<?xml version='1.0'?>
<!DOCTYPE art SYSTEM 'http://www.biomedcentral.com/xml/article.dtd'>
<art>
   <ui>1687-4153-2007-49478</ui>
   <ji>1687-4153</ji>
   <fm>
      <dochead>Research Article</dochead>
      <bibl>
         <title>
            <p>Analysis of Gene Coexpression by B-Spline Based CoD Estimation</p>
         </title>
         <aug>
            <au ca="yes" id="A1"><snm>Li</snm><fnm>Huai</fnm><insr iid="I1"/><email>huaili@mail.nih.gov</email></au>
            <au id="A2"><snm>Sun</snm><fnm>Yu</fnm><insr iid="I1"/><email>sunyu@mail.nih.gov</email></au>
            <au id="A3"><snm>Zhan</snm><fnm>Ming</fnm><insr iid="I1"/><email>zhanmi@mail.nih.gov</email></au>
         </aug>
         <insg>
            <ins id="I1"><p>Bioinformatics Unit, Branch of Research Resources, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA</p></ins>
         </insg>
         <source>EURASIP Journal on Bioinformatics and Systems Biology</source>
         <issn>1687-4153</issn>
         <pubdate>2007</pubdate>
         <volume>2007</volume>
         <issue>1</issue>
         <fpage>49478</fpage>
         <url>http://bsb.eurasipjournals.com/content/2007/1/49478</url>
         <xrefbib><pubid idtype="doi">10.1155/2007/49478</pubid></xrefbib>
      </bibl>
      <history><rec><date><day>31</day><month>7</month><year>2006</year></date></rec><revrec><date><day>3</day><month>1</month><year>2007</year></date></revrec><acc><date><day>6</day><month>1</month><year>2007</year></date></acc><pub><date><day>13</day><month>3</month><year>2007</year></date></pub></history>
      <cpyrt><year>2007</year><collab>Huai Li et al.</collab><note>This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.</note></cpyrt>
      <abs>
         <sec>
            <st>
               <p/>
            </st>
            <p>The gene coexpression study has emerged as a novel holistic approach for microarray data analysis. Different indices have been used in exploring coexpression relationship, but each is associated with certain pitfalls. The Pearson's correlation coefficient, for example, is not capable of uncovering nonlinear pattern and directionality of coexpression. Mutual information can detect nonlinearity but fails to show directionality. The coefficient of determination (CoD) is unique in exploring different patterns of gene coexpression, but so far only applied to discrete data and the conversion of continuous microarray data to the discrete format could lead to information loss. Here, we proposed an effective algorithm, CoexPro, for gene coexpression analysis. The new algorithm is based on B-spline approximation of coexpression between a pair of genes, followed by CoD estimation. The algorithm was justified by simulation studies and by functional semantic similarity analysis. The proposed algorithm is capable of uncovering both linear and a specific class of nonlinear relationships from continuous microarray data. It can also provide suggestions for possible directionality of coexpression to the researchers. The new algorithm presents a novel model for gene coexpression and will be a valuable tool for a variety of gene expression and network studies. The application of the algorithm was demonstrated by an analysis on ligand-receptor coexpression in cancerous and noncancerous cells. The software implementing the algorithm is available upon request to the authors.</p>
