Rethinking the “strong programme” in the sociology of knowledge

It is widely believed that the “strong programme” in the sociology of knowledge comes into serious conflict with mainstream epistemology. I argue that the programme has two aspects—one modest, and the other less so. The programme’s modest aspect—best represented by the “symmetry thesis”—does not contain anything to threaten much of the epistemological mainstream, but does come into conflict with a certain kind of epistemological “externalism”. The immodest aspect, however—in the form of “finitism”—pushes the programme towards a radical form of relativism about truth. Accepting these points will allow us to put an end to much unnecessary debate surrounding the strong programme, and allow a more fruitful discussion to begin.     

Structural basis of specific tRNA aminoacylation by a small in vitro selected ribozyme

In modern organisms, protein enzymes are solely responsible for the aminoacylation of transfer RNA. However, the evolution of protein synthesis in the RNA world required RNAs capable of catalysing this reaction. Ribozymes that aminoacylate RNA by using activated amino acids have been discovered through selection in vitro. Flexizyme is a 45-nucleotide ribozyme capable of charging tRNA in trans with various activated l-phenylalanine derivatives. In addition to a more than 10(5) rate enhancement and more than 10(4)-fold discrimination against some non-cognate amino acids, this ribozyme achieves good regioselectivity: of all the hydroxyl groups of a tRNA, it exclusively aminoacylates the terminal 3'-OH. Here we report the 2.8-A resolution structure of flexizyme fused to a substrate RNA. Together with randomization of ribozyme core residues and reselection, this structure shows that very few nucleotides are needed for the aminoacylation of specific tRNAs. Although it primarily recognizes tRNA through base-pairing with the CCA terminus of the tRNA molecule, flexizyme makes numerous local interactions to position the acceptor end of tRNA precisely. A comparison of two crystallographically independent flexizyme conformations, only one of which appears capable of binding activated phenylalanine, suggests that this ribozyme may achieve enhanced specificity by coupling active-site folding to tRNA docking. Such a mechanism would be reminiscent of the mutually induced fit of tRNA and protein employed by some aminoacyl-tRNA synthetases to increase specificity.     

A susceptibility locus for lung cancer maps to nicotinic acetylcholine receptor subunit genes on 15q25

Lung cancer is the most common cause of cancer death worldwide, with over one million cases annually. To identify genetic factors that modify disease risk, we conducted a genome-wide association study by analysing 317,139 single-nucleotide polymorphisms in 1,989 lung cancer cases and 2,625 controls from six central European countries. We identified a locus in chromosome region 15q25 that was strongly associated with lung cancer (P = 9 x 10(-10)). This locus was replicated in five separate lung cancer studies comprising an additional 2,513 lung cancer cases and 4,752 controls (P = 5 x 10(-20) overall), and it was found to account for 14% (attributable risk) of lung cancer cases. Statistically similar risks were observed irrespective of smoking status or propensity to smoke tobacco. The association region contains several genes, including three that encode nicotinic acetylcholine receptor subunits (CHRNA5, CHRNA3 and CHRNB4). Such subunits are expressed in neurons and other tissues, in particular alveolar epithelial cells, pulmonary neuroendocrine cells and lung cancer cell lines, and they bind to N'-nitrosonornicotine and potential lung carcinogens. A non-synonymous variant of CHRNA5 that induces an amino acid substitution (D398N) at a highly conserved site in the second intracellular loop of the protein is among the markers with the strongest disease associations. Our results provide compelling evidence of a locus at 15q25 predisposing to lung cancer, and reinforce interest in nicotinic acetylcholine receptors as potential disease candidates and chemopreventative targets.     

Defective germinal center B-cell response and reduced arthritic pathology in microRNA-29a-deficient mice

MicroRNA (miR) are short non-coding RNA sequences of 19–24 nucleotides that regulate gene expression by binding to mRNA target sequences. The miR-29 family of miR (miR-29a, b-1, b-2 and c) is a key player in T-cell differentiation and effector function, with deficiency causing thymic involution and a more inflammatory T-cell profile. However, the relative roles of different miR-29 family members in these processes have not been dissected. We studied the immunological role of the individual members of the miR-29 family using mice deficient for miR-29a/b-1 or miR-29b-2/c in homeostasis and during collagen-induced arthritis. We found a definitive hierarchy of immunological function, with the strong phenotype of miR-29a-deficiency in thymic involution and T-cell activation being reduced or absent in miR-29c-deficient mice. Strikingly, despite elevating the Th1 and Th17 responses, loss of miR-29a conferred near-complete protection from collagen-induced arthritis (CIA), with profound defects in B-cell proliferation and antibody production. Our results identify the hierarchical structure of the miR-29 family in T-cell biology, and identify miR-29a in B cells as a potential therapeutic target in arthritis.     

