Study in Cows Shows why Cloning Mammals Fails

Dolly was able to be cloned successfully because the technique of "somatic cell transfer" was used. However, cloning cattle is becoming difficult and the success remains low (fewer than 10% survive to birth). The main reason the cattle don't survive is embryonic death. Cloning cattle is important because it can be used to study mammalian development. 

Harris Lewin, professor in the UC Davis Department of Evolution and Ecology, conducted a study using RNA sequencing to understand gene expression in cloned cows during implantation to discover why there is a high rate of failed pregnancy for cloned cows. The study combined the French's expertise in cloning and reproductive biology with the U.S.'s expertise in functional genomics. This collaboration lead to understanding the mechanisms that account for embryonic losses at implantation. The study also provided insight on how implantation events drive the progression of pregnancy and shape the phenotypes of the cattle after they are born. 

The researchers studied the tissue of cloned cow embryos at 18 and 34 days of development and the endometrial lining of the cows pregnant with the clones. They also studied cows that conceived by artificial insemination with non-cloned cows. The study resulted in the finding of multiple genes that are expressed abnormally. This could explain why there is a high rate of death for cloned embryos. The researchers found abnormalities in the expression of more than 5,000 genes on day 18. Results also suggest that that the surviving clones were able to successful implant in the uterus and form a placenta, indicating that the losses of clones is due to problems of critical development genes in the extra embryonic tissue. The study also revealed other factors that could be leading to the death of the clones including problems with hormone signaling between the pregnant cow and the developing embryo.

I found this article to be fascinating. I thought if scientists were able to clone a sheep it would only be a short jump to cloning cows too. I didn't think that cloning cows in the same way as Dolly would be so difficult. This article makes me ask the question if any animals can be cloned the same way or if each animal has to be cloned separately. This study could possibly provide further insight to cloning other mammals. 

'Cow Gene' Explains Failure of Cloned Genes

A recent study conducted at the University of California showed a cow gene that demonstrated why most clones fail. Cloning mammals has proven to be a challenge; however, it was just twenty years ago that Dolly the sheep was successfully cloned. Using the technique of somatic cell nuclear transfer was originally how Dolly was cloned, or rather when a nucleus from an adult cell is transferred into unfertilized egg that has had its nucleus removed, and then begins cell growth by an electric shock. Recipient mothers then carry the transferred embryos until the clones are born.

The process of cloning cattle can be used to study development in mammals, and is important technology for agriculture; however, the success rate remains very low - less than ten percent of cloned animals survive until birth. Losses of the cloned animals may be due to a variety of reasons: failure during implantation of the embryo, embryonic death in general, or the possible development of a defective placenta. However, with recent developments into why there is so much reoccurring failure, it may be possible to get to the root of the issue. Scientists used RNA sequencing in order to look at gene expression in cows that had been cloned during implantation and attempt to understand the molecular mechanisms that lead to such a high rate of failure during pregnancy.



In this study, the researchers studied tissue from cloned cow embryos--all derived from the same cell line--at 18 and 34 days of development, as well as the corresponding endometrial lining of the pregnant cows. They also used cows that were not cloned, conceived using the process of artificial insemination. By use of RNA sequencing, multiple genes were found to be expressed abnormally, that could potentially lead to the high mortality rate of cloned embryos, as well as their failure to be implanted in the uterus and to develop a normal placenta. Researchers were able to find anomalies in expression of more than five thousand genes looking at the extra embryonic tissue of those of the cloned cows by day 18. Hopefully researchers will be able to use this find to uncover more developmental issues of the cloned embryo, and eventually lead to a higher survival rate.

As much as I find cloning of genes interesting, I do wonder about the possible risk factors involved, besides those listed above. It makes me very curious to see the future of these processes, and what could potentially come out of then. I also do think that cloning of genes as a whole could be a very useful practice, especially with genes that may be correlated to positive human growth and health. I'm sure that there is a lot left to learn about the future of cloning, and I am excited to see where it goes.

Are Clones Exactly the Same?

Dolly the sheep was the first successfully cloned mammal twenty years ago. After living a short life of 6.5 years compared to the average of eleven years, Dolly passed due to Osteoarthritis. This progressive disease in Dolly brought up an important question: Does cloning animals make them age prematurely? At the time, no one had an answer.

Nine years ago, four sheep, Daisy, Diana, Debbie, and Denise, were cloned from the same cell line as Dolly. Today, those sheep are happy and healthy. Now another question arises: How have Dolly’s clones lived longer?

To understand how this can happen, you must first understand the procedure for cloning. To clone, scientists use a process called “somatic cell nuclear transfer.” This process involves clearing DNA from an existing egg and replacing it with the new DNA. However, it is always possible that not the entire original DNA from the egg is removed. These little bits left behind can alter an animal’s cells, tissues, and even their behavior. These cloned sheep are perfect examples of this happening. All four look exactly like Dolly. However, Debbie has stiff joints especially on a cold day. Also, scientists can tell which MRI’s are hers, due to differences in her tissues and bones.

The topic of cloning can be a touchy one; there are benefits and downfalls of it. On one hand, threatened species can increase their population numbers through this process. On the other hand, there are many questions on if it is safe and morally correct. At the end of the day, there is clearly a lot more to learn about cloning from these sheep. Scientists hope to study cellular and molecular differences in these sheep.  

Cloning Farm Animals

Cloning is scientific process that allows scientists to copy the genetic traits of a plant or animal to create one or more living replicas. Essentially, cloning replicates the genetic make-up of the animal from which the cell nucleus was taken to produce the cloned offspring. It is distinct from genetic modification, which alters animal characteristics by directly changing the DNA sequence.The first clone was the sheep called Dolly, which happened to be a farm animal, in Scotland in 1996. Cloning has always been debatable, because the idea that the cloning could alter the meat and milk that is produced by the cloned animal. There have been multiple farm animals that have been cloned mice, mules, horses, deer, oxen, cows, pigs, dogs and cats. Overall there has been 15 mammals that have been cloned and none being a primate. Scientists expect that in the future, cloning technology will be conventionally used for duplicating breeding animals. This would grant the meat and dairy industries to take advantage of the genetic traits of prized cows and bulls without being limited by the animal’s natural life span. In 2003 the FDA (Food and Drug Administration) there was a ban on cloned animals in any phase of food production. In 2007, there was research that showed that cloning was only 10% successful. Also the prices to clone animals are extremely high, for cows it is approximitly $20,000, and to have a house cat cloned privately it is around $32,000. A Texas-based company began cloning champion horses in March 2006 that can sell for as much as $150,000 per horse. There is a controversy for the animals health, they live short lives and are normally born with deformity's. Also the host mother is at the risk of a high death rate.