Gene Edits for Enhancement

The fifth installment of our blog series about gene editing focuses on gene edits and editing for research purposes. We hope you that you find it informative – please Contact Us with any comments! View the other posts in this series!

Earlier this year, a Chinese scientist reported the birth of twin girls whose genomes had been modified to silence the CCR5 gene.

Human genome: All of the genetic information needed for the embryonic development and adult function of a human being.

The birth was reported to be one of a series of human embryo experiments designed to render the offspring resistant to infection by HIV and to prove the principal that gene editing was possible — and perhaps beneficial— in human embryos.

Gene: A specific sequence of A, C, G, T units that instruct the sequence of amino acids that comprise a specific protein. Humans have 20- to 25 thousand genes

The work was not reported in a scientific format, so few scientists have had the opportunity to review the data in detail.

CCR5: A member of the C-C chemokine protein. receptor family that codes for the docking protein for the HIV virus on the surface of HIV target cells.

Several ethical concerns with this report, if true, have been raised. The gene editing was not performed to correct a known, serious medical issue in the embryos. It was performed to enhance resistance to HIV. A highly controversial idea.

CRISPR/Cas: “Clustered Regularly Interspaced Short Palindromic Repeats” is a term that describes DNA sequences in the viruses that infect bacteria. The immune system of bacteria includes a family of proteins (CRISPR-associated, Cas) that recognize CRISPR sequences and degrades them. The enzyme, Cas, needs to bind to a specific RNA sequence of 120 units, which can be synthesized synthetically, in order to degrade the DNA. These two components also function well in cell types other than bacteria, and so have become a useful tool for cutting DNA, resulting in either small deletions, or successful insertions of new synthetic DNAs. Both outcomes create an edited (mutated) gene.

But a more practical problem with the work is the possibility of “off-target” gene edits. Much research has been devoted to discover, and eliminate, the random edits that may occur at other than the gene locations being specifically targeted by the CRISPR/Cas reagents.

Gene edit: A modification of a specific sequence of A, C, G, T units that instruct the sequence of amino acids that comprise a specific protein. The edit may or may not alter the amino acid sequence and the protein.

It is these potentially deleterious unintended consequences that must be addressed in order to protect the offspring produced.

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