2020 Vol. 41, No. 1

Full issue
Editorial
Articles

Hypobaric hypoxia (HH) exposure can cause serious brain injury as well as life-threatening cerebral edema in severe cases. Previous studies on the mechanisms of HH-induced brain injury have been conducted primarily using non-primate animal models that are genetically distant to humans, thus hindering the development of disease treatment. Here, we report that cynomolgus monkeys (Macaca fascicularis) exposed to acute HH developed human-like HH syndrome involving severe brain injury and abnormal behavior. Transcriptome profiling of white blood cells and brain tissue from monkeys exposed to increasing altitude revealed the central role of the HIF-1 and other novel signaling pathways, such as the vitamin D receptor (VDR) signaling pathway, in co-regulating HH-induced inflammation processes. We also observed profound transcriptomic alterations in brains after exposure to acute HH, including the activation of angiogenesis and impairment of aerobic respiration and protein folding processes, which likely underlie the pathological effects of HH-induced brain injury. Administration of progesterone (PROG) and steroid neuroprotectant 5α-androst-3β,5,6β-triol (TRIOL) significantly attenuated brain injuries and rescued the transcriptomic changes induced by acute HH. Functional investigation of the affected genes suggested that these two neuroprotectants protect the brain by targeting different pathways, with PROG enhancing erythropoiesis and TRIOL suppressing glutamate-induced excitotoxicity. Thus, this study advances our understanding of the pathology induced by acute HH and provides potential compounds for the development of neuroprotectant drugs for therapeutic treatment.

There is a growing appreciation for the specific health benefits conferred by commensal microbiota on their hosts. Clinical microbiota analysis and animal studies in germ-free or antibiotic-treated mice have been crucial for improving our understanding of the role of the microbiome on the host mucosal surface; however, studies on the mechanisms involved in microbiome-host interactions remain limited to small animal models. Here, we demonstrated that rhesus monkeys under short-term broad-spectrum antibiotic treatment could be used as a model to study the gut mucosal host-microbiome niche and immune balance with steady health status. Results showed that the diversity and community structure of the gut commensal bacteria in rhesus monkeys were both disrupted after antibiotic treatment. Furthermore, the 16S rDNA amplicon sequencing results indicated that Escherichia-Shigella were predominant in stool samples 9 d of treatment, and the abundances of bacterial functional genes and predicted KEGG pathways were significantly changed. In addition to inducing aberrant morphology of small intestinal villi, the depletion of gut commensal bacteria led to increased proportions of CD3+ T, CD4+ T, and CD16+ NK cells in peripheral blood mononuclear cells (PBMCs), but decreased numbers of Treg and CD20+ B cells. The transcriptome of PBMCs from antibiotic-treated monkeys showed that the immune balance was affected by modulation of the expression of many functional genes, including IL-13, VCAM1, and LGR4.

Previous studies have revealed faster detection of snake images in humans and non-human primates (NHPs), suggesting automatic detection of evolutionary fear-relevant stimuli. Furthermore, human studies have indicated that general fear-relevance rather than evolutionary relevance is more effective at capturing attention. However, the issue remains unclarified in NHPs. Thus, in the present study, we explored the attentional features of laboratory-reared monkeys to evolutionary and general fear-relevant stimuli (e.g., images of snakes, capturing gloves). Eye-tracking technology was utilized to assess attentional features as it can provide more accurate latency and variables of viewing duration and frequency compared with visual search task (VST) and response latency adopted in previous studies. In addition, those with autism spectrum disorder (ASD) show abnormal attention to threatening stimuli, including snake images. Rett syndrome (RTT) is considered a subcategory of ASD due to the display of autistic features. However, the attentional features of RTT patients or animal models to such stimuli remain unclear. Therefore, we also investigated the issue in MECP2 gene-edited RTT monkeys. The influence of different cognitive loads on attention was further explored by presenting one, two, or four images to increase stimulus complexity. The eye-tracking results revealed no significant differences between RTT and control monkeys, who all presented increased viewing (duration and frequency) of snake images but not of aversive stimuli compared with control images, thus suggesting attentional preference for evolutionary rather than general fear-relevant visual stimuli. Moreover, the preference was only revealed in visual tasks composed of two or four images, suggesting its cognitive-load dependency.

