Tag Archives: Publications

Transcriptional enhancement of Smn levels in motoneurons is crucial for proper axon morphology in zebrafish

by Zoltan Spiro, Angela Koh, Shermaine Tay, Kelvin See, Christoph Winkler

Scientific Reports 6, 2016  (07 June 2016)

An unresolved mystery in the field of spinal muscular atrophy (SMA) is why a reduction of the ubiquitously expressed Smn protein causes defects mostly in motoneurons. We addressed the possibility that this restricted vulnerability stems from elevated Smn expression in motoneurons. To explore this, we established an ex vivo zebrafish culture system of GFP-marked motoneurons to quantitatively measure Smn protein and smn mRNA levels as well as promoter activity in motoneurons versus other cell types. Importantly, we uncovered that Smn levels are elevated in motoneurons by means of transcriptional activation. In addition, we identified the ETS family transcription factor Etv5b to be responsible for increased smn transcription in motoneurons. Moreover, we established that the additional supply of Smn protein in motoneurons is necessary for proper axonogenesis in a cell-autonomous manner. These findings demonstrate the reliance of motoneurons on more Smn, thereby adding a novel piece of evidence for their increased vulnerability under SMA conditions.

Read online: Scientific Reports

Diffraction before destruction

by Chun Hong Yoon, Mikhail V. Yurkov, Evgeny A. Schneidmiller, Liubov Samoylova, Alexey Buzmakov, Zoltan Jurek, Beata Ziaja, Robin Santra, N. Duane Loh, Thomas Tschentscher & Adrian P. Mancuso

Scientific Reports. 6 (2016) 24791. doi: 10.1038/srep24791.

Nanometer-sized biological molecules are difficult to resolve because they are fragile: they come apart when they are imaged with energetic x-rays or electrons. Fortunately, ultra-short x-ray laser pulses billions of times brighter than previous x-ray sources can now illuminate single biomolecules to produce faint but meaningful signals. These signals are then statistically combined to yield structural information. Because these x-ray pulses are so short, they flee from biomolecules before the latter get a chance to move or show damage. This property permits so-called “diffraction before destruction”, where scientists can image unsuspecting and unperturbed nanoscale objects in their native environment.

Hundreds of experimental parameters modify how x-ray free-electron lasers are generated, focused, made to interact with biomolecules, then detected, and analysed. The combinatorial complexity of such imaging experiments is staggering, which makes designing such experiments tricky, tedious and frustratingly uncertain. Dr Duane LOH from the Centre for Bio-imaging Sciences, together with four other groups of scientists from CFEL and the European XFEL (Hamburg, Germany), has created a comprehensive multi-physics framework that realistically simulates for the first time, how specimen damage in single-particle imaging can be mitigated by instrument and algorithm design.

Read online: Scientific Reports.

Read Diffraction before destruction: Scientists in NUS have demonstrated how x-ray lasers could help us image biological macromolecules in water from NUS Faculty of Science.


Structure of the thermally stable Zika virus

by Victor A. Kostyuchenko, Elisa X. Y. Lim, Shuijun Zhang, Guntur Fibriansah, Thiam-Seng Ng, Justin S. G. Ooi, Jian Shi & Shee-Mei Lok

Nature (2016) doi:10.1038/nature17994  Published online 19 April 2016

Zika virus (ZIKV), formerly a neglected pathogen, has recently been associated with microcephaly in fetuses1, and with Guillian–Barré syndrome in adults2. Here we present the 3.7 Å resolution cryo-electron microscopy structure of ZIKV, and show that the overall architecture of the virus is similar to that of other flaviviruses. Sequence and structural comparisons of the ZIKV envelope (E) protein with other flaviviruses show that parts of the E protein closely resemble the neurovirulent West Nile and Japanese encephalitis viruses, while others are similar to dengue virus (DENV). However, the contribution of the E protein to flavivirus pathobiology is currently not understood. The virus particle was observed to be structurally stable even when incubated at 40 °C, in sharp contrast to the less thermally stable DENV3. This is also reflected in the infectivity of ZIKV compared to DENV serotypes 2 and 4 (DENV2 and DENV4) at different temperatures. The cryo-electron microscopy structure shows a virus with a more compact surface. This structural stability of the virus may help it to survive in the harsh conditions of semen4, saliva5 and urine6. Antibodies or drugs that destabilize the structure may help to reduce the disease outcome or limit the spread of the virus.

Read online: Nature.