Neopterin is a biomarker of non-specific inflammation that may result from infectious or chronic disease. Recent studies have observed declining neopterin from infancy through the juvenile period in non-human primates, as well as associations between higher neopterin levels and lower microbial diversity. These findings suggest that neopterin levels could vary with physiological and immune system development peaking during the time infants rely most heavily on innate defenses such as inflammation. We examined fecal neopterin levels in human infants over their first 16 months and in association with age at complementary feeding to further explore potential developmental patterns of neopterin expression. Samples were collected over 8 months from 35 Tsimane infants in lowland Bolivia. Families were visited every 3 weeks to collect infant stool samples and dietary and health information. Fecal samples were assayed for neopterin concentration at the University of California Santa Barbara Biodemography Laboratory in 2015, using commercial kits (Genway Biotech). Neopterin levels were preliminarily examined in separate linear regression models for infant age and feeding status. Results demonstrated that infant age (in months) was inversely associated with neopterin levels (Est. -16.22 ng/ml, p = 0.02). In the separate feeding status model, infants who had begun complementary feeding trended towards lower neopterin levels as compared to exclusively breastfeeding infants (Est. -119.52ng/ml, p = 0.65). Findings support previous observations of a decline in neopterin levels during infancy. Future work would benefit from longer observation and sample collection periods with more participants. This research has public health implications as it suggests there is age related variance in neopterin, a biomarker of gut inflammation, which should be considered in future studies investigating infant gut health and disease risk.

Genomic amplification of specific genes is a common mechanism of adaptation that also underpins many human disorders. We use yeast (Saccharomyces cerevisiae) to investigate the mechanism of one such gene amplification. When yeast are grown in sulfate-limited conditions for many generations, the population becomes dominated by cells possessing an inverted triplication of the SUL1 gene, which produces a sulfate transporter. Because of increased transporter levels, these cells have higher fitness in limited sulfate conditions. The Brewer Lab proposed a model — Origin Dependent Inverted Repeat Amplification (ODIRA) — where this gene amplification is initiated via a DNA replication error. In the ODIRA model, DNA replication fork regression at short inverted repeats leads to template switching of the replication machinery and the extrusion of a replication-competent hairpin molecule, which after replication, recombines at the original locus to produce an inverted triplication. An alternative explanation behind the amplification is that the hairpin molecule is generated by double-stranded DNA breaks (DSB). To distinguish between these possibilities, we used an engineered strain in which the selectable marker gene, URA3, is split into overlapping fragments (“ura” and “ra3”) on two different chromosomes. The complete URA3 gene is only present in yeast that undergo rare direct recombination between chromosomes or by recombination of the replicated hairpin formed by ODIRA or DSB. We used CRISPR-Cas9 to induce DSBs upstream of the ura fragment and identify the type of event that restores URA3 function with contour-clamped homogeneous electric field gels (CHEF gels), Southern blots, and polymerase chain reactions (PCR). If DSBs drive hairpin formation, cutting the chromosome upstream of the ura fragment should increase the frequency of URA3 assembly via hairpin intermediate. We demonstrate that double-stranded DNA breaks do not increase frequency of hairpin intermediates, providing further evidence that ODIRA is responsible for the inverted triplications of SUL1 in yeast.