Mosaic overgrowth with fibroadipose hyperplasia is caused by somatic activating mutations in PIK3CA

The phosphatidylinositol 3-kinase (PI3K)-AKT signaling pathway is critical for cellular growth and metabolism. Correspondingly, loss of function of PTEN, a negative regulator of PI3K, or activating mutations in AKT1, AKT2 or AKT3 have been found in distinct disorders featuring overgrowth or hypoglycemia. We performed exome sequencing of DNA from unaffected and affected cells from an individual with an unclassified syndrome of congenital progressive segmental overgrowth of fibrous and adipose tissue and bone and identified the cancer-associated mutation encoding p.His1047Leu in PIK3CA, the gene that encodes the p110α catalytic subunit of PI3K, only in affected cells. Sequencing of PIK3CA in ten additional individuals with overlapping syndromes identified either the p.His1047Leu alteration or a second cancer-associated alteration, p.His1047Arg, in nine cases. Affected dermal fibroblasts showed enhanced basal and epidermal growth factor (EGF)-stimulated phosphatidylinositol 3,4,5-trisphosphate (PIP(3)) generation and concomitant activation of downstream signaling relative to their unaffected counterparts. Our findings characterize a distinct overgrowth syndrome, biochemically demonstrate activation of PI3K signaling and thereby identify a rational therapeutic target.     

Mutations in NNT encoding nicotinamide nucleotide transhydrogenase cause familial glucocorticoid deficiency

Using targeted exome sequencing, we identified mutations in NNT, an antioxidant defense gene, in individuals with familial glucocorticoid deficiency. In mice with Nnt loss, higher levels of adrenocortical cell apoptosis and impaired glucocorticoid production were observed. NNT knockdown in a human adrenocortical cell line resulted in impaired redox potential and increased reactive oxygen species (ROS) levels. Our results suggest that NNT may have a role in ROS detoxification in human adrenal glands.     

Mutations in FRMD7, a newly identified member of the FERM family, cause X-linked idiopathic congenital nystagmus

Idiopathic congenital nystagmus is characterized by involuntary, periodic, predominantly horizontal oscillations of both eyes. We identified 22 mutations in FRMD7 in 26 families with X-linked idiopathic congenital nystagmus. Screening of 42 singleton cases of idiopathic congenital nystagmus (28 male, 14 females) yielded three mutations (7%). We found restricted expression of FRMD7 in human embryonic brain and developing neural retina, suggesting a specific role in the control of eye movement and gaze stability.     

A Mal functional variant is associated with protection against invasive pneumococcal disease, bacteremia, malaria and tuberculosis

Toll-like receptors (TLRs) and members of their signaling pathway are important in the initiation of the innate immune response to a wide variety of pathogens. The adaptor protein Mal (also known as TIRAP), encoded by TIRAP (MIM 606252), mediates downstream signaling of TLR2 and TLR4 (refs. 4-6). We report a case-control study of 6,106 individuals from the UK, Vietnam and several African countries with invasive pneumococcal disease, bacteremia, malaria and tuberculosis. We genotyped 33 SNPs, including rs8177374, which encodes a leucine substitution at Ser180 of Mal. We found that heterozygous carriage of this variant associated independently with all four infectious diseases in the different study populations. Combining the study groups, we found substantial support for a protective effect of S180L heterozygosity against these infectious diseases (N = 6,106; overall P = 9.6 x 10(-8)). We found that the Mal S180L variant attenuated TLR2 signal transduction.     

Skint1, the prototype of a newly identified immunoglobulin superfamily gene cluster, positively selects epidermal gammadelta T cells

B cells, alphabeta T cells and gammadelta T cells are conserved lymphocyte subtypes encoding their antigen receptors from somatically rearranged genes. alphabeta T cells undergo positive selection in the thymus by engagement of their T cell receptors (TCRs) with self-peptides presented by major histocompatibility complex molecules. The molecules that select gammadelta T cells are unknown. Vgamma5+Vdelta1+ cells comprise 90% of mouse epidermal gammadelta T cells. By mapping and genetic complementation using a strain showing loss of Vgamma5+Vdelta1+ cells due to a failure of thymic selection, we show that this defect is caused by mutation in Skint1, a newly identified gene expressed in thymus and skin that encodes a protein with immunoglobulin-like and transmembrane domains. Skint1 is the prototypic member of a rapidly evolving family of at least 11 genes in mouse, with greatest similarity to the butyrophilin genes. These findings define a new family of proteins mediating key epithelial-immune interactions.     

Three new species,a synonymy and taxonomic notes on southern African members of the dung beetle genera Scarabaeus s. str. Linnaeus, 1758 and Escarabaeus Zídek & Pokorný, 2011 (Scarabaeidae: Scarabaeinae)

Three new species are described in the dung beetle genera Scarabaeus s. str. L., 1758, and Escarabaeus Zídek & Pokorný, 2011. Two comprise, Scarabaeus karae sp. nov. and Escarabaeus remii sp. nov. and are novelties. The third comprises Scarabaeus geminogalenus sp. nov., which describes a new species previously misidentified by Péringuey in 1901 and involved in a false synonymy by Janssens (1940). Notes are provided on the type specimen of Scarabaeus galenus. A close relative, Scarabaeus vicinus is recorded for the first time. Scarabaeus natalensis is synonymized with Scarabaeus basuto. Relationships and validity of a further five species are discussed: Scarabaeus convexus with S. spretus and S. rusticus; S. ebenus with S. interstitialis. The type specimen of Scarabaeus rixosus is also discussed. Distribution maps are provided for the new species and those in the S. galenus species complex.

http://zoobank.org/urn:lsid:zoobank.org:pub:CEC29F9E-2B2B-4568-8AE2-4CC65F79EC96