Welfare Impact of Carbon Dioxide Euthanasia on Laboratory Mice and Rats: A Systematic Review

Background: There has been increased concern about the suitability of CO2 as a method for euthanasia of laboratory mice and rats, including the potential discomfort, pain or distress that animals may experience prior to loss of consciousness; time to loss of consciousness; best methods for use of CO2; and the availability of better alternatives. These discussions have been useful in providing new information, but have resulted in significant confusion regarding the acceptability of CO2 for rodent euthanasia. In some cases, researchers and veterinarians have become uncertain as to which techniques to recommend or use for euthanasia of laboratory mice and rats. Methods: The International Association of Colleges of Laboratory Animal Medicine (IACLAM) convened a taskforce to examine the evidence for adverse welfare indicators in laboratory rats and mice undergoing CO2 euthanasia using a SYRCLE-registered systematic review protocol. Of 3,772 papers identified through a database search (PubMed, Web of Science, CAB Direct, Agricola, and grey literature) from 1900 to 2017, 37 studies were identified for detailed review (some including more than one species or age group), including 15 in adult mice, 21 in adult rats, and 5 in neonates of both species. Experiments or reports were excluded if they only assessed parameters other than those directly affecting animal welfare during CO2 induction and/or euthanasia. Results: Study design and outcome measures were highly variable and there was an unclear to high risk of bias in many of the published studies. Changes in the outcome measures evaluated were inconsistent or poorly differentiated. It is likely that repeated exposures to carbon dioxide inhalation are aversive to adult rats and mice, based on avoidance behavior studies; however, this effect is largely indistinguishable from aversion induced by repeated exposures to other inhalant anesthetic gasses. Conclusion: There is insufficient evidence to permit an unbiased assessment of the effect of CO2 inhalation during euthanasia on welfare indicators in laboratory mice and rats. Additional well-designed, unbiased, and adequately powered studies are needed to accurately assess the welfare of laboratory mice and rats undergoing euthanasia via CO2 gas.

Profiling of cellular immune responses to Mycoplasma pulmonis infection in C57BL/6 and DBA/2 mice

Mycoplasma infections cause respiratory tract damages and atypical pneumonia, resulting in serious problems in humans and animals worldwide. It is well known that laboratory inbred mouse strains show various susceptibility to Mycoplasma pulmonis (M. pulmonis) infection, which causes murine respiratory mycoplasmosis. In this study, we aimed to demonstrate the difference in cellular immune responses between resistant strain, C57BL/6NCrSlc (B6) and susceptible strain, DBA/2CrSlc (D2) after challenging M. pulmonis infection. D2 mice showed higher amount of bacterial proliferation in lung, higher pulmonary infiltration of immune cells such as neutrophils, macrophages, and lymphocytes, and higher levels of interleukin (IL)-1β, IL-6, IL-17A, and tumor necrosis factor-α in bronchoalveolar lavage fluid than did B6 mice. The results of this study suggest that D2 mice are more susceptible than B6 mice to M. pulmonis infection due to a hyper-immune inflammatory response.

Analysis for genetic loci controlling protoscolex development in the Echinococcus multilocularis infection using congenic mice

The resistance/susceptibility to Echinococcus multilocularis infection in mice is genetically controlled. However, genetic factors responsible for these differences remain unknown. Our previous study in genetic linkage analysis has revealed that there is a significant quantitative trait locus (QTL) for the establishment of cyst (Emcys1), and a highly significant QTL for the development of protoscolex of E. multilocularis larvae (Empsc1), on mouse chromosomes 6 and 1, respectively. The current study aimed to confirm these QTLs and narrow down the critical genetic region that controls resistance/susceptibility to E. multilocularis infection by establishing congenic and subcongenic lines from C57BL/6 (B6) and DBA/2 (D2) mice. For protoscolex development phenotype, two congenic lines, B6.D2-Empsc1 and D2.B6-Empsc1 were developed, where responsible QTL, Empsc1 was introgressed from D2 into B6 background and vice versa. For cyst establishment phenotype, two congenic lines, B6.D2-Emcys1 and D2.B6-Emcys1 were developed, where responsible QTL, Emcys1 was introgressed from D2 into B6 background and vice versa. Because there was no significant difference in cyst establishment between B6.D2-Emcys1 and D2.B6-Emcys1 mice after challenge with E. multilocularis, it is suggested that the Emcys1 does not solely control the cyst establishment in mouse liver. However, infection experiments with B6.D2-Empsc1 and D2.B6-Empsc1 mice showed a significant difference in protoscolex development in the cyst. It confirms that the Empsc1 controls phenotype of the protoscolex development in the cyst. Subsequently, two subcongenic lines, B6.D2-Empsc1.1 and B6.D2-Empsc1.2 from B6.D2-Emcys1 and one subcongenic line, D2.B6-Empsc1.1 from D2.B6-Empsc1 were developed to narrow down the critical region responsible for protoscolex development. From the results of infection experiments with E. multilocularis in these subcongenic mice, it is concluded that a gene responsible for protoscolex development is located between D1Mit290 (68.1 cM) and D1Mit511 (97.3 cM).

Does the routine handling affect the phenotype of disease model mice?

The three different mouse handling methods, picking up by tails, tunnels, and open hands were performed using the ICGN glomerulonephritis mouse and the severity of symptoms was evaluated. The handling groups exhibited a tendency of more severe symptoms than the non-handling control group. Female mice handled by their tails showed significantly more severe symptoms than the control group. In addition, we subjected the normal laboratory mice, C57BL/6 and BALB/c mice to tail and tunnel handling to assess the stress conditions. The plasma corticosterone level in the tail-handled mice was higher than that in control mice. These results indicate that handling causes stress and may affect the phenotype of disease model mice.

The role of mouse 2',5'-oligoadenylate synthetase 1 paralogs

The interferon-induced oligoadenylate synthetase (OAS) family is one of the most important immune response proteins to the viral infection. The OAS protein binds dsRNA and is activated to produce 2',5'-oligoadenylates, which lead to the activation of latent form of RNase L, resulting in degradation of cellular and viral RNA and inhibition of viral replication. In mice, the Oas gene family locates on chromosome 5. The mouse Oas gene locus undergoes a recent series of duplication event, leading to the presence of eight paralogs of Oas1 genes (Oas1a through Oas1h) that forms Oas gene cluster with the Oas2, Oas3 and two OasL (OasL1 and OasL2) genes. Previous studies demonstrated that the mouse Oas1b gene conferred resistance to the flavivirus infection in mice; however, the antiviral activity of other mouse Oas1 gene family is still unknown. Therefore, in the present study, we have evaluated the mouse Oas1 paralogs regarding the enzymatic activity and antiviral activity against the two neurotropic flaviviruses, West Nile virus and tick-borne encephalitis virus. The mouse Oas1 genes were cloned from C57BL/6J (B6) as well as the Oas1b derived from feral mouse strain, MSM. The obtained results demonstrated that only Oas1a and Oas1g showed enzymatic activity. Although MSM-derived Oas1b showed antiviral activity to both viruses, all B6-derived OAS paralogs did not show antiviral activity. These results suggest that Oas1a and Oas1g play a role in potentiating viral RNA-induced interferon response in the cell, whereas the Oas1b works as a specific anti-flavivirus factor unless it is mutated. However, the role of other paralogs is unknown and should wait for further investigation.

