Michael J Lombardi

Brigham and Women's Hospital , Boston, Massachusetts, United States

Are you Michael J Lombardi?

Claim your profile

Publications (8)82.59 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Over the last decade, the introduction of microarray technology has had a profound impact on gene expression research. The publication of studies with dissimilar or altogether contradictory results, obtained using different microarray platforms to analyze identical RNA samples, has raised concerns about the reliability of this technology. The MicroArray Quality Control (MAQC) project was initiated to address these concerns, as well as other performance and data analysis issues. Expression data on four titration pools from two distinct reference RNA samples were generated at multiple test sites using a variety of microarray-based and alternative technology platforms. Here we describe the experimental design and probe mapping efforts behind the MAQC project. We show intraplatform consistency across test sites as well as a high level of interplatform concordance in terms of genes identified as differentially expressed. This study provides a resource that represents an important first step toward establishing a framework for the use of microarrays in clinical and regulatory settings.
    Nature Biotechnology 10/2006; 24(9):1151-61. · 32.44 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Over the last decade, gene expression microarrays have had a profound impact on biomedical research. The diversity of platforms and analytical methods available to researchers have made the comparison of data from multiple platforms challenging. In this study, we describe a framework for comparisons across platforms and laboratories. We have attempted to include nearly all the available commercial and 'in-house' platforms. Using probe sequences matched at the exon level improved consistency of measurements across the different microarray platforms compared to annotation-based matches. Generally, consistency was good for highly expressed genes, and variable for genes with lower expression values as confirmed by quantitative real-time (QRT)-PCR. Concordance of measurements was higher between laboratories on the same platform than across platforms. We demonstrate that, after stringent preprocessing, commercial arrays were more consistent than in-house arrays, and by most measures, one-dye platforms were more consistent than two-dye platforms.
    Nature Biotechnology 08/2006; 24(7):832-40. · 32.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Significant, sex-associated differences exist in the physiology and pathophysiology of the lacrimal gland. We hypothesize that many of these differences are due to fundamental variations in gene expression. The purpose of this study was to determine the extent to which sex-related differences in gene expression are present in the lacrimal gland. Lacrimal glands were obtained from adult male and female BALB/c mice (n=5-10mice/sex/experiment), pooled according to sex and processed for the isolation of RNA. Samples were analyzed for differentially expressed mRNAs by using Atlas Mouse cDNA Expression Arrays, cDNA amplification techniques, GEM 1 and 2 gene chips, CodeLink bioarrays and quantitative real-time PCR (qPCR) procedures. Quantitative evaluation of Atlas Array gene expression was performed with an image analysis system developed in our laboratory, whereas gene chip data were analyzed with Rosetta Resolver and GeneSifter.Net software. Statistical significance was determined by using Student's t-test. Our results with CodeLink bioarrays show that sex has a significant influence on the expression of over 490 genes in the mouse lacrimal gland. These genes are involved in a wide range of biological processes, molecular functions and cellular components, including such activities as development, growth, transcription, metabolism, signal transduction, transport, receptor activity and protein and nucleic acid binding. The expression of selected genes was confirmed by the use of GEM gene chips and qPCR. Our findings also demonstrate that certain methodological approaches are less useful in attempting to assess the magnitude of sex-associated differences in the lacrimal gland. These results support our hypothesis that sex-related differences in gene expression play a role in the sexual dimorphism of the lacrimal gland.
    Experimental Eye Research 02/2006; 82(1):13-23. · 3.03 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The hypothesis tested in the study was that the effect of estrogen and progesterone on the lacrimal gland is mediated through specific receptors and that hormonal effects involve the regulation of gene expression and protein synthesis. Lacrimal glands were collected from young adult, ovariectomized mice, that were treated with 17beta-estradiol, progesterone, 17beta-estradiol plus progesterone or vehicle for 2 weeks. Glands were pooled according to treatment, processed for the isolation of RNA, and evaluated for differentially expressed mRNAs by using gene microarrays. Bioarray data were analyzed with sophisticated bioinformatics and statistical programs. The expression of selected genes was verified by using gene chips and quantitative real-time PCR methods. The results demonstrate that 17beta-estradiol, progesterone, or both hormones together significantly influences the expression of hundreds of genes in the mouse lacrimal gland. Sex steroid treatment led