The Experts below are selected from a list of 78 Experts worldwide ranked by ideXlab platform

Jared A Jaffey - One of the best experts on this subject based on the ideXlab platform.

  • clinical metabolic and molecular genetic characterization of Hereditary Methemoglobinemia caused by cytochrome b 5 reductase deficiency in 30 dogs
    Scientific Reports, 2020
    Co-Authors: Jared A Jaffey, N A Villani, Osheiza Abdulmalik, N S Reading, R Kreisler, G Bullock, A Wiest, Tendai Mhlangamutangadura, Gary S Johnson
    Abstract:

    Genotype-phenotype correlations of humans and dogs with Hereditary Methemoglobinemia are not yet well characterized. We determined total hemoglobin and methemoglobin (MetHb) concentrations, cytochrome b5 reductase (CYB5R) enzyme activities, genotypes, and clinical signs in 30 dogs with persistent cyanosis without cardiopulmonary disease. Erythrocytic CYB5R enzyme activities were low in all dogs assayed. Owner-reported quality of life ranged from subclinical to occasional exertional syncope. Two previously reported and two novel CYB5R3 missense variants were identified among the methemoglobinemic cohort and were predicted to impair enzyme function. Two variants were recurrent: a homozygous Ile194Leu substitution was found in Pomeranians and other small dogs, and a homozygous Arg219Pro change occurred predominately in pit bull terriers. The other two variants were Thr202Ala and Gly76Ser substitutions in single dogs. Of the two common CYB5R3 genotypes, Arg219Pro was associated with a more severe metabolic phenotype. We conclude that CYB5R3 deficiency is the predominate cause of canine Hereditary Methemoglobinemia. Although this finding is unlikely to alter the clinical approach to Hereditary Methemoglobinemia in dogs, it demonstrates the possibility of how genotype-phenotype cohort analysis might facilitate precision medicine in the future in veterinary medicine.

  • clinical metabolic and molecular genetic characterization of Hereditary Methemoglobinemia caused by cytochrome b5 reductase deficiency in 30 dogs
    Scientific Reports, 2020
    Co-Authors: Jared A Jaffey, N A Villani, Osheiza Abdulmalik, N S Reading, R Kreisler, G Bullock, A Wiest, Tendai Mhlangamutangadura, Gary S Johnson
    Abstract:

    Genotype-phenotype correlations of humans and dogs with Hereditary Methemoglobinemia are not yet well characterized. We determined total hemoglobin and methemoglobin (MetHb) concentrations, cytochrome b5 reductase (CYB5R) enzyme activities, genotypes, and clinical signs in 30 dogs with persistent cyanosis without cardiopulmonary disease. Erythrocytic CYB5R enzyme activities were low in all dogs assayed. Owner-reported quality of life ranged from subclinical to occasional exertional syncope. Two previously reported and two novel CYB5R3 missense variants were identified among the methemoglobinemic cohort and were predicted to impair enzyme function. Two variants were recurrent: a homozygous Ile194Leu substitution was found in Pomeranians and other small dogs, and a homozygous Arg219Pro change occurred predominately in pit bull terriers. The other two variants were Thr202Ala and Gly76Ser substitutions in single dogs. Of the two common CYB5R3 genotypes, Arg219Pro was associated with a more severe metabolic phenotype. We conclude that CYB5R3 deficiency is the predominate cause of canine Hereditary Methemoglobinemia. Although this finding is unlikely to alter the clinical approach to Hereditary Methemoglobinemia in dogs, it demonstrates the possibility of how genotype-phenotype cohort analysis might facilitate precision medicine in the future in veterinary medicine.

  • clinical metabolic and genetic characterization of Hereditary Methemoglobinemia caused by cytochrome b5 reductase deficiency in cats
    Journal of Veterinary Internal Medicine, 2019
    Co-Authors: Jared A Jaffey, Urs Giger, Osheiza Abdulmalik, Scott N Reading, Ruben M Buckley, Sophie Johnstone, Leslie A Lyons
    Abstract:

    : Two non-pedigreed male castrated cats had persistent cyanosis over a 3-year observation period. Clinical cardiopulmonary evaluations did not reveal abnormalities, but the blood remained dark after exposure to air. Erythrocytic methemoglobin concentrations were high (~40% of hemoglobin) and cytochrome b5 reductase (CYB5R) activities in erythrocytes were low (≤15% of control). One cat remained intolerant of exertion, and the other cat developed anemia and died due to an unidentified comorbidity. Whole-genome sequencing revealed a homozygous c.625G>A missense variant (B4:137967506) and a c.232-1G>C splice acceptor variant (B4:137970815) in CYB5R3, respectively, which were absent in 193 unaffected additional cats. The p.Gly209Ser missense variant likely disrupts a nicotinamide adenine dinucleotide (NADH)-binding domain, while the splicing error occurs at the acceptor site for exon 4, which likely affects downstream translation of the protein. The 2 novel CYB5R3 variants were associated with Methemoglobinemia using clinical, biochemical, genomics, and in silico protein studies. The variant prevalence is unknown in the cat population.

