Lluís Montoliu

Two articles published in Nature describe a new genome editing technique that enables the insertion, inversion, or deletion of long DNA sequences at specific positions in the genome. This is a one-step approach that could offer a simpler method for genome editing in the future. The authors describe a technique to create reprogrammable recombinases—key enzymes in genetic recombination. These enzymes are guided by RNA, which acts as a bridge, directing the recombinase to target sites and facilitating predetermined editing.

Five out of ten potential treatments move from animal studies to human studies; four to randomised controlled clinical trials; and one in 20 moves on to approval by regulatory agencies, an analysis estimates. Concordance between positive results in animals and in clinical studies is 86%, according to the study, published in PLoS Biology, which pools the findings of 122 published studies on 54 different human diseases.  

Two independent research teams have managed to regenerate brain circuits in mice using neurons cultivated from rat stem cells. Today, both studies were published in the journal Cell. The research, in which chimeras of different species were generated, delve into how brain tissue forms and present new opportunities for restoring lost brain function due to diseases and aging.

Epigenetic editing is a technique that aims to alter gene expression without the need to modify the DNA sequence, as gene editing techniques do. In this way, Italian researchers have succeeded in silencing the PCSK9 gene in mice, thereby reducing cholesterol levels by half for at least a year. According to the authors, and assuming further evaluation is needed, their platform "could lay the foundations for the development of this type of therapy". The results are published in the journal Nature.

A team of Chinese researchers report today in the journal Nature Communications the successful cloning of a rhesus monkey, with a healthy placenta, which survived for more than two years. According to the authors, this could improve the efficiency of the monkey cloning process, which so far is very low. Previously, different teams have cloned more mammalian species, including 'Dolly the sheep' and another species of macaque (Macaca fascicularis).

A team led by the Princess Máxima Pediatric Oncology Center and the Hubrecht Institute (The Netherlands) has generated small 3D brain models--known as organoids--from human fetal brain tissue. Until now, these brain organoids-which attempt to resemble real organs on a miniature scale-were grown in the laboratory using pluripotent or embryonic stem cells. The new technique, published in the journal Cell, allows regions of brain tissue to self-organize into three-dimensional brain structures. The authors used these organoids and the CRISPR-Cas9 tool to simulate the development of one type of brain tumor, glioblastoma, and see how it responded to different drugs.

The European Medicines Agency (EMA) has recommended approval of the first drug in the European Union to use the CRISPR/Cas9 gene-editing technique. The drug, Casgevy, is indicated for the treatment of two rare inherited diseases, beta thalassaemia and sickle cell disease (sickle cell anaemia), caused by genetic mutations that affect the production or function of haemoglobin, the oxygen-carrying protein in red blood cells. Both conditions are debilitating and potentially fatal. The EMA opinion will be sent to the European Commission for a decision on an EU-wide marketing authorisation.

A Chinese research team has reported the birth of a crab-eating macaque that is a chimera: an animal generated from the mixing of embryonic cells from two different individuals; in this case, from the same species, according to the journal Cell. Until now, this type of chimera had only been developed with rodents. This is the first time it has been achieved in non-human primates.

Berna Sozen's lab at Yale University has announced a new milestone in the competition to create synthetic embryos: their human pluripotent stem cells self-organise into structures that mimic embryonic development on days 9-14 after fertilisation and include extra-embryonic tissues. Their achievement is published in Nature at the same time as another similar study, that of Magdalena Zernicka-Goetz, who a fortnight ago previewed her stem cell-derived human embryo model to The Guardian, sparking a controversy with Jacob Hanna, author of a preprint showing that she had achieved true synthetic embryos. 

The latest episode of competition between research groups working on the same topic, a very common situation in science, should not distract us from the actual achievement: synthetic human embryos, in the laboratory, made from stem cells, up to a post-implantation stage. Now, we must decide what status or condition we will grant to these synthetic embryos. Once again, science is leaping forward and testing the limits of the laws, posing new ethical challenges for us to solve.