Karl Deisseroth Is Leaving His Mark on Brain Science One Technique at a Time

NEWS FEATURE

Method man Karl Deisseroth is leaving his mark on brain science one technique at a time.

BY KERRI SMITH

hen Karl Deisseroth moved into his from the paucity of techniques to do so. “It was first lab in 2004, he found himself extremely clear that for fundamental advances NATURE Wreplacing a high-profile tenant: in these domains I would have to spend time Nobel-prizewinning physicist Steven Chu. “His developing new tools,” says Deisseroth. name was still on the door when I moved in,” His measured tone and laid-back demean- says Deisseroth, a neuroscientist, of the base- our belie the frenzy that his lab’s techniques ment space at Stanford University in California. are generating in neuroscience. First came The legacy has had its benefits. When chem- optogenetics1, which involves inserting light-

istry student Feng Zhang dropped by looking sensitive proteins from algae into neurons, FOR RAMIN RAHIMIAN/GETTY for Chu, Deisseroth convinced him to stick allowing researchers to switch the cells on around. “I don’t think he knew who I was. But and off with light. Deisseroth developed the he got interested enough.” method shortly after starting his lab, working Deisseroth is now a major name in science with Zhang and Edward Boyden, a close col- himself. He is associated with two blockbuster laborator at the time. Optogenetics has since techniques that allow researchers to show how been adopted by scientists around the world to intricate circuits in the brain create patterns of explore everything from the functions of neu- behaviour. The development of the methods, he ron subtypes to the circuits altered in depres- says, came from a desire to understand mecha- sion or autism. Deisseroth has lost count of nisms that give rise to psychiatric disease — and how many groups are using it. “We sent clones