  • clinical metabolic and genetic characterization of Hereditary Methemoglobinemia caused by cytochrome b 5 reductase deficiency in cats
    Journal of Veterinary Internal Medicine, 2019
    Co-Authors: Jared A Jaffey, Urs Giger, Osheiza Abdulmalik, Scott N Reading, Ruben M Buckley, Sophie Johnstone, Leslie A Lyons
    Abstract:

    Two non-pedigreed male castrated cats had persistent cyanosis over a 3-year observation period. Clinical cardiopulmonary evaluations did not reveal abnormalities, but the blood remained dark after exposure to air. Erythrocytic methemoglobin concentrations were high (~40% of hemoglobin) and cytochrome b5 reductase (CYB5R) activities in erythrocytes were low (≤15% of control). One cat remained intolerant of exertion, and the other cat developed anemia and died due to an unidentified comorbidity. Whole-genome sequencing revealed a homozygous c.625G>A missense variant (B4:137967506) and a c.232-1G>C splice acceptor variant (B4:137970815) in CYB5R3, respectively, which were absent in 193 unaffected additional cats. The p.Gly209Ser missense variant likely disrupts a nicotinamide adenine dinucleotide (NADH)-binding domain, while the splicing error occurs at the acceptor site for exon 4, which likely affects downstream translation of the protein. The 2 novel CYB5R3 variants were associated with Methemoglobinemia using clinical, biochemical, genomics, and in silico protein studies. The variant prevalence is unknown in the cat population.

  • long term treatment with methylene blue in a dog with Hereditary Methemoglobinemia caused by cytochrome b5 reductase deficiency
    Journal of Veterinary Internal Medicine, 2017
    Co-Authors: Jared A Jaffey, M R Harmon, N A Villani, Erica K Creighton, Gary S Johnson, Urs Giger, John R Dodam
    Abstract:

    A juvenile male mixed breed dog was presented for lethargy, exercise intolerance, and aggression when touched on the head. Cyanosis, tachycardia, and tachypnea were observed and persisted during oxygen supplementation. Arterial blood gas analysis by co-oximetry identified an increased methemoglobin concentration (27%; normal, <2%) with normal arterial oxygen tension. The Methemoglobinemia and associated clinical signs resolved after administration of methylene blue (1 mg/kg) IV, and the dog was discharged. The affected dog's whole-genome sequence contained 2 potentially causal heterozygous CYB5R3 missense mutations suggesting that cytochrome b5 reductase deficiency was responsible for the Methemoglobinemia. This hypothesis was confirmed by enzyme analysis that identified cytochrome b5 reductase activity in the affected dog's erythrocytes to only approximately 6% of that in a control sample. Clinical signs recurred 11 days after discharge but normalized and the methemoglobin concentration decreased with methylene blue administration PO (1.5 mg/kg, initially daily and then every other day).

M Takeshita - One of the best experts on this subject based on the ideXlab platform.

  • a novel point mutation in a 3 splice site of the nadh cytochrome b5 reductase gene results in immunologically undetectable enzyme and impaired nadh dependent ascorbate regeneration in cultured fibroblasts of a patient with type ii Hereditary Methemoglobinemia
    American Journal of Human Genetics, 1995
    Co-Authors: Komei Shirabe, M Takeshita, Maria Teresa Landi, Graziella Uziel, Ermellina Fedrizzi, N Borgese
    Abstract:

