Zoological Research

692−709

Authors: Mao-Sen Ye; Jin-Yan Zhang; Dan-Dan Yu; Min Xu; Ling Xu; Long-Bao Lv; Qi-Yun Zhu; Yu Fan; Yong-Gang Yao;

The Chinese tree shrew (Tupaia belangeri chinensis) is emerging as an important experimental animal in multiple fields of biomedical research. Comprehensive reference genome annotation for both mRNA and long non-coding RNA (lncRNA) is crucial for developing animal models using this species. In the current study, we collected a total of 234 high-quality RNA sequencing (RNA-seq) datasets and two long-read isoform sequencing (ISO-seq) datasets and improved the annotation of our previously assembled high-quality chromosome-level tree shrew genome. We obtained a total of 3  514 newly annotated coding genes and 50  576 lncRNA genes. We also characterized the tissue-specific expression patterns and alternative splicing patterns of mRNAs and lncRNAs and mapped the orthologous relationships among 11 mammalian species using the current annotated genome. We identified 144 tree shrew-specific gene families, including interleukin 6 (IL6) and STT3 oligosaccharyltransferase complex catalytic subunit B (STT3B), which underwent significant changes in size. Comparison of the overall expression patterns in tissues and pathways across four species (human, rhesus monkey, tree shrew, and mouse) indicated that tree shrews are more similar to primates than to mice at the tissue-transcriptome level. Notably, the newly annotated purine rich element binding protein A (PURA) gene and the STT3B gene family showed dysregulation upon viral infection. The updated version of the tree shrew genome annotation (KIZ version 3: TS_3.0) is available at http://www.treeshrewdb.org and provides an essential reference for basic and biomedical studies using tree shrew animal models.

721−725

Authors: Hang-Bo Hui; Ling Xiao; Wei Sun; Ying-Jie Zhou; Hai-Yan Zhang; Chu-Tian Ge;

SOX9 (SRY-related HMG box gene 9) is an essential regulator of male sex determination and testis differentiation in many vertebrate species. However, the functional role of Sox9 in testis differentiation has not yet been identified in any reptilian species. Herein, Sox9 knockdown in the red-eared slider turtle (Trachemys scripta) embryos at a male-producing temperature led to complete male-to-female sex reversal, characterized by the formation of an ovary-like structure, disappearance of male marker AMH, and ectopic expression of ovarian regulator FOXL2, as well as a female distribution pattern of germ cells. Conversely, in-ovo overexpression of Sox9 at a female-producing temperature resulted in partial masculinization of putative female embryos, with the coexistence of AMH and FOXL2. Our study provides the first direct evidence that Sox9 is indispensable for testicular differentiation in a reptilian species, further confirming the conserved role of Sox9 in vertebrate sexual development.

734−738

Authors: Yong-Chao Li; Jin-Feng Gao; Ya-Lun Guan; Xiao-Yue Wei; Xue-Jiao Li; Yun-Feng Li; Zhong-Qiang Huang; Shu-Hua Liu; Ge Li; Ping Xu; Guang-Jin Pan; Yu Zhang;

A new Hairless (Hr) gene mutant mouse line (SHJHhr) was identified, which showed hairless skin in adult individuals as reported in rhino mice. Through Hr gene mutant identification with polymerase chain reaction (PCR) amplification and sequencing, seven mutants were identified, including nonsense mutant site 2134C→T (R467X), which produced a truncated Hr protein. Metabolic activity and heart rate were measured using a metabolic cage and blood pressure instrument, respectively. The SHJHhr mice showed a strong metabolic rate, high heart rate, and low blood pressure. Histological analysis of the thyroid gland of SHJHhr mice showed abnormal follicular structure and hypertrophic thyrocytes. Compared to ICR mice, thyroid function in 4-month-old SHJHhr mice showed lower thyroid stimulating hormone (TSH) levels, and in 9-month-old SHJHhr mice showed significantly higher TSH and thyroid hormone levels. These data indicate that SHJHhr mice may be in a hyperthyroid state with increasing age. Thus, based on the above results, we successfully established a novel mouse model with thyroid dysfunction.

