Inducible Arginase 1 Deficiency in Mice Leads to Hyperargininemia and Altered Amino Acid Metabolism

Abstract

Arginase deficiency is a rare autosomal recessive disorder resulting from a loss of the liver arginase isoform, arginase 1 (ARG1), which is the final step in the urea cycle for detoxifying ammonia. ARG1 deficiency leads to hyperargininemia, characterized by progressive neurological impairment, persistent growth retardation and infrequent episodes of hyperammonemia. Using the Cre/loxP-directed conditional gene knockout system, we generated an inducible Arg1-deficient mouse model by crossing “floxed” Arg1 mice with CreERT2 mice. The resulting mice (Arg-Cre) die about two weeks after tamoxifen administration regardless of the starting age of inducing the knockout. These treated mice were nearly devoid of Arg1 mRNA, protein and liver arginase activity, and exhibited symptoms of hyperammonemia. Plasma amino acid analysis revealed pronounced hyperargininemia and significant alterations in amino acid and guanidino compound metabolism, including increased citrulline and guanidinoacetic acid. Despite no alteration in ornithine levels, concentrations of other amino acids such as proline and the branched-chain amino acids were reduced. In summary, we have generated and characterized an inducible Arg1-deficient mouse model exhibiting several pathologic manifestations of hyperargininemia. This model should prove useful for exploring potential treatment options of ARG1 deficiency.

Mutations and common variants in the human arginase 1 (ARG1) gene: Impact on patients, diagnostics, and protein structure considerations

“…To determine if a later onset of ARGD also resulted in death, two inducible ARG1‐deficient mouse models were created using the Cre/loxP‐directed conditional gene KO system (Kasten et al., ; Sin et al., ). Mice died ∼2 weeks after tamoxifen‐induction, regardless of the starting age of inducing the KO (Kasten et al., ; Sin et al., ).…”

Proof-of-Concept Gene Editing for the Murine Model of Inducible Arginase-1 Deficiency

“…The inducible Arg1-deficient mouse strain (herein referred to as Arg1 - Cre mice) was derived from parental strains Arg1 flox (JAX strain 008817, C57BL/6- Arg1 tm1Pmu /J) and CreER T2 (JAX strain 008463, B6.129- Gt ( ROSA ) 26Sor tm1 ( cre/ERT2 ) Tyj /J) and bred in-house as previously described 4 . All procedures were reviewed and approved by the Queen’s University Animal Care Committee (approval #Funk-2011-048-R1-A4) and conformed to the Guidelines of the Canadian Council on Animal Care.…”

“…On day 1 and day 3 after seeding, PMEFs were treated with 0.5 µM 4-hydroxy-tamoxifen (OHT) (Sigma) to induce the deletion of exons 7 and 8 of Arg1 (herein referred to as Arg1 Δ PMEFs). PCR genotyping was carried out after day 5 of seeding to confirm Cre-excision using PCR with primer sets as follows: F1 5 ′-TGCGAGTTCATGACTAAGGTT- 3′ , R1 5 ′-AAAGCTCAGGTGAATCGG- 3′ and R2 5 ′-GCACTGTCTAAGCCCGAGAGTATC- 3′ 4 .…”

Collapse of the hepatic gene regulatory network in the absence of FoxA factors

“…2B). Complete liver-specific deficiency for Arg1 is lethal due to hyperammonemia and liver damage (Sin et al 2013). Since we observed a dramatic reduction of Arg1 expression and a hyperargininemia, hypouremia and hyperammonemia similar to those present in Arg1 null mice, we attribute the lethality of the FoxA triple null mice to this defect (Fig.…”