         </sec>
      </abs>
   </fm>
   <meta><classifications><classification id="GRS" subtype="theme_series_title" type="BMC">Genetic Regulatory Networks</classification><classification id="GRS" subtype="theme_series_editor" type="BMC">Ahmed Tewfik, Edward R Dougherty, Paul Dan Cristea and Tatsuya Akutsu</classification></classifications></meta><bdy>
      <sec>
         <st>
            <p/>
         </st>
         <p>[<abbr bid="B1">1</abbr><abbr bid="B2">2</abbr><abbr bid="B3">3</abbr><abbr bid="B4">4</abbr><abbr bid="B5">5</abbr><abbr bid="B6">6</abbr><abbr bid="B7">7</abbr><abbr bid="B8">8</abbr><abbr bid="B9">9</abbr><abbr bid="B10">10</abbr><abbr bid="B11">11</abbr><abbr bid="B12">12</abbr><abbr bid="B13">13</abbr><abbr bid="B14">14</abbr><abbr bid="B15">15</abbr><abbr bid="B16">16</abbr><abbr bid="B17">17</abbr><abbr bid="B18">18</abbr><abbr bid="B19">19</abbr><abbr bid="B20">20</abbr><abbr bid="B21">21</abbr><abbr bid="B22">22</abbr><abbr bid="B23">23</abbr><abbr bid="B24">24</abbr><abbr bid="B25">25</abbr><abbr bid="B26">26</abbr><abbr bid="B27">27</abbr><abbr bid="B28">28</abbr><abbr bid="B29">29</abbr>]</p>
      </sec>
   </bdy>
   <bm>
      <refgrp><bibl id="B1"><title><p>A gene-coexpression network for global discovery of conserved genetic modules</p></title><aug><au><snm>Stuart</snm><fnm>JM</fnm></au><au><snm>Segal</snm><fnm>E</fnm></au><au><snm>Koller</snm><fnm>D</fnm></au><au><snm>Kim</snm><fnm>SK</fnm></au></aug><source>Science</source><pubdate>2003</pubdate><volume>302</volume><issue>5643</issue><fpage>249</fpage><lpage>255</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1126/science.1087447</pubid><pubid idtype="pmpid" link="fulltext">12934013</pubid></pubidlist></xrefbib></bibl><bibl id="B2"><title><p>Coexpresion analysis of human genes across many microarray data sets</p></title><aug><au><snm>Lee</snm><fnm>HK</fnm></au><au><snm>Hsu</snm><fnm>AK</fnm></au><au><snm>Sajdak</snm><fnm>J</fnm></au><au><snm>Qin</snm><fnm>J</fnm></au><au><snm>Pavlidis</snm><fnm>P</fnm></au></aug><source>Genome Research</source><pubdate>2004</pubdate><volume>14</volume><issue>6</issue><fpage>1085</fpage><lpage>1094</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1101/gr.1910904</pubid><pubid idtype="pmcid">419787</pubid><pubid idtype="pmpid" link="fulltext">15173114</pubid></pubidlist></xrefbib></bibl><bibl id="B3"><title><p>The yeast coexpression network has a small-world, scale-free architecture and can be explained by a simple model</p></title><aug><au><snm>van Noort</snm><fnm>V</fnm></au><au><snm>Snel</snm><fnm>B</fnm></au><au><snm>Huynen</snm><fnm>MA</fnm></au></aug><source>EMBO Reports</source><pubdate>2004</pubdate><volume>5</volume><issue>3</issue><fpage>280</fpage><lpage>284</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1038/sj.embor.7400090</pubid><pubid idtype="pmcid">1299002</pubid><pubid idtype="pmpid" link="fulltext">14968131</pubid></pubidlist></xrefbib></bibl><bibl id="B4"><title><p>Gene co-expression network topology provides a framework for molecular characterization of cellular state</p></title><aug><au><snm>Carter</snm><fnm>SL</fnm></au><au><snm>Brechbu&#776;hler</snm><fnm>CM</fnm></au><au><snm>Griffin</snm><fnm>M</fnm></au><au><snm>Bond</snm><fnm>AT</fnm></au></aug><source>Bioinformatics</source><pubdate>2004</pubdate><volume>20</volume><issue>14</issue><fpage>2242</fpage><lpage>2250</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1093/bioinformatics/bth234</pubid><pubid