Copper(II) Sequentially Loads onto the N-Terminal Amino Group of the Cellular Prion Protein before the Individual Octarepeats

The cellular prion protein (PrP^C) binds to Cu²⁺ ions <i>in vivo</i>, and a misfolded form of PrP^C is responsible for a range of transmissible spongiform encephalopathies. Recently, disruption of Cu²⁺ homeostasis in mice has been shown to impart resistance to scrapie infection. Using full-length PrP^C and model peptide fragments, we monitor the sequential loading of Cu²⁺ ions onto PrP^C using visible circular dichroism. We show the N-terminal amino group of PrP^C is not the principal binding site for Cu²⁺; however, surprisingly, it has an affinity for Cu²⁺ tighter than that of the individual octarepeat binding sites present within PrP^C. We re-evaluate what is understood about the sequential loading of Cu²⁺ onto the full-length protein and show for the first time that Cu²⁺ loads onto the N-terminal amino group before the single octarepeat binding sites

Rare Variant Analysis of Human and Rodent Obesity Genes in Individuals with Severe Childhood Obesity

Obesity is a genetically heterogeneous disorder. Using targeted and whole-exome sequencing, we studied 32 human and 87 rodent obesity genes in 2,548 severely obese children and 1,117 controls. We identified 52 variants contributing to obesity in 2% of cases including multiple novel variants in GNAS, which were sometimes found with accelerated growth rather than short stature as describedw previously. Nominally significant associations were found for rare functional variants in BBS1, BBS9, GNAS, MKKS, CLOCK and ANGPTL6. The p.S284X variant in ANGPTL6 drives the association signal (rs201622589, MAF∼0.1%, odds ratio = 10.13, p-value = 0.042) and results in complete loss of secretion in cells. Further analysis including additional case-control studies and population controls (N = 260,642) did not support association of this variant with obesity (odds ratio = 2.34, p-value = 2.59 × 10-3), highlighting the challenges of testing rare variant associations and the need for very large sample sizes. Further validation in cohorts with severe obesity and engineering the variants in model organisms will be needed to explore whether human variants in ANGPTL6 and other genes that lead to obesity when deleted in mice, do contribute to obesity. Such studies may yield druggable targets for weight loss therapies