20590744
A two-stage variable-stringency semiparametric method for mapping quantitative-trait loci with the use of genomewide-scan data on sib pairs.
Genomewide scans for mapping loci have proved to be extremely powerful and popular. We present a semiparametric method of mapping a quantitative-trait locus (QTL) or QTLs with the use of sib-pair data generated from a two-stage genomic scan. In a two-stage genomic scan, either the entire genome or a large portion of the genome is saturated with low-density markers at the first stage. At the second stage, the intervals that are identified as probable locations of the trait loci, by means of analysis of data from the first stage, are then saturated with higher-density markers. These data are then analyzed for fine mapping of the loci. Our statistical strategy for analysis of data from the first stage is a low-stringency method based on the rank correlation of squared trait-difference values of the sib pairs and the estimated identity-by-descent scores at the marker loci. We suggest the use of a low-stringency method at the first stage, to save on computational time and to avoid missing any marker interval that may contain the trait loci. For analysis of data from the second stage, we have developed a high-stringency nonparametric-regression approach, using the kernel-smoothing technique. Through extensive simulations, we show that this approach is more powerful than is a currently used method for mapping QTLs by use of sib pairs, particularly in the presence of dominance and epistatic effects at the trait loci.
29577210
Integrating sibship data for mapping quantitative trait loci.
Sibship methods have been shown to be more powerful than traditional sib-pair methods in mapping quantative trait loci. We propose a statistical procedure which integrates data on sibships into a so-called 'contrast function', a natural extension of the classical squared sib-pair trait difference proposed by Haseman & Elston (1972). We also develop a combined mean and contrast function which provides more information on linkage compared to the contrast function. Our method is extended to multiple, epistatically interacting trait loci. Monte-Carlo simulations are included to compare the efficiencies of the proposed procedures with some currently used methods. An application of our proposed method is presented using data on alcohol dependence.
7673591
Deciphering the genetic architecture of a multivariate phenotype.
A heritable multivariate quantitative phenotype comprises several correlated component phenotypes that are usually pleiotropically controlled by a set of major loci and environmental factors. One approach to decipher the genetic architecture of a multivariate phenotype, in particular to map the underlying loci, is to reduce the dimensionality of the data by means of a data reduction technique, such as principal component analysis. The extracted principal components are then analyzed in conjunction with marker data to map the underlying loci. We have examined the efficiency of this approach with and without taking into account the correlation structure of the multivariate phenotype when extracting principal components. We have assumed that genome-wide scan data on sibpairs are available for low-density (widely spaced) and high-density markers. Using extensive simulations, based on three models of the multivariate phenotype, we have shown that although ignoring the correlation structure of the multivariate phenotype does not have any serious impact on the efficiency of mapping the underlying trait loci in wide marker intervals, there is a significant adverse effect of this practice for fine-mapping. We, therefore, recommend that the correlation structure of the multivariate phenotype be carefully examined to decide on the strategy of extracting principal components for deciphering the genetic architecture of the multivariate phenotype.
343855
Identifying rare variants from exome scans: the GAW17 experience
Genetic Analysis Workshop 17 (GAW17) provided a platform for evaluating existing statistical genetic methods and for developing novel methods to analyze rare variants that modulate complex traits. In this article, we present an overview of the 1000 Genomes Project exome data and simulated phenotype data that were distributed to GAW17 participants for analyses, the different issues addressed by the participants, and the process of preparation of manuscripts resulting from the discussions during the workshop.
52805785
Linkage mapping of a complex trait in the New York population of the GAW14 simulated dataset: a multivariate phenotype approach
Multivariate phenotypes underlie complex traits. Thus, instead of using the end-point trait, it may be statistically more powerful to use a multivariate phenotype correlated to the end-point trait for detecting linkage. In this study, we develop a reverse regression method to analyze linkage of Kofendrerd Personality Disorder affection status in the New York population of the Genetic Analysis Workshop 14 (GAW14) simulated dataset. When we used the multivariate phenotype, we obtained significant evidence of linkage near four of the six putative loci in at least 25% of the replicates. On the other hand, the linkage analysis based on Kofendrerd Personality Disorder status as a phenotype produced significant findings only near two of the loci and in a smaller proportion of replicates.
41553407
A novel non-parametric regression reveals linkage on chromosome 4 for the number of externalizing symptoms in sib-pairs.
In this report, we present results of a genome-wide linkage scan using as a phenotype the number of externalizing symptoms associated with alcohol use disorders. Subjects were collected by the Collaborative Study on the Genetics of Alcoholism project from families in which at least three first degree relatives were affected by alcohol dependence. We use a novel non-parametric regression method based on kernel smoothing for our analysis. We report a statistically significant linkage close to the ADH gene cluster on Chromosome 4. We also obtain evidence for epistatic interaction between a region on Chromosome 1 and one on Chromosome 15. Although alcoholism as a covariate does not have any effect on the linkage scan, it has an effect on the epistatic interaction.
19067572
Long term results of surgery versus continuous hyperfractionated accelerated radiotherapy (CHART) in patients aged >70 years with stage 1 non-small cell lung cancer.
BACKGROUND
Patients with T1N0 non-small cell lung cancer (NSCLC) are preferably treated by anatomic lobectomy. However, not all such patients are suitable for lobectomy due to their age or co-morbidity. Our aim was to determine the results obtained following lobectomy, wedge resection (WR) or continuous hyperfractionated accelerated radiotherapy (CHART) in patients aged >70 years.


