Search PubMed⌕ Search

Biomedical subjects

Leroy Hood

Publications and source records attributed to Leroy Hood.

At least 55 records · Page 3Linked to original sources
PubMed2003

Proteomic analysis of human prostasomes.

BACKGROUND: Prostasomes are secretory particles in human seminal fluid. Other than a microscopic description of these secretory particles and an incomplete two-dimensional gel electrophoresis (2DE) study, little is known about the composition of proteins in prostasomes. METHODS: We employed a direct iterative approach using Gas phase fractionation and microcapillary HPLC-tandem mass spectrometry (microLC-MS/MS) to catalogue the prostasome proteome. RESULTS: We identified 139 proteins that can be divided into the following categories: (1). enzymes (33.8% of total), (2). transport/structural (19.4% of total), (3). GTP proteins (14.4% of total), (4). chaperone proteins (5.8% of total), (5). signal transduction proteins (17.3% of total), and (6). unannotated proteins (9.4% of total). A total of 128 of the 139 proteins have not previously been described as prostasomal. CONCLUSIONS: The proteins identified can be used as reference dataset in future work comparing prostasome proteins between normal and pathological states such as prostate cancer, benign prostatic hyperplasia, prostatitis, and infertility.

Enzymes↗
PubMed2003

Self-organized living systems: conjunction of a stable organization with chaotic fluctuations in biological space-time.

Living systems have paradoxical thermodynamic stability, the intrinsic property of self-organization, fluctuation and adaptation to their changing environment. Knowledge accumulated in the analytical reductionist framework has provided useful systematic descriptions of biological systems which appear to be insufficient to gain deep understanding of their behaviour in physiologic conditions and diseases. A state-of-the-art functional genomics study in yeast points to the current inability to appraise 'biological noise', leading to focus on few genes, transcripts and proteins subject to major detectable changes, while currently inaccessible small fluctuations may be major determinants of the behaviour of biological systems. We conjecture that biological systems self-organize because they operate as a conjunction between the relatively variable part of a stable organization and the relatively stable part of a chaotic network of fluctuations, and in a space with a changing number of dimensions: biological space-time. We propose to complement the precepts of the analytical reductionist framework with those of the biosystemic paradigm, in order to explore these conjectures for systems biology, combining in an iterative mode systemic modelling of biological systems, to generate hypotheses, with a high level of standardization of high-throughput experimental platforms, enabling detection of small changes of low-intensity signals, to test them.

Adaptation, Physiological↗
PubMed2003

Predicting demographic group structures based on DNA sequence data.

The ability to infer relationships between groups of sequences, either by searching for their evolutionary history or by comparing their sequence similarity, can be a crucial step in hypothesis testing. Interpreting relationships of human immunodeficiency virus type 1 (HIV-1) sequences can be challenging because of their rapidly evolving genomes, but it may also lead to a better understanding of the underlying biology. Several studies have focused on the evolution of HIV-1, but there is little information to link sequence similarities and evolutionary histories of HIV-1 to the epidemiological information of the infected individual. Our goal was to correlate patterns of HIV-1 genetic diversity with epidemiological information, including risk and demographic factors. These correlations were then used to predict epidemiological information through analyzing short stretches of HIV-1 sequence. Using standard phylogenetic and phenetic techniques on 100 HIV-1 subtype B sequences, we were able to show some correlation between the viral sequences and the geographic area of infection and the risk of men who engage in sex with men. To help identify more subtle relationships between the viral sequences, the method of multidimensional scaling (MDS) was performed. That method identified statistically significant correlations between the viral sequences and the risk factors of men who engage in sex with men and individuals who engage in sex with injection drug users or use injection drugs themselves. Using tree construction, MDS, and newly developed likelihood assignment methods on the original 100 samples we sequenced, and also on a set of blinded samples, we were able to predict demographic/risk group membership at a rate statistically better than by chance alone. Such methods may make it possible to identify viral variants belonging to specific demographic groups by examining only a small portion of the HIV-1 genome. Such predictions of demographic epidemiology based on sequence information may become valuable in assigning different treatment regimens to infected individuals.

