Up and Down: Mars and DNA

Water on Mars!

And this time, it’s liquid! Salty water flows on Mars slopes – during “warm seasons” of above 10 degrees Fahrenheit – producing streaks of hydrated minerals that NASA spotted from their Mars Reconnaissance Orbiter. The findings were announced in a news conference on Monday, September 28, and published the same day in Nature Geoscience by Lujendra Ojha et al.

The authors used spectrometers aboard the orbiter to identify streaks (“slope lineae”) of magnesium perchlorate, magnesium chlorate, and sodium perchlorate flowing over time down several large craters in Martian summers – consistent with the pattern of downstream-flowing liquid water. Because they observed the mineral deposits flowing downstream over time, these scientists are the first to find evidence of liquid water on Mars today. "When most people talk about water on Mars, they're usually talking about ancient water or frozen water… Now we know there’s more to the story,” said Ojha.

The water is extremely salty, which explains how it remains liquid at those temperatures – water containing magnesium chlorate freezes up to 70 degrees Kelvin below the freezing point of pure water. An exciting thought is that even very cold salty water could theoretically support some form of life. The authors write: “The detection described here warrants further astrobiological characterization and exploration of these unique regions on Mars.” Could an extremophile life form survive in these conditions?

Sources: NASA, Nature Geoscience

CRISPR Wars

“…And then we started to pray at the Church of CRISPR” – Dr. Tyler Jacks, UCSF Cancer Center Seminar, March 2015.

While biologists around the world are embracing the power of the CRISPR-Cas9 gene-editing technology, a fierce patent battle rages on between Emmanuelle Charpentier (Helmholtz Center for Infection Research and Umeå University) and Jennifer Doudna (University of California, Berkeley), who together first discovered the bacterial DNA-cutting process, and Feng Zhang (MIT, Broad Institute), who first adapted the technology for use in mammals. The U.S. Patent and Trademark Office gave the patent to Zhang, but the two women appealed and the battle remains unresolved. Because biotech companies are already working to incorporate the technology into their research and development, whoever ultimately controls this patent will be a very powerful person… or will they?

The CRISPR gene-editing system evolved as a form of adaptive immunity in bacteria and archaea in order to fight off viral infections that insert RNA and DNA into their targets. Any foreign DNA sequence, when inserted between CRISPR DNA repeats in the genome, is converted into RNA that guides the Cas9 DNA-cutting enzyme to recognize and cleave that particular sequence out of the genome. In addition to being a fascinating aspect of microbiology, CRISPR is a powerful tool in biomedical science where gene editing is becoming a necessary tool for discovery and therapy. For example, a knockout mouse (a laboratory mouse engineered to lack a particular gene) used to take well over a year to make; with CRISPR technology, it can be done in just a few months. Editing human DNA in this manner could be just down the road.

A new publication from Zhang’s group at MIT published online in Cell on September 25 describes a new gene-editing protein called Cpf1 that works in a similar but simplified manner to Cas9. While Cas9 requires two different RNA structures to successfully identify and remove DNA sequences from a chromosome, Cpf1 only needs one.

The characterization of this new “Class 2 CRISPR-Cas9” system will probably dilute the power of a CRISPR patent, and the authors speculate that it opens new doors: “There is little doubt that, beyond the already classified and characterized diversity of the CRISPR-Cas types, there are additional systems with distinctive characteristics that await exploration and could further enhance genome editing and other areas of biotechnology.” In an interview, Zhang sounded hopeful about the future of CRISPR-Cas9 and CRISPR-Cpf1 gene editing technologies: “Our goal is to develop tools that can accelerate research and eventually lead to new therapeutic applications.”

Sources: Cell, WIRED, MIT News