No abstract

Hepatitis C virus genotype 6 currently contains 21 recognized subtypes, 6a-6u, for which 6r and 6s lack complete genome sequences. In this study, we entirely sequenced variants QC245 and QC66 from Cambodian immigrants in Canada representing subtypes 6r and 6s, respectively. The two genomes shared 75.3% nucleotide similarities to each other and 72.0-82.9% to 21 reference sequences representing subtypes 6a-6q, 6t-6u and variants km41 and gz52557. QC66 and QC245 displayed genome lengths of 9473 and 9450 nt and each contained a single open reading frame of 9051 nt. In 10 protein encoding regions QC245 and QC66 shared common sizes with TV249/6t and 537796/6l isolates, respectively. Phylogenetic analyses demonstrated that QC245 was more closely related to subtype 6f, but both QC66 and QC245 were subtypically different from all other genotype 6 subtypes. Our full-length sequence data confirmed the status of subtype 6r and 6s within genotype 6. Analysis of partial sequences revealed seven 6t and two 6s isolates that were all isolated from Cambodian immigrants. Analysis of the hypervariable region 1 sequences of 81 genotype 6 variants revealed two unique patterns of variation. First, most variants showed an amino acid deletion at the 4th position and second, many contained a basic residue at the 7th position. Possible roles of these two variation patterns are further discussed.

AP-3 is a heterotetrameric protein complex involved in intracellular vesicle transport. Molecular analyses show that Ap3b1, which encodes the AP-3 (β)3A subunit, is altered in pearl mice. To provide genetic evidence that mutation of Ap3b1 is responsible for the pearl phenotype and to determine the null phenotype, the Ap3b1 gene was disrupted by homologous recombination. Mice homozygous for the resulting allele, Ap3b1(LN), or compound heterozygotes with pearl, displayed phenotypes similar to those of pearl mice, confirming that Ap3b1 is the causal gene for pearl. Moreover, pearl is likely to be a hypomorph as the Ap3b1(LN) homozygotes had a lighter coat color and accumulated fewer of the μ3 and (Δ)3 subunits of AP-3 than did pearl mice. Finally, immunofluorescence analysis of fibroblasts and melanocytes cultured from Ap3b1(LN) homozygotes revealed that the lysosomal membrane proteins Lamp I and Lamp II and the melanosomal membrane protein tyrosinase were mislocalized. In particular, the Lamp proteins were clustered on the cell surface. These findings strengthen the evidence for an alternate pathway via the plasma membrane for cargo normally transported to organelles by AP-3.