Hypercholesterolemia induced by spontaneous oligogenic mutations in rhesus macaques (Macaca mulatta)

BACKGROUND

A rhesus macaque with the fourth highest plasma cholesterol (CH) levels of 501 breeding macaques was identified 22 years ago. Seven offspring with gene mutations causing hypercholesterolemia were obtained.

METHODS

Activity of low-density lipoprotein receptor (LDLR), plasma CH levels and mRNA expression levels of LDLR were measured after administration of 0.1% (0.27 mg/kcal) or 0.3% CH.

RESULTS

Activity of p. (Cys82Tyr) of LDLR was 71% and 42% in the heterozygotes and a homozygote, respectively. The mRNA expression level of LDLR in the p. (Val241Ile) of membrane-bound transcription factor protease, site 2 (MBTPS2, S2P protein) was 0.83 times lower than normal levels. LDLR mRNA levels were increased for up to 4 weeks by administration of 0.3% CH before suddenly decreasing to 80% of the baseline levels after 6 weeks.

CONCLUSION

Oligogenic mutations of p. (Cys82Tyr) in LDLR and p. (Val241Ile) in MBTPS2 (S2P) caused hypercholesterolemia exceeding cardiovascular risk levels under a 0.1% CH diet.

Corrigendum: Batch and sampling time exert a larger influence on the fungal community than gastrointestinal location in model animals: A meaningful case study

[This corrects the article DOI: 10.3389/fnut.2022.1021215.].

Batch and sampling time exert a larger influence on the fungal community than gastrointestinal location in model animals: A meaningful case study

Fungi play a fundamental role in the intestinal ecosystem and health, but our knowledge of fungal composition and distribution in the whole gastrointestinal tract (GIT) is very limited. The physiological similarity between humans and pigs in terms of digestive and associated metabolic processes places, the pig in a superior position over other non-primate models. Here, we aimed to characterize the diversity and composition of fungi in the GIT of pigs. Using high-throughput sequencing, we evaluated the fungal community in different locations of GIT of 11 pigs with 128.41 ± 1.25 kg body weight acquired successively. Among them, five pigs are sacrificed in April 2019 (Batch 1) and the other six are sacrificed in January 2020 (Batch 2). All subjects with similar genetic backgrounds, housing, management, and diet. Finally, no significant difference is found in the α-diversity (Richness) of the fungal community among all intestinal segments. Basidiomycota and Ascomycota are the two predominant fungal phyla, but Batch 1 harbored a notably high abundance of Basidiomycota and Batch 2 harbored a high abundance of Ascomycota. Moreover, the two batches harbored completely different fungal compositions and core fungal genera. FUNGuild (Fungal Functional Guild) analysis revealed that most of the fungal species present in the GIT are saprotroph, plant pathogen, and animal endosymbiont. Our study is the first to report that even under the same condition, large variations in fungal composition in the host GIT still occur from batch-to-batch and sampling time. The implications of our observations serve as references to the development of better models of the human gut.

Planarians as an In Vivo Experimental Model for the Study of New Radioprotective Substances

Ionising radiation causes the death of the most actively dividing cells, thus leading to depletion of the stem cell pool. Planarians are invertebrate flatworms that are unique in that their stem cells, called neoblasts, constantly replace old, damaged, or dying cells. Amenability to efficient RNAi treatments, the rapid development of clear phenotypes, and sensitivity to ionising radiation, combined with new genomic technologies, make planarians an outstanding tool for the discovery of potential radioprotective agents. In this work, using the well-known antioxidant N-acetylcysteine, planarians are, for the first time, shown to be an excellent model system for the fast and effective screening of novel radioprotective and radio-sensitising substances. In addition, a panel of measurable parameters that can be used for the study of radioprotective effects on this model is suggested.

