can be applied to animals in zoological parks and in the wild. The study, titled “Hematologic Iron Analyte Values as an Indicator of Hepatic Hemosiderosis in Callitrichidae,” appears in the most recent edition of the The American Journal of Primatology.
“With this test, we can easily and safely monitor the iron levels in marmosets and tamarins for early identification of individuals that may be predisposed to develop hemosiderosis, an overload of iron in the body, despite the low iron diet that has been fine-tuned to the unique requirements of these species,” said Dr. Kristine Smith of the Wildlife Conservation Society’s health programs and lead author on the paper.
Tamarin and marmoset monkeys are able to absorb iron very efficiently from their food and are susceptible to developing high levels of iron in their system. This diagnostic test, also used in humans, is now being implemented as part of the periodic physical exam given to the tamarins and marmosets in WCS’s Bronx Zoo. This condition is also common in humans, with up to 10 percent of people of European origin possessing the gene which could lead to hemosiderosis. If necessary, veterinarians and curatorial staff can treat abnormalities in iron levels with minor dietary adjustments tailored to the individual animal’s needs.
A story in this week’s BBC News states that:
A global review of the world’s primates says 48% of species face extinction, an outlook described as “depressing” by conservationists.
“It is quite spectacular; we are just wiping out primates,” said Jean-Christophe Vie, deputy head of the IUCN Species Programme.
He added that the data was probably the worst assessment for any group of species on record.
“The problem with these species is that they have long lives, so it takes time to reverse the decline. It is quite depressing.”
Considering that habitat destruction and hunting by humans are believed to be the two main causes of the decline, finding ways to adapt human medical tests and treatments to our primate cousins is just one way we should help. Reducing or reversing habitat destruction and ending needless hunting must also be implemented – and the sooner the better.
Using human health tests and treatments on wild animal species may help prevent significant population losses, but in the long run we should exercise caution in interfering with natural selective and reproductive processes. If we interfere too much we could break down the protective barriers against genetic disorders created by millions of years of natural selection, and the world could end up with primate populations threatened by inherited disease.
Let’s take a lesson from the problems we see with inherited disease in domestic dog populations. In the long run, natural selection trumps artificial selection.
We always suspected that cats were evil…
Back in April we posted that owning a dog can make you a healthier person. A dog encourages you to exercise and a healthy emotional bond with your four-legged friend is good for your soul – and your body. There is also evidence that man’s best friend is also good for his children too, for young children who live with a dog appear to get an immune-system boost against asthma and other allergies.
What do our feline friends do for us? Well, from an article in NHS Choices:
“Own a cat and run the risk of eczema”, warns The Daily Mail today. They say that a study looking at 800 British and Danish babies has found that “those with mutations in a certain skin protein gene were twice as likely to get eczema in their first year. If they lived with a cat they were almost certain to develop it”. The article quoted the author of the research, Dr Hans Bisgaard, as saying, “If you haven’t got the mutation, it doesn’t matter if you have a cat. But if you have the mutation, a cat has an effect.”
Science Daily reports:
Eczema runs in families and evidence suggests it is caused by genetic and environmental factors. The same researchers recently discovered that two common “loss-of-function” variants in the gene encoding filaggrin (FLG) predispose people to eczema. Filaggrin is a protective protein normally found in skin. It acts as a physical barrier to potentially harmful substances in the environment. The researchers hypothesized that inheriting one or two defective FLG genes might weaken their physical barrier, affecting their response to environmental substances.
Dr Hans Bisgaard and colleagues from the Danish Paediatric Asthma Centre, and universities in the UK carried out the research. It’s fascinating work and the results of the study may help us further assess the connection between genes, environment and nurture in the mental and physical development of humans and animals.
And it gives us just one more reason not to have a cat.
Coming in tomorrow’s issue of Genetics Magazine in an interesting follow up to the historic studies on canine behavioral genetics summarized in a well-known book by Scott and Fuller, a study conducted by staff at the Waltham Center for Pet Nutrition, the University of Utah, Sundowner’s Kennels, and the National Human Genome Research Institute on how genes control size, lifespan, and even complex breed behaviors like pointing and herding.
The entire dog genome was first sequenced in 2005. Since then, canine genetic studies have focused primarily on genes controlling basic traits like coat color and inherited diseases. These studies have necessarily focused for the most part on just a single breed at a time. To study the genetic basis of behavior, a scoring system was developed to rate 148 breeds for traits like herding, pointing, boldness, excitability and trainability.
Dog breeds have largely developed through stringent selection to conform to specific stereotypic criteria of appearance and behavior and the results of the study strongly indicate that most breed-related (phenotypic) standardized (stereotypic) behaviors observed in dogs are the result polygenic factors.
DNA samples isolated from 148 dog breeds were used to associate SNP (single nucleotide polymorphism) markers with breed stereotypes. Size was initially used as a trait to test the method and it allowed the team to identify six significant quantitative trait loci (QTL) on five chromosomes that appear to control the size of dog breeds.
Greg Barsh of Stanford University in California, US, says the research certainly pushes forward the genetic analysis of dog personalities, but he cautions that behaviours may be difficult to explain genetically.
“We’ve learned from human genetics that classifying behaviour is not so easy,” he says. Just as one person’s schizophrenia differs from another’s, collies might herd differently than sheepdogs.
I find it a bit ironic that Dr. Barsh chose to use a comparison of the working styles of ‘collies’ and ‘sheepdogs’ (and frankly, I’m not sure at all what he’s referring to with either term) to illustrate the point that the genetic classification of behavior is, at best, in its infancy — IMO it’s a bit like saying that apples aren’t pears. Still, the complex nature of the genetics of behavior is not surprising and it does much to emphasize the importance of considering temperament and performance in breeding every litter of dogs.