Mouse chromosome 2 harbors genetic determinants of resistance to podocyte injury and renal tubulointerstitial fibrosis

Background

Tensin2 deficiency results in alterations in podocytes and subsequent glomerular and tubulointerstitial injuries. However, this pathology is critically dependent on genetic background. While the Tensin2-deficient podocytes of resistant murine strains, including C57BL/6J mice, remain almost intact, susceptible murine strains with Tensin2 deficency, including ICGN mice, develop chronic kidney disease following alterations in the podocyte foot processes. In a previous study, genome-wide linkage analysis was utilized to identify the quantitative trait loci associated with the disease phenotypes on mouse chromosome 2. This study investigated the disease phenotypes of chromosome 2 consomic and subcongenic strains.

Results

ICGN consomic mice introgressed with chromosome 2 from the C57BL/6J mouse were generated and found to exhibit milder renal failure than that in ICGN mice. We developed 6 subcongenic strains that carry C57BL/6J-derived chromosomal segments from the consomic strain. One showed significantly milder albuminuria, another showed significantly milder tubulointerstitial injury, and the both showed significantly milder glomerular injury.

Conclusions

These data indicate that mouse chromosome 2 harbors two major genes associated with the severities of nephropathy induced by Tensin2 deficiency. The proximal region on chromosome 2 contributes to the resistance to tubulointerstitial fibrosis. In contrast, the distal region on chromosome 2 contributes to the resistance to podocyte injury. This study would be helpful to discover the biological mechanism underlying the renal injury, and may lead to the identification of therapeutic targets.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-016-0378-1) contains supplementary material, which is available to authorized users.

Genetic variation in the GDNF promoter affects its expression and modifies the severity of Hirschsprung's disease (HSCR) in rats carrying Ednrb(sl) mutations

Glial cell line-derived neurotrophic factor (GDNF) is necessary for the migration of neural crest stem cells in the gut. However, mutations in GDNF per se are deemed neither necessary nor sufficient to cause Hirschsprung's disease (HSCR). In a previous study, a modifier locus on chromosome 2 in rats carrying Ednrb(sl) mutations was identified, and several mutations in the putative regulatory region of the Gdnf gene in AGH-Ednrb(sl) rats were detected. Specifically, the mutation -232C>T has been shown to be strongly associated with the severity of HSCR. In the present study, the influence of genetic variations on the transcription of the Gdnf gene was tested using dual-luciferase assay. Results showed that the mutation -613C>T, located near the mutation -232C>T in AGH-Ednrb(sl) rats, decreased Gdnf transcription in an in vitro dual-luciferase expression assay. These data suggested an important role of -613C in Gdnf transcription. Expression levels of the Gdnf gene may modify the severity of HSCR in rats carrying Ednrb(sl) mutations.

Identification of multiple genetic loci in the mouse controlling immobility time in the tail suspension and forced swimming tests

Depression is one of the most famous psychiatric disorders in humans in all over the countries and considered a complex neurobehavioral trait and difficult to identify causal genes. Tail suspension test (TST) and forced swimming test (FST) are widely used for assessing depression-like behavior and antidepressant activity in mice. A variety of antidepressant agents are known to reduce immobility time in both TST and FST. To identify genetic determinants of immobility duration in both tests, we analyzed 101 F2 mice from an intercross between C57BL/6 and DBA/2 strains. Quantitative trait locus (QTL) mapping using 106 microsatellite markers revealed three loci (two significant and one suggestive) and five suggestive loci controlling immobility time in the TST and FST, respectively. Results of QTL analysis suggest a broad description of the genetic architecture underlying depression, providing underpinnings for identifying novel molecular targets for antidepressants to clear the complex genetic mechanisms of depressive disorders.

Identification of genetic loci affecting the severity of symptoms of Hirschsprung disease in rats carrying Ednrbsl mutations by quantitative trait locus analysis

Hirschsprung’s disease (HSCR) is a congenital disease in neonates characterized by the absence of the enteric ganglia in a variable length of the distal colon. This disease results from multiple genetic interactions that modulate the ability of enteric neural crest cells to populate developing gut. We previously reported that three rat strains with different backgrounds (susceptible AGH-Ednrb^sl/sl, resistant F344-Ednrb^sl/sl, and LEH-Ednrb^sl/sl) but the same null mutation of Ednrb show varying severity degrees of aganglionosis. This finding suggests that strain-specific genetic factors affect the severity of HSCR. Consistent with this finding, a quantitative trait locus (QTL) for the severity of HSCR on chromosome (Chr) 2 was identified using an F₂ intercross between AGH and F344 strains. In the present study, we performed QTL analysis using an F₂ intercross between the susceptible AGH and resistant LEH strains to identify the modifier/resistant loci for HSCR in Ednrb-deficient rats. A significant locus affecting the severity of HSCR was also detected within the Chr 2 region. These findings strongly suggest that a modifier gene of aganglionosis exists on Chr 2. In addition, two potentially causative SNPs (or mutations) were detected upstream of a known HSCR susceptibility gene, Gdnf. These SNPs were possibly responsible for the varied length of gut affected by aganglionosis.

Quantitative trait Loci for resistance to the congenital nephropathy in tensin 2-deficient mice

The ICR-derived glomerulonephritis (ICGN) mouse is a chronic kidney disease (CKD) model that is characterized histologically by glomerulosclerosis, vascular sclerosis and tubulointerstitial fibrosis, and clinically by proteinuria and anemia, which are common symptoms and pathological changes associated with a variety of kidney diseases. Previously, we performed a quantitative trait locus (QTL) analysis to identify the causative genes for proteinuria in ICGN mice, and found a deletion mutation of the tensin 2 gene (Tns2^nph, MGI no: 2447990). Interestingly, the congenic strain carrying the Tns2^nph mutation on a C57BL/6J (B6) genetic background exhibited milder phenotypes than did ICGN mice, indicating the presence of several modifier genes controlling the disease phenotype. In this study, to identify the modifier/resistant loci for CKD progression in Tns2-deficient mice, we performed QTL analysis using backcross progenies from susceptible ICGN and resistant B6 mice. We identified a significant locus on chromosome (Chr) 2 (LOD = 5.36; 31 cM) and two suggestive loci on Chrs 10 (LOD = 2.27; 64 cM) and X (LOD = 2.65; 67 cM) with linkage to the severity of tubulointerstitial injury. One significant locus on Chr 13 (LOD = 3.49; approximately 14 cM) and one suggestive locus on Chr 2 (LOD = 2.41; 51 cM) were identified as QTLs for the severity of glomerulosclerosis. Suggestive locus in BUN was also detected in the same Chr 2 region (LOD = 2.34; 51 cM). A locus on Chr 2 (36 cM) was significantly linked with HGB (LOD = 4.47) and HCT (LOD = 3.58). Four novel epistatic loci controlling either HGB or tubulointerstitial injury were discovered. Further genetic analysis should lead to identification of CKD modifier gene(s), aiding early diagnosis and providing novel approaches to the discovery of drugs for the treatment and possible prevention of kidney disease.

