Thus completely eliminating functional gene in these mice. As a consequence, these mice were shown to have markedly reduced PPi plasma concentrations leading to reduced PPi/Pi ratio which allows ectopic mineralization to ensue. It should be noted that the asj-2J mice developed more extensive mineralization than asj mice when placed on the acceleration diet. This may reflect the differences in the type of mutations, the asj-2J having a large deletion, essentially comparable to a complete ablation of the gene, while asj mice have a missense mutation allowing residual level of ENPP1 activity. In fact, measurements of ENPP1 in the liver of asj mice revealed low levels of activity as MG132 compared to Enpp1 wild-type mice, yet there was clearly measurable activity above the background. It should be noted, however, that these two mice were on different inbred strain backgrounds, asj on C57BL/6J and asj-2J on BALB/cJ, respectively. We have previously demonstrated that different strain backgrounds can influence the degree of mineralization, an observation that may impact on our comparison of differences in asj and asj-2J mice. Nevertheless, since the mutations in the ENPP1 gene in patients with GACI result in loss-of-function, the asj-2J mouse with complete ablation of the gene appears to be a suitable model system to study this disease. A limited number of studies have been published testing the efficacy of bisphosphonates, stable non-hydrolyzable pyrophosphate analogues of pyrophosphate, to counteract the development of ectopic mineralization in patients with GACI. These case studies have yielded somewhat conflicting results; while improvement has been reported in some cases, in several studies the effects are not clear, and significant side effects from bisphosphonates have also been reported. The reasons for these diverse outcomes are not entirely clear but may relate to the fact that GACI is a complex clinical disorder with unpredictable progression, and there is no biomarker to measure the disease activity. The degree of disease progression is primarily assessed by occasional imaging studies of ectopic mineralization and the ultimate outcome of patient survival. Thus, the asj2J mouse, genetically uniform on homogeneous strain background and under controlled environmental conditions, can serve as a platform to test pharmacological compounds with anti-mineralization properties, including various bisphosphonates. In conclusion, the asj-2J mouse serves as a novel model to study molecular alterations in GACI, and it provides a platform to test various pharmacologic approaches for treatment of GACI and related, currently intractable, ectopic mineralization disorders. Lysyl hydroxylase 3 is a multifunctional enzyme possessing three enzyme activities; lysyl hydroxylase, collagen galactosyltransferase and glucosyltransferase activities. Thereby, LH3 is able to catalyze the formation of glucosylgalactosylhydroxylysine residues, which are unique posttranslational modifications of collagens and collagenous proteins. The other lysyl hydroxylase isoenzymes, LH1 and LH2, have only hydroxylation activities.