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This Week in PNAS: Jan 9, 2018

A University of Bergen- and Brown University-led team offers a cautionary note for those doing functional genomic comparisons between species. Based on their analyses of two prior studies using pairwise methods to assess cross-species gene expression, for example, the researchers argue that "comparative functional genomics studies can come to the wrong conclusions if they do not take the relationships of species into account and instead rely on pairwise comparisons between species, as is common practice." Rather, they say, "to answer evolutionary questions about genome function, it is critical to consider evolutionary relationships."

Researchers in Japan, Germany, and the US describe efforts to develop chimeric pig models of X-linked genetic diseases (XLGD) that carry normal and altered cells and remain capable of reproduction. To accomplish this, the team used normal embryonic cells to complement cloned pig embryos established by nuclear transfer from gene knockout lines, producing fertile chimeric boars capable of passing on the genotypes behind X-linked conditions such as Duchenne muscular dystrophy or severe combined immunodeficiency. "This unique reproduction system permits routine production of XLGD model pigs through the male-based breeding, thereby opening an avenue for translational research using disease model pigs," authors say.

A team from the US and Canada explores genetic factors associated with advanced age-related macular degeneration (AMD) symptoms in individuals receiving nutritional prophylaxis — a high-dose zinc and antioxidant supplementation protocol previously recommended for staving off advanced forms of the disease such as neovascular AMD. After bringing together data from three AMD cohorts, the researchers compared variants gleaned through targeted CFH and ARMS2 gene sequencing in a subset of 802 AMD-affected individuals randomized to receive the nutritional supplements or a placebo. Their results hint that progression to neovascular AMD varies after zinc and antioxidant formulation in a manner that coincides with the presence or absence of risky CFH and ARMS2 SNPs implicated in AMD in general.