Genetic polymorphisms and antiviral activity in the bovine MX1 gene

Induction and antiviral activity of ferret myxovirus resistance (Mx) protein 1 against influenza A viruses

Myxovirus resistance (Mx) proteins are products of interferon stimulated genes (ISGs) and Mx proteins of different species have been reported to mediate antiviral activity against a number of viruses, including influenza A viruses (IAV). Ferrets are widely considered to represent the 'gold standard' small animal model for studying pathogenesis and immunity to human IAV infections, however little is known regarding the antiviral activity of ferret Mx proteins. Herein, we report induction of ferret (f)Mx1/2 in a ferret lung cell line and in airway tissues from IAV-infected ferrets, noting that fMx1 was induced to higher levels that fMx2 both in vitro and in vivo. Overexpression confirmed cytoplasmic expression of fMx1 as well as its ability to inhibit infection and replication of IAV, noting that this antiviral effect of fMx1was modest when compared to cells overexpressing either human MxA or mouse Mx1. Together, these studies provide the first insights regarding the role of fMx1 in cell innate antiviral immunity to influenza viruses. Understanding similarities and differences in the antiviral activities of human and ferret ISGs provides critical context for evaluating results when studying human IAV infections in the ferret model.

Whole-Genome comparative analysis reveals genetic mechanisms of disease resistance and heat tolerance of tropical Bos indicus cattle breeds

The Bos indicus cattle breeds have been naturally selected over thousands of years for disease resistance and thermo-tolerance. However, a genetic mechanism of these specific inherited characteristics needs to be discovered. Hence, in this study, the whole-genome comparative analysis of Bos indicus cattle breeds of Kangayam, Tharparkar, Sahiwal, Red Sindhi, and Hariana of the Indian subcontinent was conducted. The genetic variants identification analysis revealed a total of 15,58,51,012 SNPs and 1,00,62,805 InDels in the mapped reads across all Bos indicus cattle breeds. The functional annotation of 17,252 genes that comprised both, SNPs and InDels, of high functional impact on proteins, has been carried out. The functional annotation results revealed the pathways that were involved in the innate immune response including toll-like receptors, a retinoic acid-inducible gene I like receptors, NOD-like receptors, Jak-STAT signaling pathways, and the non-synonymous variants in the candidate immune genes. Further, we also identified several pathways involved in heat shock response, hair and skin properties, oxidative stress response, osmotic stress response, thermal sweating, feed intake, metabolism, and the non-synonymous variants in the candidate thermo-tolerant genes. These pathways and genes were directly or indirectly contributing to the disease resistance and thermo-tolerance adaptations of Bos indicus cattle breeds.

Use of a prediction method for early pregnancy status utilizing receiver operating characteristic curve analysis of peripheral blood leukocyte interferon-stimulated genes in Japanese-Black cattle

A prediction method for early pregnancy status (pregnant or non-pregnant) in cattle that can be used within 3 weeks after insemination is desired. Interferon-stimulated genes (ISGs) in peripheral blood leukocytes (PBLs) have been examined as prediction molecules for determination of pregnancy status. Relative abundances of ISG15 and MX2 gene transcripts in PBLs were suitable biomarkers for the prediction of pregnancy status when there were assessments of Holstein cattle. In the present study, it was determined whether ISG biomarkers are applicable for predicting gestation in Japanese-Black (JB) cattle and evaluation of the applicability of receiver operating characteristic (ROC) analysis procedures for this purpose. There was assessment of the reliability of using average ISG values in PBLs collected during the estrous cycle (AVE) as a cutoff compared to the Youden index cutoff values. Application of AVE to assessment of pregnancy status in JB cattle indicated there was reliable predictions for pregnancy status when using ISG15 and MX2 values on day 21 after insemination, which coincided with the time of assessment in the previous study with Holstein cattle. The area under the curve values of the ROC curves confirmed the reliability of using ISGs to predict pregnancy from days 18 to 21 after insemination. Comparing AVE with Youden index values, there was confirmation of the accuracy of AVE for predicting gestation. The average mRNA transcript abundance values of ISG15 and MX2 may serve as excellent pregnancy biomarkers for cattle within 3 weeks of insemination.

