Lethal phenotype in conditional late-onset arginase 1 deficiency in the mouse

Area of Science:

• Biochemistry
• Genetics
• Animal Models

Background:

• Human arginase deficiency causes neurological impairment due to hyperargininemia and hyperammonemia.
• Existing neonatal mouse models exhibit lethal disease, differing from the more common attenuated human presentation.
• A need exists for a suitable animal model to study and develop therapies for arginase deficiency.

Purpose of the Study:

• To create and validate an adult conditional knockout mouse model for arginase 1 deficiency.
• To investigate if later onset of arginase deficiency in adult mice leads to lethality.
• To establish a model for studying arginase deficiency and developing therapeutic strategies.

Main Methods:

• Generated adult conditional knockout mice for arginase 1 deficiency.
• Administered tamoxifen to activate Cre-recombinase for widespread gene knockout.
• Monitored animal survival, ammonia levels, body weight, circulating amino acids, and tissue arginase.

Main Results:

• Adult conditional knockout mice exhibited 100% mortality in females and 70% in males within approximately 21 days post-tamoxifen administration.
• Elevated circulating ammonia and arginine levels were observed at the onset of phenotypic abnormalities.
• Abnormalities in brain and liver amino acid profiles were detected, consistent with the disorder's biochemistry.

Conclusions:

• The absence of arginase in adult animals results in a lethal disease profile similar to neonatal models.
• Phenotypic abnormalities in arginase deficiency are linked to the disorder's biochemistry, not solely the animal's age.
• This adult conditional knockout model provides a valuable platform for developing gene and cell-based therapies for arginase deficiency.