    Hereditary Methemoglobinemia with generalized deficiency of NADH-cytochrome b{sub 5} reductase (b{sub 5}R) (type II) is a rare disease characterized by severe developmental abnormalities, which often lead to premature death. Although the molecular relationship between the symptoms of this condition and the enzyme deficit are not understood, it is thought that an important cause is the loss of the lipid metabolizing activities of the endoplasmic reticulum-located reductase. However, the functions of the form located on outer mitochondrial membranes have not been considered previously. In this study, we have analyzed the gene of an Italian patient and identified a novel G{r_arrow}T transversion at the splice-acceptor site of the 9th exon, which results in the complete absence of immunologically detectable b{sub 5}R in blood cells and skin fibroblasts. In cultured fibroblasts of the patient, NADH-dependent cytochrome c reductase, ferricyanide reductase, and semidehydroascorbate reductase activities were severely reduced. The latter activity is known to be due to b{sub 5}R located on outer mitochondrial membranes. Thus, our results demonstrate that the reductase in its two membrane locations, endoplasmic reticulum and outer mitochondrial membranes, is the product of the same gene and suggest that a defect in ascorbate regeneration may contribute to the phenotype of Hereditarymore » Methemoglobinemia of generalized type. 37 refs., 5 figs., 2 tabs.« less

  • a novel point mutation in a 3 splice site of the nadh cytochrome b5 reductase gene results in immunologically undetectable enzyme and impaired nadh dependent ascorbate regeneration in cultured fibroblasts of a patient with type ii Hereditary Methemoglobinemia
    American Journal of Human Genetics, 1995
    Co-Authors: Komei Shirabe, M Takeshita, Maria Teresa Landi, Graziella Uziel, Ermellina Fedrizzi, Nica Borgese
    Abstract:

    Abstract Hereditary Methemoglobinemia with generalized deficiency of NADH-cytochrome b5 reductase (b5R) (type II) is a rare disease characterized by severe developmental abnormalities, which often lead to premature death. Although the molecular relationship between the symptoms of this condition and the enzyme deficit are not understood, it is thought that an important cause is the loss of the lipid metabolizing activities of the endoplasmic reticulum-located reductase. However, the functions of the form located on outer mitochondrial membranes have not been considered previously. In this study, we have analyzed the gene of an Italian patient and identified a novel G-->T transversion at the splice-acceptor site of the 9th exon, which results in the complete absence of immunologically detectable b5R in blood cells and skin fibroblasts. In cultured fibroblasts of the patient, NADH-dependent cytochrome c reductase, ferricyanide reductase, and semidehydroascorbate reductase activities were severely reduced. The latter activity is known to be due to b5R located on outer mitochondrial membranes. Thus, our results demonstrate that the reductase in its two membrane locations, endoplasmic reticulum and outer mitochondrial membranes, is the product of the same gene and suggest that a defect in ascorbate regeneration may contribute to the phenotype of Hereditary Methemoglobinemia of the generalized type.

  • an in frame deletion of codon 298 of the nadh cytochrome b5 reductase gene results in Hereditary Methemoglobinemia type ii generalized type a functional implication for the role of the cooh terminal region of the enzyme
    Journal of Biological Chemistry, 1994
    Co-Authors: Komei Shirabe, T Yubisui, Y Fujimoto, M Takeshita
    Abstract:

    Abstract The nucleotide sequence was determined for the gene of NADH-cytochrome b5 reductase of a patient of type II Hereditary Methemoglobinemia found in Yokohama, Japan. An in-frame deletion of 3 base pairs corresponding to codon 298 (TTC) was identified in the patient. The patient was homozygous for the mutation as shown by hybridization experiments using allele-specific oligonucleotides. The mutation causes deletion of Phe-298, which is the third to the COOH-terminal residue, indicating that in this mutant enzyme the sequence of this region has changed from -Cys-Phe-Val-Phe-COOH to -Cys-Val-Phe-COOH. The mutant enzyme, whose Phe-298 was deleted (F298 delta), was prepared by means of a bacterial expression system and site-directed mutagenesis. The kcat/Km value (NADH) of the enzyme was 5.7 s-1 M-1, which corresponds to 0.4% of that of the wild type. Moreover, the enzyme was much less thermostable than the wild type. To examine further the role of the COOH-terminal portion of the enzyme, various mutant enzymes were also prepared and characterized. The enzymatic properties of F298L, F300L, and F298L/F300L were essentially the same as that of the wild type. The kinetic properties of F298A, and F300A were not greatly affected, but the stability of the enzymes was somewhat impaired. Since Val-299 is naturally Ala in steer enzyme, no specific residues in the carboxyl-terminal region (298-300) are essential to the enzyme function. The instability of the F298/F300A double mutant indicates that the hydrophobicity of the carboxyl-terminal region of the enzyme might be important to maintain the conformation of the enzyme. high impairment of the activity of the F298 delta, F298stop, and F300stop mutants might be caused by the loss of the residue(s) in the carboxyl-terminal portion. These results indicate that the hydrophobicity, but not the specific amino acid residues, of the carboxyl-terminal portion of the enzyme is important for the stability of the enzyme.