Development of an ELISA using a recombinant P46-like lipoprotein for diagnosis of Mycoplasma pulmonis infection in rodents

Mycoplasma pulmonis is one of the most prevalent bacterial pathogens that infects laboratory mice and rats. To develop an M. pulmonis-specific antigen for serological diagnosis, we cloned the cDNA of P46-like lipoprotein (P46L), an M. pulmonis putative periplasmic protein. P46L is a homolog of P46, an M. hyopneumoniae antigen. We produced recombinant P46L fused to glutathione S-transferase (GST) in Escherichia coli. Immunoblot analysis revealed that sera from Mycoplasma-infected mice and rats contained anti-P46L antibodies. We developed an ELISA using the recombinant P46L-GST protein as an antigen. Thirteen of the 14 samples from rats naturally infected with M. pulmonis were determined to be positive according to the commercial ELISA (MONILISA Myco) and positive by our ELISA. Furthermore, 18/19 samples from mice experimentally infected with M. pulmonis were positive using our P46L-GST ELISA. In contrast, only 8/19 samples from infected mice were positive by the commercial ELISA. Our results indicate that P46L-GST was an appropriate antigen for developing a serological test to determine M. pulmonis infection in laboratory mice and rats.

Distinct distribution of the tensin family in the mouse kidney and small intestine

Tensin family members are cytoplasmic proteins that are localized to the integrin-mediated cell-basement membrane junctions and implicated in cytoskeletal organization, cell migration, and proliferation. The mammalian genome contains four paralogs, Tns1, Tns2, Tns3, and Tns4. Murine mutations in the Tns1 and Tns2 genes cause polycystic kidney disease and glomerular sclerosis, respectively, and Tns3-null mice exhibit an impaired intestinal epithelial development. However, the knowledge concerning the localization of each tensin is still fragmentary. In this study, the cellular and subcellular distributions of tensin members were defined and compared with each other. RT-PCR analysis indicated that Tns2 and Tns3 were more abundant in isolated glomeruli and that Tns1 was highly expressed in areas other than the glomeruli, but no Tns4 expression was observed in the kidney. All tensin members were detected in the small intestine. Immunohistochemical staining revealed that Tns1 was predominantly localized to the mesangium of glomeruli and renal tubules. In contrast, Tns2 and Tns3 were highly expressed in the podocytes and the partial collecting system. In the small intestine, Tns2 and Tns3 were highly expressed in crypt and villous epithelial cells. Furthermore, we found that Tns3 was colocalized with TJ protein ZO-1 in renal tubules. These results indicate distinct differences in the cellular expression of Tns1, Tns2, and Tns3, and suggest that they may be able to function independently of each other in the kidney and the small intestine.

Epitope mapping of the nucleocapsid protein of sendai virus and application of antigenic epitopes for the ELISA-based diagnosis of sendai virus infection

Sendai virus (SeV) is one of the most prevalent viral pathogens infecting laboratory mice and rats. To date, mature SeV virions have been used as antigens for serological diagnosis. To develop antigens that are more specific and easier to prepare for diagnosis, we examined the antigenic sites in the nucleocapsid protein (NP) of SeV with antisera from experimentally SeV-infected mice and a peptide array membrane containing overlapping 10-mer peptides covering the entire NP. We found antigenic linear sequences in two regions, amino acids 120-160 and 420-500, of the SeV-NP. From these antigenic sequences, we applied two synthesized peptides, IVKTRDMEYERTTEWL and FVTLHGAERLEEETNDE, which correspond to positions 119-134 and 458-474 of the SeV-NP, respectively, as antigens in an enzyme-linked immunosorbent assay (ELISA). Evaluation of the ELISAs using these peptides revealed that they were specific to anti-SeV antisera. Furthermore, the ELISAs using these peptides were able to distinguish between SeV-positive and SeV-negative mouse sera to the same extent as a commercial ELISA kit. These results indicate that these peptides are useful for the serological diagnosis of SeV infection.

Lymphopenia in Ednrb-deficient rat was strongly modified by genetic background

The endothelin signaling pathway plays an important role in the migration, proliferation, and differentiation of neural crest cells. Mutations in the gene encoding the endothelin receptor type B (EDNRB) cause three symptoms: aganglionosis, pigmented disorder and hearing loss. In addition, the Ednrb null mice show abnormal splenic microarchitecture with lymphopenia. In this study, we examined whether similar phenotypes are reproduced in three Ednrb-null rat strains that we established previously. AGH-Ednrb(sl)/(sl) strain showed a low white blood cell count, significant size reduction and abnormal microarchitecture of spleen. Thymus displayed a marked reduction in the size, but maintained a normal CD4/CD8 ratio. In contrast, splenic cellularity was reduced to < 15%, and splenic B and T cell numbers were reduced, showing a splenic lymphopenia. Interestingly, Ednrb-null rats in the LE and F344 genetic background did not show these abnormalities. These data show that proper T and B cell development is dependent on the endothelin signaling pathway, however, modifier gene(s) might be differentially expressed in these strain to modulate or compensate for the effect of the Ednrb deficiency.

The telocentric tandem repeat at the p-arm is not conserved in Mus musculus subspecies

Mouse chromosomes, with the exception of the Y chromosome, are telocentric. The telomere at the p-arm is separated from the centromere by the tL1 sequence and TLC tandem repeats. A previous report showed that the TLC array was also conserved in other strains of the subgenus Mus. These results suggest that the TLC arrays promote the stable evolutionary maintenance of a telocentric karyotype in the subgenus Mus. In this study, we investigated the degree of conservation of TLC arrays among a variety of wild-derived inbred strains, all of which are descendants of wild mice captured in several areas of the world. Genomic PCR analysis indicates that the sequential order of telomere-tL1 is highly conserved in all strains, whereas tL1-TLC is not. Next, Southern blot analysis of DNAs isolated from a panel of mouse subspecies showed both Mus musculus domesticus and Mus musculus castaneus subspecies possess TLC arrays. Unexpectedly, this repeat appears to be lost in almost all Mus musculus musculus and Mus musculus molossinus subspecies, which show a clear geographic divide. These results indicate that either other unknown sequences were replaced by the TLC repeat or almost all M. m. musculus and M. m. molossinus subspecies do not have any sequence between the telomere and minor satellites. Our observation suggests that the TLC array might be evolutionarily unstable and not essential for murine chromosomal conformation. This is the first example of the subspecies-specific large genome alterations in mice.

