The Anthropology of Infectious Disease: International Health Perspectives

The Anthropology of Infectious Disease: International Health Perspectives. Marcia C. Inhorn and Peter J. Brown. eds. Amsterdam, The Netherlands: Gordon and Breach, 1997. 496 pp.     

Guilt by association: the arginine case revisited

If the genetic code arose in an RNA world, present codon assignments may reflect primordial RNA-amino acid affinities. Whether aptamers selected from random pools to bind free amino acids do so using the cognate codons at their binding sites has been controversial. Here we defend and extend our previous analysis of arginine binding sites, and propose a model for the maintenance of codon-amino acid interactions through the evolution of amino acids from ribozyme cofactors into the building blocks of proteins.     

Metagenomic Guilt by Association: An Operonic Perspective

Next-generation sequencing projects continue to drive a vast accumulation of metagenomic sequence data. Given the growth rate of this data, automated approaches to functional annotation are indispensable and a cornerstone heuristic of many computational protocols is the concept of guilt by association. The guilt by association paradigm has been heavily exploited by genomic context methods that offer functional predictions that are complementary to homology-based annotations, thereby offering a means to extend functional annotation. In particular, operon methods that exploit co-directional intergenic distances can provide homology-free functional annotation through the transfer of functions among co-operonic genes, under the assumption that guilt by association is indeed applicable. Although guilt by association is a well-accepted annotative device, its applicability to metagenomic functional annotation has not been definitively demonstrated. Here a large-scale assessment of metagenomic guilt by association is undertaken where functional associations are predicted on the basis of co-directional intergenic distances. Specifically, functional annotations are compared within pairs of adjacent co-directional genes, as well as operons of various lengths (i.e. number of member genes), in order to reveal new information about annotative cohesion versus operon length. The results suggests that co-directional gene pairs offer reduced confidence for metagenomic guilt by association due to difficulty in resolving the existence of functional associations when intergenic distance is the sole predictor of pairwise gene interactions. However, metagenomic operons, particularly those with substantial lengths, appear to be capable of providing a superior basis for metagenomic guilt by association due to increased annotative stability. The need for improved recognition of metagenomic operons is discussed, as well as the limitations of the present work.     

Dilemma of Dilemmas: How Collective and Individual Perspectives Can Clarify the Size Dilemma in Voluntary Linear Public Goods Dilemmas

Empirical findings on public goods dilemmas indicate an unresolved dilemma: that increasing size—the number of people in the dilemma—sometimes increases, decreases, or does not influence cooperation. We clarify this dilemma by first classifying public goods dilemma properties that specify individual outcomes as individual properties (e.g., Marginal Per Capita Return) and group outcomes as group properties (e.g., public good multiplier), mathematically showing how only one set of properties can remain constant as the dilemma size increases. Underpinning decision-making regarding individual and group properties, we propose that individuals are motivated by both individual and group preferences based on a theory of collective rationality. We use Van Lange''s integrated model of social value orientations to operationalize these preferences as an amalgamation of outcomes for self, outcomes for others, and equality of outcomes. Based on this model, we then predict how the public good''s benefit and size, combined with controlling individual versus group properties, produce different levels of cooperation in public goods dilemmas. A two (low vs. high benefit) by three (2-person baseline vs. 5-person holding constant individual properties vs. 5-person holding constant group properties) factorial experiment (group n = 99; participant n = 390) confirms our hypotheses. The results indicate that when holding constant group properties, size decreases cooperation. Yet when holding constant individual properties, size increases cooperation when benefit is low and does not affect cooperation when benefit is high. Using agent-based simulations of individual and group preferences vis-à-vis the integrative model, we fit a weighted simulation model to the empirical data. This fitted model is sufficient to reproduce the empirical results, but only when both individual (self-interest) and group (other-interest and equality) preference are included. Our research contributes to understanding how people''s motivations and behaviors within public goods dilemmas interact with the properties of the dilemma to lead to collective outcomes.     

