Levels of complement factor H-related 4 protein do not influence susceptibility to age-related macular degeneration or its course of progression

Dysregulation of the alternative pathway (AP) of the complement system is a significant contributor to age-related macular degeneration (AMD), a primary cause of irreversible vision loss worldwide. Here, we assess the contribution of the liver-produced complement factor H-related 4 protein (FHR-4) to AMD initiation and course of progression. We show that FHR-4 variation in plasma and at the primary location of AMD-associated pathology, the retinal pigment epithelium/Bruch's membrane/choroid interface, is entirely explained by three independent quantitative trait loci (QTL). Using two distinct cohorts composed of a combined 14,965 controls and 20,741 cases, we ascertain that independent QTLs for FHR-4 are distinct from variants causally associated with AMD, and that FHR-4 variation is not independently associated with disease. Additionally, FHR-4 does not appear to influence AMD progression course among patients with disease driven predominantly by AP dysregulation. Modulation of FHR-4 is therefore unlikely to be an effective therapeutic strategy for AMD.

Exogenous peptide and protein expression levels using retroviral vectors in human cells

Pseudotyped retroviral vectors combine the advantages of broad host range, high expression, stable chromosomal integration, and ease of preparation. These vectors greatly facilitate delivery into mammalian cells of sequences encoding individual peptide inhibitors-including those with therapeutic utility-and inhibitor libraries. However, retroviral vectors vary in behavior, particularly with respect to expression levels in different cell lines. Expression level is especially important in transdominant experiments because the concentration of an inhibitor (for example, an expressed peptide) is one of the key determinants in the degree of complex formation between the inhibitor and its target. Thus, inhibitor concentration should have an impact on the expressivity and/or penetrance of an induced phenotype. Here, we compare several retroviral vectors and human cell lines for relative expression levels using a green fluorescent protein reporter. We show for a subset of these lines that cellular protein concentrations produced by single-copy vectors range up to about 2 microM. We also examine other variables that contribute to expression level, such as the nature of the expressed protein's carboxy terminus. Finally, we test the effect of increased concentration on phenotype with a nine-amino-acid peptide derived from the human papilloma virus protein E7 which overcomes E7-mediated cell growth.

Formation of primary constriction and heterochromatin in mouse does not require minor satellite DNA

Whereas the major satellite fraction in mouse extends its domain from the centromere to the distal end of the pericentric heterochromatin, the minor satellite DNA is present specifically in the centromere or primary constriction. We hybridized the biotinylated minor satellite sequence to L929 cells of mouse origin. The sequence hybridized to all chromosomes. Whereas hybridization was detected on all active centromeres, the inactive centromeres in certain dicentrics did not show any signal. This satellite, however, was detected in all inactive centromeres in a heptacentric chromosome. The intensity of fluorescence on the inactive centromeres of the heptacentric was similar to that present on the active centromeres. Several heterochromatin blocks, which were not associated with any centromere, were also found to lack hybridization with the minor satellite. The inactive centromeres, whether carrying the minor satellite DNA fraction or not, generally do not react with the antikinetochore antibodies present in the scleroderma serum. These studies are interpreted to show that (1) the primary constriction in mouse can be formed without the participation of minor satellite, (2) heterochromatin in mouse may constitute without this fraction, (3) the major and minor satellite may not be interspersed but are joined at some defined boundary, and (4) the binding of CENP-B does not depend upon the quantity of minor satellite or the number of CENP boxes present in the inactive centromeres.