Polymorphisms in MX2 Gene Are Related with SCS in Chinese Dairy Cows

Viral infections can play direct or indirect roles in the etiology of the bovine mastitis. Mx dynamin-like GTPase 2 (MX2) gene is a main effector of the antiviral innate immune defense mediated by type I interferon (IFN I), which was demonstrated to confer positive antiviral responses to many viruses. Given the importance of the MX2 in modulating the host immune response, MX2 gene may be a suitable candidate gene for studying disease resistance in dairy cattle. Here, we scanned the sequence variation of the MX2 gene in Chinese indigenous cattle breeds. Twenty-three previously reported SNPs were identified. To further analyze the effects of SNPs detected on mastitis disease, analysis of two SNPs (g.787527 C > T and g.787610 T > C) from 297 Chinese Holstein cows revealed a significant association with somatic cell score (SCS). Although functional studies are necessary to ascertain whether these two SNPs are causal polymorphisms or merely in linkage with the true causal SNPs, implementation of these two SNPs as genetic markers in the dairy industry may be beneficial in selecting individuals with lower SCS.

Molecular cloning, polymorphism, and functional activity of the bovine and water buffalo Mx2 gene promoter region

Background

Bovine Mx2 gene sequences were already reported, but further information about the gene properties is not yet available. The objective of the current study was to elucidate the structural properties of the bovine Mx2 gene mainly the promoter region and its possible functional role. If available, such information would help in assessing the functional properties of the gene, which was reported to confer antiviral action against recombinant VSV.

Results

Examinations on the bovine genomic BAC clone—confirmed to contain the Mx2 gene—revealed 883-bp sequences. A computer scan unequivocally identified a 788-bp promoter region containing a typical TATA box, three ISREs and other promoter-specific motifs. Comparative analysis of nine bovine genomic DNA samples showed 19 nucleotide substitutions suggesting the existence of five different genotypes in the promoter region. The water buffalo Mx2 promoter region was determined by using primers based on the bovine Mx2 promoter region disclosing 893-bp, with 56 substitutions, two insertions, 9 and 1 nt at two different sites. A functional analysis of the putative ISRE indicated that ISRE played a synergetic role in the activation of bovine Mx2 gene transcription.

Conclusion

Bovine and water buffalo Mx2 promoter region was identified disclosing, the conserved ISRE, located in the proximal end of the promoter region like other members of the antiviral family, suggesting functional activity under interferon stimulation.

Expression dynamics of bovine MX genes in the endometrium and placenta during early to mid pregnancy

MX belongs to a family of type I interferon (IFN)-stimulated genes, and the MX protein has antiviral activity. MX has at least two isoforms, known as MX1 and MX2, in mammals. Moreover, bovine MX1 has been found to have alternative splice variants—namely, MX1-a and MX1B. In ruminants, IFN-τ—a type I IFN—is temporarily produced from the conceptus before implantation and induces MX expression in the endometrium. However, the expression dynamics of MX after implantation are not clear. In the present study, we investigated the expression of MX1-a, MX1B and MX2 in the endometrium and placenta before and after implantation along with the expression of IFN-α, type I receptors (IFNAR1 and IFNAR2) and interferon regulatory factors (IRF3 and IRF9). Pregnant uterine samples were divided into five groups according to pregnancy days 14–18, 25–40, 50–70, 80–100, and 130–150. Tissue samples were collected from the intercaruncular endometrium (IC), caruncular endometrium (C) and fetal placenta (P). Although all the MX expressions were significantly higher in the IC and C at days 14–18, presumably caused by embryo-secreted IFN-τ stimulation, their expressions were also detectable in the IC, C and P after implantation. Furthermore, IFN-α expression was significantly higher in the IC. RT-PCR indicated IFNAR1, IFNAR2, IRF3 and IRF9 mRNA in all the tissues during pregnancy. These results suggest that all the MX genes are affected by the type I IFN pathway during pregnancy and are involved in an immune response to protect the mother and fetus.