746−760

Authors: Sheng-Yu Luo; Jing-Qian Wang; Cheng Liu; Xin-Ming Gao; Yi-Bo Zhang; Jie Ding; Cong-Cong Hou; Jun-Quan Zhu; Bao Lou; Wei-Liang Shen; Xiong-Fei Wu; Chun-Dan Zhang; Dao-Jun Tang

Oxygen is an essential molecule for animal respiration, growth, and survival. Unlike in terrestrial environments, contamination and climate change have led to the frequent occurrence of hypoxia in aquatic environments, thus impacting aquatic animal survival. However, the adaptative mechanisms underlying fish responses to environmental hypoxia remain largely unknown. Here, we used large yellow croaker (Larimichthys crocea) and large yellow croaker fry (LYCF) cells to investigate the roles of the Hif-1α/Hsf1/Hsp70 signaling pathway in the regulation of cellular redox homeostasis, and apoptosis. We confirmed that hypoxia induced the expression of Hif-1α, Hsf1, and Hsp70 in vivo and in vitro. Genetic Hsp70 knockdown/overexpression indicated that Hsp70 was required for maintaining redox homeostasis and resisting oxidative stress in LYCF cells under hypoxic stress. Hsp70 inhibited caspase-dependent intrinsic apoptosis by maintaining normal mitochondrial membrane potential, enhancing Bcl-2 mRNA and protein expression, inhibiting Bax and caspase3 mRNA expression, and suppressing caspase-3 and caspase-9 activation. Hsp70 suppressed caspase-independent intrinsic apoptosis by inhibiting nuclear translocation of apoptosis-inducing factor (AIF) and disturbed extrinsic apoptosis by inactivating caspase-8. Genetic knockdown/overexpression of Hif-1α and dual-luciferase reporter assay indicated that Hif-1α activated the Hsf1 DNA promoter and enhanced Hsf1 mRNA transcription. Hsf1 enhanced Hsp70 mRNA transcription in a similar manner. In summary, the Hif-1α/Hsf1/Hsp70 signaling pathway plays an important role in regulating redox homeostasis and anti-apoptosis in L. crocea under hypoxic stress.

772−782

Authors: Zhe-Lun Peng; Bin-Xu Yin; Rui-Min Ren; Yin-Long Liao; Hao Cai; Heng Wang

Salamanders are unique among tetrapods in their ability to regenerate the limbs throughout life. Like other poikilothermic amphibians, salamanders also show a remarkable capacity to survive long periods of starvation. Whether the physiological reserves necessary for tissue regeneration are preserved or sacrificed in starved salamanders is unknown. In the current study, we maintained Iberian ribbed newts (Pleurodeles waltl) under extreme physiological stress to assess the extent of regeneration and identify the molecular and cellular changes that may occur under such conditions. After 19 months of complete food deprivation, the animals exhibited extensive morphological and physiological adaptations but remained behaviorally active and vigilant. Autophagy was elevated in different tissues and the transformed gut microbiota indicated remodeling of the intestinal tract related to autophagy. Upon limb amputation in animals starved for 21 months, regeneration proceeded with progenitor cell proliferation and migration, leading to limb blastema formation. However, limb outgrowth and patterning were substantially attenuated.Blockage of autophagy inhibited cell proliferation and blastema formation in starved animals, but not in fed animals. Hence, tissue autophagy and the regenerative response were tightly coupled only when animals were under stress. Our results demonstrate that under adverse conditions, salamanders can exploit alternative strategies to secure blastema formation for limb regeneration.

