Figure
89%
of known disease-causing mutations can be corrected by prime editing
Figure
75%
of starlight is reflected by the lava planet TOI-561 b—almost like Venus
Figure
60-fold
increase in light sensitivity in a blind patient following gene therapy
Figure
46 → 6%
the share of neurons with genetic defects in the brain before and after birth
DNA Corrected Directly Inside the Human Body for the First Time
Doctors have for the first time administered a drug to a human patient that is intended to correct a DNA error directly inside the body using prime editing, a more precise and safer version of the CRISPR system. The first patient to receive this groundbreaking treatment has Wilson’s disease, a hereditary condition in which the liver is unable to excrete excess copper. If left untreated, the metal accumulates and progressively destroys both the liver and the brain. The clinical trials are being conducted by Prime Medicine, a company based in Cambridge, Massachusetts.
The original version of CRISPR technology operates by cutting both strands of DNA, and during the subsequent ‘repair’ process, the cell can sometimes make mistakes, which can result in the loss of entire sections of a chromosome. Prime editing, which was first introduced in 2019, nicks only a single strand and uses a guide molecule to write the corrected genetic code into the site of the error. This advanced technique is capable of not only changing individual genetic ‘letters’ but also inserting or deleting short fragments. According to its creators’ estimates, it could potentially correct up to 89% of all known disease-causing mutations.
This method has been applied to humans previously, but in those instances, cells had to be extracted from the body, edited in a laboratory, and then returned to the patient—a process that is both lengthy and very expensive. Now, the new drug, designated PM577a, is administered intravenously: lipid nanoparticles, similar to those used in mRNA vaccines, deliver the treatment directly to the liver cells. The company expects that correcting 20–30% of these cells will be sufficient for an effective treatment. In experiments on monkeys, a single injection corrected about half of the cells with no noticeable side effects.
The first results from the human clinical trials are expected in 2027. “We created prime editing as a versatile technology that could, in principle, correct nearly all types of mutations that cause genetic diseases. Today’s data represents a milestone in medicine,” said David Liu, a co-founder of Prime Medicine.
Atmosphere Discovered on Lava Planet
The James Webb Telescope has detected a dense atmosphere on planet TOI-561 b, covered in molten rock, though such a scorching world so close to its star should have lost its atmosphere long ago. The planet, 280 light-years away, reflects about 75% of starlight, almost like Venus: scientists think it is shrouded in clouds of silicate minerals. According to one hypothesis, the atmosphere is constantly replenished by an ocean of magma that, in the words of astrophysicist Anjali Piette, acts as one enormous volcano.
Sight Restored with Algae
People with retinitis pigmentosa, a severe hereditary form of blindness, were once again able to make out the outlines of objects and find doorways after undergoing an experimental gene therapy. This group of diseases affects about 1.5 million people worldwide. It gradually kills the retina’s photosensitive cells: vision first deteriorates in the dark, then peripheral vision is lost, and over time patients may go completely blind. A cure is difficult because the disease is caused by mutations in many different genes.
Instead of restoring the dead cells, scientists taught other cells to see: the ganglion cells. These normally only transmit information to the brain and survive even in the late stages of the disease. A harmless virus delivered the gene for an algal protein, ChrimsonR, into these cells. This protein acts as a light-activated switch. Patients wore special glasses equipped with a camera and a projector that capture the surroundings and project light patterns onto the retina.
The treatment proved safe for all ten participants, and seven of them experienced increased light sensitivity, in some cases by a factor of more than 60. The research was led by José-Alain Sahel of Pittsburgh and Botond Roska of Basel. Optogenetics itself grew out of work for which Karl Deisseroth, Peter Hegemann, and Georg Nagel received this year’s Nobel Prize.
The Brain Culls Defective Neurons
The human brain creates an overabundance of neurons before birth, then destroys a significant portion of them shortly before and immediately after. For a long time, neurobiologists did not understand the reason for this. A new study by Harvard Medical School and Boston Children’s Hospital, published in the journal Nature, shows it is a form of quality control.
Scientists studied the DNA and RNA of more than 44,000 individual cortical cells and discovered that up to 46% of fetal neurons carry major genetic defects, with entire sections of DNA duplicated or deleted—changes linked to autism, schizophrenia, and epilepsy. After birth, the proportion of these cells drops to about 6%. Neurons with these defects cannot produce the proteins needed for synapses and lose the competition for a place in the neural network; losing cells then initiate a death program. “This struggle for survival turned out to be a natural quality control mechanism in the brain,” says Christopher Walsh, one of the study’s leaders. He added that the scientists had not expected to find so many of these cells.
The researchers are now investigating whether this selection process is weakened in cases of autism and whether surviving defective neurons become more vulnerable in old age, potentially accelerating conditions such as Alzheimer’s disease.