Elucidating the characteristics of Mx1 and resistance to influenza A virus subtype H1N1 in the newly developed KWM/Hym mice.

BACKGROUND: Inbred mice have several advantages, including genetic similarity to humans, a well-established gene manipulation system, and strong tolerance to inbreeding. However, inbred mice derived from a limited genetic pool have a small genetic diversity. Thus, the development of new inbred strains from wild mice is needed to overcome this limitation. Hence, in this study, we used a new strain of inbred mice called KWM/Hym. We sequenced the Mx1 gene to elucidate the genetic diversities of KWM/Hym mice and observed the biological alterations of the Mx1 protein upon influenza A infection. RESULTS: The Mx1 gene in KWM/Hym mice had 2, 4, and 38 nucleotide substitutions compared to those in the Mx1 gene in A2G, CAST/EiJ, and Mus spretus mice, respectively. Moreover, the Mx1 protein in KWM/Hym mice had 2 and 25 amino acid substitutions compared to those in the Mx1 protein in CAST/EiJ and M. spretus mice, respectively. To elucidate the function of the Mx1 protein, we inoculated the influenza A virus (A/WSN/1933) in KWM/Hym mice. Nine days after infection, all infected KWM/Hym mice survived without any weight loss. Four days after infection, the lungs of the infected KWM/Hym mice showed mild alveolitis and loss of bronchiolar epithelium; however, the pulmonary viral titers of the infected KWM/Hym mice were significantly lower than that in the infected BALB/c mice (2.17 × plaque-forming units mL-1). CONCLUSIONS: Our results demonstrate that the KWM/Hym mice are resistant to influenza A virus infection. Further, these mice can be used as a model organism to understand the mechanism of influenza A virus susceptibility.

Metagenomic Analysis of the Gut Microbiota of Wild Mice, a Newly Identified Reservoir of Campylobacter.

Campylobacter, the most common etiologic agent of zoonotic gastroenteritis in humans, is present in many reservoirs including livestock animals, wildlife, soil, and water. Previously, we reported a novel Campylobacter jejuni strain SCJK02 (MLST ST-8388) from the gut of wild mice (Micromys minutus) using culture-dependent methods. However, due to fastidious growth conditions and the presence of viable but non-culturable Campylobacter spp., it is unclear whether M. minutus is a Campylobacter reservoir. This study aimed to: 1) determine the distribution and proportion of Campylobacter spp. in the gut microbiota of wild mice using culture-independent methods and 2) investigate the gut microbiota of wild mice and the relationship of Campylobacter spp. with other gut microbes. The gut microbiota of 38 wild mice captured from perilla fields in Korea and without any clinical symptoms (18 M. minutus and 20 Mus musculus) were analyzed. Metagenomic analysis showed that 77.8% (14 of 18) of the captured M. minutus harbored Campylobacter spp. (0.24-32.92%) in the gut metagenome, whereas none of the captured M. musculus carried Campylobacter spp. in their guts. Notably, 75% (6 of 8) of M. minutus determined to be Campylobacter-negative using culture-dependent methods showed a high proportion of Campylobacter through metagenome analysis. The results of metagenome analysis and the absence of clinical symptoms suggest that Campylobacter may be a component of the normal gut flora of wild M. minutus. Furthermore, linear discriminant analysis (LDA) showed that Campylobacter was the most enriched genus in the gut microbiota of M. minutus (LDA score, 5.37), whereas Lactobacillus was the most enriched genus in M. musculus (LDA score, -5.96). The differences in the presence of Campylobacter between the two species of wild mice may be attributed to the differential abundance of Campylobacter and Lactobacillus in their respective gut microbiota. In conclusion, the results indicate that wild M. minutus may serve as a potential Campylobacter reservoir. This study presents the first metagenomics analysis of the M. minutus gut microbiota to explore its possible role as an environmental Campylobacter reservoir and provides a basis for future studies using culture-independent methods to determine the role of environmental reservoirs in Campylobacter transmission.