idtype="pmpid" link="fulltext">15130938</pubid></pubidlist></xrefbib></bibl><bibl id="B5"><title><p>Bioinformatic identification of potential autocrine signaling loops in cancers from gene expression profiles</p></title><aug><au><snm>Graeber</snm><fnm>TG</fnm></au><au><snm>Eisenberg</snm><fnm>D</fnm></au></aug><source>Nature Genetics</source><pubdate>2001</pubdate><volume>29</volume><issue>3</issue><fpage>295</fpage><lpage>300</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1038/ng755</pubid><pubid idtype="pmpid" link="fulltext">11685206</pubid></pubidlist></xrefbib></bibl><bibl id="B6"><title><p>Reconciling gene expression data with known genome-scale regulatory network structures</p></title><aug><au><snm>Herrg&#229;rd</snm><fnm>MJ</fnm></au><au><snm>Covert</snm><fnm>MW</fnm></au><au><snm>Palsson</snm><fnm>B&#216;</fnm></au></aug><source>Genome Research</source><pubdate>2003</pubdate><volume>13</volume><issue>11</issue><fpage>2423</fpage><lpage>2434</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1101/gr.1330003</pubid><pubid idtype="pmcid">403761</pubid><pubid idtype="pmpid" link="fulltext">14559784</pubid></pubidlist></xrefbib></bibl><bibl id="B7"><title><p>Estimation of genetic networks and functional structures between genes by using Bayesian networks and nonparametric regression</p></title><aug><au><snm>Imoto</snm><fnm>S</fnm></au><au><snm>Goto</snm><fnm>T</fnm></au><au><snm>Miyano</snm><fnm>S</fnm></au></aug><source>Pacific Symposium on Biocomputing</source><pubdate>2002</pubdate><fpage>175</fpage><lpage>186</lpage></bibl><bibl id="B8"><title><p>Mutual information relevance networks: functional genomic clustering using pairwise entropy measurements</p></title><aug><au><snm>Butte</snm><fnm>AJ</fnm></au><au><snm>Kohane</snm><fnm>IS</fnm></au></aug><source>Pacific Symposium on Biocomputing</source><pubdate>2000</pubdate><fpage>418</fpage><lpage>429</lpage></bibl><bibl id="B9"><title><p>Construction of genomic networks using mutual-information clustering and reversible-jump Markov-chain-Monte-Carlo predictor design</p></title><aug><au><snm>Zhou</snm><fnm>X</fnm></au><au><snm>Wang</snm><fnm>X</fnm></au><au><snm>Dougherty</snm><fnm>ER</fnm></au></aug><source>Signal Processing</source><pubdate>2003</pubdate><volume>83</volume><issue>4</issue><fpage>745</fpage><lpage>761</lpage><xrefbib><pubid idtype="doi">10.1016/S0165-1684(02)00469-3</pubid></xrefbib></bibl><bibl id="B10"><title><p>Can Markov chain models mimic biological regulation?</p></title><aug><au><snm>Kim</snm><fnm>S</fnm></au><au><snm>Li</snm><fnm>H</fnm></au><au><snm>Dougherty</snm><fnm>ER</fnm></au><etal/></aug><source>Journal of Biological Systems</source><pubdate>2002</pubdate><volume>10</volume><issue>4</issue><fpage>337</fpage><lpage>357</lpage><xrefbib><pubid idtype="doi">10.1142/S0218339002000676</pubid></xrefbib></bibl><bibl id="B11"><title><p>Growing genetic regulatory networks from seed genes</p></title><aug><au><snm>Hashimoto</snm><fnm>RF</fnm></au><au><snm>Kim</snm><fnm>S</fnm></au><au><snm>Shmulevich</snm><fnm>I</fnm></au><au><snm>Zhang</snm><fnm>W</fnm></au><au><snm>Bittner</snm><fnm>ML</fnm></au><au><snm>Dougherty</snm><fnm>ER</fnm></au></aug><source>Bioinformatics</source><pubdate>2004</pubdate><volume>20</volume><issue>8</issue><fpage>1241</fpage><lpage>1247</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1093/bioinformatics/bth074</pubid><pubid