English as an International Language of Prestige: Conflicting Cultural Perspectives and Shifting Ethnolinguistic Loyalties

A wide range of conflicting cultural perspectives associated with language acquisition and ethnolinguistic loyalties exists in Mexico wherever English is taught and spoken. The interplay of socioeconomic, cultural, and ethnic tensions produce positive and negative attitudes toward learning English. Students confront an array of sociolinguistic factors associated with dominant and subordinate languages. The following study compared perceptions of students and teachers in two contrasting settings, urban and rural.     

Utz Wachil: Findings from an International Study of Indigenous Perspectives on Health and Environment

This article reports previously unpublished results of a collaborative study undertaken in 2003 by health workers of the UK-based organisation Health Unlimited, and by researchers of the London School of Hygiene and Tropical Medicine. This study marked the first of a series of collaborative activities aimed at highlighting the situation of Indigenous peoples, some in the most isolated ecosystems of the planet. While many researchers focus on quantitative analysis of the health and environmental conditions of Indigenous peoples, our 2003 study aimed at exploring the views of Indigenous peoples in isolated communities in five countries on their environment and their health. In this article we look closely at the web of knowledge and belief that underpins Indigenous peoples’ concepts of health and well-being, and their relationship to land and the environment. Although many Indigenous people have been forced off their traditional lands and live in rural settlements, towns, and cities, there are still a large number of people living in very small Indigenous communities in remote areas. This article focuses on 20 such communities in six countries. We explore traditional knowledge and practice and its relationship to Western medicine and services. The research findings highlight the importance of Indigenous knowledge systems for the emerging ecohealth community and suggest that we have much to learn from Indigenous peoples in our pursuit of a more holistic science. Utz Wachil is from the K’iche language originating in Totonicapan Department, Guatemala. It translates literally as “fine/well face-ness,” face meaning one’s aspect in general, not only physical appearance.     

Guilt by association: the nuclear envelope proteome and disease

The discovery that many inherited diseases are linked to interacting nuclear envelope proteins has raised the possibility that human genetic studies could be assisted by a fusion with proteomics. Two principles could be applied. In the first, the proteome of an organelle associated with a genetically variable disease is determined. The chromosomal locations of the genes encoding the organellar proteins are then determined. If a related disease is linked to a large chromosomal region that includes a gene identified in the organelle, then that gene has an increased likelihood of causing the disease. Directly sequencing this allele from patient samples might speed identification compared with further genetic linkage studies as has been demonstrated for multiple diseases associated with the nuclear envelope. The second principle is that if an organelle has been implicated in the pathology of a particular disorder, then comparison of the organelle proteome from control and patient cells might highlight differences that could indicate the causative protein. The distinct, tissue-specific pathologies associated with nuclear envelope diseases suggest that many tissues will have a set of disorders linked to this organelle, and there are numerous as yet unmapped or partially mapped syndromes that could benefit from such an approach.     

Gout and Hyperuricemia in Japan: Perspectives for International Research on Purines and Pyrimidines in Man

One of the best-known disorders in purine metabolism is accumulation of uric acid leading to gout. Gout is a lifestyle disease, which was nicely illustrated in the joint symposium of the Japanese Society of Gout and Nucleic Acid Metabolism and of the Purine and Pyrimidine Society held in February 2011 in Tokyo, Japan. The westernization of the Japanese diet led to an increase in hyperuricemia in Japanese, which subsequently boosted research in this field, as illustrated in this symposium. As a consequence, Japanese nucleotide research also expanded, leading to the development of not only new drugs for treatment of gout, but also for other diseases such as cancer, viral infections, and cardiovascular diseases. The research on inborn errors led to the identification of various genetic polymorphisms affecting drug metabolism, revealing differences between Asians and non-Asians. Such genetic differences may also affect the enzymatic properties of an enzyme or a transporter, necessitating specific inhibitors. This knowledge will help to introduce personalization of treatment. In this symposium, the interaction between various specialties formed an excellent basis for translational research between these specialties but also from the bench to the clinic.     

