|
| 1 | +{ |
| 2 | + "cells": [ |
| 3 | + { |
| 4 | + "cell_type": "markdown", |
| 5 | + "metadata": {}, |
| 6 | + "source": [ |
| 7 | + "# Graph of gene expression similarity inside a tissue\n", |
| 8 | + "The idea here is to build a similarity graph between gene expression.The idea is the same as for the genotype graph, see the \"genotype graph\" notebook for more info.\n", |
| 9 | + "\n", |
| 10 | + "In this notebook, proteins or gene expression are nodes of the graph. They are connected to their k nearest neighbors. The connections are weighted by the similarity between two protein expression according to a chosen distance. To each protein is associated a vector encoding its variations over the BXD mouse dataset. Two proteins are similar if their vectors are close in term of Euclidean distance." |
| 11 | + ] |
| 12 | + }, |
| 13 | + { |
| 14 | + "cell_type": "code", |
| 15 | + "execution_count": null, |
| 16 | + "metadata": {}, |
| 17 | + "outputs": [], |
| 18 | + "source": [ |
| 19 | + "import pandas as pd\n", |
| 20 | + "import numpy as np\n", |
| 21 | + "from scipy.sparse import csr_matrix\n", |
| 22 | + "import os" |
| 23 | + ] |
| 24 | + }, |
| 25 | + { |
| 26 | + "cell_type": "code", |
| 27 | + "execution_count": null, |
| 28 | + "metadata": {}, |
| 29 | + "outputs": [], |
| 30 | + "source": [ |
| 31 | + "import networkx as nx\n", |
| 32 | + "import sklearn.metrics\n", |
| 33 | + "import sklearn.neighbors\n", |
| 34 | + "import matplotlib.pyplot as plt" |
| 35 | + ] |
| 36 | + }, |
| 37 | + { |
| 38 | + "cell_type": "markdown", |
| 39 | + "metadata": {}, |
| 40 | + "source": [ |
| 41 | + "# Importing the data" |
| 42 | + ] |
| 43 | + }, |
| 44 | + { |
| 45 | + "cell_type": "code", |
| 46 | + "execution_count": null, |
| 47 | + "metadata": {}, |
| 48 | + "outputs": [], |
| 49 | + "source": [ |
| 50 | + "# Config for accessing the data on the s3 storage\n", |
| 51 | + "storage_options = {'anon':True, 'client_kwargs':{'endpoint_url':'https://os.unil.cloud.switch.ch'}}\n", |
| 52 | + "s3_path = 's3://lts2-graphnex/BXDmice/'" |
| 53 | + ] |
| 54 | + }, |
| 55 | + { |
| 56 | + "cell_type": "code", |
| 57 | + "execution_count": null, |
| 58 | + "metadata": {}, |
| 59 | + "outputs": [], |
| 60 | + "source": [ |
| 61 | + "# Load the data\n", |
| 62 | + "# Tissue\n", |
| 63 | + "tissue_name = 'LiverProt_CD'\n", |
| 64 | + "# Other examples:\n", |
| 65 | + "#tissue_name = 'Eye'\n", |
| 66 | + "#tissue_name = 'Muscle_CD'\n", |
| 67 | + "#tissue_name = 'Hippocampus'\n", |
| 68 | + "#tissue_name = 'Gastrointestinal'\n", |
| 69 | + "#tissue_name = 'Lung'\n", |
| 70 | + "tissue_path = os.path.join(s3_path, 'expression data', tissue_name + '.txt.gz')\n", |
| 71 | + "tissue = pd.read_csv(tissue_path, sep='\\t', storage_options=storage_options)\n", |
| 72 | + "print('File {} Opened.'.format(tissue_path))" |
| 73 | + ] |
| 74 | + }, |
| 75 | + { |
| 76 | + "cell_type": "markdown", |
| 77 | + "metadata": {}, |
| 78 | + "source": [ |