idtype="pmpid" link="fulltext">14871865</pubid></pubidlist></xrefbib></bibl><bibl id="B12"><title><p>Probabilistic Boolean networks: a rule-based uncertainty model for gene regulatory networks</p></title><aug><au><snm>Shmulevich</snm><fnm>I</fnm></au><au><snm>Dougherty</snm><fnm>ER</fnm></au><au><snm>Kim</snm><fnm>S</fnm></au><au><snm>Zhang</snm><fnm>W</fnm></au></aug><source>Bioinformatics</source><pubdate>2002</pubdate><volume>18</volume><issue>2</issue><fpage>261</fpage><lpage>274</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1093/bioinformatics/18.2.261</pubid><pubid idtype="pmpid" link="fulltext">11847074</pubid></pubidlist></xrefbib></bibl><bibl id="B13"><title><p>Coefficient of determination in nonlinear signal processing</p></title><aug><au><snm>Dougherty</snm><fnm>ER</fnm></au><au><snm>Kim</snm><fnm>S</fnm></au><au><snm>Chen</snm><fnm>Y</fnm></au></aug><source>Signal Processing</source><pubdate>2000</pubdate><volume>80</volume><issue>10</issue><fpage>2219</fpage><lpage>2235</lpage><xrefbib><pubid idtype="doi">10.1016/S0165-1684(00)00079-7</pubid></xrefbib></bibl><bibl id="B14"><title><p>Systematic intervention of transcription for identifying network response to disease and cellular phenotypes</p></title><aug><au><snm>Li</snm><fnm>H</fnm></au><au><snm>Zhan</snm><fnm>M</fnm></au></aug><source>Bioinformatics</source><pubdate>2006</pubdate><volume>22</volume><issue>1</issue><fpage>96</fpage><lpage>102</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1093/bioinformatics/bti752</pubid><pubid idtype="pmpid" link="fulltext">16278241</pubid></pubidlist></xrefbib></bibl><bibl id="B15"><title><p>Dynamical analysis of gene networks requires both mRNA and protein expression information</p></title><aug><au><snm>Hatzimanikatis</snm><fnm>V</fnm></au><au><snm>Lee</snm><fnm>KH</fnm></au></aug><source>Metabolic Engineering</source><pubdate>1999</pubdate><volume>1</volume><issue>4</issue><fpage>275</fpage><lpage>281</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1006/mben.1999.0115</pubid><pubid idtype="pmpid" link="fulltext">10937820</pubid></pubidlist></xrefbib></bibl><bibl id="B16"><aug><au><snm>Prautzsch</snm><fnm>H</fnm></au><au><snm>Boehm</snm><fnm>W</fnm></au><au><snm>Paluszny</snm><fnm>M</fnm></au></aug><source>B&#233;zier and B-Spline Techniques</source><publisher>Springer, Berlin, Germany</publisher><pubdate>2002</pubdate><xrefbib><pubid idtype="pmpid">21863587</pubid></xrefbib></bibl><bibl id="B17"><title><p>A data-driven clustering method for time course gene expression data</p></title><aug><au><snm>Ma</snm><fnm>P</fnm></au><au><snm>Castillo-Davis</snm><fnm>CI</fnm></au><au><snm>Zhong</snm><fnm>W</fnm></au><au><snm>Liu</snm><fnm>JS</fnm></au></aug><source>Nucleic Acids Research</source><pubdate>2006</pubdate><volume>34</volume><issue>4</issue><fpage>1261</fpage><lpage>1269</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1093/nar/gkl013</pubid><pubid idtype="pmcid">1388097</pubid><pubid idtype="pmpid" link="fulltext">16510852</pubid></pubidlist></xrefbib></bibl><bibl id="B18"><title><p>Significance analysis of time course microarray experiments</p></title><aug><au><snm>Storey</snm><fnm>JD</fnm></au><au><snm>Xiao</snm><fnm>W</fnm></au><au><snm>Leek</snm><fnm>JT</fnm></au><au><snm>Tompkins</snm><fnm>RG</fnm></au><au><snm>Davis</snm><fnm>RW</fnm></au></aug><source>Proceedings