550 | NATURE | VOL 497 | 30 MAY 2013 © 2013 Macmillan Publishers Limited. All rights reserved FEATURE NEWS to thousands of laboratories,” he says. Boyden, a PhD student with similarly ambi- breathing rate and feelings of panic and discom- Now his lab is gearing up for another rush, tious aims. The two began talking about ways fort5. They have switched on and off the activity after publishing a method called CLARITY2. to manipulate individual neurons as a side pro- of mouse neurons that use the neurotransmitter The technique uses a chemical treatment ject. “It was a very adventurous collaboration, dopamine, to show how they contribute to the to turn whole brains transparent, allowing full of exploration,” says Boyden. symptoms of depression6. The team has even researchers to examine the brain’s structure One idea involved using light to control used optogenetics to prevent cocaine-addicted in detail in three dimensions. It could help neuronal firing. Boyden and Deisseroth knew rats from seeking out the drug7. The work, says researchers to connect the brain’s function about light-sensitive channel proteins called Deisseroth, could help scientists to design anti- with its structure. “I think it’ll be de rigueur opsins, which algae use for generating energy, anxiety drugs that are less addictive than current for people to have a picture showing the treatments — affecting anxiety pathways pathways and how they sit in the brain,” but leaving reward circuitry untouched. says Richard Tsien, the neuroanatomist “It was a little hard In 2006, Boyden started his own lab at under whom Deisseroth earned his PhD the Massachusetts Institute of Technol- at Stanford. for people in the field ogy in Cambridge. Rumours emerged Deisseroth takes risks and encourages to understand what he that his relationship with Deisseroth his team to do the same, often pulling was souring. Neither is keen to discuss together people with varying expertise was trying to do.” the details, but in 2007, the two groups and keeping abreast of many different published separate papers on halo fields. Christof Koch, chief scientific officer at among other functions. Several groups — rhodopsin, an ‘off-switch’ opsin that they had the Allen Institute for Brain Science in Seattle, including that of Tsien’s brother Roger at the previously studied together8,9. “We didn’t know Washington, puts Deisseroth’s success down University of California, San Diego — were Ed was working on that until we sent our paper to these “catholic interests”. But Deisseroth trying to insert these proteins into neuron cell to Nature,” says Zhang. “Well you know, in any also has a laser-like focus on tool-building, membranes. The project needed “the where- competitive scenario people are interested in fuelled, he says, by his work as a practising withal to spend the money and find the gradu- being first,” says Boyden. psychiatrist. And although he is excited about ate students”, says Deisseroth. In 2004, having The experience might have left its mark his lab’s newest technique, Deisseroth plays it secured his own lab, he could do just that. on Deisseroth: he is careful to attribute credit down, shrugging a broad shoulder: “I’m not By July of that year, Deisseroth had man- precisely to his team members and trainees, very demonstrative,” he says. aged to coax neurons into expressing opsins in particularly with respect to CLARITY. “Karl their cellular membranes. Using cells borrowed is quite sensitive about who came up with the TAKING CONTROL from Malenka and recording equipment from idea,” says Kwanghun Chung, first author of When Tsien, who now works at New York Richard Tsien, he, Zhang and Boyden hun- the CLARITY paper2. Creating see-through University’s Langone Medical Center, first met kered down to see if the technique would fly. brains was Deisseroth’s dream, but the chemi- Deisseroth, he was struck by his determina- “It worked on pretty much the first try,” Boyden cal know-how came from Chung. They tion. “It was an unusual encounter — he came recalls. “It was like riding a wave of serendipity.” describe the finding as a co-discovery. for an interview and told me rather shyly that In the following year, Deisseroth finally the reason he came to Stanford was because he secured funding from the US National Insti- SEEING CLEARLY wanted to work with me,” Tsien remembers. tutes of Health (NIH) to further the work. He Standard techniques for examining fine-scale It was 1993 and Tsien’s lab was “crammed to had faced multiple rejections. Projects based brain structure involve slicing the brain into the gills”, he says, but Deisseroth was persistent on technologies have a harder time attract- tissue-thin segments, analysing them under and persuasive. As part of a joint programme ing support than hypothesis-driven projects, a microscope, and then — laboriously and to earn a PhD and a medical doctorate, he says Thomas Insel, director of the US National often imprecisely — stacking the images back began a project looking at calcium channels Institute for Mental Health in Bethesda, Mary- together. To bypass that process, Deisseroth in neurons. In 2000, he followed that up with land, the source of the initial federal funding had been looking for a means of chemically a multi-pronged appointment: a postdoctoral for Deisseroth’s optogenetics research. “It was a treating the brain to make it transparent. Some fellowship in the lab of Stanford neuroscientist little hard for people in the field to understand components of brain cells — especially lipids Robert Malenka and — after toying with the what he was trying to do,” says Insel. — are notoriously opaque to microscopes, so idea of neurosurgery — a residency in psychia- But neuroscientists saw the potential in the idea was to get rid of them, while preserving try at Stanford Medical School. 2005, when Deisseroth’s group published its the neuronal structure. It was a very different “Everything changed when I did my psychia- first big paper showing that the technique approach from optogenetics, and recruiting try rotation,” says Deisseroth. “A person can be worked in a dish1. Researchers could now stim- Chung — a chemical engineer by background right in front of you who looks intact, not obvi- ulate a specific type of neuron and see how that — displayed Deisseroth’s willingness to take ously injured, and yet their brain is constructing affected the cell’s — or even an entire animal’s risks. “I remember people wondering what I for them a completely different reality. At the — behaviour. Requests for the technology were was doing, what sort of plan there was in hiring same time I saw how deep the suffering was.” pouring in. this person and the direction the lab was going, Studying depression or anxiety in a dish of The technique has since been used for every because it was such a marked shift,” he says. cells was inadequate, he reasoned, because thing from studying the development of neural At first, Deisseroth wanted to immobilize only whole brains can give rise to the sophis- stem cells3 to prompting mice to recall fearful neurons by filling them with a suitable mate- ticated functions — and disorders — that memories4 (see Nature 465, 26–28; 2010). Deis- rial and removing the surrounding tissue. It characterize human behaviour. And tech- seroth and his team, with their focus on psy- turned out to be very difficult to build a stable niques for studying whole brains in humans chiatric conditions, have used rodent models structure from inside the neurons, but it was and model organisms were often limited to to explore the network easier to build one around them. simply watching them at work. NATURE.COM of brain areas that gives The team tried a few scaffolding materials, So Deisseroth began thinking about ways For interviews with rise to anxiety and have including keratin and a cellulose-like struc- to examine and control intact systems. “I was Deisseroth and a shown that one ‘hub’ ture, before settling on a hydrogel — a gel made having a lot of discussions with a lot of people,” video of CLARITY, see: controls diverse symp- mainly of water and already widely used in bio- he says. During his residency, Deisseroth met go.nature.com/zsxdld toms such as an elevated logical studies. The researchers found that a

the building keeps vibrations to a minimum, A light touch which is necessary when using the sophisticated Karl Deisseroth’s lab has produced two blockbuster techniques microscopes essential for his work. that allow researchers to visualize and manipulate the brain. The current team includes computational neuroscientists, medics, chemists and engi- neers. And a US$22.5-million Transformative Research Award from the NIH, granted last year, allows Deisseroth to keep encouraging them to take chances. “I have everyone have a hand in a high-risk and a low-risk project,” he says, “like a hedged portfolio.”