Adolescent↗
PubMed2003

ACGT-a comparative genomics tool.

SUMMARY: ACGT (a comparative genomics tool) is a genomic DNA sequence comparison viewer and analyzer. It can read a pair of DNA sequences in GenBank, Embl or Fasta formats, with or without a comparison file, and provide users with many options to view and analyze the similarities between the input sequences. It is written in Java and can be run on Unix, Linux and Windows platforms. AVAILABILITY: The ACGT program is freely available with documentation and examples at website: http://db.systemsbiology.net/projects/local/mhc/acgt/

Computer Graphics↗
PubMed2003

Regulatory gene networks and the properties of the developmental process.

Genomic instructions for development are encoded in arrays of regulatory DNA. These specify large networks of interactions among genes producing transcription factors and signaling components. The architecture of such networks both explains and predicts developmental phenomenology. Although network analysis is yet in its early stages, some fundamental commonalities are already emerging. Two such are the use of multigenic feedback loops to ensure the progressivity of developmental regulatory states and the prevalence of repressive regulatory interactions in spatial control processes. Gene regulatory networks make it possible to explain the process of development in causal terms and eventually will enable the redesign of developmental regulatory circuitry to achieve different outcomes.

Animals↗
PubMed2003

The digital code of DNA.

The discovery of the structure of DNA transformed biology profoundly, catalysing the sequencing of the human genome and engendering a new view of biology as an information science. Two features of DNA structure account for much of its remarkable impact on science: its digital nature and its complementarity, whereby one strand of the helix binds perfectly with its partner. DNA has two types of digital information--the genes that encode proteins, which are the molecular machines of life, and the gene regulatory networks that specify the behaviour of the genes.

Animals↗
PubMed2003

The DNA sequence and analysis of human chromosome 14.

Chromosome 14 is one of five acrocentric chromosomes in the human genome. These chromosomes are characterized by a heterochromatic short arm that contains essentially ribosomal RNA genes, and a euchromatic long arm in which most, if not all, of the protein-coding genes are located. The finished sequence of human chromosome 14 comprises 87,410,661 base pairs, representing 100% of its euchromatic portion, in a single continuous segment covering the entire long arm with no gaps. Two loci of crucial importance for the immune system, as well as more than 60 disease genes, have been localized so far on chromosome 14. We identified 1,050 genes and gene fragments, and 393 pseudogenes. On the basis of comparisons with other vertebrate genomes, we estimate that more than 96% of the chromosome 14 genes have been annotated. From an analysis of the CpG island occurrences, we estimate that 70% of these annotated genes are complete at their 5' end.

5' Untranslated Regions↗
PubMed2003

Systems biology: integrating technology, biology, and computation.

The Human Genome Project has changed the worlds of biology and medicine-helping to catalyze two major paradigm changes: systems biology and predictive, preventive and personalized medicine. These two themes will dominate 21st century biology and medicine. I will discuss these changes and indicate how they may interface with with the process of aging.

Animals↗
PubMed2003

Isolation and characterization of human and mouse WDR19,a novel WD-repeat protein exhibiting androgen-regulated expression in prostate epithelium.

Androgens regulate important processes involved in the normal development and function of the human and rodent prostate glands. Here we report the isolation and characterization of a new androgen-regulated gene, designated WDR19, that encodes repeating sequence motifs found in the WD-repeat family of proteins. The WD repeat is a conserved domain of approximately 40 amino acids that is typically bracketed by glycine-histidine and tryptophan-aspartic acid (WD) dipeptides. WD-repeat proteins are a large group of structurally related proteins that participate in a wide range of cellular functions, including transmembrane signaling, mRNA modification, vesicle formation, and vesicular trafficking. The WDR19 gene comprises 36 exons and is located on chromosome 4p15-4p11. The predicted protein contains six WD repeats, a clathrin heavy-chain repeat, and three transmembrane domains. Sequence analysis reveals that the WDR19 gene is conserved from Caenorhabditis elegans to human. WDR19 is expressed in normal and neoplastic prostate epithelium as demonstrated by RNA in situ hybridization and is regulated by androgenic hormones. WDR19 transcripts exhibit alternative splicing in which two isoforms appear to be prostate restricted, a property that could be exploited for designing diagnostic or therapeutic strategies for prostate carcinoma.