  • enzymatic instability of nadh cytochrome b5 reductase as a cause of Hereditary Methemoglobinemia type i red cell type
    Journal of Biological Chemistry, 1992
    Co-Authors: Komei Shirabe, Toshitsugu Yubisui, N Borgese, Chuanye Tang, Donald E Hultquist, M Takeshita
    Abstract:

    Abstract Nucleotide substitutions in the gene for NADH-cytochrome b5 reductase were identified in three independent probands of Hereditary Methemoglobinemia type I. Patients in Kagoshima and Okinawa in Japan were shown to possess the same base change, from guanine to adenine at codon 57, which results in amino acid substitution from Arg to Gln. This nucleotide change was the same as formerly found in a patient in Toyoake, Japan (Katsube, T., Sakamoto, N., Kobayashi, Y., Seki, R., Hirano, M., Tanishima, K., Tomoda, A., Takazakura, E., Yubisui, T., Takeshita, M., Sakaki, Y., and Fukumaki, Y. (1991) Am. J. Hum. Genet. 48, 799-808). A type I patient in Italy was shown to have a base change from guanine to adenine at codon 105 which causes substitution from Val to Met. To characterize the enzymes of type I patients, Arg-57----Gln and Val-105----Met mutant enzymes were overexpressed in Escherichia coli and purified to homogeneity. kcat/Km values (NADH) of these two enzymes were 25% in Arg-57----Gln and 14.5% in Val-105----Met compared with that of the wild type enzyme, while the value of type II (generalized, severe form of the disease) mutant enzyme was 3% of the normal value (Yubisui, T., Shirabe, K., Takeshita, M., Kobayashi, Y., Fukumaki, Y., Sakaki, Y., and Takano, T. (1991) J. Biol. Chem. 266, 66-70). The type I mutant enzymes were less heat-stable and more susceptible to proteinase treatment than the wild type. From these results we conclude that restriction of enzyme deficiency to red cells in Hereditary Methemoglobinemia type I may be generally derived from instability and increased proteolytic susceptibility of variant NADH-cytochrome b5 reductases due to a point mutation.

Komei Shirabe - One of the best experts on this subject based on the ideXlab platform.

  • a novel point mutation in a 3 splice site of the nadh cytochrome b5 reductase gene results in immunologically undetectable enzyme and impaired nadh dependent ascorbate regeneration in cultured fibroblasts of a patient with type ii Hereditary Methemoglobinemia
    American Journal of Human Genetics, 1995
    Co-Authors: Komei Shirabe, M Takeshita, Maria Teresa Landi, Graziella Uziel, Ermellina Fedrizzi, N Borgese
    Abstract:

    Hereditary Methemoglobinemia with generalized deficiency of NADH-cytochrome b{sub 5} reductase (b{sub 5}R) (type II) is a rare disease characterized by severe developmental abnormalities, which often lead to premature death. Although the molecular relationship between the symptoms of this condition and the enzyme deficit are not understood, it is thought that an important cause is the loss of the lipid metabolizing activities of the endoplasmic reticulum-located reductase. However, the functions of the form located on outer mitochondrial membranes have not been considered previously. In this study, we have analyzed the gene of an Italian patient and identified a novel G{r_arrow}T transversion at the splice-acceptor site of the 9th exon, which results in the complete absence of immunologically detectable b{sub 5}R in blood cells and skin fibroblasts. In cultured fibroblasts of the patient, NADH-dependent cytochrome c reductase, ferricyanide reductase, and semidehydroascorbate reductase activities were severely reduced. The latter activity is known to be due to b{sub 5}R located on outer mitochondrial membranes. Thus, our results demonstrate that the reductase in its two membrane locations, endoplasmic reticulum and outer mitochondrial membranes, is the product of the same gene and suggest that a defect in ascorbate regeneration may contribute to the phenotype of Hereditarymore » Methemoglobinemia of generalized type. 37 refs., 5 figs., 2 tabs.« less

  • a novel point mutation in a 3 splice site of the nadh cytochrome b5 reductase gene results in immunologically undetectable enzyme and impaired nadh dependent ascorbate regeneration in cultured fibroblasts of a patient with type ii Hereditary Methemoglobinemia
    American Journal of Human Genetics, 1995
    Co-Authors: Komei Shirabe, M Takeshita, Maria Teresa Landi, Graziella Uziel, Ermellina Fedrizzi, Nica Borgese
    Abstract:

    Abstract Hereditary Methemoglobinemia with generalized deficiency of NADH-cytochrome b5 reductase (b5R) (type II) is a rare disease characterized by severe developmental abnormalities, which often lead to premature death. Although the molecular relationship between the symptoms of this condition and the enzyme deficit are not understood, it is thought that an important cause is the loss of the lipid metabolizing activities of the endoplasmic reticulum-located reductase. However, the functions of the form located on outer mitochondrial membranes have not been considered previously. In this study, we have analyzed the gene of an Italian patient and identified a novel G-->T transversion at the splice-acceptor site of the 9th exon, which results in the complete absence of immunologically detectable b5R in blood cells and skin fibroblasts. In cultured fibroblasts of the patient, NADH-dependent cytochrome c reductase, ferricyanide reductase, and semidehydroascorbate reductase activities were severely reduced. The latter activity is known to be due to b5R located on outer mitochondrial membranes. Thus, our results demonstrate that the reductase in its two membrane locations, endoplasmic reticulum and outer mitochondrial membranes, is the product of the same gene and suggest that a defect in ascorbate regeneration may contribute to the phenotype of Hereditary Methemoglobinemia of the generalized type.

  • an in frame deletion of codon 298 of the nadh cytochrome b5 reductase gene results in Hereditary Methemoglobinemia type ii generalized type a functional implication for the role of the cooh terminal region of the enzyme
    Journal of Biological Chemistry, 1994
    Co-Authors: Komei Shirabe, T Yubisui, Y Fujimoto, M Takeshita
    Abstract:

    Abstract The nucleotide sequence was determined for the gene of NADH-cytochrome b5 reductase of a patient of type II Hereditary Methemoglobinemia found in Yokohama, Japan. An in-frame deletion of 3 base pairs corresponding to codon 298 (TTC) was identified in the patient. The patient was homozygous for the mutation as shown by hybridization experiments using allele-specific oligonucleotides. The mutation causes deletion of Phe-298, which is the third to the COOH-terminal residue, indicating that in this mutant enzyme the sequence of this region has changed from -Cys-Phe-Val-Phe-COOH to -Cys-Val-Phe-COOH. The mutant enzyme, whose Phe-298 was deleted (F298 delta), was prepared by means of a bacterial expression system and site-directed mutagenesis. The kcat/Km value (NADH) of the enzyme was 5.7 s-1 M-1, which corresponds to 0.4% of that of the wild type. Moreover, the enzyme was much less thermostable than the wild type. To examine further the role of the COOH-terminal portion of the enzyme, various mutant enzymes were also prepared and characterized. The enzymatic properties of F298L, F300L, and F298L/F300L were essentially the same as that of the wild type. The kinetic properties of F298A, and F300A were not greatly affected, but the stability of the enzymes was somewhat impaired. Since Val-299 is naturally Ala in steer enzyme, no specific residues in the carboxyl-terminal region (298-300) are essential to the enzyme function. The instability of the F298/F300A double mutant indicates that the hydrophobicity of the carboxyl-terminal region of the enzyme might be important to maintain the conformation of the enzyme. high impairment of the activity of the F298 delta, F298stop, and F300stop mutants might be caused by the loss of the residue(s) in the carboxyl-terminal portion. These results indicate that the hydrophobicity, but not the specific amino acid residues, of the carboxyl-terminal portion of the enzyme is important for the stability of the enzyme.

  • enzymatic instability of nadh cytochrome b5 reductase as a cause of Hereditary Methemoglobinemia type i red cell type
    Journal of Biological Chemistry, 1992
    Co-Authors: Komei Shirabe, Toshitsugu Yubisui, N Borgese, Chuanye Tang, Donald E Hultquist, M Takeshita
    Abstract:

    Abstract Nucleotide substitutions in the gene for NADH-cytochrome b5 reductase were identified in three independent probands of Hereditary Methemoglobinemia type I. Patients in Kagoshima and Okinawa in Japan were shown to possess the same base change, from guanine to adenine at codon 57, which results in amino acid substitution from Arg to Gln. This nucleotide change was the same as formerly found in a patient in Toyoake, Japan (Katsube, T., Sakamoto, N., Kobayashi, Y., Seki, R., Hirano, M., Tanishima, K., Tomoda, A., Takazakura, E., Yubisui, T., Takeshita, M., Sakaki, Y., and Fukumaki, Y. (1991) Am. J. Hum. Genet. 48, 799-808). A type I patient in Italy was shown to have a base change from guanine to adenine at codon 105 which causes substitution from Val to Met. To characterize the enzymes of type I patients, Arg-57----Gln and Val-105----Met mutant enzymes were overexpressed in Escherichia coli and purified to homogeneity. kcat/Km values (NADH) of these two enzymes were 25% in Arg-57----Gln and 14.5% in Val-105----Met compared with that of the wild type enzyme, while the value of type II (generalized, severe form of the disease) mutant enzyme was 3% of the normal value (Yubisui, T., Shirabe, K., Takeshita, M., Kobayashi, Y., Fukumaki, Y., Sakaki, Y., and Takano, T. (1991) J. Biol. Chem. 266, 66-70). The type I mutant enzymes were less heat-stable and more susceptible to proteinase treatment than the wild type. From these results we conclude that restriction of enzyme deficiency to red cells in Hereditary Methemoglobinemia type I may be generally derived from instability and increased proteolytic susceptibility of variant NADH-cytochrome b5 reductases due to a point mutation.