Guilt by association: What p120-catenin has to hide

Members of the p120-catenin family associate with cadherins and regulate their stability at the plasma membrane. How p120-catenin limits cadherin endocytosis has long remained a mystery. In this issue, Nanes et al. (2012. J. Cell Biol. doi:10.1083/jcb.201205029) identify a conserved acidic motif within cadherins that acts as a physical platform for p120-catenin binding. However, in the absence of p120-catenin, the motif acts as an endocytic signal. These results provide new insight into p120-catenin’s role as guardian of intercellular junction dynamics.Adhesion receptors of the classical cadherin family have a major role in establishing tissue organization and maintaining tissue homeostasis (Gumbiner, 1996). Classical cadherins are transmembrane glycoproteins that use their extracellular domains to establish calcium-dependent trans homophilic interactions with cadherins in neighboring cells. To enhance adhesive strength, cadherin ectodomains oligomerize through lateral (cis) interactions, whereas their cytoplasmic domains anchor to the actomyosin cytoskeleton. The cytoplasmic domain of cadherins is highly conserved and binds to proteins called catenins. p120-catenin (p120) associates with the transmembrane adjacent domain (juxtamembrane; JMD) of the cadherin cytoplasmic tail, whereas β-catenin interacts with the more distal portion of cadherin’s cytoplasmic domain. β-Catenin in turn, binds α-catenin, which, through multiple interactions, both indirect and direct, can associate with the actin cytoskeleton (Perez-Moreno and Fuchs, 2006).Cellular rearrangements are orchestrated by dynamic assembly/disassembly of cadherin complexes. The process is fueled by endocytosis of cadherin complexes (Le et al., 1999; de Beco et al., 2009). Endocytosis can be stimulated by proteins that associate with cadherin–catenin complexes, including proteases that shed the cadherin ectodomains, and the ubiquitin ligase Hakai (Fujita et al., 2002). Cadherin internalization can be regulated by different pathways depending on the cellular context, involving clathrin-dependent and clathrin-independent mechanisms. These endocytic processes must be carefully regulated, as an untimely destabilization of cadherin-mediated adhesion can lead to alterations in tissue architecture and growth, features of several diseases, including cancers (Mosesson et al., 2008).In the past decade, p120 catenins (p120, ARVCF, δ-catenin, and p0071) have emerged as critical regulators of cadherin-mediated adhesion (Reynolds, 2007). p120, the founding family member, is a component of cadherin complexes (Reynolds et al., 1994), and its association with the cadherin JMD is important for retaining cadherins at the membrane (Ireton et al., 2002). Moreover, p120 loss causes rapid internalization of cadherins, followed by proteasomal and/or lysosomal-mediated degradation (Davis et al., 2003; Xiao et al., 2003a,b, 2005; Miyashita and Ozawa, 2007).Although these studies expose p120 as a master regulator of cadherin levels at the membrane, exactly how p120 governs cadherin endocytosis rates has remained unclear. Based upon experiments in which endocytic machinery components (clathrin, dynamin, and AP2) have been impaired (Chiasson et al., 2009) or cadherin endocytic motifs have been mutated (Hong et al., 2010; Troyanovsky et al., 2007), researchers have posited that p120 binding to cadherins may in some way prevent junctional complex endocytosis. In this issue, Nanes et al. add new molecular insights into the mechanism. The authors show that the VE-cadherin JMD functions as a bimodal platform for either p120 binding or endocytic signaling. Moreover, they identify a key conserved amino acid residue within the JMD, which, when mutated, blocks endocytosis without the need for p120.Recently, the cocrystallization of p120 bound to E-cadherin’s JMD has yielded insights into the essential residues of this binding interface (Ishiyama et al., 2010). Previous studies had attributed the core function of p120-cadherin to its ability to bind and mask a dileucine endocytic motif present in the JMD (Miyashita and Ozawa, 2007; Hong et al., 2010). The crystal structure showed that interactions between p120 and the JMD domain might be sufficient to sterically prevent accessibility of the dileucine cadherin endocytic motif to endocytic adaptors such as the AP2-clathrin adaptor, thereby placing this motif at the crux of the bimodal switch controlling the mutually exclusive binding of either p120 or the endocytic machinery.The affinity of p120 and AP2 for the JMD dileucine motif is similar, pointing toward the existence of a balanced regulation of cadherin endocytic rates and cadherin retention at the membrane. However, evaluating this balance in cellular contexts has not been possible because of the inability to uncouple p120 binding to the JMD and endocytosis. Nanes et al. (2012) have now overcome this hurdle. They first used a simulated model of the p120–E-cadherin crystal structure, which highlighted a conserved p120-binding region that is present in the JMD of both VE- and E-cadherin. However, the VE-cadherin JMD lacked endocytic dileucine and tyrosine residues present in E-cadherin, which are involved in clathrin internalization and Hakai-dependent ubiquitination, respectively.Because both types of adherens junctions undergo dynamic endocytic-based remodeling, the authors astutely realized that they might be able to exploit VE- and E-cadherin differences to unearth novel endocytic signals within the sequence that might be conserved among cadherins. To this end, the author first used mutant VE-cadherin chimeric proteins, consisting of the cytoplasmic domain