An integrated semiconductor device enabling non-optical genome sequencing

The seminal importance of DNA sequencing to the life sciences, biotechnology and medicine has driven the search for more scalable and lower-cost solutions. Here we describe a DNA sequencing technology in which scalable, low-cost semiconductor manufacturing techniques are used to make an integrated circuit able to directly perform non-optical DNA sequencing of genomes. Sequence data are obtained by directly sensing the ions produced by template-directed DNA polymerase synthesis using all-natural nucleotides on this massively parallel semiconductor-sensing device or ion chip. The ion chip contains ion-sensitive, field-effect transistor-based sensors in perfect register with 1.2 million wells, which provide confinement and allow parallel, simultaneous detection of independent sequencing reactions. Use of the most widely used technology for constructing integrated circuits, the complementary metal-oxide semiconductor (CMOS) process, allows for low-cost, large-scale production and scaling of the device to higher densities and larger array sizes. We show the performance of the system by sequencing three bacterial genomes, its robustness and scalability by producing ion chips with up to 10 times as many sensors and sequencing a human genome.     

Dominant missense mutations in ABCC9 cause Cantú syndrome

Cantú syndrome is characterized by congenital hypertrichosis, distinctive facial features, osteochondrodysplasia and cardiac defects. By using family-based exome sequencing, we identified a de novo mutation in ABCC9. Subsequently, we discovered novel dominant missense mutations in ABCC9 in 14 of the 16 individuals with Cantú syndrome examined. The ABCC9 protein is part of an ATP-dependent potassium (K(ATP)) channel that couples the metabolic state of a cell with its electrical activity. All mutations altered amino acids in or close to the transmembrane domains of ABCC9. Using electrophysiological measurements, we show that mutations in ABCC9 reduce the ATP-mediated potassium channel inhibition, resulting in channel opening. Moreover, similarities between the phenotype of individuals with Cantú syndrome and side effects from the K(ATP) channel agonist minoxidil indicate that the mutations in ABCC9 result in channel opening. Given the availability of ABCC9 antagonists, our findings may have direct implications for the treatment of individuals with Cantú syndrome.     

Regulation of centriolar satellite integrity and its physiology

Centriolar satellites comprise cytoplasmic granules that are located around the centrosome. Their molecular identification was first reported more than a quarter of a century ago. These particles are not static in the cell but instead constantly move around the centrosome. Over the last decade, significant advances in their molecular compositions and biological functions have been achieved due to comprehensive proteomics and genomics, super-resolution microscopy analyses and elegant genetic manipulations. Centriolar satellites play pivotal roles in centrosome assembly and primary cilium formation through the delivery of centriolar/centrosomal components from the cytoplasm to the centrosome. Their importance is further underscored by the fact that mutations in genes encoding satellite components and regulators lead to various human disorders such as ciliopathies. Moreover, the most recent findings highlight dynamic structural remodelling in response to internal and external cues and unexpected positive feedback control that is exerted from the centrosome for centriolar satellite integrity.     

In situ demonstration of the activity of 3 beta-hydroxysteroid dehydrogenase on steroid hormone secreting cells within the paraaortic lymph nodes of golden hamster

The in situ activity of 3 beta-hydroxysteroid dehydrogenase was detected in clustered cells which showed steroid-producing morphology, within the capsule of the paraaortic lymph node. In light and electron microscopic studies, the positive reaction products were detected on intracapsular cell clusters. This result indicates that these unique cells may have a steroid secreting function within the lymph nodes.     

Realism without tears I: Müller’s Doctrine of Specific Nerve Energies

The Doctrine of Specific Nerve Energies has been and continues to be enormously influential in the physiology, psychology, and philosophy of perception. In simple terms, the Doctrine states that we directly perceive in the first instance the activity of our nerves, rather than properties in the external world. The canonical early statement of the Doctrine by the physiologist Johannes Peter Müller had profound influence on both the philosophy and psychology of the 19^th and early 20^th centuries, especially as reformulated and transmitted by Müller’s student Helmholtz. A common assumption of historical and ongoing debate about the Doctrine has been its supposedly idealist or skeptical implications. What is not commonly recognized is that Müller himself advanced a realist interpretation along lines that would be recognized today as a form of epistemic structural realism. This paper analyzes Müller’s structuralist epistemology in detail and reconstructs his articulation and defense of the Doctrine of Specific Nerve Energies in its canonical form. Part II argues for the continued importance of the Doctrine and its structuralist interpretation for contemporary psychology, philosophy of perception, and history of philosophy of science.     

Multiple knockout analysis of genetic robustness in the yeast metabolic network

Genetic robustness characterizes the constancy of the phenotype in face of heritable perturbations. Previous investigations have used comprehensive single and double gene knockouts to study gene essentiality and pairwise gene interactions in the yeast Saccharomyces cerevisiae. Here we conduct an in silico multiple knockout investigation of a flux balance analysis model of the yeast's metabolic network. Cataloging gene sets that provide mutual functional backup, we identify sets of up to eight interacting genes and characterize the 'k robustness' (the depth of backup interactions) of each gene. We find that 74% (360) of the metabolic genes participate in processes that are essential to growth in a standard laboratory environment, compared with only 13% previously found to be essential using single knockouts. The genes' k robustness is shown to be a solid indicator of their biological buffering capacity and is correlated with both the genes' environmental specificity and their evolutionary retention.     

De novo assembly and genotyping of variants using colored de Bruijn graphs

Detecting genetic variants that are highly divergent from a reference sequence remains a major challenge in genome sequencing. We introduce de novo assembly algorithms using colored de Bruijn graphs for detecting and genotyping simple and complex genetic variants in an individual or population. We provide an efficient software implementation, Cortex, the first de novo assembler capable of assembling multiple eukaryotic genomes simultaneously. Four applications of Cortex are presented. First, we detect and validate both simple and complex structural variations in a high-coverage human genome. Second, we identify more than 3 Mb of sequence absent from the human reference genome, in pooled low-coverage population sequence data from the 1000 Genomes Project. Third, we show how population information from ten chimpanzees enables accurate variant calls without a reference sequence. Last, we estimate classical human leukocyte antigen (HLA) genotypes at HLA-B, the most variable gene in the human genome.