Frequent gene conversion events between the X and Y homologous chromosomal regions in primates

<p>Abstract</p> <p>Background</p> <p>Mammalian sex-chromosomes originated from a pair of autosomes. A step-wise cessation of recombination is necessary for the proper maintenance of sex-determination and, consequently, generates a four strata structure on the X chromosome. Each stratum shows a specific per-site nucleotide sequence difference (<it>p-</it>distance) between the X and Y chromosomes, depending on the time of recombination arrest. Stratum 4 covers the distal half of the human X chromosome short arm and the <it>p</it>-distance of the stratum is ~10%, on average. However, a 100-kb region, which includes <it>KALX </it>and <it>VCX</it>, in the middle of stratum 4 shows a significantly lower <it>p</it>-distance (1-5%), suggesting frequent sequence exchanges or gene conversions between the X and Y chromosomes in humans. To examine the evolutionary mechanism for this low <it>p</it>-distance region, sequences of a corresponding region including <it>KALX</it>/<it>Y </it>from seven species of non-human primates were analyzed.</p> <p>Results</p> <p>Phylogenetic analysis of this low <it>p</it>-distance region in humans and non-human primate species revealed that gene conversion like events have taken place at least ten times after the divergence of New World monkeys and Catarrhini (<it>i.e</it>., Old World monkeys and hominoids). A <it>KALY</it>-converted <it>KALX </it>allele in white-handed gibbons also suggests a possible recent gene conversion between the X and Y chromosomes. In these primate sequences, the proximal boundary of this low <it>p</it>-distance region is located in a <it>LINE </it>element shared between the X and Y chromosomes, suggesting the involvement of this element in frequent gene conversions. Together with a palindrome on the Y chromosome, a segmental palindrome structure on the X chromosome at the distal boundary near <it>VCX</it>, in humans and chimpanzees, may mediate frequent sequence exchanges between X and Y chromosomes.</p> <p>Conclusion</p> <p>Gene conversion events between the X and Y homologous regions have been suggested, mainly in humans. Here, we found frequent gene conversions in the evolutionary course of primates. An insertion of a <it>LINE </it>element at the proximal end of the region may be a cause for these frequent conversions. This gene conversion in humans may also be one of the genetic causes of Kallmann syndrome.</p

A Review of the Studies on Adaptive Testing : Ability Measurement and Diagnosis

Adaptive testing, in contrast to the conventional tests in which all the examinees take the same set of test items, presents an examinee only the items that are informative on the examinee\u27s ability. Therefore, in adaptive testing, examinees don\u27t have to answer items that are too easy or too difficult to them. In 70s to 80s, research concerns concentrated on its psychometric characteristics; the precision and the efficiency of measurement. It was found that the adaptive testing, typically computerized and based on the item response theory, can measure ability in about half the test length without compromising the precision of measurement. In last ten years, however, research efforts were added to make the (computerized) adaptive testing more useful, more valid, examiniee-friendly, and diagnostic. The efforts to elaborate the IRT model, to balance the content domain, to investigate the individual difference, and to incorporate the artificial intelligence or expert systems in this context are also reviewed

An Attempt to Improve the Precision of Measurements by a Multiple-Choice Test

In attempt to improve the measurement precision by a multiple-choice test, two IRT multi-category models were applied to an English test and compared to a binary model. The multi-category models were graded response model and nominal response model. Each item of the test consisted of 5 alternatives, which were classified according to their correctness into 3 categories : "correct, " "nearly correct, " and "far from correct." It was found that the two multi-category models showed the almost equal effect on improving the measurement precision compared to 2-parameter logistic model. The improvement was most remarkable for subjects with low ability

Low serum free light chain is associated with risk of COPD exacerbation

Background: Most exacerbations of chronic obstructive pulmonary disease (COPD) are triggered by respiratory tract infections. Adaptive immunity via antibody production is important in preventing infections. Impaired antibody production is reported to be associated with an increased risk of exacerbations of COPD. In the present study, we elucidated whether reduced free light chains (FLCs), which are excessive amounts of light chains produced during antibody synthesis and can be used to estimate systemic antibody production, may be a promising biomarker to predict the risk of exacerbations of COPD. Methods: We enrolled stable male patients with COPD and prospectively observed them for 2 years. At baseline, serum combined FLC (cFLC; sum of kappa and lambda values) and pulmonary function were evaluated. Exacerbation was defined as a worsening of symptoms requiring treatments with antibiotics, corticosteroids or both. Results: 63 patients with stable COPD were enrolled (72.8±8.1 years, GOLD A/B/C/D=24/28/6/5), and 51 patients completed the 2-year follow-up. Serum cFLC was 31.1 mg·L−1 on average and ranged widely (1.4 to 89.9 mg·L−1). The patients with low cFLC (below the mean−sd, n=6) experienced a significantly shorter time to the first exacerbation of COPD (p<0.0001 by the log-rank test). A multivariate Cox proportional hazard model, including the COPD assessment test score, % predicted forced expiratory volume in 1 s (FEV1 % pred), and number of previous exacerbations demonstrated that low cFLC and low FEV1 % pred were independently and significantly correlated with the risk for exacerbations of COPD. Conclusion: Low cFLC may be a B-cell-associated novel biomarker associated with risk of COPD exacerbation