Gary S Johnson - One of the best experts on this subject based on the ideXlab platform.

  • clinical metabolic and molecular genetic characterization of Hereditary Methemoglobinemia caused by cytochrome b 5 reductase deficiency in 30 dogs
    Scientific Reports, 2020
    Co-Authors: Jared A Jaffey, N A Villani, Osheiza Abdulmalik, N S Reading, R Kreisler, G Bullock, A Wiest, Tendai Mhlangamutangadura, Gary S Johnson
    Abstract:

    Genotype-phenotype correlations of humans and dogs with Hereditary Methemoglobinemia are not yet well characterized. We determined total hemoglobin and methemoglobin (MetHb) concentrations, cytochrome b5 reductase (CYB5R) enzyme activities, genotypes, and clinical signs in 30 dogs with persistent cyanosis without cardiopulmonary disease. Erythrocytic CYB5R enzyme activities were low in all dogs assayed. Owner-reported quality of life ranged from subclinical to occasional exertional syncope. Two previously reported and two novel CYB5R3 missense variants were identified among the methemoglobinemic cohort and were predicted to impair enzyme function. Two variants were recurrent: a homozygous Ile194Leu substitution was found in Pomeranians and other small dogs, and a homozygous Arg219Pro change occurred predominately in pit bull terriers. The other two variants were Thr202Ala and Gly76Ser substitutions in single dogs. Of the two common CYB5R3 genotypes, Arg219Pro was associated with a more severe metabolic phenotype. We conclude that CYB5R3 deficiency is the predominate cause of canine Hereditary Methemoglobinemia. Although this finding is unlikely to alter the clinical approach to Hereditary Methemoglobinemia in dogs, it demonstrates the possibility of how genotype-phenotype cohort analysis might facilitate precision medicine in the future in veterinary medicine.

  • clinical metabolic and molecular genetic characterization of Hereditary Methemoglobinemia caused by cytochrome b5 reductase deficiency in 30 dogs
    Scientific Reports, 2020
    Co-Authors: Jared A Jaffey, N A Villani, Osheiza Abdulmalik, N S Reading, R Kreisler, G Bullock, A Wiest, Tendai Mhlangamutangadura, Gary S Johnson
    Abstract:

    Genotype-phenotype correlations of humans and dogs with Hereditary Methemoglobinemia are not yet well characterized. We determined total hemoglobin and methemoglobin (MetHb) concentrations, cytochrome b5 reductase (CYB5R) enzyme activities, genotypes, and clinical signs in 30 dogs with persistent cyanosis without cardiopulmonary disease. Erythrocytic CYB5R enzyme activities were low in all dogs assayed. Owner-reported quality of life ranged from subclinical to occasional exertional syncope. Two previously reported and two novel CYB5R3 missense variants were identified among the methemoglobinemic cohort and were predicted to impair enzyme function. Two variants were recurrent: a homozygous Ile194Leu substitution was found in Pomeranians and other small dogs, and a homozygous Arg219Pro change occurred predominately in pit bull terriers. The other two variants were Thr202Ala and Gly76Ser substitutions in single dogs. Of the two common CYB5R3 genotypes, Arg219Pro was associated with a more severe metabolic phenotype. We conclude that CYB5R3 deficiency is the predominate cause of canine Hereditary Methemoglobinemia. Although this finding is unlikely to alter the clinical approach to Hereditary Methemoglobinemia in dogs, it demonstrates the possibility of how genotype-phenotype cohort analysis might facilitate precision medicine in the future in veterinary medicine.

