Orit Shmueli

Genome-wide midrange transcription profiles reveal expression level relationships in human tissue specification

MOTIVATION Genes are often characterized dichotomously as either housekeeping or single-tissue specific. We conjectured that crucial functional information resides in genes with midrange profiles of expression. RESULTS To obtain such novel information genome-wide, we have determined the mRNA expression levels for one of the largest hitherto analyzed set of 62 839 probesets in 12 representative normal human tissues. Indeed, when using a newly defined graded tissue specificity index tau, valued between 0 for housekeeping genes and 1 for tissue-specific genes, genes with midrange profiles having 0.15< tau<0.85 were found to constitute >50% of all expression patterns. We developed a binary classification, indicating for every gene the I(B) tissues in which it is overly expressed, and the 12-I(B) tissues in which it shows low expression. The 85 dominant midrange patterns with I(B)=2-11 were found to be bimodally distributed, and to contribute most significantly to the definition of tissue specification dendrograms. Our analyses provide a novel route to infer expression profiles for presumed ancestral nodes in the tissue dendrogram. Such definition has uncovered an unsuspected correlation, whereby de novo enhancement and diminution of gene expression go hand in hand. These findings highlight the importance of gene suppression events, with implications to the course of tissue specification in ontogeny and phylogeny. AVAILABILITY All data and analyses are publically available at the GeneNote website, http://genecards.weizmann.ac.il/genenote/ and, GEO accession GSE803. CONTACT doron.lancet@weizmann.ac.il SUPPLEMENTARY INFORMATION Four tables available at the above site.

Human Gene-Centric Databases at the Weizmann Institute of Science: GeneCards, UDB, CroW 21 and HORDE

Recent enhancements and current research in the GeneCards (GC) (http://bioinfo.weizmann.ac.il/cards/) project are described, including the addition of gene expression profiles and integrated gene locations. Also highlighted are the contributions of specialized associated human gene-centric databases developed at the Weizmann Institute. These include the Unified Database (UDB) (http://bioinfo.weizmann.ac.il/udb) for human genome mapping, the human Chromosome 21 database at the Weizmann Insti-tute (CroW 21) (http://bioinfo.weizmann.ac.il/crow21), and the Human Olfactory Receptor Data Explora-torium (HORDE) (http://bioinfo.weizmann.ac.il/HORDE). The synergistic relationships amongst these efforts have positively impacted the quality, quantity and usefulness of the GeneCards gene compendium.

GeneCards™ 2002: towards a complete, object-oriented, human gene compendium

MOTIVATION In the post-genomic era, functional analysis of genes requires a sophisticated interdisciplinary arsenal. Comprehensive resources are challenged to provide consistently improving, state-of-the-art tools. RESULTS GeneCards (Rebhan et al., 1998) has made innovative strides: (a). regular updates and enhancements incorporating new genes enriched with sequences, genomic locations, cDNA assemblies, orthologies, medical information, 3D protein structures, gene expression, and focused SNP summaries; (b). restructured software using object-oriented Perl, migration to schema-driven XML, and (c). pilot studies, introducing methods to produce cards for novel and predicted genes.

Targeted mutagenesis of Lis1 disrupts cortical development and LIS1 homodimerization

Lissencephaly is a severe brain malformation in humans. To study the function of the gene mutated in lissencephaly (LIS1), we deleted the first coding exon from the mouse Lis1 gene. The deletion resulted in a shorter protein (sLIS1) that initiates from the second methionine, a unique situation because most LIS1 mutations result in a null allele. This mutation mimics a mutation described in one lissencephaly patient with a milder phenotype. Homozygotes are early lethal, although heterozygotes are viable and fertile. Most strikingly, the morphology of cortical neurons and radial glia is aberrant in the developing cortex, and the neurons migrate more slowly. This is the first demonstration, to our knowledge, of a cellular abnormality in the migrating neurons after Lis1 mutation. Moreover, cortical plate splitting and thalomocortical innervation are also abnormal. Biochemically, the mutant protein is not capable of dimerization, and enzymatic activity is elevated in the embryos, thus a demonstration of the in vivo role of LIS1 as a subunit of PAF-AH. This mutation allows us to determine a hierarchy of functions that are sensitive to LIS1 dosage, thus promoting our understanding of the role of LIS1 in the developing cortex.