An Analysis of Essay Examination Data Using Graded Response Model

The purpose of this study is to investigate the reliability of essay test scores when the scores are expressed by using several rating categories and applied to graded response model. The data were obtained by assigning an essay examination to high school students. The 165 essays were evaluated holisticaly and given marks between 0 to 100 points. The marks were then classified into the 2 to 5 categories according to the two criterions : percentile and standard deviation. It was found that the reliability of the 5-category data (standard deviation criterion) was almost as good as that of the original 100-point data, which indicates validity of categorical rating. The characteristics of some of the raters were also described by their information functions

Genetic Analyses of Elys Mutations in Drosophila Show Maternal-Effect Lethality and Interactions with Nucleoporin Genes

ELYS determines the subcellular localizations of Nucleoporins (Nups) during interphase and mitosis. We made loss-of-function mutations of Elys in Drosophila melanogaster and found that ELYS is dispensable for zygotic viability and male fertility but the maternal supply is necessary for embryonic development. Subsequent to fertilization, mitotic progression of the embryos produced by the mutant females is severely disrupted at the first cleavage division, accompanied by irregular behavior of mitotic centrosomes. The Nup160 introgression from D. simulans shows close resemblance to that of the Elys mutations, suggesting a common role for those proteins in the first cleavage division. Our genetic experiments indicated critical interactions between ELYS and three Nup107–160 subcomplex components; hemizygotes of either Nup37, Nup96 or Nup160 were lethal in the genetic background of the Elys mutation. Not only Nup96 and Nup160 but also Nup37 of D. simulans behave as recessive hybrid incompatibility genes with D. melanogaster. An evolutionary analysis indicated positive natural selection in the ELYS-like domain of ELYS. Here we propose that genetic incompatibility between Elys and Nups may lead to reproductive isolation between D. melanogaster and D. simulans, although direct evidence is necessary

GLYCOSAMINOGLYCANS AND PROTEOGLYCANS IN PALMAR FASCIA OF PATIENTS WITH DUPUYTREN

Objective: To evaluate and compare the behavior of glycosaminoglycans (GAGs) in Dupuytren disease (DD). Methods: This is an experimental study with 23 patients diagnosed with DD. Tissue collected through fasciectomy with incision type Brunner or McCash were evaluated by electrophoresis for identification of GAGs. The quantification was carried out by immunofluorescence and dosage of proteins for different types of glycosaminoglycans. The results were expressed in percentage and statistically evaluated. Results: A significant increase was observed through eletrophoresis in GAGs, as compared to the control (p<0.05). Immunofluorescence of hyaluronic acid was reduced (23 times) when compared to the control (p<0.0001). Conclusion: An increase of sulfated GAGs in Dupuytren's disease, mainly dermatan sulfate, was evident from our results, as well as a pronounced decrease of hyaluronic acid in the palmar aponeurosis from the same patients.Univ Fed Sao Paulo Unifesp, Escola Paulista Med, Dept Orthoped & Traumatol, Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Dept Orthoped & Traumatol, Sao Paulo, SP, BrazilUniv Fed Sao Paulo Unifesp, Escola Paulista Med, Dept Orthoped & Traumatol, Sao Paulo, SP, BrazilUniv Fed Sao Paulo, Dept Orthoped & Traumatol, Sao Paulo, SP, BrazilWeb of Scienc

A combination of a DNA-chimera siRNA against PLK-1 and zoledronic acid suppresses the growth of malignant mesothelioma cells in vitro.

Although novel agents effective against malignant mesothelioma (MM) have been developed, the prognosis of patients with MM is still poor. We generated a DNA-chimeric siRNA against polo-like kinase-1 (PLK-1), which was more stable in human serum than the non-chimeric siRNA. The chimeric PLK-1 siRNA inhibited MM cell proliferation through the induction of apoptosis. Next, we investigated the effects of zoledronic acid (ZOL) on MM cells, and found that ZOL also induced apoptosis in MM cells. Furthermore, ZOL augmented the inhibitory effects of the PLK-1 siRNA. In conclusion, combining a PLK-1 siRNA with ZOL treatment is an attractive strategy against MM