of the National Academy of Sciences of the United States of America</source><pubdate>2005</pubdate><volume>102</volume><issue>36</issue><fpage>12837</fpage><lpage>12842</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1073/pnas.0504609102</pubid><pubid idtype="pmcid">1201697</pubid><pubid idtype="pmpid" link="fulltext">16141318</pubid></pubidlist></xrefbib></bibl><bibl id="B19"><title><p>Continuous representations of time-series gene expression data</p></title><aug><au><snm>Bar-Joseph</snm><fnm>Z</fnm></au><au><snm>Gerber</snm><fnm>GK</fnm></au><au><snm>Gifford</snm><fnm>DK</fnm></au><au><snm>Jaakkola</snm><fnm>TS</fnm></au><au><snm>Simon</snm><fnm>I</fnm></au></aug><source>Journal of Computational Biology</source><pubdate>2003</pubdate><volume>10</volume><issue>3-4</issue><fpage>341</fpage><lpage>356</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1089/10665270360688057</pubid><pubid idtype="pmpid" link="fulltext">12935332</pubid></pubidlist></xrefbib></bibl><bibl id="B20"><title><p>SPLINDID: a semi-parametric, model-based method for obtaining transcription rates and gene regulation parameters from genomic and proteomic expression profiles</p></title><aug><au><snm>Bhasi</snm><fnm>K</fnm></au><au><snm>Forrest</snm><fnm>A</fnm></au><au><snm>Ramanathan</snm><fnm>M</fnm></au></aug><source>Bioinformatics</source><pubdate>2005</pubdate><volume>21</volume><issue>20</issue><fpage>3873</fpage><lpage>3879</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1093/bioinformatics/bti624</pubid><pubid idtype="pmcid">2607482</pubid><pubid idtype="pmpid" link="fulltext">16096347</pubid></pubidlist></xrefbib></bibl><bibl id="B21"><title><p>A spline function approach for detecting differentially expressed genes in microarray data analysis</p></title><aug><au><snm>He</snm><fnm>W</fnm></au></aug><source>Bioinformatics</source><pubdate>2004</pubdate><volume>20</volume><issue>17</issue><fpage>2954</fpage><lpage>2963</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1093/bioinformatics/bth339</pubid><pubid idtype="pmpid" link="fulltext">15180936</pubid></pubidlist></xrefbib></bibl><bibl id="B22"><title><p>Clustering of time-course gene expression data using a mixed-effects model with B-splines</p></title><aug><au><snm>Luan</snm><fnm>Y</fnm></au><au><snm>Li</snm><fnm>H</fnm></au></aug><source>Bioinformatics</source><pubdate>2003</pubdate><volume>19</volume><issue>4</issue><fpage>474</fpage><lpage>482</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1093/bioinformatics/btg014</pubid><pubid idtype="pmpid" link="fulltext">12611802</pubid></pubidlist></xrefbib></bibl><bibl id="B23"><title><p>Estimating mutual information using B-spline functions&#8212;an improved similarity measure for analysing gene expression data</p></title><aug><au><snm>Daub</snm><fnm>CO</fnm></au><au><snm>Steuer</snm><fnm>R</fnm></au><au><snm>Selbig</snm><fnm>J</fnm></au><au><snm>Kloska</snm><fnm>S</fnm></au></aug><source>BMC Bioinformatics</source><pubdate>2004</pubdate><volume>5</volume><issue>1</issue><fpage>118</fpage><xrefbib><pubidlist><pubid idtype="doi">10.1186/1471-2105-5-118</pubid><pubid idtype="pmcid">516800</pubid><pubid idtype="pmpid" link="fulltext">15339346</pubid></pubidlist></xrefbib></bibl><bibl id="B24"><title><p>Summaries of Affymetrix GeneChip probe level