# Editors' Choice

Science  19 Dec 2014:
Vol. 346, Issue 6216, pp. 1477
1. Ancient DNA

# Document DNA shows agriculture's course

1. Elizabeth Pennisi

Finding a good source of ancient DNA can be tough, due to weathering and bacterial contamination. But parchment—made from livestock hides—offers an abundant, well-preserved, and often dated source of DNA, report Teasdale et al. The researchers worked with a 2-cm-square piece, but have so refined their sequencing technique that it only requires a tiny sliver of parchment; they hope eventually to do nondestructive testing. These data, they note, can reveal the history of agriculture over the past 700 years.

Philos. Trans. R. Soc. London Ser. B, 10.1098/rstb.2013.0379 (2014).

2. Network Biology

# Meeting the demands of a complex network

1. Laura M. Zahn

Cells face intense metabolic demands. Meeting these demands requires genes to interact in complex networks. But what happens to these networks when the participating genes acquire mutations? To find out, Bajić et al. computationally mapped how genes that regulate cellular metabolism interact in yeast lacking specific metabolic enzymes or in yeast that had accumulated neutral mutations (mutations that did not affect their overall fitness). Their model predicted that deleting specific genes would lead to alternative enzymatic reactions and rewired signaling pathways, depending on the degree of network connectivity. In the case of neutral mutations, their model suggested that network rewiring would occur along with a loss of plasticity. Experimental data supported these predictions.

Genome Biol. Evol. 10.1093/gbe/evu255 (2014).

3. Stem Cells

# Better cloning through expression

1. Michael D. Crabtree

One method of generating pluripotent cells for cloning is to transfer the nucleus of a differentiated cell into an oocyte (egg cell) that has had its nucleus removed, a procedure known as somatic cell nuclear transfer (SCNT). However, very few SCNT embryos develop to term. To investigate why, Matoba et al. compared gene expression in embryos produced by in vitro fertilization (IVF) and SCNT. They found that SCNT but not IVF embryos repressed certain regions of DNA. Removing this repression enhanced the efficiency of SCNT, suggesting that the expression of one or more of these genes is important for cellular reprogramming.

Cell 159, 884 (2014).

4. Neuroscience

# Neuronal function requires the real deal

1. Peter Stern

Brain slice experiments are a mainstay of modern neuroscience: They allow scientists to probe the molecular details of the brain while keeping brain architecture intact. Scientists usually bathe these slices in artificial cerebrospinal fluid (CSF) instead of CSF obtained from humans. This typically works well, but neurons in brain slices are often quieter than those in intact brains. However, when Bjorefeldt et al. replaced articial CSF with real human CSF, they observed a neuronal activity boost. Pyramidal neurons exhibited lower action potential thresholds and their excitability increased. The authors hypothesized that endogenous neuromodulating substances in the human CSF increased the excitability of the nerve cells.

J. Physiol. 10.1113/jphysiol.2014.284711 (2014).

5. Paleobiology

# Parasites are rising with the seas

1. Nicholas S. Wigginton

Extrapolating from the fossil record, the prevalence of aquatic parasites should grow along with the extent of anthropogenic climate change. Huntley et al. quantified the abundance of pits in nearly 4000 mollusk shells from Holocene Pearl River (China) delta sediments. Pitting is caused by trematodes, or flatworms. Trematode prevalence over the course of ∼10,000 years was highest just after the onset of sea-level rise and lowest during maximum flooding. Although a number of variables can change with sea-level rise, parasite prevalence was not statistically explained by changes in salinity or host abundance.

Proc. Natl. Acad. Sci. U.S.A 10.1073/pnas.1416747111 (2014).

6. Education

# Translating clicks into efficiency

1. Melissa McCartney

As the number of web-based resources for science education increases, evaluation of these websites remains limited. In order to enhance learning experiences, website managers should know how to draw an audience, provide an optimal user experience, and assess any learning that has taken place. Using their own website as an example, Goldsmith et al. describe how this evaluation can be done using clickstream analytics. Specifically, the authors determined where their audience came from and what content they did or did not use. With this information, website managers can better allocate their resources to fit their users' needs, making online science education efforts more targeted and efficient.

Ecosphere 5, 131 (2014).

7. Materials Science

# The right combination of additives

1. Marc S. Lavine

The formation of ceramic-based materials and composites occurs in nature under mild conditions, aided by a range of organic additives. With this template in mind, Bawazer et al. explored whether a combination of organic molecules could be used to make quantum dot assemblies under similar conditions. To discover the right mix, they turned to combinatorial methods paired with genetic algorithms. The recipes that showed the highest fluorescence intensity became the basis for the next set of experiments. These converged on products that fluoresced after 7 days, and in all three, the same set of four additives was conserved.

Diarrheal diseases caused by poor sanitary conditions are a leading cause of childhood mortality worldwide. In Sub-Saharan Africa, improved sanitation has been particularly difficult to implement in rural areas, where the cost to install a latrine toilet is nearly $190. In a survey of 2000 rural households in Benin, where nearly 95% of the country lacks access to proper sanitation, Gross and Günther found that as much as 50% of the country could have access to latrines if their cost could be reduced to$50 each. However, the survey also found that cost is not the only socioeconomic factor contributing to poor sanitation, and that sanitation promotion programs should focus on the health security and protection provided by latrines as further reasons to install them.