BioQuakes

AP Biology class blog for discussing current research in Biology

Tag: dogs

What is the Real Reason Dog Breeds Vary in Size?

Dog (Canis lupus familiaris) (6)

Do you like big dogs or small dogs? This question is frequently asked, but how did we even come about having this option? Ancient domesticated dogs in the past 30,000 years differed in size but nothing as extreme as the modern size differences. Dogs now can range from 40 times in size, and these drastic differences emerged just in the past 200 years as humans started establishing more and more breeds. In a study conducted by Ewen Callaway, he looked at why dogs differ so much in size and how a mutation could be the cause of this. The mutation behind all of this has been traced all the way back to ancient wolves. It lies near a gene called IGF1(insulin growth factor) which researchers found to have a major role in the size variations of domestic dogs. IGF1 is a hormone that manages the effects of growth hormones and is primarily produced by the liver so liver diseases can cause its levels to change.

One variant stood out when comparing the region around IGF1 and dog sizes. This variant “lies in the stretch of DNA that encodes a molecule called a long non-coding RNA which lives in controlling levels of the IGF1 protein.” A gene variant is a permanent change in the DNA sequence that makes up a gene. Variants can be inherited from a parent or can just occur during a person’s lifetime. If a variant is inherited from a parent they are present in pretty much every cell of the body while a variant that occurs during someone’s lifetime is present only in certain cells. Most variants that lead to disease are not common in the general population; however, some variants occur often enough in the general population to be considered common genetic variations. Examples of this would be eye color, hair color, and blood type. Even though DNA variants can be seen as a negative, as it is explained not all variants produce fatalistic effects.

There are two identified versions (alleles) of the variant, which Callaway identified. An allele is a form of a gene and each organism inherits two alleles, one from each parent. Dogs who have two copies of one allele typically weigh more than 55 pounds and have higher IGF1 protein levels in their blood. Whereas, dogs with two copies of the other allele tend to weigh less than 33 pounds. In addition, there are dogs with one copy of each version and they tend to be intermediate in size. Researchers determined that the same relationship was present in other canids as well, such as foxes, coyotes, and wolves.

Protein IGF1R PDB 1igr

IGF1 structure

The allele linked to small-bodied animals is seen to be much more evolutionary than alleles linked to large-bodied animals. Coyotes, jackals, foxes, and a lot of other candids have two copies of the small version, suggesting that this variation could have been present in their ancestors. However, it is not as clear as to when the large-bodied allele formed. It has been traced back 53,000 years ago to an ancient wolf living in Siberia, and since then has been found in other ancient wolves. Robert Wayne, an evolutionary biologist at UCLA, states that the view used to be that animals that have a small body size can be linked to genetic changes that could be unique to domestic dogs. This study could be a sign that dogs were domesticated from smaller wolves rather than present-day gray wolves.

Overall researchers have discovered a big part as to why dogs vary so much in size, however, the story of dog size is far from complete as IGF1 proteins only make up 15% of the difference in dog size. Even though this is such a small percentage, we are 85% closer to finding the whole meaning.

Is the Difference in Size of a German Shepherd and a TeaCup Poodle Due to a Gene Mutation?

Out of all the mammals on the planet, dogs differ in size the most. The biggest dog breeds are around 40 times bigger than the smallest breeds. A recent study has shown that this occurs because of a gene mutation that lies near a gene called IGF1. This gene was originally flagged 15 years ago as playing a major role in the variations of dog sizes. Ancient dogs that were domesticated from wolves in the past 30,000 years differ very little in size, however, in the past 200 years the largest difference in breed size has been recorded as people began to breed the more modern dog breeds during this time. 

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The IGF1 gene was studied comparing to body size of dogs and wild canids. There was one variant that stood out to researchers; this gene mutation was found in a stretch of DNA that works to encode a molecule called a long non-coding RNA. Long non-coding RNAs are a type of mammalian genome that lack protein coding capabilities. Specifically, the long non-coding RNA that was found to affect the size of dog breeds is involved with the levels of the IGF1 protein in the dogs bloodstream. As we learned in AP Biology, mutations in genes occur during the DNA replication phase of mitosis. Mitosis is the division of one mother cell into two daughter cells. DNA replication happens during the S phase of interphase. During this phase, the single stranded chromosome will duplicate and turn into two identical sister chromatids. The mutation will occur when copying the DNA, which would cause the sister chromatids to not be identical. 

This study identified that there are two alleles of this variant. Dogs carrying two copies of the small-bodied allele were most likely to weigh 15 kilograms or less, meanwhile, dogs carrying two copies of the large-bodied allele were most likely to weigh more than 25 kilograms. Dogs that carry one copy of each allele tend to be of an intermediate size. Additionally, dogs containing the larger-bodied allele contain  higher levels of the IGF1 proteins in their bloodstream compared to dogs who carry the smaller-bodied allele. Researchers also recorded a similar relationship in wild canids.