Photoperiod-independent testicular development in the model newt Pleurodeles waltl

Urodele amphibian newts have unique biological properties in male gametogenesis, in addition to their extreme regenerative capacity. Male newts are able to regenerate new testes even after reaching sexual maturity and can possess multiple testes. Notably, these animals maintain primordial germ cell-like cells in a tissue adjacent to the testis. Spermatogenesis proceeds while synchronizing in a region-specific manner in the testis. However, the newt species that have been used most commonly require 2-3 years to achieve sexual maturity, and spermatogenesis in these species shows seasonality. These traits have restricted the use of newts for studies on testicular development and spermatogenesis, and testis development in newts remains poorly characterized. Recently, the Iberian ribbed newt Pleurodeles waltl has been established as an emerging model organism. P. waltl reaches sexual maturity more quick after birth than do other newts and is capable of breeding year-round. Thus, P. waltl is expected to serve as an appealing experimental model for studying the mechanisms of male gametogenesis in the urodeles. In the present study, we use P. waltl to describe the entire developmental process of the newt testis from primordial gonad to maturity. Notably, the mature testes show synchronized progression of spermatogenesis along the anteroposterior axis. Additionally, we demonstrate that the process of spermatogenesis in P. waltl proceeds irrespective of day length. Our results show that P. waltl newts are a suitable model for investigating the process of testicular development. We also expect that these results will be useful for the maintenance of P. waltl bioresources.

A Decade in Review after Idiopathic Scoliosis Was First Called a Complex Trait-A Tribute to the Late Dr. Yves Cotrel for His Support in Studies of Etiology of Scoliosis

Adolescent Idiopathic Scoliosis (AIS) is a prevalent and important spine disorder in the pediatric age group. An increased family tendency was observed for a long time, but the underlying genetic mechanism was uncertain. In 1999, Dr. Yves Cotrel founded the Cotrel Foundation in the Institut de France, which supported collaboration of international researchers to work together to better understand the etiology of AIS. This new concept of AIS as a complex trait evolved in this setting among researchers who joined the annual Cotrel meetings. It is now over a decade since the first proposal of the complex trait genetic model for AIS. Here, we review in detail the vast information about the genetic and environmental factors in AIS pathogenesis gathered to date. More importantly, new insights into AIS etiology were brought to us through new research data under the perspective of a complex trait. Hopefully, future research directions may lead to better management of AIS, which has a tremendous impact on affected adolescents in terms of both physical growth and psychological development.

Nucleated red blood cells participate in myocardial regeneration in the toad Bufo Gargarizan Gargarizan

Heart regeneration is negligible in humans and mammals but remarkable in some ectotherms. Humans and mammals lack nucleated red blood cells (NRBCs), while ectotherms have sufficient NRBCs. This study used Bufo gargarizan gargarizan, a Chinese toad subspecies, as a model animal to verify our hypothesis that NRBCs participate in myocardial regeneration. NRBC infiltration into myocardium was seen in the healthy toad hearts. Heart needle-injury was used as an enlarged model of physiological cardiomyocyte loss. It recovered quickly and scarlessly. NRBC infiltration increased during the recovery. Transwell assay was done to in vitro explore effects of myocardial injury on NRBCs. In the transwell system, NRBCs could infiltrate into cardiac pieces and could transdifferentiate toward cardiomyocytes. Heart apex cautery caused approximately 5% of the ventricle to be injured to varying degrees. In the mildly to moderately injured regions, NRBC infiltration increased and myocardial regeneration started soon after the inflammatory response; the severely damaged region underwent inflammation, scarring, and vascularity before NRBC infiltration and myocardial regeneration, and recovered scarlessly in four months. NRBCs were seen in the newly formed myocardium. Enzyme-linked immunosorbent assay and Western blotting showed that the levels of tumor necrosis factor-α, interleukin- 1β, 6, and11, cardiotrophin-1, vascular endothelial growth factor, erythropoietin, matrix metalloproteinase- 2 and 9 in the serum and/or cardiac tissues fluctuated in different patterns during the cardiac injury-regeneration. Cardiotrophin-1 could induce toad NRBC transdifferentiation toward cardiomyocytes in vitro. Taken together, the results suggest that the NRBC is a cell source for cardiomyocyte renewal/regeneration in the toad; cardiomyocyte loss triggers a series of biological processes, facilitating NRBC infiltration and transition to cardiomyocytes. This finding may guide a new direction for improving human myocardial regeneration.

