We have a collaboration with the lab of Prof. Lawrence Smith, on studying the genome of horse clones! Very exciting project that Pamela explained this morning at lab meeting – and this awesome horse picture she displayed. As soon as the data is available (hard disk issues…), we will tell you more about it.

In the meantime, do you know the details of cloning Dolly, the world’s most famous sheep? She was born from three mothers and created using the technique of somatic cell nuclear transfer. The first mother provided the DNA, the second the egg and the last the uterus. In this technique, the nucleus of the egg cell is removed and replaced by one of a somatic cell from the animal to be cloned. After stimulation (with a shock), the reprogrammed egg will begin to divide. From there, there are two avenues : therapeutic cloning, where stem cells can be obtained from the clone embryo, or reproductive cloning, where the clone embryo is implanted into a host mother until birth.

High neonatal death make the process of reproductive cloning difficult, and the reasons for this remain unknown. Also, in non-human species, imprinting disorders in cloned offspring are observed, possibly linked to the absence of meiosis-specific mechanisms, or simply absence of a sperm cell. In fact, somatic cell nuclear transfer can also be done using a sperm cell, along with a fertilized egg nucleus and an enucleated egg cell, leading to a child with three biological parents. All three parents contribute genetically: dad and mom #1 contribute nuclear DNA, and mom #2 contributes mitochondrial DNA. This is called mitochondrial replacement therapy. It can be used to allow women with severe mitochondrial diseases to have disease-free children, but it still poses many ethicals, social and legal concerns. Furthermore, coordinated mitochondrial-nuclear interactions may have become highly specific over evolutionary time, so are they likely to be a problem?

Further reading

Smith et al. Benefits and problems with cloning animals. Can Vet J. 2000; 41(12): 919–924

Rideout III et al. Nuclear Cloning and Epigenetic Reprogramming of the Genome. Science. 2001; 293(5532): 1093-1098

Reinhardt et al. Mitochondrial Replacement, Evolution, and the Clinic. Science. 2013; 341 (6152): 1345-6