  • long term treatment with methylene blue in a dog with Hereditary Methemoglobinemia caused by cytochrome b5 reductase deficiency
    Journal of Veterinary Internal Medicine, 2017
    Co-Authors: Jared A Jaffey, M R Harmon, N A Villani, Erica K Creighton, Gary S Johnson, Urs Giger, John R Dodam
    Abstract:

    A juvenile male mixed breed dog was presented for lethargy, exercise intolerance, and aggression when touched on the head. Cyanosis, tachycardia, and tachypnea were observed and persisted during oxygen supplementation. Arterial blood gas analysis by co-oximetry identified an increased methemoglobin concentration (27%; normal, <2%) with normal arterial oxygen tension. The Methemoglobinemia and associated clinical signs resolved after administration of methylene blue (1 mg/kg) IV, and the dog was discharged. The affected dog's whole-genome sequence contained 2 potentially causal heterozygous CYB5R3 missense mutations suggesting that cytochrome b5 reductase deficiency was responsible for the Methemoglobinemia. This hypothesis was confirmed by enzyme analysis that identified cytochrome b5 reductase activity in the affected dog's erythrocytes to only approximately 6% of that in a control sample. Clinical signs recurred 11 days after discharge but normalized and the methemoglobin concentration decreased with methylene blue administration PO (1.5 mg/kg, initially daily and then every other day).

Osheiza Abdulmalik - One of the best experts on this subject based on the ideXlab platform.

  • clinical metabolic and molecular genetic characterization of Hereditary Methemoglobinemia caused by cytochrome b 5 reductase deficiency in 30 dogs
    Scientific Reports, 2020
    Co-Authors: Jared A Jaffey, N A Villani, Osheiza Abdulmalik, N S Reading, R Kreisler, G Bullock, A Wiest, Tendai Mhlangamutangadura, Gary S Johnson
    Abstract:

    Genotype-phenotype correlations of humans and dogs with Hereditary Methemoglobinemia are not yet well characterized. We determined total hemoglobin and methemoglobin (MetHb) concentrations, cytochrome b5 reductase (CYB5R) enzyme activities, genotypes, and clinical signs in 30 dogs with persistent cyanosis without cardiopulmonary disease. Erythrocytic CYB5R enzyme activities were low in all dogs assayed. Owner-reported quality of life ranged from subclinical to occasional exertional syncope. Two previously reported and two novel CYB5R3 missense variants were identified among the methemoglobinemic cohort and were predicted to impair enzyme function. Two variants were recurrent: a homozygous Ile194Leu substitution was found in Pomeranians and other small dogs, and a homozygous Arg219Pro change occurred predominately in pit bull terriers. The other two variants were Thr202Ala and Gly76Ser substitutions in single dogs. Of the two common CYB5R3 genotypes, Arg219Pro was associated with a more severe metabolic phenotype. We conclude that CYB5R3 deficiency is the predominate cause of canine Hereditary Methemoglobinemia. Although this finding is unlikely to alter the clinical approach to Hereditary Methemoglobinemia in dogs, it demonstrates the possibility of how genotype-phenotype cohort analysis might facilitate precision medicine in the future in veterinary medicine.

  • clinical metabolic and molecular genetic characterization of Hereditary Methemoglobinemia caused by cytochrome b5 reductase deficiency in 30 dogs
    Scientific Reports, 2020
    Co-Authors: Jared A Jaffey, N A Villani, Osheiza Abdulmalik, N S Reading, R Kreisler, G Bullock, A Wiest, Tendai Mhlangamutangadura, Gary S Johnson
    Abstract:

    Genotype-phenotype correlations of humans and dogs with Hereditary Methemoglobinemia are not yet well characterized. We determined total hemoglobin and methemoglobin (MetHb) concentrations, cytochrome b5 reductase (CYB5R) enzyme activities, genotypes, and clinical signs in 30 dogs with persistent cyanosis without cardiopulmonary disease. Erythrocytic CYB5R enzyme activities were low in all dogs assayed. Owner-reported quality of life ranged from subclinical to occasional exertional syncope. Two previously reported and two novel CYB5R3 missense variants were identified among the methemoglobinemic cohort and were predicted to impair enzyme function. Two variants were recurrent: a homozygous Ile194Leu substitution was found in Pomeranians and other small dogs, and a homozygous Arg219Pro change occurred predominately in pit bull terriers. The other two variants were Thr202Ala and Gly76Ser substitutions in single dogs. Of the two common CYB5R3 genotypes, Arg219Pro was associated with a more severe metabolic phenotype. We conclude that CYB5R3 deficiency is the predominate cause of canine Hereditary Methemoglobinemia. Although this finding is unlikely to alter the clinical approach to Hereditary Methemoglobinemia in dogs, it demonstrates the possibility of how genotype-phenotype cohort analysis might facilitate precision medicine in the future in veterinary medicine.