The chicken 2'-5' oligoadenylate synthetase A inhibits the replication of West Nile virus

West Nile virus (WNV) is a pathogen to cause West Nile encephalitis when the infection occurs in the brain. Previous studies in mice identified the 2'-5' oligoadenylate synthetase 1b (Oas1b) gene as a determining factor for resistance to WNV infection. In addition, it has been suggested that human OAS1 and OASL are associated with the resistance to the WNV infection. WNV is maintained in nature through a complex life cycle involving wildbirds and mosquitoes. Birds are not only susceptible to the WNV, but also act as reservoir hosts, thus participating in the spread of the disease. It has previously been reported that chicken OASL possesses the oligoadenylate synthetase activity. However, until now the antiviral activity of chicken OASL has not been determined. In this study, we investigated the putative antiviral activity of chicken OASL by ectopic expression of this enzyme in mammalian cells and then infecting these cells with WNV replicon. We demonstrate that chicken OASL has an antiviral activity against the WNV. This is the first report to show that chicken OASL is associated with the resistance to the WNV infection.

The 129 genetic background affects susceptibility to glomerulosclerosis in tensin2-deficient mice

The ICGN mouse strain is a glomerulosclerosis (GS) model that shows significant proteinuria, podocyte morphological abnormalities and increased extracellular matrix accumulation in the glomeruli, which represent the final common pathology associated with a variety of kidney diseases leading to end-stage renal failure. Previously, we demonstrated that GS in ICGN mice can be attributed to the deletion mutation of the tensin2 (Tns2) gene (Tns2(nep)). Further, the C57BL/6J (B6) mouse is resistant to GS caused by this mutation. 129/Sv is also a popular strain; however, its susceptibility to GS has not been defined. Thus, to determine whether 129/Sv is resistant or susceptible to GS, we produced a congenic strain carrying Tns2(nep) on the 129(+Ter)/Sv (129T) background. 129T congenic mice (129T-Tns2(nep)) did not exhibit albuminuria, renal anemia, increases in BUN, or any severe pathological changes until at least 16 weeks of age. These results indicate that 129T is resistant to GS. Although their usage in biomedical studies is already widespread, 129/Sv mice may afford a late-onset and unique strain applicable to kidney disease research.

Identifying quantitative trait loci affecting resistance to congenital hypothyroidism in 129/SvJcl strain mice

Tyrosylprotein sulfotransferase 2 (TPST2) is one of the enzymes responsible for tyrosine O-sulfation and catalyzes the sulfation of the specific tyrosine residue of thyroid stimulating hormone receptor (TSHR). Since this modification is indispensable for the activation of TSH signaling, a non-functional TPST2 mutation (Tpst2(grt)) in DW/J-grt mice leads to congenital hypothyroidism (CH) characterized by severe thyroid hypoplasia and dwarfism related to TSH hyporesponsiveness. Previous studies indicated that the genetic background of the 129(+Ter)/SvJcl (129) mouse strain ameliorates Tpst2(grt)-induced CH. To identify loci responsible for CH resistance in 129 mice, we performed quantitative trait locus (QTL) analysis using backcross progenies from susceptible DW/J and resistant 129 mice. We used the first principal component calculated from body weights at 5, 8 and 10 weeks as an indicator of CH, and QTL analysis mapped a major QTL showing a highly significant linkage to the distal portion of chromosome (Chr) 2; between D2Mit62 and D2Mit304, particularly close to D2Mit255. In addition, two male-specific QTLs showing statistically suggestive linkage were also detected on Chrs 4 and 18, respectively. All QTL alleles derived from the 129 strain increased resistance to growth retardation. There was also a positive correlation between recovery from thyroid hypoplasia and the presence of the 129 allele at D2Mit255 in male progenies. These results suggested that the major QTL on Chr 2 is involved in thyroid development. Moreover, since DW/J congenic strain mice carrying both a Tpst2(grt) mutation and 129 alleles in the major QTL show resistance to dwarfism and thyroid hypoplasia, we confirmed the presence of the resistant gene in this region, and that it is involved in thyroid development. Further genetical analysis should lead to identification of genes for CH tolerance and, from a better understanding of thyroid organogenesis and function, the subsequent development of new treatments for thyroid disorders.

QTL analysis identifies a modifier locus of aganglionosis in the rat model of Hirschsprung disease carrying Ednrb(sl) mutations

Hirschsprung disease (HSCR) exhibits complex genetics with incomplete penetrance and variable severity thought to result as a consequence of multiple gene interactions that modulate the ability of enteric neural crest cells to populate the developing gut. As reported previously, when the same null mutation of the Ednrb gene, Ednrb^sl, was introgressed into the F344 strain, almost 60% of F344-Ednrb^sl/sl pups did not show any symptoms of aganglionosis, appearing healthy and normally fertile. These findings strongly suggested that the severity of HSCR was affected by strain-specific genetic factor (s). In this study, the genetic basis of such large strain differences in the severity of aganglionosis in the rat model was studied by whole-genome scanning for quantitative trait loci (QTLs) using an intercross of (AGH-Ednrb^sl×F344-Ednrb^sl) F₁ with the varying severity of aganglionosis. Genome linkage analysis identified one significant QTL on chromosome 2 for the severity of aganglionosis. Our QTL analyses using rat models of HSCR revealed that multiple genetic factors regulated the severity of aganglionosis. Moreover, a known HSCR susceptibility gene, Gdnf, was found in QTL that suggested a novel non-coding sequence mutation in GDNF that modifies the penetrance and severity of the aganglionosis phenotype in EDNRB-deficient rats. A further identification and analysis of responsible genes located on the identified QTL could lead to the richer understanding of the genetic basis of HSCR development.

Anatomic modifications in the enteric nervous system of JF1 mice with the classic piebald mutation

The Japanese Fancy Mouse 1 (JF1) has a characteristic coat color similar to a very old mutant, piebald. The mutation in JF1 and the classic piebald was previously thought to be the same recessive allele in the endothelin B receptor gene (Ednrb) according to the haplotype pattern, which is insufficient for this conclusion. In this study, we identified the same insertion of a retroposon-like element in intron 1 of the Ednrb gene in JF1 as in the classic piebald mutation by PCR. Further, we investigated whether the intestine shows neuronal intestinal malformations such as hypoganglionosis and immaturity of ganglion cells by histochemical staining. Though it has been assumed that the defect of neural crest-derived lineages is restricted to melanocytes in JF1, we found that the enteric innervation and neuronal density were impaired throughout the whole colon in JF1 mice.