of VE-cadherin fused to the extracellular domain of the IL-2 receptor, and internalization assays. They discovered that the core p120-binding region on its own was endocytosed, in a fashion similar to the full VE-cadherin cytoplasmic tail. This occurred in a clathrin-dependent manner, as previously observed in Kowalzcyk’s laboratory (Chiasson et al., 2009). Point mutagenesis identified some mutants no longer able to bind p120, which is consistent with previous findings (Thoreson et al., 2000). But the authors made an interesting finding: mutations in a conserved acidic motif (DEE) within the p120-core binding region of the JMD displayed loss of p120 binding and also blocked cadherin internalization (Fig. 1). Moreover, DEE mutant VE-cadherins localized stably at the membrane even in the absence of p120, although with an increased diffusion within the membrane. This increase in mobility suggests a reduction in cadherin lateral clustering, a process modulated by the binding of p120 to the JMD (Yap et al., 1998). Interestingly, in crystal structures, the E-cadherin JMD binding to p120 induced oligomerization of the complex (Ishiyama et al., 2010).Open in a separate windowFigure 1.Model of VE-cadherin stabilization at the cell membrane. (A) VE-cadherin binds to p120 and β-catenin. p120 associates with the juxtamembrane (JMD) domain of the cadherin cytoplasmic tail, whereas β-catenin binds to the more distal portion (catenin binding domain, CBD). Cadherin internalization is triggered by p120 dissociation, exposing a conserved endocytic factor recognition motif (DEE; 646–648) within the JMD. (B) When this motif is mutated in VE-cadherin, adherens junctions are resistant to endocytosis independent of p120 binding.These new tools now allow uncoupling of p120 binding from cadherin endocytosis, which will be instrumental in unraveling new p120 cadherin roles in cell adhesion. The VE-cadherin mutant that fails to bind to p-120 still coimmunoprecipitates with β-catenin. These findings are intriguing, given that overexpression of p120 can rescue the otherwise poor adhesive properties of cadherins mutant for β-catenin binding (Ohkubo and Ozawa, 1999). In addition, interactions between p120 and α-catenin at adherens junctions seem to contribute in preventing cadherin endocytosis (Troyanovsky et al., 2011). Given these collective results, it will be interesting in the future to measure the binding affinities of endocytosis-uncoupled VE-cadherin mutants for its binding partners.Overall, these data provide strong evidence that the JMD landing pad provides the nuts and bolts of the decision of whether an adherens junction remains at the cell surface or whether it is internalized. But who makes the decision? Recent results from Gumbiner’s group provide a possible clue. They show that cadherin activation stimulates the dephosphorylation of specific Ser/Thr residues within the N-terminal domain of p120, and this in turn stabilizes intercellular adhesion (Petrova et al., 2012).The new tools developed by Kowalczyk’s group (Nanes et al., 2012) will pave the way for researchers to dig further into the mechanism. In the current study, the authors use their newfound tools to analyze the consequences to cell migration when p120-JMD binding is uncoupled from endocytosis. In scratched monolayers of endothelial cells, cell migration was decreased. Importantly, when they examined the VE-cadherin mutant in which p120 binding was blocked but cadherin internalization could proceed normally, cell migration was largely normal. These findings indicate that the migration defects seen in the cells expressing the E-cadherin mutant are rooted in inhibition of endocytosis, rather than lack of p120 recruitment to junctions. They further suggest that endocytic trafficking of cadherins is necessary to transiently destabilize cell–cell contacts that otherwise impede migration. This notion is particularly intriguing given that when E-cadherins are stabilized at intercellular junctions, they can sequester proteins that are required for integrin-based migration (Livshits et al., 2012). Kowalczyk’s findings (Nanes et al., 2012) now suggest a means by which dynamic changes in intercellular adhesion can be achieved to trigger such downstream events.Although less well characterized, there are other regulatory circuits that might also be affected by transiently liberating p120 from intercellular junctions. Thus, for example, p120 enhances cadherin stability through its ability to interact with afadin and Rap1, thereby bridging connections with nectin intercellular junctions (Hoshino et al., 2005). Other direct and indirect p120 associates that might affect cadherin internalization include the endocytic adaptor Numb (Sato et al., 2011) and the signaling enzyme γ-secretase (Kiss et al., 2008). Additionally, p120 can also regulate Rac1 activity, which influences cadherin endocytosis in a clathrin-independent way (Akhtar and Hotchin, 2001). Thus, removing p120 or devising additional mutations to uncouple these interactions may be needed to fully unravel all the mysteries underlying p120’s power in governing intercellular adhesion in tissue development and maintenance (Davis and Reynolds, 2006; Elia et al., 2006; Perez-Moreno et al., 2006; Smalley-Freed et al., 2010; Marciano et al., 2011; Stairs et al., 2011; Chacon-Heszele et al., 2012; Kurley et al., 2012). That said, by dissecting p120’s web at the crossroads between intercellular junction stabilization and endocytosis, Kowalczyk and coworkers (Nanes et al., 2012) now illustrate the power of their approach and provide new insights into how similar strategies might ultimately enable this molecular crossword puzzle to be solved.     

