The overall objective of the proposed research is to identify and characterize the disease gene causing Kenny-Caffey Syndrome (KCS). KCS is an osteosclerotic bone dysplasia with associated hypocalcemia, often accompanied by hypoparathyroidism, ocular anomalies, mental retardation, and immunodeficiency. Both autosomal dominant and autosomal recessive inheritance patterns have been described. Using eight consanguineous Kuwaiti kindreds, a genome-wide search for linkage to the gene causing the autosomal recessive form of KCS was performed with polymorphic short tandem repeat (STR) markers. Significant linkage was obtained with a maximal two-point LOD score of 13.30, and haplotype analysis identified recombination events defining the KCS locus to a 4-cM interval. All affected individuals in these unrelated kindreds were homozygous for identical alleles at the two central markers, suggesting a single ancestral mutation underlying the disease in these families. The observed alleles for the flanking markers varied between families, evidence of numerous additional ancestral recombination events. A contig of yeast artificial chromosome (YAC) clones has been established spanning the KCS critical region. To facilitate the identification of the KCS gene, a positional cloning/candidacy strategy will be used. Specifically, the KCS critical region will be refined by: 1) developing novel STRs between the flanking and central markers; 2) physically mapping newly-released single nucleotide polymorphisms (SNPs) and then genotyping with the relevant ones; and 3) recruiting additional KCS patients and families to obtain additional informative alleles and to determine whether the genetic forms of KCS are allelic. A contig of smaller-insert genomic clones (PACs and BACs) will be established to facilitate the mapping of STRs and expressed sequence tags (ESTs), as well as the identification of novel genes in the KCS critical region. Finally, efforts will be directed to mapping the numerous ESTs, identified from human transcript maps, to the KCS critical region. Candidate genes with known or putative functions of relevance, particularly those mapping to the central portion of the KCS critical region, will be cloned and scanned for mutations. If identified during the period covered by this application, studies will be undertaken to elucidate the normal biological role of the KCS gene, as well as the disease pathogenesis. It is suggested, based on the phenotype, that this gene will likely prove important for bone metabolism and calcium homeostasis and, therefore, have relevance and/or suggest novel therapeutic strategies for this and, perhaps, a variety of related disorders.