PATIENTS
Two hundred and fifteen consecutive patients aged >70 years, with pathologic stage 1 NSCLC in our unit between 1991 and 2001 were studied. Of these patients, 149 had a lobectomy, 47 had a WR and 19 had CHART. Follow-up was 100% complete.


RESULTS
Analysis demonstrated the WR and CHART patients to have reduced pulmonary function (FEV(1) 59% and 52%, respectively, of predicted vs. 76%, P<0.001) when compared to the lobectomy group but there were no differences among the groups with regard to mean age and histologic tumour type. There were no operative mortality among patients after WR; however, a 2.7% 30-day operative mortality among patients undergoing lobectomy (P=0.29). Kaplan-Meier survival curves at 1 and 5 years for patients undergoing WR, lobectomy and CHART was 98% and 74% vs. 97% and 68% vs. 80% and 39%, respectively (P=0.0484). The frequency of local/regional recurrence in the WR group (19.1%) was not significantly higher than in the lobectomy group (18.4%, P=0.38) when compared to the CHART group (27%, P=0.07).


CONCLUSION
Loco-regional recurrence and survival after WR and lobectomy in elderly patients with stage I NSCLC are comparable. Although the numbers are small, these data suggest that CHART is a reasonable treatment option for those who are not suitable candidates for surgery.
905090
27 kDa Fasciola gigantica Glycoprotein for the Diagnosis of Prepatent Fasciolosis in Cattle
An indirect enzyme-linked immunosorbent assay (ELISA) using 27 kDa glycoprotein of Fasciola gigantica has been evaluated for its potential use in the diagnosis of bovine fasciolosis. Following experimental infection of rabbits, F. gigantica infection-induced antibodies were isolated and later used as ligands in affinity chromatography for isolation of infection-induced antibody-specific proteins. Among the five infection-specific proteins isolated, a glycoprotein of 27 kDa was later isolated by second-step purification using concanavalin A matrix. In crossbred cattle receiving different doses of infection (100, 200 and 400 metacercariae), the anti-27 kDa antibodies were detected as early as the 2nd week post infection. No direct correlation between initial dose, antibody response and fluke establishment was recorded. No cross-reaction was noted with the sera of goats experimentally infected with Paramphistomum epiclitum. ELISA with the 27 kDa glycoprotein could be a feasible diagnostic tool for the early detection of bovine fasciolosis.
45939646
Full genomic analysis of a simian SA11-like G3P[2] rotavirus strain isolated from an asymptomatic infant: identification of novel VP1, VP6 and NSP4 genotypes.
We report here the full genomic analysis of a simian SA11-like G3P[2] group A rotavirus (GAR) strain, B10, isolated from an asymptomatic infant in Kenya in 1987. By nucleotide sequence identities and phylogenetic analyses, the VP7-VP4-VP2-VP3-NSP1-NSP2-NSP3-NSP5 genes of strain B10 exhibited maximum genetic relatedness to those of the different isolates of simian strain SA11, and were assigned to the G3-P[2]-C5-M5-A5-N5-T5-H5 genotypes, respectively. On the other hand, the VP1, VP6 and NSP4 genes of strain B10 did not belong to any of the established GAR genotypes, and therefore, were assigned to new genotype numbers R8, I16 and E13, respectively, by the Rotavirus Classification Working Group. These observations suggested that strain B10 might have originated from reassortment event/s involving simian SA11-like strains and GAR strains from unknown animal host species (possibly other wild animals) preceding transmission to humans. Alternatively, considering the lack of data on simian GARs, it might be also possible that the VP1, VP6 and NSP4 genes of strain B10 are those of unknown simian strains, and that strain B10 might be a typical simian strain that was directly transmitted to humans. Therefore, either hypothesis pointed towards a rare instance of possible direct transmission of GARs from an animal host (possibly a monkey or some other wild animal) to humans. This was corroborated by the presence of different species of wild animals including non-human primates, and unhygienic conditions at the sampling site. To our knowledge, the present study is the first report on the detection of a simian SA11-like G3P[2] GAR strain in humans.
12219567
Application of rbcL based molecular diversity analysis to algae in wastewater treatment plants.
The molecular diversity of algae in the final clarifier or denitrification filter outfall from three wastewater treatment plants (WWTPs) with activated sludge based treatment was analyzed using the rbcL gene as a phylogenetic marker. The rbcL gene encodes the large subunit of the CO(2) fixing enzyme RuBisCO. Among algae identified at the WWTPs were diatoms, green algae, cyanobacteria, Eustigmatophyceae, and unknown heterokonts. A high level of diversity was observed within WWTPs with 19-24 unique rbcL sequences detected at each plant. Algae composition also varied between treatment plants. Our results show that the rbcL gene can be used as a phylogenetic marker for algae diversity analysis in a wastewater treatment context.
207044347
Resolution of the spectroscopy versus crystallography issue for NO intermediates of nitrite reductase from Rhodobacter sphaeroides.
Copper nitrite reductase (NiR) is a homotrimeric enzyme, containing a T1 copper site, which transfers electrons to the T2 catalytic site, where nitrite is reduced by one electron to nitric oxide (NO2− + 2H+ + e− → NO + H2O).1–3 Recently a side-on bound copper nitrosyl complex of NiR has been crystallized by reacting the reduced enzyme with excess NO.4 Based on the EPR spectrum of the species generated by the reaction of reduced NiR with saturated NO in solution, it has been assigned as an η 2-NO−Cu2+species. However, spectroscopic data on several Cu-nitrosyl model complexes5 and an NO adduct formed by reacting reduced NiR with nitrite6 and DFT calculations on an η2-NOCu species7 describe these complexes as Cu+NO•. In this study, we define the species generated in solution by reacting reduced NiR with NO, using EPR, MCD and ENDOR spectroscopy and correlate these with that observed by crystallography. 
 