data</p></title><aug><au><snm>Irizarry</snm><fnm>RA</fnm></au><au><snm>Bolstad</snm><fnm>BM</fnm></au><au><snm>Collin</snm><fnm>F</fnm></au><au><snm>Cope</snm><fnm>LM</fnm></au><au><snm>Hobbs</snm><fnm>B</fnm></au><au><snm>Speed</snm><fnm>TP</fnm></au></aug><source>Nucleic Acids Research</source><pubdate>2003</pubdate><volume>31</volume><issue>4</issue><fpage>e15</fpage><xrefbib><pubidlist><pubid idtype="doi">10.1093/nar/gng015</pubid><pubid idtype="pmcid">150247</pubid><pubid idtype="pmpid" link="fulltext">12582260</pubid></pubidlist></xrefbib></bibl><bibl id="B25"><title><p>Investigating semantic similarity measures across the gene ontology: the relationship between sequence and annotation</p></title><aug><au><snm>Lord</snm><fnm>PW</fnm></au><au><snm>Stevens</snm><fnm>RD</fnm></au><au><snm>Brass</snm><fnm>A</fnm></au><au><snm>Goble</snm><fnm>CA</fnm></au></aug><source>Bioinformatics</source><pubdate>2003</pubdate><volume>19</volume><issue>10</issue><fpage>1275</fpage><lpage>1283</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1093/bioinformatics/btg153</pubid><pubid idtype="pmpid" link="fulltext">12835272</pubid></pubidlist></xrefbib></bibl><bibl id="B26"><title><p>Bone morphogenetic protein signaling in prostate cancer cell lines</p></title><aug><au><snm>Brubaker</snm><fnm>KD</fnm></au><au><snm>Corey</snm><fnm>E</fnm></au><au><snm>Brown</snm><fnm>LG</fnm></au><au><snm>Vessella</snm><fnm>RL</fnm></au></aug><source>Journal of Cellular Biochemistry</source><pubdate>2004</pubdate><volume>91</volume><issue>1</issue><fpage>151</fpage><lpage>160</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1002/jcb.10679</pubid><pubid idtype="pmpid" link="fulltext">14689587</pubid></pubidlist></xrefbib></bibl><bibl id="B27"><title><p>Diverse biological effect and Smad signaling of bone morphogenetic protein 7 in prostate tumor cells</p></title><aug><au><snm>Yang</snm><fnm>S</fnm></au><au><snm>Zhong</snm><fnm>C</fnm></au><au><snm>Frenkel</snm><fnm>B</fnm></au><au><snm>Reddi</snm><fnm>AH</fnm></au><au><snm>Roy-Burman</snm><fnm>P</fnm></au></aug><source>Cancer Research</source><pubdate>2005</pubdate><volume>65</volume><issue>13</issue><fpage>5769</fpage><lpage>5777</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1158/0008-5472.CAN-05-0289</pubid><pubid idtype="pmpid" link="fulltext">15994952</pubid></pubidlist></xrefbib></bibl><bibl id="B28"><title><p>Involvement of chemokine receptors in breast cancer metastasis</p></title><aug><au><snm>M&#252;ller</snm><fnm>A</fnm></au><au><snm>Homey</snm><fnm>B</fnm></au><au><snm>Soto</snm><fnm>H</fnm></au><etal/></aug><source>Nature</source><pubdate>2001</pubdate><volume>410</volume><issue>6824</issue><fpage>50</fpage><lpage>56</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1038/35065016</pubid><pubid idtype="pmpid" link="fulltext">11242036</pubid></pubidlist></xrefbib></bibl><bibl id="B29"><title><p>Chemokines and their role in tumor growth and metastasis</p></title><aug><au><snm>Wang</snm><fnm>JM</fnm></au><au><snm>Deng</snm><fnm>X</fnm></au><au><snm>Gong</snm><fnm>W</fnm></au><au><snm>Su</snm><fnm>S</fnm></au></aug><source>Journal of Immunological Methods</source><pubdate>1998</pubdate><volume>220</volume><issue>1-2</issue><fpage>1</fpage><lpage>17</lpage><xrefbib><pubidlist><pubid idtype="doi">10.1016/S0022-1759(98)00128-8</pubid><pubid idtype="pmpid" link="fulltext">9839921</pubid></pubidlist></xrefbib></bibl></refgrp>
   </bm>
</art>