Prior to this study, researchers believed that certain dog breeds were smaller-bodied because of relatively new genetic changes. However, scientists now believe that the smaller-bodied allele is evolutionary and is actually much older than the bigger-bodied allele. They believe this to be true because the smaller-bodied allele was found in coyotes, foxes, jackals, and other smaller canids; this leads us to believe that this allele was present in one common predecessor. More studies must be done to truly determine how these variants impact the levels of  IGF1 proteins in a mammals bloodstream. The IGF1 gene only accounts for about 15% of size variation in dogs, so there is still much more research do be done. This study is just the beginning to really figuring out how we came to have dogs as large as German Shepherds and as small as TeaCup Poodles. Which allele do you think your dog has?

 

Neurological Implications of a Dog’s Brain

In this article, the brains of dogs and their neurological capacity is explored.

Biology Letters published their results on the mechanisms of a dog’s brain.

Gregory Berns, a senior on this study stated, “Our work not only shows that dogs use a similar part of their brain to process numbers of objects as humans do — it shows that they don’t need to be trained to do it.”

In the study, an fMRI was used to scan the dogs’ brains. On these images, it was shown that the parietotemporal cortex produced a lot of contrast and response.

This system supports the ability to rapidly estimate of objects in a scene, such as the number of threats approaching or the amount of food available.

However, much of the research conducted included an intensive training of the dogs.

Berns is founder of the Dog Project which is an organization that studies the evolution of dogs. The project was to first to train dogs to voluntarily enter an fMRI scanner.

Berns states his findings, “Our results provide some of the strongest evidence yet that numerosity is a shared neural mechanism that goes back at least that far.”

Overall this study found that “new canine numerosity study suggests that a common neural mechanism has been deeply conserved across mammalian evolution.”‘

Is Training Your Dog Useless?

For about 100 years, humans have been trying to train the domestic animals, such as dogs, that they live with. They put in lots of time and effort for teach their dogs simple tricks such as sitting, lying down, and staying in place. While it is rewarding to have a dog listen to commands after teaching and training them, this may not as great of an accomplishment as previously thought. As a dog owner myself, this had me worried, but as a recent ScienceNews post says, the answer to how to train a dog may just lie in their genetics. 

Training Dogs May Be an Outdated Practice

This was the hypothesis that Noah Snyder-Mackler had as he and a few other colleagues from the University of Washington in Seattle attempted to prove its legitimacy. Primarily, the group collected data about 101 different breeds of dogs from two dog genotypes databases and a survey titled C-BARQ, a survey where dog owners submit information about behavior from their dogs such as aggressiveness or ability to listen. As the data came in, there were over 14,000 submissions and they were all scored on 14 different traits. Overall, Snyder-Mackler and his group found that poodles and border collies had higher traits of trainability and Chihuahuas and dachshunds had higher traits of aggressiveness. However this does not means that training a dog is rendered useless since there was about a small correlation, 50%, between energy level and fearfulness.

Aggression Could Have Been Caused from Genetics

Next the researchers tried to see if certain traits correlated with certain genes. After doing more research they found that no genes specially aligned with a breeds behaviors, but this does not mean that the research is useless since even though this  does not show that a gene brings about a behavioral trait, but it shows that this subject needs more research to be able to determine the validity of Snyder-Mackler’s original hypothesis.

Dogs are very complex genetically and therefore behavioral traits are both a combination of genetics and training. As Carlos Alvarez, a researcher at the Nationwide Children’s Hospital in Columbus, Ohio, says, “Dogs are a really powerful system to investigate the genetics of many traits and diseases because generations of domestication and breeding have simplified their genomes. This study shows that behavior is no different.” Overall while this research is just the start and is incomplete in totality, it shows that there is much more to discover regarding this topic. If you have any traits that you think correlate with either your dog’s genes or breed, please post a comment a explain why.

 

Hope for Duchenne Patients?

Duchenne muscular dystrophy is a genetic disorder currently without a cure. It causes progressive muscle degeneration and weakness. Duchenne Muscular Dystrophy, or DMD, is characterized by an absence of dystrophinDystrophin is a protein that keeps muscles intact, which when absent lead to a loss of muscle function and strength. This lack of dystrophin begins in early childhood between ages three and five mostly in males with 1 in 5,000 males inflicted and a rare

File:PBB Protein DMD image.jpg

Dystrophin Protein

occurrence in females. By later ages, individuals are forced into wheelchairs and put on respirators as their diaphragms weaken until an early death usually in their 20’s or early 30’s due to heart failure or an inability to breath.

Despite not having a cure for Duchenne Muscular Dystrophy, scientists are performing the first trials in large mammals, dogs. Many dog breeds can also be inflicted by the lack of dystrophin and thus have Duchenne Muscular Dystrophy. Four of these inflicted dogs have been chosen at only one-month-old to be treated using a harmless virus called adeno-associated virus or AAV. This harmless virus is delivering the CRISPR Cas9 protein gene-editing components to make a single strategic cut in faulty DNA to “exon 51, one of the 79 exons that comprise the dystrophin gene.”