Alternative Splicing↗
PubMed2003

Hematopoietic stem cells contribute to the regeneration of renal tubules after renal ischemia-reperfusion injury in mice.

Ischemia-reperfusion injury (I/R injury) is a common cause of acute renal failure. Recovery from I/R injury requires renal tubular regeneration. Hematopoietic stem cells (HSC) have been shown to be capable of differentiating into hepatocytes, cardiac myocytes, gastrointestinal epithelial cells, and vascular endothelial cells during tissue repair. The current study tested the hypothesis that murine HSC can contribute to the regeneration of renal tubular epithelial cells after I/R injury. HSC isolated from male Rosa26 mice that express beta-galactosidase constitutively were transplanted into female nontransgenic mice after unilateral renal I/R injury. Four weeks after HSC transplantation, beta-galactosidase-positive cells were detected in renal tubules of the recipients by X-Gal staining. PCR analysis of the male-specific Sry gene and Y chromosome fluorescence in situ hybridization confirmed the presence of male-derived cells in the kidneys of female recipients. Antibody co-staining showed that beta-galactosidase was primarily expressed in renal proximal tubules. This is the first report to show that HSC can differentiate into renal tubular cells after I/R injury. Because of their availability, HSC may be useful for cell replacement therapy of acute renal failure.

Animals↗
PubMed2003

Analysis of the gene-dense major histocompatibility complex class III region and its comparison to mouse.

In mammals, the Major Histocompatibility Complex class I and II gene clusters are separated by an approximately 700-kb stretch of sequence called the MHC class III region, which has been associated with susceptibility to numerous diseases. To facilitate understanding of this medically important and architecturally interesting portion of the genome, we have sequenced and analyzed both the human and mouse class III regions. The cross-species comparison has facilitated the identification of 60 genes in human and 61 in mouse, including a potential RNA gene for which the introns are more conserved across species than the exons. Delineation of global organization, gene structure, alternative splice forms, protein similarities, and potential cis-regulatory elements leads to several conclusions: (1) The human MHC class III region is the most gene-dense region of the human genome: >14% of the sequence is coding, approximately 72% of the region is transcribed, and there is an average of 8.5 genes per 100 kb. (2) Gene sizes, number of exons, and intergenic distances are for the most part similar in both species, implying that interspersed repeats have had little impact in disrupting the tight organization of this densely packed set of genes. (3) The region contains a heterogeneous mixture of genes, only a few of which have a clearly defined and proven function. Although many of the genes are of ancient origin, some appear to exist only in mammals and fish, implying they might be specific to vertebrates. (4) Conserved noncoding sequences are found primarily in or near the 5'-UTR or the first intron of genes, and seldom in the intergenic regions. Many of these conserved blocks are likely to be cis-regulatory elements.

Alternative Splicing↗
PubMed2003

Initial proteome analysis of model microorganism Haemophilus influenzae strain Rd KW20.