Specific intracellular localization and antiviral property of genetic and splicing variants in bovine Mx1

In bovine Mx1, only an amino acid substitution between Ile and Met at position 120 was detected by the nucleotide sequence and mismatched PCR-RFLP technique. The Ile variant was assumed to distribute mainly in the bovine population since the gene frequency was 79.3%. Furthermore, we cloned water buffalo Mx1 cDNA, which showed 51 nucleotide and 20 amino acid substitutions in comparison with that of the cow. Another kind of Mx1 cDNA, bovine Mx1B cDNA, was found and it was deduced to cause 27 amino acid substitutions at the N-terminus compared to the original Mx1 by alternative splicing. However, no variation was detected in 27 amino acids specific for Mx1B among 29 cows and a water buffalo. We established four kinds of mRNA-expressing 3T3 cells and Vero cells. When infection experiments were performed using recombinant vesicular stomatitis virus (VSVDeltaG*-G), bovine Ile and Met types and water buffalo Mx1 mRNA-expressing cell lines showed equally positive antiviral activities (p < 0.05). On the other hand, bovine Mx1B mRNA-expressing cell lines did not have activity against VSVDeltaG*-G. Intracellular localization of bovine Mx1 and Mx1B proteins was examined by a transiently GFP-fused expression system in 3T3 cells. Bovine Mx1 was localized in the cytoplasm, while bovine Mx1B was mainly localized in the nucleus. An arginine-rich nuclear localization signal was found in 27 amino acids specific for Mx1B. N-terminus-deleted Mx1B was only localized in the cytoplasm, and the deleted Mx1B-expressing cell lines showed significantly positive antiviral activities (p < 0.05) against VSVDeltaG*-G.

Polymorphisms of the chicken antiviral MX gene

The Mx gene was originally found in laboratory mice in an infection experiment using influenza virus (Lindermann, 1962). Almost all of the mouse strains in that experiment died from the infection, and only the A2G strain had resistance to the virus. This resistant character was shown to be inherited as a single autosomal dominant trait (Lindermann et al., 1963; Lindermann, 1964; Haller et al., 1979). A congenic mouse strain was established by introducing the Mx+ allele of the A2G resistant strain into the Mx- sensitive inbred strain BALB/c (Staeheli et al., 1984). By immunizing parental BALB/c mice with extracts of interferon (IFN)-treated cultured cells from congenic BALB/c-Mx+ mice, a specific antibody against Mx protein was obtained (Horisberger et al., 1983; Staeheli et al., 1985). The Mx protein was detected in the nucleus of IFN-alpha/beta-treated mouse cells by immunofluorescence using the anti-Mx antibody (Dreiding et al., 1985). Thereafter, by using the antibody as an indicator, cDNA encoding the Mx protein was cloned from a cDNA library constructed from IFN-treated cells of congenic BALB/c-Mx+ mice (Staeheli et al., 1986a). IFN-treated Mx+ mouse cells contained a 3.5-kb Mx mRNA in the Northern blot, while Mx- cells failed to express the transcript. The functional Mx+ gene from an A2G mouse was found to contain 14 exons and encode 631 amino acids. The Mx- allelic mouse strains were found to be missing sequence of exons 9 through 11 or to contain a point mutation that converts lysine at position 389 to a stop codon (Staeheli et al., 1988). If these polymorphisms of the Mx gene could be detected in domestic animals, it would be possible to produce breeds that show resistance to infectious diseases.

Cellular Localization and Function of the Antiviral Protein, Ovine Mx1 (oMx1): II. The oMx1 Protein Is a Regulator of Secretion in an Ovine Glandular Epithelial Cell Line

PROBLEM

Embryonic loss is a major contributor to infertility. Understanding factors affecting embryonic loss will help increase fertility.

METHOD OF STUDY

We investigated if ovine Mx1 (oMx1) mediated secretion by ovine glandular epithelial (oGE) cells using small interfering RNA (siRNA). Effects on secretion were examined through the conventional endoplasmic reticulum-Golgi pathway using beta2- microglobulin (beta2MG) as a marker, and interferon-stimulated gene 15 (ISG15) as a marker for unconventional secretion.