Reduced NiR reacted with saturated NO solution generates the EPR spectrum in Figure 1A red, which is equivalent to the spectrum reported by Tocheva et al.4 This species has an EPR signal characteristic of an oxidized T2 Cu (g|| = 2.30 and A|| = 117 G). The MCD spectrum (Fig. 1B, red) has low energy d-d bands, also indicative of a T2 cupric complex. Both EPR and MCD spectra show a negligible T1 contribution indicating that this site is reduced (Fig. S1). 
 
 
 
Figure 1 
 
Overlay of reduced NiR with excess NO (red) and nitrite bound NiR (blue) A) EPR B) MCD, C) N14 ENDOR, D) H1 ENDOR, with exchangeable features with 8.5 MHz coupling. Parts A and B have nitrite bound to T2 site with the T1 Cu reduced to remove intense overlaying ... 
 
 
 
Nitrite binds to the T2 site of the resting WT enzyme,8,9 but the EPR and, in particular, the MCD features of the nitrite bound T2 site are obscured by the dominant T1 Cu signals. However under these conditions (nitrite bound), the T1 Cu could be selectively reduced with acsorbate. The EPR spectrum of the nitrite bound T2 species (Fig. 1A, blue) is identical to that produced above by reacting reduced NiR with excess NO. The MCD spectrum (Fig. 1B, blue) of the T1 reduced T2-nitrite bound form is also identical to that generated by the reduced enzyme with NO. The T2 EPR spectrum and the MCD d-d bands of the resting WT enzyme are very sensitive to nitrite binding (Fig. S1C, D). Thus the EPR and MCD data strongly indicate that the species generated by the reaction of excess NO with reduced NiR has T1 reduced and T2 oxidized with nitrite bound. 
 
Further N14 and H1 ENDOR data for this species generated by the reaction of reduced NiR with an NO solution (Fig. 1C, D, red) and those for a form with T1+T2 oxidized and nitrite bound (collected at g=2.266 where there is no contribution from T1, Fig. 1C, D, blue) have the same features. The nitrogen features (Fig. 1C) from Cu2+NO2− bound T2 are from its histidines, and these features all show lower ENDOR frequencies and smaller hyperfine couplings due to the change of the T2 axial ligand from aquo to nitrite.10 
 
From the above results the reaction of reduced NiR with excess NO gives T1 reduced T2 Cu2+-NO2−. However, the reaction of the reduced enzyme with limited NO has an EPR signal (Fig. 2A, green), characteristic of a Cu+NO• species.6 This species lacks d-d bands in the MCD spectrum (Fig. S3), further confirming that the Cu is reduced. Therefore, reduced NiR forms a Cu+NO• species at low concentrations of NO. 
 