PLATELET-ACTIVATING FACTOR (PAF) ACETYLHYDROLASE ACTIVITY, LIS1 EXPRESSION, AND SEIZURES

Lissencephaly patients are born with severe brain malformations and suffer from recurrent seizures. LIS1, the gene mutated in isolated lissencephaly patients, is a subunit of the heterotrimeric cytosolic enzyme platelet‐activating factor acetylhydrolase (PAF‐AH), interacts with tubulin, and affects microtubule dynamics. In order to gain molecular insights into the possible involvement of LIS1 in seizures in lissencephaly patients, we induced seizures in rats by injection of kainate. PAF‐AH activity was markedly reduced as early as 30 min following initiation of seizures, making this parameter a sensitive indicator of seizure events. PAF‐AH activity returned to and surpassed control values 1 week following initiation of seizures. Expression of LIS1 in the dentate gyrus changed significantly in a manner similar to that of PAF‐AH enzymatic activity. This is the first correlation found between LIS1 expression and PAF‐AH activity. Furthermore, the expression of the α2 catalytic subunit, which is the major PAF‐AH catalytic subunit in rat adult brain, changed in a dramatic fashion. An additional higher‐mobility LIS1 cross‐reactive band was detected in samples isolated a week following seizure occurrence. This LIS1 isoform was enriched in the microtubule‐associated fraction. We propose that LIS1 expression is an important factor in regulation of PAF‐AH activity. We postulate that reductions in LIS1 protein levels found in lissencephaly patients may render them more susceptible to seizures. J. Neurosci. Res. 57:176–184, 1999.

GeneTide—Terra Incognita Discovery Endeavor: a new transcriptome focused member of the GeneCards/GeneNote suite of databases

GeneCards® is an automatically mined database of human genes that strives to create, along with its auxiliary databases—GeneLoc, GeneNote and GeneAnnot—the most inclusive resource of gene-centered information of the human genome. GeneTide, the Gene Terra Incognita Discovery Endeavor (http://genecards.weizmann.ac.il/genetide/), the newest addition to this family, is a transcriptome-focused database which aims to enhance GeneCards with additional expressed sequence tag (EST)-based genes. This is achieved by comprehensively mapping >85% of the ∼5.6 million human ESTs currently available at dbEST to known genes by means of data mining and integration of genomic resources including UniGene, DoTS, AceView and in-house resources. GeneTide thus creates comprehensive links between ESTs and GeneCards genes. Furthermore, groups of unassociated transcripts serve as a basis for defining novel EST-based GeneCards Candidates (EGCs). These EGCs, nearly 25 000 of which were defined in version 0.3 of GeneTide, are further annotated with various parameters, including splicing evidence and expression data extracted from the GeneNote database, to determine their validity as possible de novo genes.

Expression of chLIS1, a chicken homolog of LIS1.

Abstract We have isolated the chicken LIS1 homolog, chLIS1, with DNA sequence similarity of over 68% to the human cDNA and 99% amino acid identity. Additionally, we describe the pattern of chLIS1 expression in the chicken embryo. The early embryonic expression is highly specific to the developing nervous system, whereas later the expression is more widespread.

The GeneCards/spl trade/ family of databases: GeneCards, GeneLoc, GeneNote and GeneAnnot

The popular GeneCards/spl trade/ integrated database of human genes, genomic maps, proteins and diseases has recently spawned three related functional genomics efforts. As sequence data rapidly accumulates, the bottleneck in biology shifts from data production to analysis; researchers seek a profound understanding of the role of each gene, and of the way genes function together. GeneLoc integrates human gene collections by comparing genomic coordinates at the exon level, eliminating redundancies, and assigning unique and meaningful location-based identifiers. GeneCards expression tissue vectors are provided by GeneNote, the first effort to present sophisticated expression analyses for a variety of normal human tissues using the full complement of gene representations (Affymetrix arrays HG-U95A-E). The GeneAnnot system aligns probe-sets with the major public repositories of human mRNA sequences, and provides detailed annotation for each probe-set, with links to GeneCards.

GeneCards/spl trade/ 2002: an evolving human gene compendium

GeneCards/spl trade/ (http://bioinfo.weizmann.ac.il/cards/) is an automated, integrated database of human genes, genomic maps, proteins, and diseases, with software that retrieves, consolidates, searches, and displays human genome information. Over the past few years, the system has consistently, added new features including sequence accessions, genomic locations, cDNA assemblies, orthologies, medical information, 3D protein structures, SNP summaries, and gene expression. In parallel, its infrastructure is being upgraded to use object-oriented Perl to produce, display, and search data that is formatted in Extensible Markup Language (XML, (http://www.w3.org/XML), providing a basis for schema-driven display code and context-specific searches.

GeneTide - Terra Incognita Discovery Endeavor mining ESTs and expression data to elucidate known and de-novo GeneCards/spl reg/ genes

The construction of a complete EST-based gene index is an intricate task yet to be accomplished. GeneTide, the Gene Terra Incognita Discovery Endeavor (http://genecards.weizmann.ac.il/genetide/), which is the newest addition to the GeneCards suite of databases, comprehensively maps >4.5 of the /spl sim/5.5 million human ESTs currently available at dbEST with either known or newly defined putative human genes. The association is accomplished via data mining genomic resources, and integrating using a unified scoring scheme. Groups of unassociated transcripts serve as a basis for defining EST-based gene candidates (EGCs). These EGCs are annotated with various parameters, including expression data, to determine their validity as possible de-novo genes. An immediate application of GeneTide to microarray annotation has increased, in a specific example, the number of annotated Affymetrix HGU95A-E probe sets by 50% in comparison to previous attempts.