LINKAGE ANALYSIS IN 2 LARGE ITALIAN PEDIGREES AFFECTED WITH NAIL-PATELLA SYNDROME

Nail patella syndrome (NPS) or osteo-onychodysplasia, is an autosomal dominant disorder characterised by nail dysplasia, absent or hypoplast ic patellae, iliac horns and nephropathy. Previous studies have demons trated linkage of the nail patella locus to the ABO and adenylate kina se loci on human chromosome 9q34. Recently, informative recombination events placed the NPS locus within a 1-2 cM interval within D9S60 and the AK1 gene. We describe here linkage analysis performed in two large Italian pedigrees with 10 and 11 members affected, respectively. A se t of highly informative markers have been analysed and the allele segr egation in the two families confirmed the linkage to chromosome 9. The presence of three recombination events allows definition of the criti cal region with a centrometric boundary between markers D9S1881 and D9 S1840 and a telomeric boundary between markers D9S315 and D9S290.