The proteome of Haemophilus influenzae strain Rd KW20 was analyzed by liquid chromatography (LC) coupled with ion trap tandem mass spectrometry (MS/MS). This approach does not require a gel electrophoresis step and provides a rapidly developed snapshot of the proteome. In order to gain insight into the central metabolism of H. influenzae, cells were grown microaerobically and anaerobically in a rich medium and soluble and membrane proteins of strain Rd KW20 were proteolyzed with trypsin and directly examined by LC-MS/MS. Several different experimental and computational approaches were utilized to optimize the proteome coverage and to ensure statistically valid protein identification. Approximately 25% of all predicted proteins (open reading frames) of H. influenzae strain Rd KW20 were identified with high confidence, as their component peptides were unambiguously assigned to tandem mass spectra. Approximately 80% of the predicted ribosomal proteins were identified with high confidence, compared to the 33% of the predicted ribosomal proteins detected by previous two-dimensional gel electrophoresis studies. The results obtained in this study are generally consistent with those obtained from computational genome analysis, two-dimensional gel electrophoresis, and whole-genome transposon mutagenesis studies. At least 15 genes originally annotated as conserved hypothetical were found to encode expressed proteins. Two more proteins, previously annotated as predicted coding regions, were detected with high confidence; these proteins also have close homologs in related bacteria. The direct proteomics approach to studying protein expression in vivo reported here is a powerful method that is applicable to proteome analysis of any (micro)organism.

Aerobiosis↗
PubMed2002

Coordinate regulation of energy transduction modules in Halobacterium sp. analyzed by a global systems approach.

The extremely halophilic archaeon Halobacterium NRC-1 can switch from aerobic energy production (energy from organic compounds) to anaerobic phototrophy (energy from light) by induction of purple membrane biogenesis. The purple membrane is made up of multiple copies of a 1:1 complex of bacterioopsin (Bop) and retinal called bacteriorhodopsin that functions as a light-driven proton pump. A light- and redox-sensing transcription regulator, Bat, regulates critical genes encoding the biogenesis of the purple membrane. To better understand the regulatory network underlying this physiological state, we report a systems approach using global mRNA and protein analyses of four strains of Halobacterium sp.: the wild-type, NRC-1; and three genetically perturbed strains: S9 (bat+), a purple membrane overproducer, and two purple membrane deficient strains, SD23 (a bop knockout) and SD20 (a bat knockout). The integrated DNA microarray and proteomic data reveal the coordinated coregulation of several interconnected biochemical pathways for phototrophy: isoprenoid synthesis, carotenoid synthesis, and bacteriorhodopsin assembly. In phototrophy, the second major biomodule for ATP production, arginine fermentation, is repressed. The primary systems level insight provided by this study is that two major energy production pathways in Halobacterium sp., phototrophy and arginine fermentation, are inversely regulated, presumably to achieve a balance in ATP production under anaerobic conditions.

Adenosine Triphosphate↗
PubMed2002

QUOD ERAT FACIENDUM: sequence analysis of the H2-D and H2-Q regions of 129/SvJ mice.

The H2-D and -Q regions of the mouse major histocompatibility complex ( Mhc or H2) have been sequenced from strain 129/SvJ (haplotype bc), revealing a D/Q region different from all other investigated haplotypes, including the closely related b haplotype. The 300-kb class I-rich region consists of the classical class I, H2-D, and 11 non-classical class I genes. The Q region was formed by two series of tandem duplications. Comparison of the segment between the D and Q1 genes with the H2-K region provides evidence that class I genes were translocated from the K region to the D region, and gives a new explanation for the weak locus specificity of the H-Kand H2-Dalleles.

Amino Acid Sequence↗
PubMed2002

The program of androgen-responsive genes in neoplastic prostate epithelium.

The human prostate gland is an important target organ of androgenic hormones. Testosterone and dihydrotestosterone interact with the androgen receptor to regulate vital aspects of prostate growth and function including cellular proliferation, differentiation, apoptosis, metabolism, and secretory activity. Our objective in this study was to characterize the temporal program of transcription that reflects the cellular response to androgens and to identify specific androgen-regulated genes (ARGs) or gene networks that participate in these responses. We used cDNA microarrays representing about 20,000 distinct human genes to profile androgen-responsive transcripts in the LNCaP adenocarcinoma cell line and identified 146 genes with transcript alterations more than 3-fold. Of these, 103 encode proteins with described functional roles, and 43 represent transcripts that have yet to be characterized. Temporal gene expression profiles grouped the ARGs into four distinct cohorts. Five uncharacterized ARGs demonstrated exclusive or high expression levels in the prostate relative to other tissues studied. A search of available DNA sequence upstream of 28 ARGs identified 25 with homology to the androgen response-element consensus-binding motif. These results identify previously uncharacterized and unsuspected genes whose expression levels are directly or indirectly regulated by androgens; further, they provide a comprehensive temporal view of the transcriptional program of human androgen-responsive cells.