High-resolution linkage mapping of the rat hooded locus

To identify a gene responsible for the hooded phenotype in the rat, high-resolution linkage mapping for the hooded locus was performed using IS (non-hooded) and LEA (hooded) rats. The map revealed that only Kit gene existed in the critical region, suggesting that the Kit is a strong candidate gene. However, mutation was not found in the coding region of the LEA rat Kit gene. Further, the expressions of Kit mRNA were not different in fetal neural tubes and both neonatal and adult skins between IS and LEA rats. Furthermore, Kit-positive cells, possibly melanocytes, were found in the non-pigmented hair follicles of hooded phenotype rats. Several hypotheses are conceivable to account for mechanisms in the appearance of hooded phenotype.

Development and application of West Nile virus subgenomic replicon RNA expressing secreted alkaline phosphatase

We have developed a West Nile virus (WNV) subgenomic replicon harboring the secreted alkaline phosphatase (SEAP) reporter gene instead of viral structural genes (designated repWNV/SEAP). The repWNV/SEAP allowed easy evaluation of viral replication efficiency by direct measurement of SEAP secretion in the cell culture medium in physical containment level 2 facilities. Furthermore, we validated the availability of this system using a known anti-flavivirus gene, mouse oligoadenylate synthetase 1b (Oas1b). The Oas1b-transfected cells were more resistant to repWNV/SEAP replication than the original cells. Thus, this system not only affords a useful tool for identification/evaluation of anti-flavivirus genes/drugs in terms of safety, ease of use and reliability, but should be able to reduce or replace the bioassay using laboratory animals.

Hypothyroid phenotype of the Tpst2 mutant mouse is dependent upon genetic background

DW/J-grt is a congenital hypothyroid mouse model that is characterized by growth retardation, significantly lowered T3 and T4 levels, and severe thyroid hypoplasia related to TSH hyporesponsiveness. Previously, we identified the point mutation of the Tpst2 gene in DW/J-grt mice that causes a decrease in the enzymatic activity, and demonstrated that the Tpst2 transgene rescues the mutant phenotypes both in vitro and in vivo. The severity of hypothyroidism is highly variable indicating the influence of modifier genes in humans. In this study, to identify the modifier/resistant gene(s) to hypothyroidism, we produced congenic strains carrying this Tpst2(grt) mutation on the C57BL/6J and 129/SvJcl (129) genetic backgrounds and analyzed growth rate and thyroid function. Interestingly, the 129 congenic mice exhibited normal growth and thyroid function. The result suggests that 129 strain has the modifier(s) of attenuation of hypothyroidism. Therefore, the identification of the modifier loci of 129 mice will provide important new information about the gene(s) related to congenital hypothyroidism.

Contiguous gene deletion of Ptprk and Themis causes T-helper immunodeficiency (thid) in the LEC rat

The LEC rat has a spontaneous mutation of T-helper immunodeficiency (thid), which causes a marked defect in T cell maturation from double positive (DP) to CD4 single positive (SP) cells in the thymus. Previously, we identified the contiguous gene deletion of Ptprk and Themis genes in the thid locus that causes the simultaneous loss of expression of both genes, and the exogenous Ptprk expression partially rescued this phenotype. To determine whether the deletion of Themis influences thid phenotype, bone marrow (BM) cells were transduced with lentiviral vector expressing Themis gene, and were transplanted into X-ray-irradiated LEC rats. Interestingly, the exogenous Themis expression rescued the development of CD4 SP cells as well as Ptprk. The result suggests that the deficiency of both genes is responsible for the thid mutation, and that both genes are indispensable for the development of SP cells from DP cells in the thymus.

Genetic background strongly influences the severity of glomerulosclerosis in mice

The ICGN mouse strain is a glomerulosclerosis (GS) model that shows characteristic proteinuria, podocyte morphological abnormalities and increased extracellular matrix accumulation in the glomeruli, which are the final common pathology associated with a variety of kidney diseases leading to end-stage renal failure. Previously, we performed a quantitative trait locus (QTL) analysis to identify the causative genes for GS in ICGN mice and found the deletion mutation of the tensin2 (Tns2) gene that creates both a premature stop codon and dramatically decreases mRNA expression levels within the region of the major QTL (this mutation was designated Tns2(nep)). The severity of GS varies considerably in humans and other animals, indicating the influence of several genes controlling the disease phenotype. In this study, to identify the modifier/resistant gene(s) for GS, we produced congenic strains carrying the Tns2(nep) mutation on the C57BL/6J (B6) genetic background and analyzed GS severity. Interestingly, the B6 congenic mice exhibited milder phenotypes than the ICGN strain mice. The results suggest that B6 mice have a modifier(s) of GS resistance. Therefore, identification of the modifier loci in B6 mice will provide important new information regarding gene interactions controlling GS.

Genetic analysis of modifiers for the hooded phenotype in the rat

The hooded phenotype is one of the coat color phenotype seen peculiarly in the rat. The hooded locus showing autosomal recessive inheritance is mapped to chromosome (Chr) 14 and that the hooded phenotype receives modification by hooded-modifier gene showing the linkage to the hooded locus. However, a gene responsible for either the hooded or hooded-modifier gene is not yet identified. To clarify genetic control of hooded phenotype, we carried out genetic linkage studies using BN and LEA rats. For determination of phenotypic variation, we measured ratio of pigmented coat area in parental and their F1 and F2 rats. We, then, conducted a genome-wide scan on 152 F2 rats for linkage with ratio of pigmented coat area for the dorsal, ventral, and total regions. A major quantitative trait locus (QTL), D14Got40, showing highly significant linkage contributing 70-90% of the variance for hooded phenotype was detected on Chr 14, which may be correspondent to the hooded locus. In addition, another QTL, D17Rat2, showing highly significant linkage was also detected on Chr 17 in dorsal region phenotype as well as a QTL showing suggestive linkage on Chr15 in ventral region phenotype. We, further, investigated a genome-wide scan for epistatic interactions and detected significant interactions between D14Got40 and D20Mit1, and between D14Got40 and D17Rat2 in the dorsal region phenotype. These results suggest that a major QTL in Chr 14, which is possibly correspondent to the hooded locus, mainly regulates the hooded phenotype with some modifier loci, two of which show epistatic interactions with the hooded locus.