Aged black garlic extract regulates lipid metabolism by inhibiting lipogenesis and promoting lipolysis in mature 3T3-L1 adipocytes.

As the mechanism of aged black garlic (ABG) extract affecting lipid metabolism in adipocytes remains unclear, this study evaluated the effect of ABG extract on lipid metabolism and the expression of related proteins in mature 3T3-L1 adipocytes. ABG extract treatments at 0, 0.625, 1.25, and 2.5, and 5 mg/mL had no effect on cell morphology or viability in adipocytes. ABG extract suppressed lipogenesis and induced lipolysis in a dose-dependent manner compared to control. Furthermore, ABG extract at 2.5 and 5 mg/mL significantly reduced protein expression of proliferator activated receptor γ (PPARγ) and perilipin in mature 3T3-L1 adipocytes. The hormone-sensitive lipase (HSL) and Ser563-pHSL levels were also significantly reduced by treatment with 5 mg/mL of ABG extract. Taken together, these results suggest that ABG extract has anti-lipogenic and lipolytic effects in mature 3T3-L1 adipocytes, indicating a potential in anti-obesity therapies.

Genetic and morphometric characteristics of Korean wild mice (KWM/Hym) captured at Chuncheon, South Korea.

Laboratory inbred mice are used widely and commonly in biomedical research, but inbred mice do not have a big enough gene pool for the research. In this study, genetic and morphometric analyses were performed to obtain data on the characteristics of a newly developing inbred strain (KWM/Hym) captured from Chuncheon, Korea. All of five Korean wild male mice have the zinc-finger Y (ZfY) gene. Also, all of 19 Korean wild mice used in this analysis have the AKV-type murine leukemia virus gene, indicating that Korean wild mice might be Mus musculus musculus. To identify the genetic polymorphism in KWM/Hym, SNP analysis was performed. In a comparison with 28 SNP markers, there was a considerable difference between KWM/Hym and several inbred strains. The homogeneity between KWM/Hym and the inbred strains was as follows: C57BL/6J (39.3%), BALB/c AJic (42.9%), and DBA/2J (50%). KWM/Hym is most similar to the PWK/PhJ inbred strain (96.4%) derived from wild mice (Czech Republic). To identify the morphometric characteristics of KWM/Hym, the external morphology was measured. The tail ratio of male and female was 79.60±3.09 and 73.55±6.14%, respectively. KWM/Hym has short and agouti-colored hairs and its belly is white with golden hair. Taking these results together, KWM/Hym, a newly developing inbred mouse originated from wild mouse, might be use as new genetic resources to overcome the limitations of the current laboratory mice.

Improving glycemic control in model mice with type 2 diabetes by increasing superoxide dismutase (SOD) activity using silk fibroin hydrolysate (SFH).

Islet cell dysfunction in type 2 diabetes is primarily attributed to the increased apoptosis of pancreatic beta cells. Silk fibroin hydrolysate (SFH) has an effect on blood in type 2 diabetes model mice (C57BL/KsJ-db/db). However, its exact mechanism is unknown. The type 2 diabetes model mice were randomly divided into non-diabetic mice (ND), diabetic mice (DB), and diabetic mice treated with silk fibroin hydrolysate (DB-SFH). The results showed that SFH significantly decreased fasting blood glucose and hemoglobin A1c (HbA1c). The oral glucose tolerance and insulin tolerance were significantly improved in the DB-SFH group. The DB-SFH group exhibited increased superoxide dismutase (SOD) activity in the plasma, as well as increased Mn-SOD and CuZn-SOD activities in the pancreatic islets. Furthermore, the pancreatic islet cells' death was decreased in the DB-SFH group. In the DB-SFH group, the protein expression of caspase-3 was significantly decreased compared with the DB group. The expression of the Nkx6.1 and Pdx1 proteins were increased in the DB-SFH group. The results suggest that SFH prevents the degeneration of pancreatic islets via increasing SOD while hyperglycemia is alleviated by maintaining beta cell mass in type 2 diabetes model mice.

