New technique gives permanency to gene therapy

Scientists from the Mount Sinai School of Medicine developed a technique to insert genes into non-coding regions of the genome so there is no danger of interfering with the functioning of other genes. Once inserted, the gene remains a permanent part of the cell’s genome.

“To date gene therapy has relied upon vectors that randomly insert genes into the cell’s genome,” said Dr Savio Woo, professor at the School of Medicine. “The technique we developed identifies a specific sequence which only occurs in a few places in the mammalian genome. These sequences occur between genes so there is no danger of the insertion of the gene damaging existing genes in the cell. Because the genes are inserted permanently, a few applications would suffice to permanently correct a disease.”

The researchers were able to cure phenylketonuria (PKU) in mice with just three intravenous injections. The levels of phenylalanine in the treated mice dropped to normal range and remained stable thereafter. Their fur color also changed from gray to black, indicating that they were now producing normal levels of melanin, a pigmentation which is under-produced in mice and humans with this metabolic disorder.

In addition to PKU, the technique could be used to cure other genetic diseases caused by missing liver enzymes including hemophilia and urea cycle enzyme deficiencies, as well as cholesterol clearing from the blood and others.

“The current challenge is to identify a suitable means of introducing DNA into liver cells,” said Dr Woo. “Once that technology is developed, this new technique will provide a safe and efficient means of integrating the DNA into the cell’s genome.”