rim2 (recombination-induced mutation 2) is a new allele of pearl and a mouse model of human Hermansky-Pudlak syndrome (HPS): genetic and physical mapping

Abnormal Expression and Subcellular Distribution of Subunit Proteins of the AP-3 Adaptor Complex Lead to Platelet Storage Pool Deficiency in the Pearl Mouse

The pearl mouse is a model for Hermansky Pudlak Syndrome (HPS), whose symptoms include hypopigmentation, lysosomal abnormalities, and prolonged bleeding due to platelet storage pool deficiency (SPD). The gene for pearl has recently been identified as the beta3A subunit of the AP-3 adaptor complex. The objective of these experiments was to determine if the expression and subcellular distribution of the AP-3 complex were altered in pearl platelets and other tissues. The beta3A subunit was undetectable in all pearl cells and tissues. Also, expression of other subunit proteins of the AP-3 complex was decreased. The subcellular distribution of the remaining AP-3 subunits in platelets, macrophages, and a melanocyte-derived cell line of pearl mice was changed from the normal punctate, probably endosomal, pattern to a diffuse cytoplasmic pattern. Ultrastructural abnormalities in mutant lysosomes were likewise apparent in mutant kidney and a cultured mutant cell line. Genetically distinct mouse HPS models had normal expression of AP-3 subunits. These and related experiments strongly suggest that the AP-3 complex regulates the biogenesis/function of organelles of platelets and other cells and that abrogation of expression of the AP-3 complex leads to platelet SPD.

The genomic organization of type I keratin genes in mice

We isolated two new keratin cDNAs by screening a cDNA library constructed from poly(A)+ RNA of the dorsal and abdominal skin of C57BL/10J mice with a probe of human KRT14. Due to its high sequence homology to human keratin 17 cDNA, one full-length cDNA is most likely to be mouse keratin 17 (Krt1-17) cDNA. The other is the putative full-length cDNA of a novel type I keratin gene, designated Krt1-c29. These two keratin genes were mapped to the distal portion of Chromosome 11, where the mouse keratin gene complex-1 (Krt1) is localized. To elucidate the genomic organization of Krt1 in mice, we carried out genetic and physical analyses of Krt1. A large-scale linkage analysis using intersubspecific backcrosses suggested that there are two major clusters in Krt1, one containing Krt1-c29, Krt1-10, and Krt1-12 and the other containing Krt1-14, -15, -17, and -19. Truncation experiments with two yeast artificial chromosome clones containing the two clusters above have revealed that the gene order of Krt1 is centromere-Krt1-c29-Krt1-10-Krt1-12-Krt1-13-K rt1-15-Krt1-19-Krt1-14-K rt1-17-telomere. Finally, we analyzed sequence divergence between the genes belonging to the Krt1 complex. The results clearly indicated that genes are classified into two major groups with respect to phylogenetic relationship. Each group consists of the respective gene cluster demonstrated by genetic and physical analyses in this study, suggesting that the physical organization of the Krt1 complex reflects the evolutionary process of gene duplication of this complex.