Amelioration of anemia in the ICGN mouse, a renal anemia model, with a subcutaneous bolus injection of erythropoietin adsorbed to hydroxyapatite matrix

The recombinant human erythropoietin (rhEPO) is used for the treatment of patients with renal anemia. However, rhEPO should be administered subcutaneously or intravenously three times a week. The repetitive injections of rhEPO result in burdens to patients. To resolve this problem, we investigated the sustaining release methods using an rhEPO-hydroxyapatite (HAp) made by spray-drying technique as the drug delivery system. Two types of rhEPO-HAp formulations were prepared; zinc (Zn) formulation and Zn and poly-L-lactic acid (PLA) formulation. These formulations were examined in genetically anemic model, ICGN (ICR-derived glomerulonephritis) mice. According to in vivo release test of rhEPO from HAp in ICGN mice, elevated plasma concentration of rhEPO could be maintained for more than 7 days. These mice showed the amelioration of anemia for more than 3 weeks post-administration without causing any side effect. In conclusion, Zn or Zn/PLA formulation of HAp was considered to be one of the useful carriers of rhEPO for long-term improvement of anemia.

Generation of congenic mouse strains by introducing the virus-resistant genes, Mx1 and Oas1b, of feral mouse-derived inbred strain MSM/Ms into the common strain C57BL/6J

Mx1 (Myxovirus resistance protein) and Oaslb (Oligoadenylate synthetase-1), induced by type 1 interferon (IFN), play a role in early antiviral innate immunity by inhibiting the replication of viruses. In mice, Mx1 and Oas1b confer resistance to the infection of orthomyxoviruses including influenza viruses and flaviviruses including West Nile viruses, respectively. Laboratory mice have been used to study the mechanisms of the pathogenesis of these virus infections; however, it is possible that they are not a suitable model system to study these viruses, since most of the inbred laboratory mouse strains lack both genes. It has been reported that feral mouse-derived inbred strains show resistance to the infection of these viruses due to the presence of intact both genes. In this study, we generated congenic strains in which the Mx or Oas locus of the MSM/Ms (MSM) mouce was introduced to the most widely used mouse strain, C57BL/6J (B6). B6.MSM-Mx mice showed resistance to the infection of influenza virus but not of West Nile virus. On the other hand, B6.MSM-Oas mice showed resistance to the infection of West Nile virus but not of influenza virus. Our results indicate that Mx1 and Oaslb show highly antiviral specificity in mice possessing the same genetic background. Therefore, these congenic mice are useful for not only infection study but also investigation of host defense mechanism to these viruses.

Sustained efficacy of erythropoietin with a hydroxyapatite carrier administered in mice

For chronic kidney disease patients with renal anemia, recombinant human erythropoietin (rHuEPO) is a very effective drug; however, the treatment regime is troublesome, requiring multiple administrations each week. In the present study, we examined the efficiency of hydroxyapatite (HAp) as a drug delivery carrier for the sustained release of erythropoietin (EPO) to reduce the frequency of administration. Spray-dried HAp microparticles, formed from zinc-containing HAp (Zn-HAp) and Zn-HAp calcined at 400 degrees C, were used as carriers of EPO, and five Zn-HAp formulation samples incorporating EPO were prepared; no formulation, poly-L-lactic acid (PLA) formulation, zinc (Zn) formulation, Zn/PLA formulation, and calcined/Zn/PLA formulation. ICR mice were administered these samples or commercial rHuEPO (Epogin) as a control from dorsal neck subcutaneous, and hematological and histopathological analyses, including enzyme-linked immunosorbent assay for plasma EPO concentration, were performed. An increase in the blood EPO level was detected on days 3 and 8 post-administration. Peak hematopoiesis was delayed and higher hematological values were obtained on day 14 post-administration with no serious adverse reactions compared with the control. The Zn/PLA formulation sample was found to be most effective in reducing the initial peak while sustaining the delayed release of EPO. In conclusion, the Zn-HAp formulation samples were considered to be useful carriers for the sustained release of EPO, and the Zn/PLA formulation appears to be the most effective of five Zn-HAp formulation samples in sustaining EPO release.

Characterization and epitope mapping of monoclonal antibodies to the nucleocapsid protein of severe acute respiratory syndrome coronavirus

The sudden emergence of severe acute respiratory syndrome (SARS) at the end of 2002 resulted in 774 reported deaths from more than 8000 cases worldwide. As no effective vaccines or antiviral agents are available, the most effective measure to prevent the expansion of a SARS epidemic is the rapid diagnosis and isolation of SARS patients. To establish specific diagnostic methods, we generated nine clones of monoclonal antibodies to nucleocapsid protein (NP) of SARS-coronavirus (SARS-CoV). On immunofluorescent antibody assay and Western blotting analysis, none of the monoclonal antibodies showed cross-reactivity to authentic and recombinant NPs of human coronavirus (HCoV) 229E strain. To determine the region on the NP molecule where the monoclonal antibodies bind, we generated four truncated recombinant NPs and analyzed the reactivity between monoclonal antibodies and truncated NPs. Two monoclonal antibodies reacted with a truncated NP covering from amino acid residues 111 to 230, and seven reacted with another truncated NP covering from amino acid residues 221 to 340. Epitope mapping analysis indicated that monoclonal antibody SN5-25 recognized the amino acid sequence Q(245)TVTKK(250) On SARS-NP. Within the epitope, Q245, T246, V247, K249, and K250 appeared to form an essential motif for monoclonal antibody SN5-25 to bind. The information about binding sites and epitopes of monoclonal antibodies may be useful for the development of new diagnostic methods for SARS and for analyzing the function of N protein of SARS-CoV.

A deletion mutation of the protein tyrosine phosphatase kappa (Ptprk) gene is responsible for T-helper immunodeficiency (thid) in the LEC rat

Bone marrow (BM)-derived T-cell progenitors differentiate into CD4 or CD8 single-positive (SP) cells in the thymus. We have previously reported that a single autosomal mutation, thid, causes a defect in the maturation of CD4 SP thymocytes and an abnormality of peripheral helper T cells in the LEC rat. In this study we attempted to identify a gene responsible for the thid mutation. We first performed genetic linkage analysis and mapped the thid locus between Myb and D1Rat392 on Chr 1. In this region we found an approximately 380-kb deletion from intron 3 of the Ptprk gene, which encodes a receptor-like protein tyrosine phosphatase type kappa (RPTPkappa) to intron 1 of the RGD1560849 predicted gene in the LEC rat genome. Reconstitution with syngenic BM cells transduced Ptprk but not the RGD1560849 predicted gene rescued development of CD4 SP cells in the LEC rat thymus. It is confirmed by this result that the Ptprk gene is responsible for the thid mutation in the LEC rat. Our results further suggest that RPTPkappa plays a critical role in the development of CD4 SP cells in the thymus.

A mutation in Tpst2 encoding tyrosylprotein sulfotransferase causes dwarfism associated with hypothyroidism

The growth-retarded (grt) mouse has an autosomal recessive, fetal-onset, severe thyroid hypoplasia related to TSH hyporesponsiveness. Through genetic mapping and complementation experiments, we show that grt is a missense mutation of a highly conserved region of the tyrosylprotein sulfotransferase 2 (Tpst2) gene, encoding one of the two Tpst genes implicated in posttranslational tyrosine O-sulfation. We present evidence that the grt mutation leads to a loss of TPST2 activity, and TPST2 isoform has a high degree of substrate preference for TSH receptor (TSHR). The expression of TPST2 can restore TSH-TSHR-mediated cAMP production in fibroblasts derived from grt mice. Therefore, we propose that the tyrosine sulfation of TSHR by TPST2 is crucial for TSH signaling and resultant thyroid gland function.