| 79 | + "## Computing the distances" |
| 80 | + ] |
| 81 | + }, |
| 82 | + { |
| 83 | + "cell_type": "code", |
| 84 | + "execution_count": null, |
| 85 | + "metadata": {}, |
| 86 | + "outputs": [], |
| 87 | + "source": [ |
| 88 | + "# Remove the columns (mouse strains) where there are no measurement:\n", |
| 89 | + "tissue = tissue.dropna(axis=1)\n", |
| 90 | + "# Extract the data as a numpy array (drop the first columns)\n", |
| 91 | + "tissue_values = tissue.iloc[:,2:].values" |
| 92 | + ] |
| 93 | + }, |
| 94 | + { |
| 95 | + "cell_type": "markdown", |
| 96 | + "metadata": {}, |
| 97 | + "source": [ |
| 98 | + "### Normalizing\n", |
| 99 | + "If unormalized, the graph of gene expression may not account for correlated expressions but only for similar concentration." |
| 100 | + ] |
| 101 | + }, |
| 102 | + { |
| 103 | + "cell_type": "code", |
| 104 | + "execution_count": null, |
| 105 | + "metadata": {}, |
| 106 | + "outputs": [], |
| 107 | + "source": [ |
| 108 | + "from sklearn.preprocessing import normalize\n", |
| 109 | + "tissue_values = normalize(tissue_values, norm='l2', axis=1)\n", |
| 110 | + "tissue_values.shape" |
| 111 | + ] |
| 112 | + }, |
| 113 | + { |
| 114 | + "cell_type": "code", |
| 115 | + "execution_count": null, |
| 116 | + "metadata": {}, |
| 117 | + "outputs": [], |
| 118 | + "source": [ |
| 119 | + "# Default distance is Euclidean\n", |
| 120 | + "num_neighbors = 4\n", |
| 121 | + "tissue_knn = sklearn.neighbors.kneighbors_graph(tissue_values, num_neighbors, mode='distance')\n", |
| 122 | + "# Optionally, one can use the following function to compute all the distances:\n", |
| 123 | + "#geno_distances = sklearn.metrics.pairwise_distances(geno_values)" |
| 124 | + ] |
| 125 | + }, |
| 126 | + { |
| 127 | + "cell_type": "code", |
| 128 | + "execution_count": null, |
| 129 | + "metadata": {}, |
| 130 | + "outputs": [], |
| 131 | + "source": [ |
| 132 | + "# Distribution of weights\n", |
| 133 | + "plt.hist(tissue_knn.data, bins=50)\n", |
| 134 | + "plt.title('Distribution of distances')\n", |
| 135 | + "plt.xlabel('Distance')\n", |
| 136 | + "plt.ylabel('Nb of edges')\n", |
| 137 | + "plt.show()" |
| 138 | + ] |
| 139 | + }, |
| 140 | + { |
| 141 | + "cell_type": "code", |
| 142 | + "execution_count": null, |
| 143 | + "metadata": {}, |
| 144 | + "outputs": [], |
| 145 | + "source": [ |
| 146 | + "# Distance to weight\n", |
| 147 | + "# Modify the non-zero values to turn them into weights instead of distances\n", |
| 148 | + "def distance2weight(d):\n", |
| 149 | + " sigma = 1\n", |
| 150 | + " return np.exp(- sigma * d)\n", |
| 151 | + " \n", |
| 152 | + "M = tissue_knn.copy() #csr_matrix(tissue_knn.shape)\n", |
| 153 | + "M.data = distance2weight(tissue_knn.data)\n", |
| 154 | + "\n", |
| 155 | + "print('A distance of 1 becomes a weight of {}.'.format(str(distance2weight(1))))" |
| 156 | + ] |
| 157 | + }, |
| 158 | + { |
| 159 | + "cell_type": "code", |
| 160 | + "execution_count": null, |
