Endocrine Abstracts (2007) 13 P12

Localisation of a renal calcification locus to a 5 Mbp-region on mouse chromosome 11D-E2

Bushra Ahmad1, Nellie Loh1, Anita Reed1, Michael Stechman1, Michelle Stewart2, Terry Hacker3, Sara Wells2, Tertius Hough2, Liz Bentley3, Brian Harding1, Paul Christie1, Roger Cox3, Neil Dear2, Steve Brown3 & Rajesh Thakker1

1Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom; 2Mary Lyon Centre, Medical Research Council, Harwell, Oxfordshire, United Kingdom; 3Mammalian Genetics Unit, Medical Research Council, Harwell, Oxfordshire, United Kingdom.

Kidney stones, which affect 5% of adults, are most frequently associated with hypercalciuria or hypercalcaemia. Furthermore, kidney stones may occur in families in ∼40% of patients, thereby implicating the involvement of genetic mechanisms. To further elucidate these, we have established a mouse model for renal calcification, designated Rcalc2, and determined its chromosomal localisation. Mice were kept in accordance with UK Home Office welfare guidelines and project license restrictions. The founder of Rcalc2 was identified by radiological investigation of 1745 twelve month-old male offspring of N-ethyl-N-nitrosourea mutagenised male BALB/c mice. Progeny were generated by in-vitro fertilisation of C3H oocytes using stored frozen sperm from this founder to yield forty-three second-generation (G2) progeny. These G2 mice were investigated for renal calcification at 18–34 weeks, by histological examination of haematoxylin-eosin and von Kossa stained sections. Twenty-four mice were found to have renal calcification, yielding an affected:unaffected ratio of 1.3:1 which is consistent with an autosomal dominant mode of inheritance with high penetrance. A genome-wide search using chromosome-specific sets of sixty single nucleotide polymorphisms (SNPs) at 20–30 cM intervals in 13 affected mice revealed co-segregation of Rcalc2 and chromosome 11 loci in 85% of mice. An extended analysis in all of the affected and unaffected mice using eight simple sequence length polymorphisms (SSLPs) from chromosome 11 demonstrated co-segregation of Rcalc2 with loci from chromosome 11D-E2 in twenty (83%) mice and yielded a peak LOD score of 3.55, at 18% recombination. An analysis of recombinants defined the locus order as; D11Mit61-(D11Mit168, D11Mit128,D11Mit253, D11Mit214, D11Mit338, Rcalc2)-SNP117. This narrows the search for Rcalc2 to a 5 Mb region that contains about 80 genes including NHERF-1 (Na+/H+ exchanger regulatory factor-1). Thus, our studies have established a mouse model for renal calcification and identified a locus on chromosome 11D-E2 that is likely to have an important role in renal calcium regulation.