The invention provides a mutant non-human mammal having a disrupted SCA2 gene, in particular, a mutant mouse having a disrupted SCA2 gene. The invention also provides methods of identifying a therapeutic agent for use in treating obesity or memory impairment by administering a compound to the mutant non-human mammal having a disrupted SCA2 gene and screening said mutant non-human mammal for reduced obesity, thereby identifying a therapeutic agent for use in treating obesity.