Oxidoreductase interactions include a role for ERp72 engagement with mutant thyroglobulin from the rdw/rdw rat dwarf

Newly synthesized thyroglobulin (Tg), the secretory glycoprotein that serves as precursor in thyroid hormone synthesis, normally forms transient covalent protein complexes with oxidoreductases of the endoplasmic reticulum (ER). The Tg-G2320R mutation is responsible for congenital hypothyroidism in rdw/rdw rats, in which a lack of secondary thyroid enlargement (goiter) implicates death of thyrocytes as part of disease pathogenesis. We found that mutant Tg-G2320R was retained within the ER with no detectable synthesis of thyroxine, had persistent exposure of free cysteine thiols, and was associated with activated ER stress response but incomplete ER-associated degradation (ERAD). Tg-G2320R associated with multiple ER resident proteins, most notably ERp72, including covalent Tg-ERp72 interactions. In PC Cl3 thyrocytes, inducible overexpression of ERp72 increased the ability of cells to maintain Tg cysteines in a reduced state. Noncovalent interactions of several ER chaperones with newly synthesized Tg-G2320R diminished over time in parallel with ERAD of the mutant protein, yet a small ERAD-resistant Tg fraction remained engaged in covalent association with ERp72 even 2 days post-synthesis. Such covalent protein aggregates may set the stage for apoptotic thyrocyte cell death, preventing thyroid goiter formation in rdw/rdw rats.

Development of serological assays for Thottapalayam virus, an insectivore-borne Hantavirus

Thottapalayam virus (TPMV), a member of the genus Hantavirus in the family Bunyaviridae, was isolated from an insectivore, Suncus murinus (musk shrew), captured in southern India in 1964. While the isolation of TPMV predates the discovery of the prototype Hantaan virus, little is known about its genetics and biology. To date, preliminary evidence suggests that TPMV differs significantly, both antigenically and genetically, from all known rodent-borne hantaviruses. However, since detailed epizootiological studies have not been conducted, it is unclear if TPMV is naturally harbored by an insectivore host or if TPMV represents a "spillover" from its natural rodent reservoir host. Moreover, to what extent TPMV causes infection and/or disease in humans is not known. To address these issues, we first studied the antigenic profile of TPMV using monoclonal antibodies against Hantaan and Seoul viruses and polyclonal immune sera against Puumala virus and TPMV. Armed with this newfound information, we developed an enzyme-linked immunosorbent assay system for the diagnosis of TPMV infections in shrews and humans, using a recombinant TPMV N antigen manipulated to have an E5/G6 epitope to be captured by monoclonal antibody clone E5/G6. Using this assay, we found anti-TPMV antibodies in sera from a patient with high fever of unknown etiology in Thailand and from two shrews captured in Indonesia. Seropositivity was verified by the indirect immunofluorescence antibody test, Western blotting analysis, and focus reduction neutralization test. Collectively, our data indicate that TPMV is harbored by Suncus murinus as its host in nature and is capable of infecting humans.

Deficiency of the tensin2 gene in the ICGN mouse: an animal model for congenital nephrotic syndrome

The ICGN mouse is a model for nephrotic syndrome (NS) which presents with proteinuria, hyperlipidemia, and edema. In this study we attempted to identify the gene(s) responsible for NS. By analyzing albuminuria in 160 (ICGN x MSM)F(1) x ICGN backcross progenies, we found that NS in the ICGN mouse is caused by more than one gene. We then performed a quantitative trait locus (QTL) analysis and detected a QTL with a very high LOD score peak in the telomeric region of Chr 15. By analyzing the nucleotide sequence of 22 genes located close to the QTL, we found that the tensin2 gene of the ICGN mouse possessed an 8-nucleotide deletion mutation in exon 18, leading to a frameshift and giving rise to a terminal codon at a premature position. Analyses of in situ hybridization and immunohistochemistry revealed that tensin2 was expressed in podocytes and tubular epithelial cells in normal mice but not in the ICGN mouse. These data raise the possibility that a mutation of the tensin2 gene is responsible for NS of the ICGN mouse and tensin2 is a prerequisite for the normal kidney function.

Analysis of the cell cycle of fibroblasts derived from the LEC rat after X-irradiation

The LEC rat is reported to exhibit hypersensitivity to X-irradiation, deficiency in DNA double-strand break repair, and radio-resistant DNA synthesis. This character of the LEC rat has been thought to be due to abnormal G1 arrest in cells after X-irradiation. In this report, we re-investigated the effect of X-irradiation on the cell cycle in primary-cultured fibroblasts. Primary-cultured fibroblasts derived from LEC and BN rats were exposed to 4 Gy of X-ray and their cell cycle analysis was performed with a flow cytometer. Fibroblasts derived from both rats showed normal response of the cell cycle, indicating the arrest at both G1--and G2/M-phase and no difference in the cell cycle population between fibroblasts derived from both rats. In contrast, when the same analysis was performed using the cell line, L7 and W8, which had been established from the lung fibroblasts of LEC and control WKAH rats, respectively, by immortalizing with SV40 T-antigen, L7 cells but not W8 cells showed impaired G1 arrest and abnormal cell cycle. These results suggest that fibroblasts derived from LEC rats possess the normal cell cycle response after X-irradiation, if they are kept naive as not immortalized with SV40 T-antigen.

Intracellular localization and antiviral property of canine Mx proteins

Mx is an interferon (IFN)-induced protein that shows antiviral activities against RNA viruses. We examined an expression of mRNA, an intracellular localization of protein, and an antiviral property of canine Mx1 and Mx2. Both Mx1 and Mx2 mRNAs were induced in a canine kidney cell line Madin-Darby canine kidney (MDCK), stimulated with an IFN-inducer, poly(I) x poly(C) for 12 h, suggesting the presence of regulatory mechanisms consistent with Mx genes in other species. By immunostaining BALB/3T3 fibroblasts transiently transfected FLAG epitope-tagged canine Mx1 and Mx2 cDNAs with an anti-FLAG tag, it was revealed that both Mx1 and Mx2 proteins are localized in cytoplasm. BALB/3T3 fibroblasts expressing stably Mx2 but not Mx1 had an antiviral activity against recombinant vesicular stomatitis virus (VSV). This is the first report demonstrating the functional analysis of canine Mx proteins.