789−791

Authors: Xiaochun Xie; Jian-Bao Han; Guanqin Ma; Xiao-Li Feng; Xiaohong Li; Qing-Cui Zou; Zhong-Hua Deng; Jianxiong Zeng

Although it first appeared almost two years ago, the COVID-19 pandemic continues to have an impact on a global scale, in part due to newly emerging SARS-CoV-2 variants such as Delta and Lambda. The B.1.621 variant, first identified in Colombia in January 2021, was classified as a variant of interest (VOI) and designated as Mu by the World Health Organization (WHO) in August 2021. However, its infectivity and resistance to neutralizing antibodies remain largely unknown. Here, in comparison to Delta, the Mu variant showed an unexpectedly enhanced immune resistance to inactivated vaccine-elicited antibodies. Nevertheless, Mu demonstrated less infectivity than Delta, implying a biological trade-off between viral transmission and immune escape. This study strongly calls for urgent evaluation of the protective efficacy of current COVID-19 vaccines against the Mu variant. Variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are of concern regarding control of the global COVID-19 pandemic (Wang et al., 2021). The SARS-CoV-2 B.1.621 variant was first identified in Colombia in January 2021. Considering its epidemiological prevalence, the WHO defined B.1.621 (named Mu) as a VOI on 30 August 2021. As of September 2021, the WHO has classified four variants of concern (VOC), i.e., Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), and Delta (B.1.617.2), and two VOI, i.e., Lambda (C.37) and Mu (B.1.621) (Supplementary Figure S1A).

796−799

Authors: Na Zhao; Hao-Bing Guo; Lei Jia; Qiu-Xia Deng; Chun-Hua Zhu; Bo Zhang

In the present study, we successfully assembled a high-quality genome of Planiliza haematocheila (redlip mullet) based on Oxford Nanopore long read, single-tube long fragment read (stLFR), and Hi-C chromatin interaction sequencing. The size of the P. haematocheila genome was 652.91 Mb. More than 93.8% of BUSCO genes were detected, and the N50 lengths of contigs and scaffolds reached 7.21 Mb and 28.01 Mb, respectively, thus demonstrating outstanding genome completeness and sequence continuity. A total of 21  045 protein-coding genes were predicted in the assembled genome, and 99.77% of those genes were functionally annotated. Comparative genomic and phylogenetic analyses revealed the adaptability of P. haematocheila to complex living environments at the genomic level, highlighting its broad adaptability and resistance to multiple stresses as an important economic fish. The high-quality reference chromosome-level genome of P. haematocheila provides a powerful genomic resource for further systematic study of Mugilidae.

825−833

Authors: Qiao-Yun Wang; Kai-Dan Zheng; Xue-Song Han; Fang He; Xiang Zhao; Peng-Fei Fan; Lu Zhang

As a top predator, the Eurasian otter (Lutra lutra) is an indicator of healthy freshwater ecosystems and a flagship species for conservation. Once widespread in China, the species is now distributed mainly in the upper reaches of the great rivers of western China. However, a lack of knowledge on local otter populations continues to hinder their conservation in China. Here, we conducted a detailed study on habitat use of Eurasian otters in Yushu City and Tangjiahe National Nature Reserve in western China using transect surveys. At both study sites, otters preferred to defecate on large rocks close to or protruding from the river and about 50 cm above the waterline. In Yushu, no spraints were found along the 5 km river bank section in the downtown area, with otters preferring sprainting sites with natural banks, riparian zones, and lower human population density. However, this pattern was not obvious at Tangjiahe, where river transformation and human disturbance are minor. Otter river use intensity was negatively correlated with elevation and human population density in Yushu in both seasons. In Tangjiahe, otter river use intensity was positively correlated with prey mass and flow rate and negatively correlated with human population in spring, but positively correlated with human population and negatively correlated with flow rate in autumn. These results reflect the flexible habitat use strategies of otters at different sites, underlining the necessity to study otters living in different regions and habitat types. We provide suggestions for river modification and call for more site-specific studies to promote otter conservation in China.