Posted on April 11, 2019 at 10:50 PM
By Jon Holmlund
This week’s news is that a group of Chinese researchers have
birthed and studied a small number of rhesus monkeys that were
“transgenic” for a human gene associated with brain development. In this work, monkey eggs (oocytes) were
altered by adding the human form of a gene that is believed important to the
development of the brain. This gene is
one of the relative few that is different between humans and primates (monkeys,
as in the work described here, or apes, such as chimpanzees or gorillas). That gene is abnormal in cases of human
babies with small heads and brains, making it a good candidate for a gene that
is critical to normal human brain development.
The gene was added to the monkeys’ egg cells using a viral
delivery mechanism. The monkey genes
were not, in this case, “edited” to the human form using CRISPR/Cas9. (Presumably, that experiment is coming.) Using the altered eggs, 8 monkey embryos were
then conceived and implanted in females.
Six of these survived to birth, and 5 of them lived long enough to do
tests on their brains. These monkeys’
brains looked, on imaging studies and under the microscope, more like human
brains than normal monkey brains do, and these monkeys’ brains developed more
slowly than normal, mimicking the human situation, in which brain development
occurs largely in late pregnancy and then a lot more in infancy and
childhood. The five surviving monkeys
also did better on some short-term memory tests than did “natural”
monkeys given the same tests side-by-side.
How strong this finding is appears debatable; the number of monkeys
tested was small, and your correspondent cannot say how useful the tests are.
The scientists also took sperm from these transgenic monkeys
and conceived three other monkeys (again, using IVF, they apparently did not
try to breed the animals), all of which were sacrificed before birth, and whose
brains apparently showed some of the same features as their
Genetically modifying non-human primates is generally frowned
upon in the West, largely on grounds of the animals’ welfare, but in China,
it’s full-speed ahead. The Chinese
scientists apparently agree with Western scientists that the brains of apes (chimpanzees)
should not be genetically altered because they are too much like us humans for
comfort. Monkeys are not so close, in
the Darwinian schema.
The investigators in this case think they are learning important
lessons about the genetics of human brain development in a model that is enough
like humans to be informative. They also
think they are shedding light on human evolution (assuming that the evolutionary
model is correct). Those conclusions
seem to be a reach. The gene in question
had already been identified as a candidate of interest, and its association
with brain development arguably could be studied in other ways, within the
ethical bounds of human subject research.
And it seems unlikely that a creature such as created in this work would
ever have arisen from random mutation. Rather,
these transgenic monkeys seem to be an artifact of the investigators’ design,
with uncertain relevance.
In any event—off to the races. Anticipate more work to alter monkeys’, if
not eventually apes’, brains genetically.
They might get something really interesting—and hard to know quite what
to do with.