RESULTS

Mx1 siRNA reduced oMx1 mRNA levels at 12 and 24 hr after IFN-tau treatment (P < 0.05), without affecting levels of oMx2, ISG15, 2',5'-oligoadenylate synthetas or beta2MG. Mx1 siRNA reduced Mx1 protein levels at 48 and 120 hr after treatment (P < 0.05) and protein levels remained low at 120 hr. Transient oMx1 knock-down reduced secretion of oMx1 (P < 0.01). ISG15 protein in secretions was reduced without affecting intracellular levels (P < 0.05). Levels of beta2MG in secretions were not affected by Mx1 siRNA.

CONCLUSION

We showed that oMx1 protein is secreted by oGE cells and that reduction in oMx1 protein levels by siRNA reduced secretion of ISG15, but not beta2MG. Results support the hypothesis that oMx1 is a regulator of secretion through unconventional secretory pathway(s).

Bovine and water buffalo Mx2 genes: polymorphism and antiviral activity

Millennia-long selective pressure of single-strand RNA viruses on the bovine Mx locus has increased the advantages of using the bovine Mx protein to evaluate the ultimate significance of the antiviral role of Mx proteins. The conclusions of research based only on the bovine Mx1 protein showed the need for comprehensive studies that demonstrate the role of all isoforms, individually or together, especially in the presence of a second isoform, the bovine Mx2 gene. This study provides information about bovine and water buffalo Mx2 genes, as well as their allelic polymorphism and basic antiviral potential. Observation of an Mx2 cDNA sequence (2,381 bp) obtained from 15 animals from 11 breeds using primers based on a previous sequence (NCBI accession no. AF335147) revealed several nucleotide substitutions, with eight different alleles and two amino acid exchanges: Gly to Ser at position 302 and Ile to Val at position 354, though the latter was found only in the NCBI database. A water buffalo Mx2 cDNA sequence was identified for the first time, revealing 46 nucleotide substitutions with 12 amino acid variations, in addition to a 9-bp insertion in the 5' untranslated region UTR, compared with the bovine Mx2 cDNA. Transfected 3T3 cells expressing bovine Mx2 mRNAs coding Gly or Ser at position 302, water buffalo Mx2 mRNA, positive control bovine Mx1 mRNA-expressing cells, and negative control parental 3T3 were subjected to infection with recombinant vesicular stomatitis virus (VSVDeltaG*-G), as were empty pCI-neo vector-transfected cells. The positive control and all cells expressing Mx2 mRNAs displayed significantly higher levels of antiviral activity against VSVDeltaG*-G (P < 0.01) than did the negative controls.

Identification of a missense mutation in the bovine ABCG2 gene with a major effect on the QTL on chromosome 6 affecting milk yield and composition in Holstein cattle

We previously localized a quantitative trait locus (QTL) on chromosome 6 affecting milk fat and protein concentration to a 4-cM confidence interval, centered on the microsatellite BM143. We characterized the genes and sequence variation in this region and identified common haplotypes spanning five polymorphic sites in the genes IBSP, SPP1, PKD2, and ABCG2 for two sires heterozygous for this QTL. Expression of SPP1 and ABCG2 in the bovine mammary gland increased from parturition through lactation. SPP1 and all the coding exons of ABCG2 and PKD2 were sequenced for these two sires. The single nucleotide change capable of encoding a substitution of tyrosine-581 to serine (Y581S) in the ABCG2 transporter was the only polymorphism corresponding to the segregation status of all 3 heterozygous and 15 homozygous sires for the QTL in the Israeli and U.S. Holstein populations. The allele substitution fixed effects on the genetic evaluations of 335 Israeli sires were -341 kg milk, +0.16% fat, and +0.13% protein (F-value = 200). No other polymorphism gave significant effect for fat and protein concentration in models that also included Y581S. The allele substitution effects on the genetic evaluations of 670 cows, daughters of two heterozygous sires, were -226 kg milk, 0.09% fat, and 0.08% protein (F-value = 394), with partial dominance towards the 581S homozygotes. We therefore propose that Y581S in ABCG2 is the causative site for this QTL.