Amino Acid Motifs↗
PubMed2002

Whole-genome shotgun assembly and analysis of the genome of Fugu rubripes.

The compact genome of Fugu rubripes has been sequenced to over 95% coverage, and more than 80% of the assembly is in multigene-sized scaffolds. In this 365-megabase vertebrate genome, repetitive DNA accounts for less than one-sixth of the sequence, and gene loci occupy about one-third of the genome. As with the human genome, gene loci are not evenly distributed, but are clustered into sparse and dense regions. Some "giant" genes were observed that had average coding sequence sizes but were spread over genomic lengths significantly larger than those of their human orthologs. Although three-quarters of predicted human proteins have a strong match to Fugu, approximately a quarter of the human proteins had highly diverged from or had no pufferfish homologs, highlighting the extent of protein evolution in the 450 million years since teleosts and mammals diverged. Conserved linkages between Fugu and human genes indicate the preservation of chromosomal segments from the common vertebrate ancestor, but with considerable scrambling of gene order.

Animals↗
PubMed2002

A provisional regulatory gene network for specification of endomesoderm in the sea urchin embryo.

We present the current form of a provisional DNA sequence-based regulatory gene network that explains in outline how endomesodermal specification in the sea urchin embryo is controlled. The model of the network is in a continuous process of revision and growth as new genes are added and new experimental results become available; see http://www.its.caltech.edu/~mirsky/endomeso.htm (End-mes Gene Network Update) for the latest version. The network contains over 40 genes at present, many newly uncovered in the course of this work, and most encoding DNA-binding transcriptional regulatory factors. The architecture of the network was approached initially by construction of a logic model that integrated the extensive experimental evidence now available on endomesoderm specification. The internal linkages between genes in the network have been determined functionally, by measurement of the effects of regulatory perturbations on the expression of all relevant genes in the network. Five kinds of perturbation have been applied: (1) use of morpholino antisense oligonucleotides targeted to many of the key regulatory genes in the network; (2) transformation of other regulatory factors into dominant repressors by construction of Engrailed repressor domain fusions; (3) ectopic expression of given regulatory factors, from genetic expression constructs and from injected mRNAs; (4) blockade of the beta-catenin/Tcf pathway by introduction of mRNA encoding the intracellular domain of cadherin; and (5) blockade of the Notch signaling pathway by introduction of mRNA encoding the extracellular domain of the Notch receptor. The network model predicts the cis-regulatory inputs that link each gene into the network. Therefore, its architecture is testable by cis-regulatory analysis. Strongylocentrotus purpuratus and Lytechinus variegatus genomic BAC recombinants that include a large number of the genes in the network have been sequenced and annotated. Tests of the cis-regulatory predictions of the model are greatly facilitated by interspecific computational sequence comparison, which affords a rapid identification of likely cis-regulatory elements in advance of experimental analysis. The network specifies genomically encoded regulatory processes between early cleavage and gastrula stages. These control the specification of the micromere lineage and of the initial veg(2) endomesodermal domain; the blastula-stage separation of the central veg(2) mesodermal domain (i.e., the secondary mesenchyme progenitor field) from the peripheral veg(2) endodermal domain; the stabilization of specification state within these domains; and activation of some downstream differentiation genes. Each of the temporal-spatial phases of specification is represented in a subelement of the network model, that treats regulatory events within the relevant embryonic nuclei at particular stages.

Animals↗