One of the latest high-risk projects uses UNIV. K. CHUNG/K. DEISSEROTH/STANFORD RIGHT: light-field microscopy, which records images from a variety of perspectives simultane- ously, to image the brain. Elsewhere in the lab, Chung and collaborator Viviana Gradinaru are still trying to build hydrogel structures inside

neurons in the hope of preserving networks of UNIV.; MOGRI/K. DEISSEROTH/STANFORD GRADINARU/J. CARNETT/M. V. LEFT: specific cell types — freezing in place all the neurons of a certain type, for example, or all the cells that express a particular gene. The team continues to improve optogenetics, too, developing new opsins and perfecting meth- Optogenetics CLARITY ods for delivering light to the brain. Deisseroth has already added space to the laboratory to cater for all the visiting scien- Viruses are used to ferry genes encoding Proteins and other molecules in the brain 1 light-sensitive receptors (opsins) into 1 are hybridized to a hydrogel matrix, fixing tists coming to learn how to use optogenetics specific neurons. them in place. and CLARITY. There were more than 200 in Animals are fitted with an ‘optrode’, a Densely packed, light-blocking lipids are 2010–12. The group has “done yeoman’s work 2 fibre-optic cable with an electrode. 2 washed away using detergents. in making this relatively straightforward to set up”, says Van Essen. “They’re not going to hold Light beamed down the optrode will open or close The clarified brain can be stained and washed 3 ion channels while the electrode records neuronal 3 multiple times, allowing scientists to observe hostage a methodology that people really can firing and researchers record behaviours. different molecules and cell types. set up in their own lab.” The tools are freely available; Stanford has filed patents on some aspects, says Deisseroth, but that it is to ensure hydrogel scaffold could bind components of function, says Eve Marder, a neuroscientist at unfettered access to the technology. He does neurons in place, including proteins, neuro Brandeis University in Waltham, Massachu- not make money from the patents. chemicals and even DNA and RNA (see ‘A setts. But analysing large networks in detail is Deisseroth struggles with his decision to light touch’). With the structure locked down, challenging. Marder usually works with simple spend more time on research than with the a detergent called SDS could wash away lipid circuits of 30 or so neurons, and says that even patients who inspire it. He still runs a weekly membranes, leaving the tissue transparent (see those have a scarily exponential number of per- psychiatry clinic, but has to balance this with a Nature 496, 151; 2013). mutations. “My only personal hope is that peo- packed travel schedule and mentoring duties. Within a week of publication, Deisseroth ple who venture into doing circuit work in larger He carries on, however, hopeful that his studies had already received several dozen requests for brains pay attention to the lessons learned and will ultimately benefit those that medicine can- information. “We’ve been very much… I’m try- mistakes that we made along the way,” she says. not. “We can help patients right now with many ing to find a verb that doesn’t make it seem like CLARITY is already shedding light on clini- psychiatric symptoms,” he says. “But for others a problem,” he says. He settles on describing the cal disorders. In the paper describing the tech- we can’t. So that really helps me in mentally free- e-mails that the lab received as an “outpouring”. nique2, the researchers analysed brain tissue ing up the time needed for research.” CLARITY stunned people in the same way from a seven-year-old boy who had autism That desire to help is buoyed by simple, that optogenetics did, says Insel. “Usually when spectrum disorder. They found that neurons boundless curiosity. “I think all scientists have someone has at an early stage of their career in his cortex had joined together in ladder- a little bit in them,” he says. “That wonder and made an important advance, they tend to rest like patterns, rather than the branches seen in curiosity about the natural world — not only on those laurels. Karl quite quickly decided to typical brains. Animal models of autism-like how it is, but how it could be.” ■ do the next big thing.” conditions had hinted at this difference, but Other researchers will tailor CLARITY to CLARITY made it possible to look for the Kerri Smith is senior audio editor for Nature their own projects. David Van Essen, a neuro- irregularity in human brain samples. in London. scientist at Washington University in St. Louis, 1. Boyden, E. S., Zhang, F., Bamberg, E., Nagel, G. Missouri, is interested in testing CLARITY in RISK AND REWARD & Deisseroth, K. Nature Neurosci. 8, 1263–1268 the brain’s white matter, the bundles of neu- Deisseroth’s office and much of his lab are still (2005). ronal projections called axons that carry nerve in the same basement that he moved into in 2. Chung, K. et al. Nature 497, 332–337 (2013). 3. Stroh, A. et al. Stem Cells 29, 78–88 (2011). impulses. This will help his group study pat- 2004, although the team — now including 35 4. Liu, X. et al. Nature 484, 381–385 (2012). terns of connectivity that link brain regions. people — has branched out into lab space else- 5. Kim, S.-Y. et al. Nature 496, 219–223 (2013). Using CLARITY with techniques such as where. The labs are strewn with gadgetry, like 6. Chaudhury, D. et al. Nature 493, 532–536 (2013). 7. Stefanik, M. T. et al. Addiction Biology 18, 50–53 optogenetics, or using it to analyse brains after the bedroom of a technology-obsessed teen- (2013). behavioural studies, will be a powerful way to ager. There is no natural light in the basement, 8. Han, X. & Boyden, E. S. PLoS ONE 2, e299 (2007). extract information about how brain networks but Deisseroth likes it; being at the bottom of 9. Zhang, F. et al. Nature 446, 633–639 (2007).