HPRT-APRT-deficient mice are not a model for lesch-nyhan syndrome.

Complete hypoxanthine-guanine phosphoribosyl-transferase (HPRT) deficiency in humans results in the Lesch-Nyhan syndrome which is characterized, among other features, by compulsive self-injurious behavior.
HPRT-deficient mice generated using mouse embryonic stem cells exhibit none of the behavioral symptoms associated with the Lesch-Nyhan syndrome.
Administration of drugs that inhibit adenine phosphoribosyltransferase (APRT) in HPRT-deficient mice has produced the suggestion that deficiency of APRT in combination with HPRT-deficiency in mice may lead to self-mutilation behavior [C. L. Wu and D. W. Melton (1993) Nature Genet. 3, 235-240]. To test this proposition, we bred HPRT-APRT-deficient mice.
Although the doubly-deficient mice excrete adenine and its highly insoluble derivative, 2, 8-dihydroxyadenine, which are also associated with human APRT deficiency, additional abnormalities or any self-injurious behavior were not detected.
Thus, APRT-HPRT-deficient mice, which are devoid of any purine salvage pathways, show no novel phenotype and are not a model for the behavioral abnormalities associated with the Lesch-Nyhan syndrome as previously suggested 