The mRNA regulation of porcine double-stranded RNA-activated protein kinase gene

The double-stranded RNA (dsRNA)-activated protein kinase (PKR), which is one of the products of interferon (IFN)-stimulated genes, participates in the biological actions of IFN such as antiviral effects and immune response. In the present study, we identified the primary structure of porcine PKR proteins by cDNA cloning. Porcine PKR protein consisted of 537 amino acids and had two dsRNA-binding domains similarly existing in PKR proteins of other species. The treatment with IFN-alpha induced the expression of PKR 3.9-fold in a porcine kidney cell line, LLC-PK1. The same results were obtained when the cells were treated with poly(I).poly(C), but treatment with either IFN-gamma or LPS did not induce this gene in LLC-PK1 cells. These results suggest similarity of the regulatory mechanisms in the PKR gene among mammalian species.

Examination of the Lunatic fringe and Uncx4.1 expression by whole-mount in situ hybridization in the embryo of the CKH-Jsr (jumbled spine and ribs) mouse

The CKH-Jsr (jumbled spine and ribs) mouse was found as a spontaneous mutant with malformation of vertebrae, that is, a short trunk and kinky tail. We examined Lunatic Fringe (Lfng) and Uncx4.1 expression in the presomitic mesoderm (PSM) and somites of Jsr-mutant (CKH-Jsr/+) embryos to elucidate pathogenesis of the Jsr mutation. Expression pattern of Lfng in the PSM of Jsr-mutant embryos was similar to that of the normal (C57BL/6) embryos. However, expression pattern of Uncx4.1 in the somites of Jsr-mutant embryos was impaired to be irregular and mosaic, suggesting that the anterior-posterior (A-P) polarity is disordered in the Jsr mutant. These results indicate that the Jsr mutation disrupts the A-P polarity of somites during the somitogenesis without altering Lfng expression pattern in the PSM.

Quantitative trait loci analysis of heat stress resistance of spermatocytes in the MRL/MpJ mouse

The MRL/MpJ mouse has previously been reported to possess an interesting phenotype in which spermatocytes are resistant to the abdominal temperature heat shock. In this study genetic analysis for it was performed. The phenotypes of F2 progenies produced by mating MRL/MpJ and control strain C57BL/6 mice were not segregated into two types as parental phenotypes, suggesting that the phenotype is controlled by multiple genetic loci. Thus, quantitative trait loci (QTL) analysis was performed using 98 microsatellite markers. The weight ratio of the cryptorchid testis to the intact testis (testis weight ratio) and the Sertoli cell index were used for quantitative traits. QTL analysis revealed two significant QTLs located on Chrs 1 and 11 for testis weight ratio and one significant QTL located in the same region of Chr 1 for the Sertoli cell index. A microsatellite marker locus located in the peak of the QTL on Chr 1 did not recombine with the exonuclease 1 (Exo1) gene locus in 140 F2 progenies. Mutation of the Exo1 gene was previously reported to be responsible for metaphase-specific apoptosis (MSA) of spermatocytes in the MRL/MpJ mouse. These results raise the possibility that mutation of the Exo1 gene is responsible for both MSA and heat stress resistance of spermatocytes in the MRL/MpJ mouse.

Exon skipping of exonuclease 1 in MRL/MpJ mice is caused by a nucleotide substitution of the branchpoint sequence in intron eight

In MRL/MpJ mice, there is a genetic mutation of exonuclease 1 (Exo1), in which the exon 9 is sometimes deleted. In the present study, to check the generation of the spliced exons, exon 8-intron 8-exon 9 (pCX/Ex/EIE/B and pCX/Ex/EIE/M) plasmids were temporally transfected in vitro into BALB 3T3 cells, and RT-PCR using appropriate primer pair was carried out 1 day after transfection. In these constructions, pCX/Ex/EIE/B was derived from genomic sequence of C57BL/6 mice, and pCX/Ex/EIE/M was from MRL/MpJ. A spliced band was detected in pCX/Ex/EIE/B, but was present little or very weakly in pCX/Ex/EIE/M. Next, the same spliced band was demonstrated in the pCX/Ex/EIE/M(T) plasmid, in which the branchpoint sequence (BPS) of pCX/Ex/EIE/M including the exon 9 was changed into that of pCX/Ex/EIE/B. The splicing did not occur in the dell1/B mutant, in which 1960 nucleotides of the intron 8 were deleted, whereas it was detected in the del2/B plasmid deleted 1036 nucleotides in its middle region. These results suggest that the nucleotide T to A mutation of the BPS in the intron 8 is at least a sufficient for generation of splice variants (tr-1 and tr-2 Exo1).

Epitope analysis of monoclonal antibody E5/G6, which binds to a linear epitope in the nucleocapsid protein of hantaviruses

Monoclonal antibody E5/G6 recognized a linear epitope common to hantavirus nucleocapsid proteins. Using synthetic peptides, we identified epitope E5/G6 as the 9 mer YEDVNGIRK (NP 165-173), in which D167, G170, I171, and R172 are indispensable. Furthermore, all the peptides synthesized using various hantavirus sequences bound MAb E5/G6 consistently, despite the existence of several amino acid variations in this region. These results indicate that MAb E5/G6 is a useful tool for detecting hantavirus antigen in rodent or patient tissues using Western blotting or other immunohistochemical assays.

Native antiviral specificity of chicken Mx protein depends on amino acid variation at position 631

An attempt was made to determine whether amino acid variation at position 631 in the chicken Mx protein definitely influences antiviral specificity, using an artificial mutation technique by which a single amino acid was reciprocally substituted between Ser (AGT) and Asn (AAT) at position 631 of the negative and positive chicken Mx, respectively. Using permanently transfected 3T3 cell lines, the antiviral potential of chicken Mx against vesicular stomatitis virus infection was analysed. The results indicated that the phenotype of antiviral activity depends on the amino acid difference at position 631; that is, the genotype coding Asn at position 631 corresponds to the positive antiviral phenotype, and the genotype coding Ser corresponds to the negative phenotype. The present study has confirmed that the antiviral specificity of chicken Mx protein is determined by an amino acid substitution at the carboxy terminus.

Differences in spermatogenesis in cryptorchid testes among various strains of mice

The purpose of the study reported here was to define strain differences in spermatogenesis in cryptorchid testes in mice. Mice of strains A/J, BALB/c, CBA/N, C3H/He, C57BL/6 (B6), ddY and ICR were found to be sensitive to heat stress attributable to experimentally induced cryptorchidism. In contrast, mice of strains AKR/N (AKR), MRL/MpJ-+/+ (M+) and MRL/MpJ-lpr/lpr (lpr) were resistant to heat stress. Relative increases of apoptotic cells were detected in the sensitive group, but not in the resistant group. A decrease of proliferating cell nuclear antigen-immunoreactive cells after experimentally induced cryptorchidism was observed only in the sensitive group. These results suggested that heat stress-resistant germ cells were present in MRL and AKR strains, possibly originating from the genetic background.