The Restoration of the Dire Wolf: Remarkable and Controversial
In an undisclosed location, two nine-month old, so-called dire wolf pups, named Romulus and Remus, along with a younger sister, Khaleesi, romp. Canis dirus is the Latin for “terrible wolf”. The anglicized “dire” is derived from dirus. However, Canis dirus has been reclassified Aenocyon dirus. It is not a wolf; rather, it is more closely related to the African Jackal. Their genetic lineage, apparently, diverged significantly from wolf species around 6 million years ago. So-called dire wolves were thirty-pound canids present in the North American paleontological record from at least 250,000 to about 13,000 years ago, the end of the Pleistocene epoch. California’s Rancho La Brea tar seeps contain numerous dire wolf fossils.
Colossal Bioscience sequenced the genome of the dire wolf from the DNA of a 13000-year-old tooth and a 72000-year-old bone. With that template, they used the gene editing technique CRISPR to modify the genome of the cell of a gray wolf to include some features of the dire wolf. The development of this gene editing technique garnered the 2020 Nobel Prize in Chemistry for Jennifer Doudna of U.C. Berkeley and Emmanuelle Charpentier of the Max Planck Unit for the Science of Pathogens in Berlin. The first Nobel Prize shared by two women. CRISPR, short for Clustered Regularly Interspaced Short Palindromic Repeats, is a natural bacterial “immune” system modified to be a gene-editing tool. In bacteria, it functions to protect them from invading viruses (bacteriophages) by capturing and storing fragments of viral DNA, then using this "memory" to recognize and destroy the same viruses in future infections. In the laboratory, CRISPR functions as a molecular scissors, allowing DNA to be cut and edited, precisely. It has the potential to correct selective human genetic errors and, thereby, cure certain inherited diseases. It has revolutionized biological, medical, pharmaceutical and agricultural research.
In this case, they used CRISPR to edit twenty loci on 14 genes in the genome of a gray wolf’s cell, but the resulting genome was not that of a dire wolf. It was a gray wolf with a few features of a dire wolf, such as coat color and skull size. Thereafter, they removed the nucleus from the edited cell and inserted into the enucleated egg of a domestic dog. An early embryo developed from the incubation of this egg cell in vitro. They, then, implanted the embryo into the uterus of a large domestic dog, the surrogate mother. Three such procedures resulted in three dire wolf-like pups designated Romulus, Remus and Khaleesi. It was certainly a technological achievement using reproductive cloning.
Attempts at “de-extinction” may be more controversial and less useful than preventing extinction by increasing the number of a critically endangered current species, such as the red wolf (Canis rufus). Colossal Biosciences, also, wants to restore the wooly mammoth. The large genome (circa 22000 genes) of the Asian elephant has 99.6% identity with that of the wooly mammoth, but that represents a difference of nearly 90 genes. The closest they may get would be a “mammophant”. For ecological and biological reasons, this would be a very controversial (and a very difficult) goal. Focusing on preventing extinction of threatened species and preserving ecosystems are worthier goals, many experts argue.
Fig 1A. Two newborn dire wolf pups.
Figure 1B. The dire wolf.
