This Week in PNAS
ENGINEERING
Lab-on-a-chip with modular architecture
Kashan Shaikh et al. have developed modular microfluidic architecture in which different biochip components, grouped by functionality, can be built separately and connected. Microfabrication methods have advanced the use of microfluidic laboratory-on-a-chip technologies, but conventional designs for such biochips have been limited to integrated architectures that make customization time-consuming and costly. Shaikh et al. used a precisely manufactured microfluidic breadboard (FBB) containing active components such as valves, pumps, and mixers. The FBB was paired with customizable, fast-turnaround chip layers that contain passive elements such as chemical reactors and channels. The design allows for other FBBs to be added or interchanged. The authors demonstrated the use of this microarchitecture for applications involving the detecting of protein cancer markers and metal ions. In each case, a standard FBB with custom passive chip was used, which was designed and built in 1 day. — R.N.
Bonding a passive fluidic chip with an FBB.
“A modular microfluidic architecture for integrated biochemical analysis” by Kashan A. Shaikh, Kee Suk Ryu, Edgar D. Goluch, Jwa-Min Nam, Juewen Liu, C. Shad Thaxton, Thomas Chiesl, Annelise Barron, Yi Lu, Chad A. Mirkin, and Chang Liu (see pages 9745–9750)
BIOCHEMISTRY
Soluble epoxide hydrolase as a target for inflammation
Although much antiinflammatory research has focused on inhibiting the processing of fatty acid derivatives by cyclooxygenase (COX) and lipoxygenase (LOX) enzymes, Kara Schmelzer et al. explored another potential pharmacological target: soluble epoxide hydrolase (sEH). Cytochrome P450 enzymes transform arachidonic and linoleic acids into biologically active compounds including epoxyeicosatrienoic acids (EETs), which have antiinflammatory properties. EETs are further metabolized by sEH, and the authors surmised that inhibiting sEH would cause blood levels of EET to increase and inflammation to decrease. The authors measured sEH inhibition on acute inflammation in mice challenged with lipopolysaccharide (LPS). All untreated, LPS-challenged mice developed severe hypotension and died within 4 days. Treatment with a small-molecule sEH inhibitor prevented death and restored blood pressure to normal within 24 hours. The sEH inhibitor decreased the plasma levels of proinflammatory cytokines and nitric oxide and promoted the formation of lipoxins to help resolve inflammation. The sEH inhibitor also affected the LOX and COX cascades, demonstrating a possible use of this compound as a multitarget therapeutic. — L.B./N.Z.
“Soluble epoxide hydrolase is a therapeutic target for acute inflammation” by Kara R. Schmelzer, Lukas Kubala, John W. Newman, In-Hae Kim, Jason P. Eiserich, and Bruce D. Hammock (see pages 9772–9777)
BIOCHEMISTRY
Telomerase can act as a terminal transferase
Neal Lue et al. report the identification of a manganese-dependent, template-independent terminal transferase (TT) activity for human and yeast telomerase. Telomerase consists of an RNA template and the evolutionarily conserved, reverse transcriptase-like protein TERT, which synthesizes terminal repeats at the end of chromosomes. Previous research has shown that the metal cation manganese (Mn2+) has a mutagenic effect on polymerases. Lue et al. added Mn2+ to telomerase reactions in vitro and found that it reduced the enzyme's processivity and ability to synthesize DNA. However, Mn2+ addition allowed the enzyme to retain its catalytic activity after RNase treatment. The metal cation forced telomerase to act as a TT, incorporating nucleotides such as dATP and dCTP that were not complementary to the RNA template. The authors localized the transferase activity to TERT. In the TT mode of DNA synthesis, telomerase preferred extending GT-rich oligonucleotides. This preference, the authors say, is consistent with yeast telomerase's native activity and reflects an intrinsic protein-mediated sequence recognition. The investigators also observed significant telomere shortening in a yeast mutant with a defect in Mn2+ transport, suggesting that Mn2+ can affect telomerase function in vivo. — F.A.
“Telomerase can act as a template- and RNA-independent terminal transferase” by Neal F. Lue, Dimitry Bosoy, Tara J. Moriarty, Chantal Autexier, Brian Altman, and Siyang Leng (see pages 9778–9783)
PLANT BIOLOGY
Arabidopsis mutant cannot acclimate
Jianhua Zhu et al. report that the hos10-1 Arabidopsis mutant is unable to acclimate to cold temperatures and other environmental stresses due to the loss of function of a putative MYB transcription factor. In Arabidopsis, regulation of some stress-responsive genes is thought to involve transcription factor binding and activation of the RD29A (responsive to dehydration 29A) promoter, though the pathways responsible are poorly understood. Zhu et al. mutagenized Arabidopsis expressing a RD29A–luciferase transgene. The investigators screened for plants with high levels of luciferase activity grown under conditions of environmental stress. The hos10-1 mutant exhibited an almost 4-fold increase in luciferase expression in conditions of low temperature, abscisic acid, and high salt (NaCl). In addition, hos10-1 plants formed shorter roots, lost water faster, flowered earlier, and synthesized lower amounts of NCED3, a key enzyme in the dehydration-acclimatization pathway, compared with wild type. Zhu et al. isolated the gene responsible for the phenotype and found that it shared the highest sequence similarities with R2R3-type MYB transcription factors. A HOS10–GFP fusion protein revealed that the protein localizes to the nucleus, supporting its possible role as a transcription factor. — F.A.
Cold-acclimated wild-type (Left) and hos10-1 (Right) Arabidopsis plants.
“HOS10 encodes an R2R3-type MYB transcription factor essential for cold acclimation in plants” by Jianhua Zhu, Paul E. Verslues, Xianwu Zheng, Byeong-ha Lee, Xiangqiang Zhan, Yuzuki Manabe, Irina Sokolchik, Yanmei Zhu, Chun-Hai Dong, Jian-Kang Zhu, Paul M. Hasegawa, and Ray A. Bressan (see pages 9966–9971)
PSYCHOLOGY
Neuroimaging posthypnotic reductions in cognitive conflict
Amir Raz et al. used neuroimaging methods to illuminate the brain regions involved in reducing cognitive conflict in highly hypnotizable individuals. The authors had previously shown that posthypnotic suggestions could eliminate Stroop effects—interference of performance in timed color-identification tasks—and thus reduce cognitive conflict in highly hypnotizable subjects. To extend these behavioral findings to specific areas of the brain, the authors coregistered functional magnetic resonance imaging data, which provide excellent localization, with event-related electrical activity potentials, which offer high temporal resolution. In highly hypnotizable persons, posthypnotic suggestion to construe Stroop words as nonsense strings reduced conflict and decreased activity in the anterior cingulate cortex and visual areas of the brain. Reductions in posterior activation were also seen in highly hypnotizable persons under suggestion, pointing to visual system alterations. Highly hypnotizable persons were compared with less-hypnotizable controls or with those receiving no posthypnotic suggestion. The findings highlight the role of posthypnotic suggestions in altering cognitive processes and may elucidate the neural correlates of other suggestion-based interventions. — L.B./R.N.
Brain activity with posthypnotic suggestion.
“Hypnotic suggestion reduces conflict in the human brain” by Amir Raz, Jin Fan, and Michael I. Posner (see pages 9978–9983)