Forward genetic approach for behavioral neuroscience using animal models

Forward genetics is a powerful approach to understand the molecular basis of animal behaviors. Fruit flies were the first animal to which this genetic approach was applied systematically and have provided major discoveries on behaviors including sexual, learning, circadian, and sleep-like behaviors. The development of different classes of model organism such as nematodes, zebrafish, and mice has enabled genetic research to be conducted using more-suitable organisms. The unprecedented success of forward genetic approaches was the identification of the transcription-translation negative feedback loop composed of clock genes as a fundamental and conserved mechanism of circadian rhythm. This approach has now expanded to sleep/wakefulness in mice. A conventional strategy such as dominant and recessive screenings can be modified with advances in DNA sequencing and genome editing technologies.

Role of brown adipose tissue in body temperature control during the early postnatal period in Syrian hamsters and mice

Brown adipose tissue (BAT) contributes to non-shivering thermogenesis and plays an important role in body temperature control. The contribution of BAT thermogenesis to body temperature control in a non-cold environment was evaluated using developing hamsters. Immunostaining for uncoupling protein 1 (UCP1), a mitochondrial protein responsible for BAT thermogenesis, indicated that interscapular fat tissue had matured as BAT at day 14. When pups were placed on a thermal plate kept at 23°C, the body surface temperature decreased in day 7- and 10-day-old pups but was maintained at least for 15 min in 14-day-old pups, indicating that hamsters are unable to maintain their body temperature until around day 14 even in a non-cold environment. Body temperature maintenance was also evaluated in UCP1-deficient mice. BAT analysis showed that the UCP1 protein level in Ucp1^+/− Hetero mice was 61.3 ± 1.4% of that in wild-type (WT) mice and was undetected in Ucp1^−/− knockout (KO) mice. When 12-day-old pups were place on a thermal plate at 23°C, body surface temperature was maintained for at least 15 min in WT and Hetero mice but gradually dropped by 2.4 ± 0.2°C in 15 min in KO mice. It is concluded that BAT thermogenesis is indispensable for body temperature maintenance in pups of hamsters and mice, even in the non-cold circumstances. The early life poikilothermy and the later acquirement of homeothermy in hamsters may be because of the postnatal development of BAT.

Hatano rats are a suitable metabolic syndrome model for studying feeding behavior, blood pressure levels, and percent body fat

Currently, metabolic syndrome is a worldwide concern. Thus, it is imperative to understand the mechanism of metabolic syndrome by establishing various metabolic syndrome models. In this study, we used Hatano high-avoidance animals (HAA) and low-avoidance animals (LAA), both derived from Sprague–Dawley rats by selective breeding to determine high- or low-avoidance rates in shuttle-box active avoidance tests. HAA and LAA rats have some strain differences related to eating and appetite. Therefore, we determined whether Hatano rats could be used as a metabolic syndrome model. We compared food intake, body weights, blood pressure levels, plasma component levels, and fat contents between HAA and LAA rats. The HAA rats showed more active eating, higher blood pressure, higher percentage fat, and higher triglyceride levels than the LAA rats—these features correspond to some of the risk factors associated with metabolic syndrome. Our study suggests that HAA rats can be considered as a metabolic syndrome model by focusing on their feeding behavior, blood pressure levels, and percent body fat.

Frailty and Caenorhabditis elegans as a Benchtop Animal Model for Screening Drugs Including Natural Herbs

Caenorhabditis elegans has been used in research for years to clarify the genetic cascades and molecular mechanisms of aging, longevity, and health span. Health span is closely related to frailty; however, frailty has a different concept and is evaluated using various parameters in humans, such as Fried's Frailty Criteria. The C. elegans model has several advantages when performing a chemical screen to identify drug candidates. Several mouse models of frailty were recently developed, including a homozygous IL-10 knockout. These mouse models are useful for understanding human frailty; however, they are not appropriate for primary drug screening because they require large spaces, expensive cost, and time consuming assessments. Therefore, a combination of these models may be a promising tool for discovering drugs and understanding the mechanisms of frailty. In addition, natural products, and herbs are attractive sources of novel drugs with pharmacological activity and low toxicity, in fact, over 60% of currently-available drugs are estimated to be related to natural compounds. In this review, the possibility of identifying natural agents (i.e., herb extracts and compounds) that could improve frailty are proposed, and the advantages and limitations of these models are also discussed.

