CRISPR Gene Editing Teach-Out

As you’ve learned, CRISPR has a wide range of applications, one of which is genetic modification of humans. However, editing the human genome tends to be the most talked about use, as it has many scientific and ethical implications.

One thing to note is that not all human genetic modifications are equal. It depends on the type of cell the edit is made to. Germline cells are reproductive (i.e., sperm, eggs, embryos). Their genomes are transmitted to subsequent generations. Thus, edits to germline cells are inheritable. Somatic cells are all the other cells in the body, and not related to reproduction. Edits to these cells are not transmitted to subsequent generations, so are not heritable.

Functionally all genetic editing in humans at the present is taking place in somatic cells. For example, an ongoing clinical trial takes a blood sample from a patient, uses CRISPR to edit the blood stem cell, and reinjects it to the patient as a type of gene therapy. The descendents of this patient will not inherit the CRISPR-edited gene.

Later in the Teach-Out, you will hear the story of He Jiankui, a researcher, who announced in 2018 that he had edited the genes of two human embryos to make them more resistant to HIV, creating the world’s first genetically engineered babies. It's a complicated story of science, ambition, and ethics, and shaped by the motivations of both He Jiankui and the babies’ parents. As you progress through the Teach-Out, it is important to note that not all human gene editing is alike and that edits to germline cells, resulting in heritable changes, is not widely accepted. Instead, it is a significant source of debate, and you will hear many opinions on the topic.