Over-expression of myosin7A in cochlear hair cells of circling mice.

Circling mouse (C57BL/6J-cir/cir) deleted the transmembrane inner ear (Tmie) gene is an animal model for human non-syndromic recessive deafness, DFNB6. In circling mouse, hair cells in the cochlea have degenerated and hair bundles have become irregularity as time goes on. Tmie protein carries out a function of the mechanoelectrical transduction channel in cochlear hair cells. Myosin7a (MYO7A) protein has key roles in development of the cochlear hair bundles as well as in the function of cochlear hair cells. To find whether Tmie protein interacts with MYO7A proteins in the cochlea postnatal developmental stage, we investigated expression of the MYO7A proteins in the cochlear hair cells of circling mice by western blot analysis and whole mount immunofluorescence at postnatal day 5 (P5). The expression of MYO7A showed statistically significant increase in the cochlea of C57BL/6J-+/cir and C57BL/6J-cir/cir mice than that of C57BL/6J-+/+ mice. The MYO7A intensity of the cochlear hair cells also increased in C57BL/6J-+/cir and C57BL/6J-cir/cir mice compared with those of C57BL/6J-+/+ mice. Taken together, the results indicate that Tmie protein may have an important role with MYO7A protein in the development and maintenance of the stereociliary bundles during postnatal developmental stage of the cochlea.

Reduction of dynamin 1 in the hippocampus of aged mice is associated with the decline in hippocampal­dependent memory.

Dynamin 1 is a known synaptic protein, which has is key in the presynaptic regulation of endocytosis. The present study investigated the association between age and the observed changes in Morris water maze performance, and immunoreactivity and protein levels of dynamin 1 in the mouse hippocampal formation. In addition, the effects of dynasore, an inhibitor of dynamin 1, on the hippocampal dependent memory were determined to elucidate the correlation between dynamin 1 and memory. In the training phase of the Morris water maze task, the mean escape latency of the aged group (24 months old) was significantly longer, compared with that of the adult group (4 months old), although the average swimming speed and the total distance traveled during the probe trial were similar in the two groups. In the aged group, the time spent locating the target platform was significantly longer and the time spent in the correct quadrant was significantly shorter, compared with those in the adult group. In the adult group, a moderate level of dynamin 1 was detected in the hippocampal CA1 and CA3 regions, and in the dentate gyrus. In the aged group, the immunoreactivity of dynamin 1 was almost eliminated in the CA3 region and the dentate gyrus. In addition, the protein levels of dynamin 1 in the brain were significantly lower in the aged group, compared with those in the adult group. The direct infusion of dynasore, significantly reduced the contextual memory, compared with that of animals in the vehicle­treated group. These results suggested that dynamin 1 was susceptible to the aging process, and that a reduction in dynamin 1 may result in hippocampal­dependent memory deficits by disrupting endocytosis and the release of neurotransmitters.

Erratum: Rapid and efficient identification of the mouse leptin receptor mutation (C57BLKS/J-Lepr(db) ) by tetra-primer amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) analysis.

[This corrects the article on p. 70 in vol. 32, PMID: 27051445.].

Rapid and efficient identification of the mouse leptin receptor mutation (C57BL/KsJ-db/db) by tetra-primer amplification refractory mutation system-polymerase chain reaction (ARMS-PCR) analysis.

The C57BLKS/J-Lepr(db) mouse has a point mutation in the leptin receptor gene and is one of the most useful animal model for non-insulin dependent diabetes mellitus in human. Since the homozygote of C57BLKS/J-Lepr(db) mouse is infertile, detection of point mutation in the leptin receptor gene is important for efficient maintaining strains as well as mass production of homozygotes. To develop a rapid and efficient genotyping method for C57BLKS/J-Lepr(db) mouse, the tetra-primer amplification-refractory mutation system polymerase chain reaction (ARMS-PCR) was used. The 407 and 199 bp PCR products were amplified from normal (+/+) mice; while the 407 and 268 bp PCR products were amplified from homozygotes (db/db) mice; and the 407, 268, and 199 bp PCR products were amplified from heterozygotes (db/+) mice. This result showed that the tetra-primer ARMS-PCR analysis by us is suitable to detect point mutation of the leptin receptor gene. Taken together, our method will dramatically reduce animal use for maintenance of strains as well as production of homozygote in the C57BLKS/J-Lepr(db) strains.

