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Posted on September 12, 2019 at 11:28 PM

A new effort at “somatic” gene editing in China is
reported this week.  The
key summary

“As the researchers report in the New England
Journal of Medicine

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they transplanted [blood stem]
cells that had undergone CRISPR-based editing [of a gene that encodes for
a receptor, or “docking station”] into a patient with HIV and acute
lymphoblastic leukemia. While [the edited cells lasted for a long time in the
bloodstream of the HIV-infected recipient], they only made up between 5 percent
and 8 percent of blood cells. A higher percentage is needed for this to be an
HIV cure…”

In “somatic” gene editing, mature
cells, such as “adult stem cells” or diseased tissues, are gene
edited for the purples of treating a fully-formed individual with a disease.  That is what appears to be in view here.  Similar efforts are in progress to treat sickle
cell anemia and other genetic diseases. 
The ethical issues are relatively well-understood, and fit within the
regime of regulating cells-as-medicines in clinical trials of humans, under the
ethical and regulatory regime that governs the latter.

That’s in contrast to “heritable”
gene editing, which attempts to edit genes in embryos, fertilized eggs
(zygotes), or gametes (sperm or eggs) with changes that would be passed on
through the generations, as recent entries on this blog have been addressing.  The Chinese twin girls who were reported to
have undergone gene editing late in 2018 are examples of an attempt at
“heritable” gene editing.

A second
report from Nature
describes efforts to use human
“reprogrammed” stem cells, aka pluripotent stem cells, to make human
“embryo-like structures.”  This
is distinct from making a human embryo, for example in IVF, then removing
cells, likely destroying it, for use in research or to develop medical
treatments.  In conservative commentaries
in recent years, these “reprogrammed” stem cells are considered the
“ethical embryonic stem cells,” because they can’t form a full
individual and they don’t require creation and destruction of an embryo, that
would under normal circumstances form a full individual.

Thing is, these “embryo-like
structures” can still form something called a “primitive streak,”
which, in normal embryos, is the first sign of formation of a nervous
system.  The primitive streak usually
forms 14 days after fertilization, so, to try to avoid concerns about research
on embryos, scientists who think such research is ethical in limited
circumstances have operated under a “14-day rule”–voluntary in the
US, mandated by law in the UK–after which embryos would not be destroyed for
research.  These “embryo-like
structures” may form a primitive streak, it appears.  The situation is similar to “synthetic
human entities with embryo-like features,” or “SHEEFs,” which
may bypass the primitive streak but raise similar issues of whether something
too like a natural human being is being engineered by this work for it to be

A developmental biologist at Caltech
says, the California Institute of Technology in Pasadena. “We will have to
confront ourselves with the question of what is a human embryo, and whether
these models really have the potential to develop into one.”  The researchers making these synthetic embryos
argue that they lack a placenta and other cells needed for development, so
could not develop into a person.

At least for now.

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