D-dopachrome tautomerase (DDT), a member of the macrophage migration inhibitory factor (MIF) protein superfamily, is a newly described cytokine with chemokine-like characteristics. However, research on fish DDT remains limited. In this study, we identified a DDT homolog (LjDDT) from the Japanese sea bass, Lateolabrax japonicus. Sequence analysis showed that LjDDT had typical sequence features of known DDT and MIF homologs and was most closely related to DDT of rock bream (Oplegnathus fasciatus). LjDDT transcripts were detected in all tested tissues of healthy Japanese sea bass, with the highest expression found in the liver. Upon infection with Vibrio harveyi, LjDDT transcripts were significantly down-regulated in the three tested tissues, including the liver, spleen, and head kidney. Recombinant LjDDT (rLjDDT) and the corresponding antibody (anti-rLjDDT) were subsequently prepared. The administration of 100 μg/g anti-rLjDDT had a statistically significant protective effect on the survival of V. harveyi-infected fish. Moreover, rLjDDT was able to induce the migration of monocytes/macrophages (MO/MФ) and lymphocytes both in vitro and in vivo, but without significant influence on the migration of neutrophils. rLjDDT exhibited chemotactic activity for lipopolysaccharide (LPS) -stimulated M1-type MO/ MΦ in vitro, but not for cAMP-stimulated M2-type MO/MΦ. Furthermore, the knockdown of LjCD74, but not LjCXCR4, significantly down-regulated the rLjDDT-enhanced migration of MO/MΦ and relieved the rLjMIF-inhibited migration of MO/MΦ. These results indicate that LjCD74 may be the major chemotactic receptor of LjDDT and LjMIF in Japanese sea bass MO/MΦ. Combined rLjDDT+ rLjMIF treatment had no significant effect on the migration of MsiRNA, LjCD74si-, or LjCXCR4sitreated MO/MΦ compared to the control group, suggesting that the roles of LjDDT and LjMIF may be antagonistic. In conclusion, our study demonstrates for the first time that DDT may play a role in the immune responses of fish against bacterial infection through chemotactic recruitment of MO/MΦ via mediation of CD74 as an antagonist of MIF.

Molecular studies on donkey mitochondrial sequences have clearly defined two distinct maternal lineages involved in domestication. However, domestication histories of these two lineages remain enigmatic. We therefore compared several population characteristics between these two lineages based on global sampling, which included 171 sequences obtained in this study (including Middle Asian, East Asian, and African samples) plus 536 published sequences (including European, Asian, and African samples). The two lineages were clearly separated from each other based on whole mitochondrial genomes and partial non-coding displacement loop (D-loop) sequences, respectively. The Clade I lineage experienced an increase in population size more than 8 000 years ago and shows a complex haplotype network. In contrast, the population size of the Clade II lineage has remained relatively constant, with a simpler haplotype network. Although the distribution of the two lineages was almost equal across the Eurasian mainland, they still presented discernible but complex geographic bias in most parts of Africa, which are known as their domestication sites. Donkeys from sub-Saharan Africa tended to descend from the Clade I lineage, whereas the Clade II lineage was dominant along the East and North coasts of Africa. Furthermore, the migration routes inferred from diversity decay suggested different expansion across China between the two lineages. Altogether, these differences indicated non-simultaneous domestication of the two lineages, which was possibly influenced by the response of pastoralists to the desertification of the Sahara and by the social expansion and trade of ancient humans in Northeast Africa, respectively.

Report

Tylorrhynchus heterochaetus is a widespread benthic polychaete worm found in coastal brackish waters of the west Pacific. It has high ecological and economic value as a biomarker of water quality and as a high-quality feed in aquaculture and fisheries and is considered a delicacy in some areas of Asia. However, it has experienced a marked reduction in recent years due to overexploitation as well as changes in the environment and climate. Here, to comprehensively understand its genetic background and thus provide insights for better conservation and utilization of this species, we assessed the genetic variability and demographic history of T. heterochaetus individuals sampled from eight locations along the coasts of southeast China and north Vietnam based on mitochondrial cytochrome c oxidase I (COI) sequences. We observed high haplotype diversity (Hd), with an average of 0.926, but relatively low nucleotide diversity (π), with a mean of 0.032 across all samples. A total of 94 polymorphic sites and 85 haplotypes were identified among 320 individuals. The pairwise genetic distances among haplotypes ranged from 0.001 to 0.067, with the high intraspecific divergence possibly reflecting geographic isolation and gene pool fragmentation. Significant genetic structures were revealed among the studied locations; specifically, the eight locations could be treated as six genetically different populations based on pairwise ΦST results (0.026–0.951, P<0.01). A significant pattern of isolation-by-distance was detected between the genetic and geographic distances (r=0.873, P=0.001). Three geographic lineages were defined based on phylogenetic tree and network analyses of COI haplotypes. AMOVA results indicated that genetic variations mainly occurred among the three lineages (89.96%). Tests of neutrality and mismatch distribution suggested that T. heterochaetus underwent recent population expansion. These results provide the first report on the genetic status of T. heterochaetus and will be valuable for the management of genetic resources and better understanding of the ecology and evolution in this species.

Letters to the editor

Many functional elements associated with traits and diseases are located in non-coding regions and act on distant target genes via chromatin looping and folding, making it difficult for scientists to reveal the genetic regulatory mechanisms. Capture Hi-C is a newly developed chromosome conformation capture technology based on hybridization capture between probes and target genomic regions. It can identify interactions among target loci and all other loci in a genome with low cost and high resolution. Here, we developed CaptureProbe, a user-friendly, graphical Java tool for the design of capture probes across a range of target sites or regions. Numerous parameters helped to achieve and optimize the designed probes. Design testing of CaptureProbe showed high efficiency in the design success ratio of target loci and probe specificity. Hence, this program will help scientists conduct genome spatial interaction research. CaptureProbe and source code are available at https://sourceforge.net/projects/captureprobe/.