High-continuity genome assembly of the jellyfish Chrysaora quinquecirrha

DEAR EDITOR,The Atlantic sea nettle(Chrysaora quinquecirrha)has an important evolutionary position due to its high ecological value.However,due to limited sequencing technologies and complex jellyfish genomic sequences,the current C.quinquecirrha genome assembly is highly fragmented.Here,we used the most advanced high-throughput chromosome conformation capture(Hi-C)technology to obtain high-coverage sequencing data of the C.quinquecirrha genome.We then anchored these data to the previously published contig-level assembly to improve the genome.Finally,a high-continuity genome sequence of C.quinquecirrha was successfully assembled,which contained 1882 scaffolds with a N50 length of 3.83 Mb.The N50 length of the genome assembly was 5.23 times longer than the previously released one,and additional analysis revealed that it had a high degree of genomic continuity and accuracy.Acquisition of the high-continuity genome sequence of C.quinquecirrha not only provides a basis for the study of jellyfish evolution through comparative genomics but also provides an important resource for studies on jellyfish growth and development.

Etomidate affects the anti-oxidant pathway to protect retinal ganglion cells after optic nerve transection

Our previous studies revealed that etomidate, a non-barbiturate intravenous anesthetic agent, has protective effects on retinal ganglion cells within 7 days after optic nerve transection. Whether this process is related to anti-oxidative stress is not clear. To reveal its mechanism, we established the optic nerve transection injury model by transecting 1 mm behind the left eyeball of adult male Sprague-Dawley rats. The rats received an intraperitoneal injection of etomidate(4 mg/kg) once per day for 7 days. The results showed that etomidate significantly enhanced the number of retinal ganglion cells retrogradely labeled with Fluorogold at 7 days after optic nerve transection. Etomidate also significantly reduced the levels of nitric oxide and malonaldehyde in the retina and increased the level of glutathione at 12 hours after optic nerve transection. Thus, etomidate can protect retinal ganglion cells after optic nerve transection in adult rats by activating an anti-oxidative stress response. The study was approved by the Animal Ethics Committee at Air Force Medical University, China(approval No. 20180305) on March 5, 2018.

Infrared nanoimaging of nanoscale sliding dislocation of collagen fibrils

Collagen,one of the major components in the mammalian connective tissues,plays an essential role in many vital physiological processes.Many common diseases,such as fibrosis,overuse injuries,and bone fracture,are associated with collagen arrangement defects.However,the underlying mechanism of collagen arrangement defects remains elusive.In this study,we applied infrared scattering-type scanning near-field optical microscopy to study collagen fibrils’structural properties.Experimentally,we observed two types of collagen fibrils’arrangement with different periodic characteristics.A crystal sliding model was employed to explain this observation qualitatively.Our results suggest that the collagen dislocation propagates in collagen fibrils,which may shed light on many collagen diseases’pathogenesis.These findings help to understand the regulation mechanism of hierarchical biological structure.

SeHed,a novel gene expression system with stress-evoked hydrogen peroxide elimination property and anti-aging effect

Dear Editor,The moderate level of reactive oxygen species(ROS)contributes to cellular functions such as proliferation,differentiation,and infection resistance,but the excessive level of ROS causes oxidative damage which underlies the basic mechanism for aging and geriatric diseases.1 Therefore,precisely managing cellular ROS levels,meaning to keep redox homeostasis properly,stands as an aim for health and longevity.Actually,this aim is challenging,as it asks not only to restrain excessive ROS accumulation at the right time and right place but also to guarantee proper ROS levels for fitting physiological requirements.Traditional ways for eliminating ROS put more attention on the efficiency and identified a variety of drugs and enzymes with antioxidant properties,known as enzymatic and non-enzymatic ROS scavengers,respectively.However,how to accurately manage the integrative effect of ROS scavengers in vivo remains a problem.Actually,the effectiveness of non-enzymatic antioxidants in vivo is controversial,explained mostly by the uncertainty to reach a given organ with the appropriate concentration or to work there persistently.2 As to enzymatic ROS scavengers,although their overexpression in a given place can be achieved,this mode is often unwieldy or harmful to intrinsic physiologic functions in cases.3 For this reason,we attempt to develop new ways for in vivo antioxidation,for establishing a high-quality balance between efficiency and safety.As the consequence,we innovated a gene expression system that can limit the excessive ROS accumulation but keep the physiological level of ROS.