  • clinical metabolic and genetic characterization of Hereditary Methemoglobinemia caused by cytochrome b5 reductase deficiency in cats
    Journal of Veterinary Internal Medicine, 2019
    Co-Authors: Jared A Jaffey, Urs Giger, Osheiza Abdulmalik, Scott N Reading, Ruben M Buckley, Sophie Johnstone, Leslie A Lyons
    Abstract:

    : Two non-pedigreed male castrated cats had persistent cyanosis over a 3-year observation period. Clinical cardiopulmonary evaluations did not reveal abnormalities, but the blood remained dark after exposure to air. Erythrocytic methemoglobin concentrations were high (~40% of hemoglobin) and cytochrome b5 reductase (CYB5R) activities in erythrocytes were low (≤15% of control). One cat remained intolerant of exertion, and the other cat developed anemia and died due to an unidentified comorbidity. Whole-genome sequencing revealed a homozygous c.625G>A missense variant (B4:137967506) and a c.232-1G>C splice acceptor variant (B4:137970815) in CYB5R3, respectively, which were absent in 193 unaffected additional cats. The p.Gly209Ser missense variant likely disrupts a nicotinamide adenine dinucleotide (NADH)-binding domain, while the splicing error occurs at the acceptor site for exon 4, which likely affects downstream translation of the protein. The 2 novel CYB5R3 variants were associated with Methemoglobinemia using clinical, biochemical, genomics, and in silico protein studies. The variant prevalence is unknown in the cat population.

  • clinical metabolic and genetic characterization of Hereditary Methemoglobinemia caused by cytochrome b 5 reductase deficiency in cats
    Journal of Veterinary Internal Medicine, 2019
    Co-Authors: Jared A Jaffey, Urs Giger, Osheiza Abdulmalik, Scott N Reading, Ruben M Buckley, Sophie Johnstone, Leslie A Lyons
    Abstract:

    Two non-pedigreed male castrated cats had persistent cyanosis over a 3-year observation period. Clinical cardiopulmonary evaluations did not reveal abnormalities, but the blood remained dark after exposure to air. Erythrocytic methemoglobin concentrations were high (~40% of hemoglobin) and cytochrome b5 reductase (CYB5R) activities in erythrocytes were low (≤15% of control). One cat remained intolerant of exertion, and the other cat developed anemia and died due to an unidentified comorbidity. Whole-genome sequencing revealed a homozygous c.625G>A missense variant (B4:137967506) and a c.232-1G>C splice acceptor variant (B4:137970815) in CYB5R3, respectively, which were absent in 193 unaffected additional cats. The p.Gly209Ser missense variant likely disrupts a nicotinamide adenine dinucleotide (NADH)-binding domain, while the splicing error occurs at the acceptor site for exon 4, which likely affects downstream translation of the protein. The 2 novel CYB5R3 variants were associated with Methemoglobinemia using clinical, biochemical, genomics, and in silico protein studies. The variant prevalence is unknown in the cat population.

  • Hereditary Methemoglobinemia in a cyanotic cat presented for ovariohysterectomy
    Canadian Veterinary Journal-revue Veterinaire Canadienne, 2019
    Co-Authors: Emily Vasiliadou, Urs Giger, Vasiliki Karakitsou, George Kazakos, Ioannis L Oikonomidis, Theodora K Tsouloufi, Panagiotis V Kosmas, Osheiza Abdulmalik, Christos K Koutinas, Mathios E Mylonakis
    Abstract:

    A 1-year-old, female, domestic shorthair cat with a history of cyanotic mucous membranes for several months was referred for ovariohysterectomy. Blood samples exhibited a noticeably brownish discoloration, while laboratory screening revealed mild-to-moderate erythrocytosis and near normal partial arterial oxygen pressure. Blood methemoglobin content was 41% of total hemoglobin concentration, and erythrocytic methemoglobin reductase activity was < 1% compared with control samples. A diagnosis of Hereditary Methemoglobinemia was established. After an intravenous injection of methylene blue, the cat's mucous membranes became transiently pink, and the ovariohysterectomy was uneventful. Methylene blue may have improved safety during anesthesia and surgery. Hereditary Methemoglobinemia should be considered in persistently cyanotic cats with normal partial arterial oxygen pressure and lack of evidence of cardiopulmonary disease, anemia, or toxin exposure.