In This Issue
APPLIED BIOLOGICAL SCIENCES
At the Drosophila CAFE
Drosophila melanogaster is widely used as a model organism in the study of development and aging and has also been used to investigate appetite and eating disorders. Until recently, researchers interested in the science of eating, known as prandiology, have only been able to indirectly measure the frequency of meals and quantity of food eaten by Drosophila. William Ja et al. developed a quantitative technique that will remove uncertainty. The concept is simple: a capillary feeder (CAFE), similar to those used for pet hamsters, but on a much smaller scale. A feeding fly drains sugar solution from CAFE, causing the meniscus to drop a measurable distance. The authors showed that the unusual geometry of CAFE did not affect the flies' desire to feed. On average, Drosophila consumes 1.7 times its body weight in food daily. Adding ethanol to the sugar solution caused flies to drink less, although their net gain in energy increased. Flies preferred food that contained ethanol. The authors expect that CAFE will become a valuable tool in quantitative studies of food and drug consumption in Drosophila. — K.M.
The capillary feeder (CAFE) assay.
“Prandiology of Drosophila and the CAFE assay” by William W. Ja, Gil B. Carvalho, Elizabeth M. Mak, Noelle N. de la Rosa, Annie Y. Fang, Jonathan C. Liong, Ted Brummel, and Seymour Benzer (see pages 8253–8256)
BIOPHYSICS
Living optical fibers in the vertebrate retina
A fiberoptic plate is a “zero-length window” that optical engineers can use to transmit an image without using a lens. Certain cells in the vertebrate eye appear to perform a similar function. An image focused by the lens on the front surface of the retina is conveyed by Müller cells to rods and cones on the retina's rear face. Kristian Franze et al. observed that, when light is applied to the dissected retina of a guinea pig, a lattice of bright spots 2 μm in diameter and spaced 6 μm apart appears on the far side. The authors stained the retina with dyes and antibodies specific to Müller cells and confirmed that these long, funnel-shaped cells, which bridge the full thickness of the retina, are responsible for the light transmission. Held in a laser trap, Müller cells transmitted light efficiently across an optical gap. The cells' refractive index is higher than that of surrounding tissue, and although their shape is not as regular as that of artificial optical fibers, they effectively function as such. — K.M.
Living optical fibers.
“Müller cells are living optical fibers in the vertebrate retina” by Kristian Franze, Jens Grosche, Serguei N. Skatchkov, Stefan Schinkinger, Christian Foja, Detlev Schild, Ortrud Uckermann, Kort Travis, Andreas Reichenbach, and Jochen Guck (see pages 8287–8292)
DEVELOPMENTAL BIOLOGY
Core genes of the mammalian male germ line identified
During sexual reproduction, meiosis and gametogenesis ensure the transmission of genetic material to subsequent generations. Although many of the genes involved in these processes have been characterized in model organisms such as yeast and nematodes, few loci are known in mammals, particularly in humans. Frédéric Chalmel et al. conducted cross-species whole-genome expression profiling analysis of the mammalian male germ line. Using high-density oligonucleotide microarrays and purified somatic Sertoli cells, mitotic spermatogonia, meiotic spermatocytes, and postmeiotic spermatids together with whole gonad samples, the authors discovered the core male meiotic transcriptome in mice, rats, and humans. Across all three species, 357 conserved core loci displayed similar meiotic and postmeiotic patterns of transcriptional induction. Genes known to be important for sexual reproduction were significantly enriched among these loci. Most of these genes were not detected in up to 17 nontesticular somatic tissues, correlating transcriptional activation and specific function in the male germ line. Chalmel et al.'s research provides a comprehensive map of the mammalian testicular expression program at a cell type-specific level. — F.A.
Testicular coexpression of conserved mammalian genes.
“The conserved transcriptome in human and rodent male gametogenesis” by Frédéric Chalmel, Antoine D. Rolland, Christa Niederhauser-Wiederkehr, Sanny S. W. Chung, Philippe Demougin, Alexandre Gattiker, James Moore, Jean-Jacques Patard, Debra J. Wolgemuth, Bernard Jégou, and Michael Primig (see pages 8346–8351)
ECOLOGY
Frogs have nowhere to hide
Frog populations are declining worldwide, and even frogs in protected, old-growth habitats are disappearing. One suspected cause of amphibian population decline is a fungal infection. Steven Whitfield et al. studied populations in the protected rainforest at La Selva Biological Station in Costa Rica to investigate whether this infection could explain the decline of frogs. Data collected over 35 years provided the authors with historical perspective on populations of frogs and lizards. Lizards live in the same habitat but, because they are reptiles, are not susceptible to the fungus. The authors found that both amphibian and reptile populations declined by 75% over the 35-year period, indicating a culprit other than fungal infection. Whitfield et al. suggest that an associated decline in the amount of leaf litter on the forest floor is responsible. Because lizards and frogs depend on the leaf litter for habitat, its loss, via a warming climate, leads to population loss for more than frogs. — T.H.D.
“Amphibian and reptile declines over 35 years at La Selva, Costa Rica” by Steven M. Whitfield, Kristen E. Bell, Thomas Philippi, Mahmood Sasa, Federico Bolaños, Gerardo Chaves, Jay M. Savage, and Maureen A. Donnelly (see pages 8352–8356)
GENETICS
Mutation showers
The “Big Blue” transgenic mouse is a well validated model for the study of mutation. The mouse genome includes the lacI gene within a stretch of bacteriophage DNA that, when extracted and inserted into Escherichia coli, causes a blue plaque if a mutation has occurred. Steven Sommer's laboratory previously found that mutations tend to cluster in the lacI transgene, rather than occur randomly. In an extension of this research, Jicheng Wang et al. present evidence that multiple mutations can occur quickly and over many kilobases, a process termed a “mutation shower.” They sequenced DNA from Big Blue mice in which single or multiple mutations had occurred in lacI to analyze the spatial distribution and extent of the mutations. In DNA regions close to and remote from lacI, mutations in the flanking region were much more likely to occur in cases where lacI contained more than one mutation. The data support a mechanism in which mutations occur near-simultaneously within many, but generally <30, kilobases, and these events may be responsible for 1% or more of total mutation events. The authors suggest that mutation showers may be one path by which cancer originates. — K.M.
Big Blue shuttle vector.
“Evidence for mutation showers” by Jicheng Wang, Kelly D. Gonzalez, William A. Scaringe, Kimberly Tsai, Ning Liu, Dongqing Gu, Wenyan Li, Kathleen A. Hill, and Steve S. Sommer (see pages 8403–8408)