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Right Affected Individual        Left Unaffected Individual

These dogs were tracked and within several weeks of the CRISPR editing the missing protein was reported in muscle tissue throughout the body with as much as 92% correction in the heart and 58% correction within the diaphragm, which is the main muscle needed for breathing. While there is a clear success in the current trials with improvements greater than 15%, they are still far from human clinical trials as the question still remains if the stable levels of dystrophin do not have adverse side effects. The corrections made using CRISPR was previously noted in having successfully corrected mice and human cells only increasing the hope provided by these trials. The trial is already being called “promising” and might one day be considered “groundbreaking.”

Not only providing hope for those with DMD, but these trials also provide a significant step towards single gene editing to treat an incurable disease. While larger studies are still to be conducted, the individuals working on this study at the Royal Veterinary College in London and UT Southwestern Medical Center in the United States are eager for the study to grow. One such leader in this study, Dr.Olson from UT Southwestern has even gone as far as spawning a biotechnological company called Exonics Therapeutics Inc. with the hope of further optimizing this technology for the clinic on top of his role at the University.  

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Doggone Average

Studies have shown that, when compared to other social hunters and carnivorans (an order including dogs, wolves, bears, lions, and hyenas), dogs are not as exceptionally clever as humans might think. Researchers from the University of Exeter and Canterbury Christ Church University tested dogs in trials against other animals in this order. They set out to prove how “clever” dogs really were.

They found that, in previous tests, dogs were commonly compared to chimpanzees, where they often won (which only added to dogs’ reputations). But, when these researchers tested dogs against other social hunters and carnivorans, dogs did not test so well. In fact, dogs may have been domesticated so much that their instincts are now no longer as refined as their wild counterparts. Wolves, who still must hunt for their next meal, will need more honed instincts to survive. In the end, the results weren’t a disappointment. Instead, they were a social commentary on the expectations people put on their pets.

Czechoslovak Wolf Dog “Luna” Chews on Stick

 

 

The Weirder Side of CRISPR

If you’ve been following science news at all, you’ve heard of CRISPR, the gene-editing tool which is rapidly becoming a very hot topic. Since its discovery, CRISPR has been used for some truly extraordinary things. It’s also done some other things, which stray from medical miracles into the realm of the strange.

Alphr.com reports some of the weirder projects using CRISPR. This includes manufacturing super-dogs, as well as the possibility of bringing back the woolly mammoth! This is all being done as you read this through CRISPR CAS-9

Another project mentioned in the article is an effort to create organs in pigs suitable for human transplants. This has become a larger topic of conversation, as there is always an ample need for organs, and if this project comes to fruition, waiting lists for organ transplants could possibly be abolished completely.

To read the other weird projects using CRISPR right now, check out the article.

Comment below your thoughts on this article, and the uses of CRISPR in general. I, for one, would love to see a mammoth before my own eyes!

Smile, it makes your dog happy!

Looking at your dog can bring a smile to your face, and looking at you can actually make your dog smile too!  A new study shows that dogs have an emotional response to our facial expressions; dogs like smiling faces, and don’t like angry faces. This is linked to the hormone oxytocin, which influences what and how a dog emotionally experiences what it sees. Oxytocin is a neurotransmitter, dubbed the “love hormone,” so an increase in oxytocin yields a positive reaction.

University of Helsinki researchers studied 43 domestic dogs. The dogs were presented with pictures of unfamiliar faces with happy or angry expressions. Each dog was tested twice; once under the influence of oxytocin, and once without oxytocin. The dogs reactions were determined by their gaze and pupil size, because emotions and attentiveness regulate these reactions (for more information on the relationship between pupil size and emotions, click here). According to the authors, “dogs typically focus on the most remarkable aspect of each situation, such as threatening stimuli in a frightening situation.” Therefore in the trial, dogs will focus on the most remarkable face, either the happy or angry one.

The dogs under the influence of oxytocin were more interested in the smiling faces, and the oxytocin influenced their emotional state, as indicated by their pupil size. They had a larger emotional response to smiling faces under oxytocin, because their pupils were wider. When the dogs weren’t under the influence of oxytocin, their pupils were wider when looking at angry faces, so they were more focused on and had a larger emotional response to the angry faces. The researchers concluded that oxytocin made the angry faces seem less threatening, and the happy faces seem more appealing. This is why the dogs focused on happy faces with oxytocin, and angry faces without oxytocin.

This photo is credited to Max Pixel.

To further the studies, the scientists said that more studies are needed to determine wether the results are only for domestic dogs or if the same reaction occurs with other animals. More studies should also be conducted on dogs with familiar faces, to see if familiarity would change the results of oxytocin on emotional face processing. They also added that in future studies, account of the dog breed, sex, and personality traits should be taken into account because oxytocin does not have uniform effects.

For more information, click here. For the research, click here.

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