Comparison of N-methyl-D-aspartate receptor subunit 1 and 4-hydroxynonenal in the hippocampus of natural and chemical-induced aging accelerated mice.

In this study, we compared N-methyl-D-aspartate receptor type 1 (NMDAR1) and 4-hydroxynonenal (4-HNE) in the hippocampus of D-galactose (D-gal)-induced and naturally aging models of mice. These markers represent general phenotypes in aging, and they allowed us to examine the possibility of D-gal as a chemical model agent for aging. We observed an age-dependent reduction of NMDAR1 and an increase in 4-HNE in the dentate gyrus, CA1, and CA3 regions of the hippocampus via immunohistochemistry and western blot analyses. In the D-gal-induced chemical aging model, we observed similar changes in NMDAR1 and 4-HNE although the degree of reduction/increase in NMDAR1/4-HNE was not as severe as that in the naturally aged mice. These results suggest that the D-gal-induced aging model is comparable to naturally aged mice and may be useful for studies of the aging hippocampus.

A high resolution genetic mapping of the faded (fe) gene to a region between D10mit156 and D10mit193 on mouse chromosome 10.

The C57BL/6J-fe/fe mouse is a coat color mutant. The coat color of the homozygote mouse becomes progressively lighter with advancing age. The faded gene (fe) of C57BL/6J-fe/fe was mapped in a 2.0 cM distal to D10mit191 by our group. To make a high-resolution map, we used the Korean wild mouse (KWHM) for a backcross panel, which was captured in 1995 and has been maintained as an inbred line by our laboratory. In the inter-specific backcross panel (N=400), the fe gene was mapped to 1.0 cM distal to D10mit156. The gene order was defined: centromere -D10mit3/85 (1.3±0.6 cM)-D10mit155 (1.3±0.6 cM)-D10mit191 (2.0±0.7 cM)-D10mit156 (1.0±0.5 cM)-fe-D10mit193 (1.3±0.6 cM)-D10mit54 (1.0±0.5 cM)-D10mit44 (8.5±1.4 cM)-D10mit42 (10.0±1.5 cM). The measured distance between D10mit191 and D10mit 44 differed in both inter-specific (DBA/2) and intra-specific (KWHM) backcross panels (14.2 vs 13.8 cM). Taken together, our high-resolution linkage map of the fe locus from an intra-specific backcross panel will provide a good entry point to isolate the fe gene.

Silk fibroin hydrolysate exerts an anti-diabetic effect by increasing pancreatic ß cell mass in C57BL/KsJ-db/db mice.

Components of silk including silk fibroin have long been used as anti-diabetic remedies in oriental medicine. However, detailed mechanisms underlying these antidiabetic effects remain unclear. In this study, we examined the anti-diabetic activity of silk fibroin hydrolysate (SFH) in C57BL/KsJ db/db (db/db) mice, a well-known animal model of non-insulin dependent diabetes mellitus. When the db/db mice were administered SFH in drinking water for 6 weeks, hyperglycemia in the animals gradually disappeared and the level of glycosylated hemoglobin decreased, indicating that SFH plays important role in reducing the symptoms of diabetes. In addition, SFH-treated db/db mice exhibited improved glucose tolerance with increased plasma insulin levels. Immunohistochemical and morphological analyses showed that SFH up-regulated insulin production by increasing pancreatic ß cell mass in the mice. In summary, our results suggest that SFH exerts anti-diabetic effects by increasing pancreatic ß cell mass in a non-insulin dependent diabetes mellitus mouse model.