The Establishment of a CSF-Contacting Nucleus "Knockout" Model Animal

To establish an entirely cerebrospinal fluid (CSF)-contacting nucleus-deficient model animal, we used cholera toxin B subunit (CB)- saporin (SAP), which is an analog of CB-HRP that specifically labels the CSF-contacting nucleus, to exclusively damage the nucleus. The effectiveness and specificity of the ablation were evaluated upon days 1-10 after CB-SAP microinjection into the brain ventricular system. The vital status, survival, and common physiological parameters of the model animals were also assessed during the experimental period. The results demonstrated that CB-SAP damaged only the CSF-contacting nucleus, but not other functional structures, in the brain. The complete ablation occurred by day 7 after CB-SAP microinjection. A model animal that had no CSF-contacting nucleus was established after survival beyond that time point. No obvious effects were observed in the vital status of the model animals, and their survival was ensured. The common physiological parameters of model animals were stable. The present study provides a method to establish a CSF-contacting nucleus "knockout" model animal, which is similar to a gene knockout model animal for studying this particular nucleus in vivo.

Exploring the pathogenetic mechanisms underlying Parkinson's disease in medaka fish

Teleost fish have recently been employed as a model for human neurodegenerative diseases. We used toxin exposure and genetic engineering to develop models of Parkinson's disease (PD) in the teleost fish, medaka. Among the toxins examined, 1-methyl-4-phenyl-1,2,3,4-tetrahydropyridine (MPTP), 6-hydroxydopamine (6-OHDA), proteasome inhibitors, lysosome inhibitors, and tunicamycin all induced important features of PD in medaka. Specifically, these agents induced dopaminergic cell loss and reduced spontaneous movement, and the latter three toxins produced inclusion bodies that were ubiquitously distributed in the medaka brain. Despite the extensive distribution of these inclusion bodies, the middle diencephalic dopaminergic neurons were particularly susceptible to the effect of the toxins, suggesting that this cluster of dopaminergic neurons is analogous to the human substantia nigra. We have also created a variety of different genetic models using the Targeting Induced Local Lesions in Genomes (TILLING) method, and found that neither PTEN-induced putative kinase 1 (PINK1) mutants nor Parkin mutants disclosed significant dopaminergic cell loss. Surprisingly however, PINK1 and Parkin double mutants exhibited selective dopamine cell loss, as well as aggregation and deficit of mitochondrial activity. Another mutant, the ATP13A2 mutant, also expressed a PD phenotype, exhibiting marked cathepsin D reduction and fingerprint-like structures that are generally found in lysosome storage diseases. Taken together, these data indicate that medaka fish can serve as a new animal model for PD. In this review, we summarize our data and discuss the potential for future application of this animal model.

Characterization of a novel genetically obese mouse model demonstrating early onset hyperphagia and hyperleptinemia

Obesity is a critical risk factor for the development of metabolic syndrome, and many obese animal models are used to investigate the mechanisms responsible for the appearance of symptoms. To establish a new obese mouse model, we screened ∼13,000 ICR mice and discovered a mouse demonstrating spontaneous obesity. We named this mouse "Daruma" after a traditional Japanese ornament. Following the fixation of the genotype, these animals exhibited obese phenotypes according to Mendel's law of inheritance. In the Daruma mouse, the leptin receptor gene sequence carried two base mutations that are good candidates for the variation(s) responsible for the obese phenotype. The Daruma mice developed characteristic visceral fat accumulation at 4 wk of age, and the white adipose and liver tissues exhibited increases in cell size and lipid droplets, respectively. No histological abnormalities were observed in other tissues of the Daruma mice, even after the mice reached 25 wk of age. Moreover, the onset of impaired leptin signaling was early and manifested as hyperleptinemia and hyperinsulinemia. Pair feeding completely inhibited obesity, although these mice rapidly developed hyperphagia and obesity followed by hyperleptinemia when pair feeding ceased and free-access feeding was permitted. Therefore, the Daruma mice exhibited unique characteristics and may be a good model for studying human metabolic syndrome.

