Caenorhabditis elegans centriolar protein SAS-6 forms a spiral that is consistent with imparting a ninefold symmetry.

Centrioles are evolutionary conserved organelles that give rise to cilia and flagella as well as centrosomes. Centrioles display a characteristic ninefold symmetry imposed by the spindle assembly abnormal protein 6 (SAS-6) family. SAS-6 from Chlamydomonas reinhardtii and Danio rerio was shown to form ninefold symmetric, ring-shaped oligomers in vitro that were similar to the cartwheels observed in vivo during early steps of centriole assembly in most species. Here, we report crystallographic and EM analyses showing that, instead, Caenorhabotis elegans SAS-6 self-assembles into a spiral arrangement. Remarkably, we find that this spiral arrangement is also consistent with ninefold symmetry, suggesting that two distinct SAS-6 oligomerization architectures can direct the same output symmetry. Sequence analysis suggests that SAS-6 spirals are restricted to specific nematodes. This oligomeric arrangement may provide a structural basis for the presence of a central tube instead of a cartwheel during centriole assembly in these species

Planning benchmark study for SBRT of early stage NSCLC

Purpose The aim was to evaluate stereotactic body radiation therapy (SBRT) treatment planning variability for early stage nonsmall cell lung cancer (NSCLC) with respect to the published guidelines of the Stereotactic Radiotherapy Working Group of the German Society for Radiation Oncology (DEGRO). Materials and methods Planning computed tomography (CT) scan and the structure sets (planning target volume, PTV; organs at risk, OARs) of 3 patients with early stage NSCLC were sent to 22 radiotherapy departments with SBRT experience: each department was asked to prepare a treatment plan according to the DEGRO guidelines. The prescription dose was 3 fractions of 15 Gy to the 65% isodose. Results In all, 87 plans were generated: 36 used intensity-modulated arc therapy (IMAT), 21 used three-dimensional conformal radiation therapy (3DCRT), 6 used static field intensity-modulated radiation therapy (SF-IMRT), 9 used helical radiotherapy and 15 used robotic radiosurgery. PTV dose coverage and simultaneously kept OARs doses were within the clinical limits published in the DEGRO guidelines. However, mean PTV dose (mean 58.0 Gy, range 52.8-66.4 Gy) and dose conformity indices (mean 0.75, range 0.60-1.00) varied between institutions and techniques (p <= 0.02). OARs doses varied substantially between institutions, but appeared to be technique independent (p = 0.21). Conclusion All studied treatment techniques are well suited for SBRT of early stage NSCLC according to the DEGRO guidelines. Homogenization of SBRT practice in Germany is possible through the guidelines; however, detailed treatment plan characteristics varied between techniques and institutions and further homogenization is warranted in future studies and recommendations. Optimized treatment planning should always follow the ALARA (as low as reasonably achievable) principle