Genetic Admixture and Population Substructure in Guanacaste Costa Rica

The population of Costa Rica (CR) represents an admixture of major continental populations. An investigation of the CR population structure would provide an important foundation for mapping genetic variants underlying common diseases and traits. We conducted an analysis of 1,301 women from the Guanacaste region of CR using 27,904 single nucleotide polymorphisms (SNPs) genotyped on a custom Illumina InfiniumII iSelect chip. The program STRUCTURE was used to compare the CR Guanacaste sample with four continental reference samples, including HapMap Europeans (CEU), East Asians (JPT+CHB), West African Yoruba (YRI), as well as Native Americans (NA) from the Illumina iControl database. Our results show that the CR Guanacaste sample comprises a three-way admixture estimated to be 43% European, 38% Native American and 15% West African. An estimated 4% residual Asian ancestry may be within the error range. Results from principal components analysis reveal a correlation between genetic and geographic distance. The magnitude of linkage disequilibrium (LD) measured by the number of tagging SNPs required to cover the same region in the genome in the CR Guanacaste sample appeared to be weaker than that observed in CEU, JPT+CHB and NA reference samples but stronger than that of the HapMap YRI sample. Based on the clustering pattern observed in both STRUCTURE and principal components analysis, two subpopulations were identified that differ by approximately 20% in LD block size averaged over all LD blocks identified by Haploview. We also show in a simulated association study conducted within the two subpopulations, that the failure to account for population stratification (PS) could lead to a noticeable inflation in the false positive rate. However, we further demonstrate that existing PS adjustment approaches can reduce the inflation to an acceptable level for gene discovery

Tumor-Associated Macrophages (TAMs) Form an Interconnected Cellular Supportive Network in Anaplastic Thyroid Carcinoma

BACKGROUND: A relationship between the increased density of tumor-associated macrophages (TAMs) and decreased survival was recently reported in thyroid cancer patients. Among these tumors, anaplastic thyroid cancer (ATC) is one of the most aggressive solid tumors in humans. TAMs (type M2) have been recognized as promoting tumor growth. The purpose of our study was to analyze with immunohistochemistry the presence of TAMs in a series of 27 ATC. METHODOLOGY/PRINCIPAL FINDINGS: Several macrophages markers such as NADPH oxidase complex NOX2-p22phox, CD163 and CD 68 were used. Immunostainings showed that TAMs represent more than 50% of nucleated cells in all ATCs. Moreover, these markers allowed the identification of elongated thin ramified cytoplasmic extensions, bestowing a "microglia-like" appearance on these cells which we termed "Ramified TAMs" (RTAMs). In contrast, cancer cells were totally negative. Cellular stroma was highly simplified since apart from cancer cells and blood vessels, RTAMs were the only other cellular component. RTAMs were evenly distributed and intermingled with cancer cells, and were in direct contact with other RTAMs via their ramifications. Moreover, RTAMs displayed strong immunostaining for connexin Cx43. Long chains of interconnected RTAMs arose from perivascular clusters and were dispersed within the tumor parenchyma. When expressed, the glucose transporter Glut1 was found in RTAMs and blood vessels, but rarely in cancer cells. CONCLUSION: ATCs display a very dense network of interconnected RTAMs in direct contact with intermingled cancer cells. To our knowledge this is the first time that such a network is described in a malignant tumor. This network was found in all our studied cases and appeared specific to ATC, since it was not found in differentiated thyroid cancers specimens. Taken together, these results suggest that RTAMs network is directly related to the aggressiveness of the disease via metabolic and trophic functions which remain to be determined

Group II mGlu receptor agonists fail to protect against various neurotoxic insults induced in murine cortical, striatal and cerebellar granular pure neuronal cultures

Since group II metabotropic glutamate (mGlu) receptors are a potential target for the amelioration of neuronal injury, we evaluated the ability of group II mGlu receptor agonists to attenuate toxicity induced by various insults in cortical, striatal and cerebellar granular (CGCs) pure neuronal cultures. The three cultures, when maintained under serum-free, anti-oxidant rich conditions for up to 13 days in vitro (div) were shown by immunocytochemistry to contain a maximum of 2-7% glia. At 6, 9 and 13 div a graded pattern of injury to cortical and striatal cultures was achieved with either hydrogen peroxide (60-110 muM), staurosporine (1 muM), N-methyl-D-aspartate (NMDA, 70 muM), alpha -amino-3-hydroxy-methylisoxazole-4-propionate (AMPA, 100 muM) or kainate (100 muM) over either 4, 24 or 48 h. CGCs were similarly exposed to low K+ (5.4 mM KCI). Cell viability was examined via phase-contrast microscopy and assessed by a 3-(4,5-dimethylthiazole-2-yl)-2.5-diphenyltetrazolium bromide assay. Treatment with group II mGlu receptor agonists (1-300 muM), 2R,4R-3-aminopyrrolidine-2,4-dicarboxylate ((2R,4R)-APDC), (2S,1'S,2'S)-2-(carboxycyclopropyl)glycine (L-CCG-I), (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV) and N-acetylaspartylglutamate (NAAG) failed to attenuate the toxicity. Pretreatment of cultures with the agonists and treatment following acute insult also failed to attenuate toxicity. Further investigations demonstrated the presence of second messenger activation whereby (2R,4R)-APDC reduced forskolin-stimulated production of cAMP in each culture. Thus, despite receptor coupling to intracellular signaling cascades, and regardless of culture development, agonist concentration, extent and mode of injury, group II mGlu receptor agonists were unable to protect against injury induced in cortical, striatal and cerebellar granular pure neuronal cultures. This result is in contrast to mixed cultures of neurones and glia and implies an important role for glia in the neuroprotective effects of group II mGlu receptor agonists. (C) 2001 Elsevier Science Ltd. All rights reserved

Kainate receptors, cellular signaling and excitotoxic neuronal death: New pharmacological evidence for the functional involvement of low-affinity and metabotropic kainate receptors

The characteristics of the kainic acid (KA) subtype of ionotropic receptor for L-glutamate (GluR) are less well understood than those of other ion-gated GluRs. Described here are studies that focus on KA receptor neurobiology,, especially novel aspects of neurochemical anatomy, pathology and cellular signaling. Low-affinity KA receptors (GluR5-7) as mapped by receptor autoradiography using [H-3](2S,4R)-4-methylglutamic acid (4MG), were widely and topographically distributed through the neuroaxes of old and new world monkeys. Binding of [H-3]4MG (KD 20nM) was fully inhibited by KA, domoate and Glu, whilst putative GluR5-7 agonists inhibited 40-50% of specific binding. These low affinity KA agonists produced concentration-dependent neurotoxicity of mouse neocortical neurons in culture across an apoptotic-necrotic continuum of injury. Rank order of neurotoxic potency differed from that found in [H-3]4MG binding suggestive of mixed actions at ionotropic GluRs, a conclusion supported by the neuroprotection found with various ionotropic GluR antagonists. Using cerebellar granule cells (CGCs), a metabotropic KA receptor linked to the phosphoinositide cascade was revealed. KA (EC50 150 mum) produced a concentration- and calcium-dependent stimulation (200% Li+ control) of phosphoinositide turnover that was insensitive to concanavalin A. KA receptor-mediated neurotoxicity of CGCs was purely apoptotic, likely to involve low affinity receptors, and was accompanied by the expression of BAX and cyclin D1 protein. Olomoucine, a cyclin-dependent kinase inhibitor, attenuated KA-induced neurotoxicity emphasizing that post-receptor events are neuroprotective targets in excitotoxic injury. Our studies of the native KA receptors highlight their diversity and the need for more selective drugs