to numerous alterations in gene activities related to transcriptional control, cell growth and/or maintenance, cell communication, signal transduction, enzyme catalysis, immune expression, and the binding and metabolism of nucleic acids and proteins. A number of the 17beta-estradiol, progesterone or 17beta-estradiol plus progesterone effects on gene expression were similar, but most were unique to each treatment. Of particular interest was the finding that these hormones seem to contribute little to the known sex-related differences in gene expression of the lacrimal gland. These results support the hypothesis that estrogen's and progesterone's action on the lacrimal gland involves the regulation of numerous genes. However, these hormone effects do not appear to represent a major factor underlying the sexual dimorphism of gene expression in lacrimal tissue.
    Investigative Ophthalmology &amp Visual Science 02/2006; 47(1):158-68. · 3.44 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In prior work, it has been found that the meibomian gland is an androgen target organ, that androgens modulate lipid production within this tissue, and that androgen deficiency is associated with glandular dysfunction and evaporative dry eye. This study's purpose was to test the hypothesis that the androgen control of the meibomian gland involves the regulation of gene expression. Meibomian glands were obtained from orchiectomized mice that were treated with placebo or testosterone for 14 days. Tissues were processed for the analysis of differentially expressed mRNAs by using gene bioarrays, gene chips, and real-time PCR procedures. Bioarray data were analyzed with GeneSifter software (VizX Labs LLC, Seattle, WA). The results show that testosterone influenced the expression of more than 1590 genes in the mouse meibomian gland. This hormone action involved a significant upregulation of 1080 genes (e.g., neuromedin B), and a significant downregulation of 518 genes (e.g., small proline-rich protein 2A). Some of the most significant androgen effects were directed toward stimulation of genes associated with lipid metabolism, sterol biosynthesis, fatty acid metabolism, protein transport, oxidoreductase activity, and peroxisomes. These findings demonstrate that testosterone regulates the expression of numerous genes in the mouse meibomian gland and that many of these genes are involved in lipid metabolic pathways.
    Investigative Ophthalmology &amp Visual Science 11/2005; 46(10):3666-75. · 3.44 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The objective of this study was to determine the nature and extent of androgen influence on gene expression in the lacrimal gland. Lacrimal glands were obtained from orchiectomized mice that had been treated with testosterone or vehicle for 2 weeks, as well as from testicular feminized mice and their Tabby controls. Samples were pooled according to experiment, processed for the isolation of RNA, and analyzed for differentially expressed mRNAs by using primarily CodeLink Bioarrays, GEM 1 and 2 gene chips and quantitative real-time PCR (qPCR) procedures. Gene chip data were analyzed with GeneSifter.Net software. Our results demonstrate that testosterone regulates the expression of over 2000 genes in the lacrimal gland. Gene ontologies most affected by androgen treatment included those related to cell growth, proliferation and metabolism, cell communication and transport, nucleic acid binding, signal transduction and receptor activities. Our findings also indicate that androgen action may be mediated, at least in part, through classical androgen receptors, and may contribute to the sex-related differences in gene expression of lacrimal tissue. Overall, these results support our working hypothesis that androgen action on the lacrimal gland is mediated primarily through a receptor-associated regulation of gene transcription.
    The Journal of Steroid Biochemistry and Molecular Biology 10/2005; 96(5):401-13. · 3.98 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Sex-related differences exist in the structure and function of the major glands in a variety of species. Moreover, many of these variations appear to be unique to each tissue. We hypothesized that this sexual dimorphism is due, at least in part, to gland-specific differences in gene expression between males and females. Glands were collected from male and female BALB/c mice (n = 5/sex/experiment), and total RNA was isolated. Samples were analyzed for differentially expressed mRNAs with CodeLink microarrays, and data were evaluated by GeneSifter. Our results demonstrate that significant (P < 0.05) sex-related differences exist in the expression of numerous genes in the major salivary glands, and many of these differences were tissue-specific. These findings support our hypothesis that sex-related differences in the salivary glands are due, at least in part, to tissue-specific variations in gene expression.
    Journal of Dental Research 03/2005; 84(2):160-5. · 3.83 Impact Factor
  • Neurobiology of Aging - NEUROBIOL AGING. 01/2004; 25.

Publication Stats

1k Citations
82.59 Total Impact Points

Institutions

  • 2005–2006
    • Brigham and Women's Hospital
      • Center for Neurologic Diseases
      Boston, Massachusetts, United States
    • Schepens Eye Research Institute
      Boston, Massachusetts, United States
    • Massachusetts Eye and Ear Infirmary
      • Schepens Eye Research Institute
      Boston, MA, United States