Pedigrees of 14 GPS families included in the study and the microsatellite markers used to establish linkage. The microsatellite markers listed in the top left corner of the figure are the set of markers located within the homozygosity region that is indicated by the small gray bars placed under affected individuals in the pedigrees. These gray bars indicate that, for this segment of chromosome 3, these patients inherited the same set of microsatellite genotypes from their mother and father; hence they are homozygous by descent. *Physical map positions are based on UCSC genome browser version hg18. **Genetic map positions in centiMorgans are based on Marshfield map. Patients in families 12, 13, and 14 did not display a homozygous haplotype in the linked region.