Coronavirus disease 2019 (COVID-19) is a fatal pandemic disease that is caused by infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). As of 13 December, 2020, over 70,000,000 cases and 1,500,000 deaths have been reported over a period of several months; however, the mechanism underlying the pathogenesis of COVID-19 has not been elucidated. To identify the novel risk genetic biomarker for COVID-19, we evaluated the correlation between the case fatality rate of COVID-19 and the genetic polymorphisms of several potential COVID-19-related genes, including interferon-induced transmembrane protein 3 (IFITM3), the angiotensin I converting enzyme 2 (ACE2) gene, transmembrane protease, serine 2 (TMPRSS2), interleukin 6 (IL6), leucine zipper transcription factor-like protein 1 (LZTFL1), and the ABO genes, in various ethnic groups. We obtained the number of COVID-19 cases and deaths from the World Health Organization (WHO) COVID-19 dashboard and calculated the case fatality rate of each ethnic group. In addition, we obtained the allele distribution of the polymorphisms of the IFITM3, ACE2, TMPRSS2, IL6, LZTFL1, and ABO genes from the 1000 Genomes Project and performed Log-linear regression analysis using SAS version 9.4. We found different COVID-19 case fatality rates in each ethnic group. Notably, we identified a strong correlation between the case fatality rate of COVID-19 and the allele frequency of the rs6598045 single nucleotide polymorphism (SNP) of the IFITM3 gene. To the best of our knowledge, this report is the first to describe a strong correlation between the COVID-19 case fatality rate and the rs6598045 SNP of the IFITM3 gene at the population-level.

Prion disease has displayed large infection host ranges among several species; however, dogs have not been reported to be infected and are considered prion disease-resistant animals. Case-controlled studies in several species, including humans and cattle, indicated a potent association of prion protein gene (PRNP) polymorphisms in the progression of prion disease. Thus, because of the proximal location and similar structure of the PRNP gene among the prion gene family, the prion-like protein gene (PRND) was noted as a novel candidate gene that contributes to prion disease susceptibility. Several case-controlled studies have confirmed the relationship of the PRND gene with prion disease vulnerability, and strong genetic linkage disequilibrium blocks were identified in prion-susceptible species between the PRNP and PRND genes. However, to date, polymorphisms of the dog PRND gene have not been reported, and the genetic linkage between the PRNP and PRND genes has not been examined thus far. Here, we first investigated dog PRND polymorphisms in 207 dog DNA samples using direct DNA sequencing. A total of four novel single nucleotide polymorphisms (SNPs), including one nonsynonymous SNP (c.149G>A, R50H), were identified in this study. We also found two major haplotypes among the four novel SNPs. In addition, we compared the genotype and allele frequencies of the c.149G>A (R50H) SNP and found significantly different distributions among eight dog breeds. Furthermore, we annotated the c.149G>A (R50H) SNP of the dog PRND gene using in silico tools, PolyPhen-2, PROVEAN, and PANTHER. Finally, we examined linkage disequilibrium between the PRNP and PRND genes in dogs. Interestingly, we did not find a strong genetic linkage between these two genes. To the best of our knowledge, this was the first genetic study of the PRND gene in a prion disease-resistant animal, a dog.

Prion diseases are caused by misfolded prion protein (PrP^Sc) and are accompanied by spongiform vacuolation of brain lesions. Approximately three centuries have passed since prion diseases were first discovered around the world; however, the exact role of certain factors affecting the causative agent of prion diseases is still debatable. In recent studies, somatic mutations were assumed to be cause of several diseases. Thus, we postulated that genetically unstable cancer tissue may cause somatic mutations in the prion protein gene (PRNP), which could trigger the onset of prion diseases. To identify somatic mutations in the PRNP gene in cancer tissues, we analyzed somatic mutations in the PRNP gene in cancer patients using the Cancer Genome Atlas (TCGA) database. In addition, to evaluate whether the somatic mutations in the PRNP gene in cancer patients had a damaging effect, we performed in silico analysis using PolyPhen-2, PANTHER, PROVEAN, and AMYCO. We identified a total of 48 somatic mutations in the PRNP gene, including 8 somatic mutations that are known pathogenic mutations of prion diseases. We identified significantly different distributions among the types of cancer, the mutation counts, and the ages of diagnosis between the total cancer patient population and cancer patients carrying somatic mutations in the PRNP gene. Strikingly, although invasive breast carcinoma and glioblastoma accounted for a high percentage of the total cancer patient population (9.9% and 5.4%, respectively), somatic mutations in the PRNP gene have not been identified in these two cancer types. We suggested the possibility that somatic mutations of the PRNP gene in glioblastoma can be masked by a diagnosis of prion disease. In addition, we found four aggregation-prone somatic mutations, these being L125F, E146Q, R151C, and K204N. To the best of our knowledge, this is the first specific analysis of the somatic mutations in the PRNP gene in cancer patients.