 
 
Figure 2 
 
EPR spectra A) following the reaction of reduced NiR with sub-stoichiometric NO solution (10:1 enzyme: NO) trapped at 1 second (green) 4 second (red) and 18 seconds (purple). B) following the reaction of the resting oxidized enzyme (black) with NO gas ... 
 
 
 
The reaction of reduced NiR with excess NO involves two one-electron oxidations; reduced T2 → oxidized T2, and NO → NO2−. A similar reaction has been observed for the coupled binuclear Cu active sites in hemocyanins11 (Scheme S1). Deoxyhemocyanin (2Cu+) reacts with NO generating N2O, and a met (2Cu2+) form, which further reacts with NO to generate the half-met (Cu2+Cu+) nitrite bound form. N2O evolution is in fact detected during the reaction of reduced NiR with excess NO, using nitrous oxide reductase (35 μmols N2O reduced min−1mg−1of enzyme), which requires N2O as its substrate.12 Reaction of the resting WT NiR (analogous to the met form of hemocyanin) with NO generates the T1 reduced, T2 oxidized form of the enzyme (g||=2.30, A||=150G), which converts to the nitrite bound T2 form (Fig. 2B, D →F → G, Scheme 1), indicating NO is oxidized to nitrite and nitrite binding is slow. 
 
 
 
Scheme 1 
 
Proposed mechanism for the formation of nitrite bound T2 NiR from reduced enzyme with excess NO. Red boxes = species observed. 
 
 
 
To evaluate the entire reaction mechanism, reduced NiR was reacted with limited NO solutions and intermediates were trapped at different times. We were able to trap the Cu+NO• form at shorter times, leading to the formation of the T1 reduced, T2 oxidized form, and ultimately generating the T1 reduced, T2 oxidized nitrite bound form (Fig. 2A, Scheme 1 A → B → F → G) at longer times. A reaction mechanism consistent with these results is presented in Scheme 1. Note that in the scheme, intermediate E is not observed because of rapid ET from T2 → T1.13 The experimental details and kinetic rates are provided in the supporting information. 
 
There is still one issue to resolve on correlating the spectroscopy with crystallography. The Cu-NO species trapped in the crystal structure has a side-on conformation.4 DFT calculations indicate that this species is best described as a Cu+-NO• species.7 However an end-on Cu-NO species is also trapped after limited exposure to NO gas (B, in scheme 1) which is equivalent to the species generated by reacting reduced NiR with nitrite (η1-CuNO).6 Geometry optimized DFT calculations (B3LYP/6–311g* on Cu, N, O and 6–31g* on C, H)14 of both side-on (Fig. 3, red) and end-on (Fig. 3, blue) Cu-NO adducts indicate that both forms have a Cu+NO• electronic configuration and that the end-on structure is more stable by 7 kcal/mol. However the orientation of the 2nd sphere aspartic acid residue (Asp129)9,15 appears to play a key role in determining the geometry of the Cu-NO species. In the side-on adduct this residue is perpendicular to the Cu-N-O plane and H-bonds to the O of N- O (Fig. 3 red) while in the end-on structure the Asp129 residue H-bonds to the O of NO and is parallel to the Cu-N-O plane (Fig. 3 blue). Both orientations of the Asp129 residue have been observed in crystal structures.15 The Asp129 residue exists in the perpendicular orientation in the crystal structures of the oxidized and reduced NiR and H-bonds to the axial ligand. However, to form the more stable end-on Cu+NO• adduct this aspartate residue has to rotate 90° which can occur in solution but may not be feasible in a crystal. 
 
 
 
Figure 3 
 
Overlay of the DFT optimized side-on bound NO (red) and end-on bound NO (blue) structures indicating the different orientations of the aspartate residue. 
 
 
 
In summary, the species generated in solution during the reaction of reduced NiR with excess NO is the T1 reduced, T2 oxidized nitrite bound form and not the side-on Cu-NO species observed in the crystal structure. The latter is best described as Cu+NO• rather than Cu2+NO−. The mechanism for the reaction of reduced NiR with excess NO involves its two electron oxidation, generating N2O. This oxidized form of the enzyme oxidizes NO generating nitrite bound to the oxidized T2 site generated by ET from T2 → T1. DFT calculations provide insight into factors which favor the η2-NO•Cu+ complex in the crystal structure.