| 161 | + "metadata": {}, |
| 162 | + "outputs": [], |
| 163 | + "source": [ |
| 164 | + "# Distribution of weights\n", |
| 165 | + "plt.hist(M.data, bins=20)\n", |
| 166 | + "plt.title('Distribution of weights')\n", |
| 167 | + "plt.xlabel('Weight value')\n", |
| 168 | + "plt.ylabel('Nb of edges')\n", |
| 169 | + "plt.show()" |
| 170 | + ] |
| 171 | + }, |
| 172 | + { |
| 173 | + "cell_type": "markdown", |
| 174 | + "metadata": {}, |
| 175 | + "source": [ |
| 176 | + "## Building the graph" |
| 177 | + ] |
| 178 | + }, |
| 179 | + { |
| 180 | + "cell_type": "code", |
| 181 | + "execution_count": null, |
| 182 | + "metadata": {}, |
| 183 | + "outputs": [], |
| 184 | + "source": [ |
| 185 | + "G = nx.from_scipy_sparse_matrix(M)" |
| 186 | + ] |
| 187 | + }, |
| 188 | + { |
| 189 | + "cell_type": "code", |
| 190 | + "execution_count": null, |
| 191 | + "metadata": {}, |
| 192 | + "outputs": [], |
| 193 | + "source": [ |
| 194 | + "# Adding info on the nodes of the graph\n", |
| 195 | + "tissueinfo_dic = tissue[['gene']].to_dict()\n", |
| 196 | + "nx.set_node_attributes(G, tissueinfo_dic['gene'], name='Gene') # gene name" |
| 197 | + ] |
| 198 | + }, |
| 199 | + { |
| 200 | + "cell_type": "code", |
| 201 | + "execution_count": null, |
| 202 | + "metadata": {}, |
| 203 | + "outputs": [], |
| 204 | + "source": [ |
| 205 | + "# Saving the graph as a gexf file readable with Gephi.\n", |
| 206 | + "nx.write_gexf(G,tissue_name + 'graph.gexf')" |
| 207 | + ] |
| 208 | + }, |
| 209 | + { |
| 210 | + "cell_type": "markdown", |
| 211 | + "metadata": {}, |
| 212 | + "source": [ |
| 213 | + "Graph plotted using Gephi, colored by community (communities found automatically with Gephi). The gene expression forms two distinct clusters. \n", |
| 214 | + "\n", |
| 215 | + "" |
| 216 | + ] |
| 217 | + }, |
| 218 | + { |
| 219 | + "cell_type": "markdown", |
| 220 | + "metadata": {}, |
| 221 | + "source": [ |
| 222 | + "## Applications of the graph\n", |
| 223 | + "There are different possible applications of this graph, see the \"genotype graph\" notebook for examples." |
| 224 | + ] |
| 225 | + }, |
| 226 | + { |
| 227 | + "cell_type": "code", |
| 228 | + "execution_count": null, |
| 229 | + "metadata": {}, |
| 230 | + "outputs": [], |
| 231 | + "source": [] |
| 232 | + } |
| 233 | + ], |
| 234 | + "metadata": { |
| 235 | + "kernelspec": { |
| 236 | + "display_name": "venv", |
| 237 | + "language": "python", |
| 238 | + "name": "venv" |
| 239 | + }, |
| 240 | + "language_info": { |
| 241 | + "codemirror_mode": { |
| 242 | + "name": "ipython", |
| 243 | + "version": 3 |
| 244 | + }, |
| 245 | + "file_extension": ".py", |
| 246 | + "mimetype": "text/x-python", |
| 247 | + "name": "python", |
| 248 | + "nbconvert_exporter": "python", |
| 249 | + "pygments_lexer": "ipython3", |
| 250 | + "version": "3.8.0" |
| 251 | + } |
| 252 | + }, |
| 253 | + "nbformat": 4, |
| 254 | + "nbformat_minor": 4 |
| 255 | +} |
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