Transmissible spongiform encephalopathies (TSEs) have been reported in a wide range of species. However, TSE infection in natural cases has never been reported in dogs. Previous studies have reported that polymorphisms of the prion protein gene (PRNP) have a direct impact on the susceptibility of TSE. However, studies on polymorphisms of the canine PRNP gene are very rare in dogs. We examined the genotype, allele, and haplotype frequencies of canine PRNP in 204 dogs using direct sequencing and analyzed linkage disequilibrium (LD) using Haploview version 4.2. In addition, to evaluate the impact of nonsynonymous polymorphisms on the function of prion protein (PrP), we carried out in silico analysis using PolyPhen-2, PROVEAN, and PANTHER. Furthermore, we analyzed the structure of PrP and hydrogen bonds according to alleles of nonsynonymous single nucleotide polymorphisms (SNPs) using the Swiss-Pdb Viewer program. Finally, we predicted the impact of the polymorphisms on the aggregation propensity of dog PrP using AMYCO. We identified a total of eight polymorphisms, including five novel SNPs and one insertion/deletion polymorphism, and found strong LDs and six major haplotypes among eight polymorphisms. In addition, we identified significantly different distribution of haplotypes among eight dog breeds, however, the kinds of identified polymorphisms were different among each dog breed. We predicted that p.64_71del HGGGWGQP, Asp182Gly, and Asp182Glu polymorphisms can impact the function and/or structure of dog PrP. Furthermore, the number of hydrogen bonds of dog PrP with the Glu182 and Gly182 alleles were predicted to be less than those with the Asp182 allele. Finally, Asp163Glu and Asp182Gly showed more aggregation propensity than wild-type dog PrP. These results suggest that nonsynonymous SNPs, Asp182Glu and Asp182Gly, can influence the stability of dog PrP and confer the possibility of TSE infection in dogs.

Bovine spongiform encephalopathy (BSE) is a prion disease characterized by spongiform degeneration and astrocytosis in the brain. Unlike classical BSE, which is caused by prion-disease-contaminated meat and bone meal, the cause of atypical BSE has not been determined. Since previous studies have reported that the somatic mutation in the human prion protein gene (PRNP) has been linked to human prion disease, the somatic mutation of the PRNP gene was presumed to be one cause of prion disease. However, to the best of our knowledge, the somatic mutation of this gene in cattle has not been investigated to date. We investigated somatic mutations in a total of 58 samples, including peripheral blood; brain tissue including the medulla oblongata, cerebellum, cortex, and thalamus; and skin tissue in 20 individuals from each breed using pyrosequencing. In addition, we estimated the deleterious effect of the K211 somatic mutation on bovine prion protein by in silico evaluation tools, including PolyPhen-2 and PANTHER. We found a high rate of K211 somatic mutations of the bovine PRNP gene in the medulla oblongata of three Holsteins (10% ± 4.4%, 28% ± 2%, and 19.55% ± 3.1%). In addition, in silico programs showed that the K211 somatic mutation was damaging. To the best of our knowledge, this study is the first to investigate K211 somatic mutations of the bovine PRNP gene that are associated with potential BSE progression.

Prion diseases are fatal neurodegenerative disorders characterized by vacuolation and gliosis in the brain. Prion diseases have been reported in several mammals, and genetic polymorphisms of the prion protein gene (PRNP) play an essential role in the vulnerability of prion diseases. However, to date, investigations of PRNP polymorphisms are rare in cats, which are the major host of feline spongiform encephalopathy (FSE). Thus, we investigated the genetic polymorphisms of the cat PRNP gene and analyzed the structural characteristics of the PrP of cats compared to those of dog, prion disease-resistant animal. To investigate the genetic variations of the cat PRNP gene in 208 cats, we performed amplicon sequencing and examined the genotype, allele and haplotype frequencies of cat PRNP polymorphisms. We evaluated the influence of cat PRNP polymorphisms using PolyPhen-2, PANTHER, PROVEAN and AMYCO. In addition, we carried out structural analysis of cat PrP according to the allele of nonsynonymous single nucleotide polymorphism (SNP) (c.457G > A, Glu153Lys) using Swiss-PdbViewer. Finally, we compared the structural differences between cat and canine PrPs for SNPs associated with prion disease resistance in dogs. We identified a total of 15 polymorphisms, including 14 novel SNPs and one insertion/deletion polymorphism (InDel). Among them, Glu153Lys was predicted to affect the structural stability and amyloid propensity of cat PrP. In addition, asparagine at codon 166 of cat PrP was predicted to have longer hydrogen bond than aspartic acid at codon 163 of canine PrP. Furthermore, substitution to dog-specific amino acids in cat PrP showed an increase in structural stability. To the best of our knowledge, this is the first study regarding the structural characteristics of cat PRNP gene.