Collective Intelligence Meets Medical Decision-Making: The Collective Outperforms the Best Radiologist

While collective intelligence (CI) is a powerful approach to increase decision accuracy, few attempts have been made to unlock its potential in medical decision-making. Here we investigated the performance of three well-known collective intelligence rules (“majority”, “quorum”, and “weighted quorum”) when applied to mammography screening. For any particular mammogram, these rules aggregate the independent assessments of multiple radiologists into a single decision (recall the patient for additional workup or not). We found that, compared to single radiologists, any of these CI-rules both increases true positives (i.e., recalls of patients with cancer) and decreases false positives (i.e., recalls of patients without cancer), thereby overcoming one of the fundamental limitations to decision accuracy that individual radiologists face. Importantly, we find that all CI-rules systematically outperform even the best-performing individual radiologist in the respective group. Our findings demonstrate that CI can be employed to improve mammography screening; similarly, CI may have the potential to improve medical decision-making in a much wider range of contexts, including many areas of diagnostic imaging and, more generally, diagnostic decisions that are based on the subjective interpretation of evidence.     

Breastfeeding: Biocultural Perspectives

Breastfeeding: Biocultural Perspectives. Patricia Stuart-Macadam and Katherine A. Dettwyler. eds. New York: Aldine de Gruyter Press, 1995. xiii. 430.     

The Anthropology of Infectious Disease: International Health Perspectives and The Kiss of Death: Chagas' Disease in the Americas

The Anthropology of Infectious Disease: International Health Perspectives. Marcia C. Inhorn and Peter J. Brown. eds. Amsterdam: Gordon and Breach, Publishers, 1997. xv+ 495 pp.
The Kiss of Death: Chagas' Disease in the Americas. Joseph William Bastien. Salt Lake City: The University of Utah Press, 1998. xxiv +301 pp.