Early diagnosis of rats with acute myocardial infarction by measurement of brain natriuretic peptide

The aim of this study was to detect early changes (within 1–4 h) in the brain natriuretic peptide (BNP) levels of rats with acute myocardial infarction (AMI). A total of 35 Wistar rats were established as models of AMI and 30 sham-operated rats were used as the control group. The myocardia of the two groups were observed using a transmission electron microscope (TEM) prior to and following surgery. A double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) was used to detect the serum BNP and cardiac troponin I (cTnI) concentrations before and 1–4 h after surgery. Following the successful establishment of the AMI models, serum BNP concentrations were significantly increased within 1–4 h compared with the values prior to surgery and with those of the control group (all P<0.01). The serum BNP concentration reached its highest level 2 h after AMI (532.25±15.16 ng/l). No significant changes were observed in the cTnI serum levels of the AMI group within 1–4 h compared with the values before AMI and those in the control group (all P>0.05). In the 1–4 h following the establishment of the AMI model, significant positive correlations were identified between the serum BNP concentrations and the size of the AMI and the most marked correlation occurred 2 h after AMI (r=0.72, P<0.05). No significant differences were noted in the serum concentrations of BNP and cTnI in the control group prior to and following the sham surgery (all P>0.05). BNP may be used as a blood marker for the early diagnosis of AMI, particularly 1–4 h after the onset of AMI, and to predict the size of the infarct area.

Medaka fish Parkinson's disease model

The teleost fish has been widely used in creating neurodegenerative models. Here we describe the teleost medaka fish Parkinson's disease (PD) models we developed using toxin treatment and genetic engineering. 1-Methyl-4-phenyl-1,2,3,4-tetrahydropyridine (MPTP), 6-hydroxydopamine (6-OHDA), proteasome inhibitors, lysosome inhibitors and tunicamycin treatment in our model fish replicated some salient features of PD: selective dopamine cell loss and reduced spontaneous movement with the last three toxins producing inclusion bodies ubiquitously in the brain. Despite the ubiquitous distribution of the inclusion bodies, the middle diencephalic dopaminergic neurons were particularly vulnerable to these toxins, supporting the idea that this dopamine cluster is similar to the human substantia nigra. PTEN-induced putative kinase 1 (PINK1) homozygous mutants also showed reduced spontaneous swimming movements. These data indicate that medaka fish can serve as a new model animal of PD. In this review we summarize our previous data and discuss future prospects.

Assessing learning and memory in pigs

In recent years, there has been a surge of interest in (mini) pigs (Sus scrofa) as species for cognitive research. A major reason for this is their physiological and anatomical similarity with humans. For example, pigs possess a well-developed, large brain. Assessment of the learning and memory functions of pigs is not only relevant to human research but also to animal welfare, given the nature of current farming practices and the demands they make on animal health and behavior. In this article, we review studies of pig cognition, focusing on the underlying processes and mechanisms, with a view to identifying. Our goal is to aid the selection of appropriate cognitive tasks for research into pig cognition. To this end, we formulated several basic criteria for pig cognition tests and then applied these criteria and knowledge about pig-specific sensorimotor abilities and behavior to evaluate the merits, drawbacks, and limitations of the different types of tests used to date. While behavioral studies using (mini) pigs have shown that this species can perform learning and memory tasks, and much has been learned about pig cognition, results have not been replicated or proven replicable because of the lack of validated, translational behavioral paradigms that are specially suited to tap specific aspects of pig cognition. We identified several promising types of tasks for use in studies of pig cognition, such as versatile spatial free-choice type tasks that allow the simultaneous measurement of several behavioral domains. The use of appropriate tasks will facilitate the collection of reliable and valid data on pig cognition.