Gilles Leblanc

Bio: Gilles Leblanc is an academic researcher from Laval University. The author has contributed to research in topics: Gene & Complementary DNA. The author has an hindex of 14, co-authored 17 publications receiving 1870 citations.

A candidate prostate cancer susceptibility gene at chromosome 17p.

Abstract: It is difficult to identify genes that predispose to prostate cancer due to late age at diagnosis, presence of phenocopies within high-risk pedigrees and genetic complexity. A genome-wide scan of large, high-risk pedigrees from Utah has provided evidence for linkage to a locus on chromosome 17p. We carried out positional cloning and mutation screening within the refined interval, identifying a gene, ELAC2, harboring mutations (including a frameshift and a nonconservative missense change) that segregate with prostate cancer in two pedigrees. In addition, two common missense variants in the gene are associated with the occurrence of prostate cancer. ELAC2 is a member of an uncharacterized gene family predicted to encode a metal-dependent hydrolase domain that is conserved among eukaryotes, archaebacteria and eubacteria. The gene product bears amino acid sequence similarity to two better understood protein families, namely the PSO2 (SNM1) DNA interstrand crosslink repair proteins and the 73-kD subunit of mRNA 3' end cleavage and polyadenylation specificity factor (CPSF73).

Full Length cDNA Structure and Deduced Amino Acid Sequence of Human β-Hydroxy-5-Ene Steroid Dehydrogenase

Abstract: Polyclonal antibodies raised against 3β-hydroxysteroid dehydrogenase isolated from human placenta were used to screen a λgt11 expression cDNA library from the same tissue. The protein deduced from cDNA sequences contains 372 amino acids with a calculated mol wt of 42,216. Since 3β-hydroxysteroid dehydrogenase is the enzyme catalyzing the formation of all classes of hormonal steroids, the availability of the cDNA encoding this enzyme opens new possibilities for a detailed investigation of the factors regulating the expression and activity of this crucial enzyme in adrenal, gonadal as well as peripheral tissues. INTRODUCTION The formation of Δ4-3-keto steroids from Δ5-ene, 3β-hydroxy precursors is a key step in the biosynthesis of all classes of hormonal steroids, namely glucocorticoids, mineralocorticoids, progesterone, androgens, and estrogens. This reaction is catalyzed by the enzymatic system 3β-hydroxy-5-ene-steroid dehydrogenase (EC 1.1.1.145) and steroid Δ5-Δ4-ene-isomerase (EC-5.3.3.1), hereafter ca...

Characterization of cDNAs for Human Estradiol 17β-Dehydrogenase and Assignment of the Gene to Chromosome 17: Evidence of two mRNA Species with Distinct 5′-Termini in Human Placenta

Abstract: Human placental estradiol 17β-dehydrogenase (E2DH) cDNA clones were isolated from a λgt11 expression library by screening with 33 mer synthetic oligonucleotides derived from the amino acid sequence of the catalytic site of E2DH and with polyclonal antibodies raised against the enzyme purified from human placenta. Using 32P-labeled fragments from the coding and 5′-untranslated regions, two mRNA species have been identified in poly(A)+ RNA from human placenta, a major species migrating at 1.3 kilobases (kb) while a minor one is found at 2.2 kb. Primer extension analysis identifies the major mRNA as starting 9–10 nucleotides upstream from the in-frame ATG initiating codon while the longer mRNA has at least 814 noncoding nucleotides at its 5′-terminus. Sequence analysis of the longest cDNA clone (2092 base pairs) shows that this clone possesses identical coding and noncoding sequences in the regions of overlap with the shorter cDNA clones. The 32P-labeled 5′-noncoding fragment hybridized only to the 2.2 kb ba...

Structure of two in tandem human 17β-hydroxysteroid dehydrogenase genes

Abstract: Two human 17β-hydroxysteroid dehydrogenase (17β-HSD) genes (h17β-HSDI and h17β-HSDII) included in tandem within an approximately 13 kilobase pair fragment were isolated from a genomic λEMBL3 DNA library using cDNA encoding human 17β-HSD (hpE2DH216) as probe. We have determined the complete exon and intron sequences of the two genes as well as their 5′ and 3′-flanking regions. Human 17β-HSDII contains six exons and five short introns for a total length of 3250 base pairs. The exon sequence of h17β-HSDII is identical to the previously reported hpE2DH216 cDNA while the overlapping nucleotide sequences of the corresponding exons and introns of h17β-HSDI and h170-HSDII show 89% homology. In addition, we have used the hpE2DH216 cDNA to demonstrate the widespread expression of 17β-HSD mRNAs in steroidogenic and peripheral target tissues. These new findings provide the basis for a better understanding of the molecular mechanisms involved in 17β-HSD deficiency and peripheral sex steroid metabolism.

Extra Precision Glide: Docking and Scoring Incorporating a Model of Hydrophobic Enclosure for Protein-Ligand Complexes

Abstract: A novel scoring function to estimate protein-ligand binding affinities has been developed and implemented as the Glide 4.0 XP scoring function and docking protocol. In addition to unique water desolvation energy terms, protein-ligand structural motifs leading to enhanced binding affinity are included: (1) hydrophobic enclosure where groups of lipophilic ligand atoms are enclosed on opposite faces by lipophilic protein atoms, (2) neutral-neutral single or correlated hydrogen bonds in a hydrophobically enclosed environment, and (3) five categories of charged-charged hydrogen bonds. The XP scoring function and docking protocol have been developed to reproduce experimental binding affinities for a set of 198 complexes (RMSDs of 2.26 and 1.73 kcal/mol over all and well-docked ligands, respectively) and to yield quality enrichments for a set of fifteen screens of pharmaceutical importance. Enrichment results demonstrate the importance of the novel XP molecular recognition and water scoring in separating active and inactive ligands and avoiding false positives.

Linkage of early-onset familial breast cancer to chromosome 17q21

Abstract: Human breast cancer is usually caused by genetic alterations of somatic cells of the breast, but occasionally, susceptibility to the disease is inherited. Mapping the genes responsible for inherited breast cancer may also allow the identification of early lesions that are critical for the development of breast cancer in the general population. Chromosome 17q21 appears to be the locale of a gene for inherited susceptibility to breast cancer in families with early-onset disease. Genetic analysis yields a lod score (logarithm of the likelihood ratio for linkage) of 5.98 for linkage of breast cancer susceptibility to D17S74 in early-onset families and negative lod scores in families with late-onset disease. Likelihood ratios in favor of linkage heterogeneity among families ranged between 2000:1 and greater than 10(6):1 on the basis of multipoint analysis of four loci in the region.

Score Tests for Association between Traits and Haplotypes when Linkage Phase Is Ambiguous

Abstract: A key step toward the discovery of a gene related to a trait is the finding of an association between the trait and one or more haplotypes. Haplotype analyses can also provide critical information regarding the function of a gene; however, when unrelated subjects are sampled, haplotypes are often ambiguous because of unknown linkage phase of the measured sites along a chromosome. A popular method of accounting for this ambiguity in case-control studies uses a likelihood that depends on haplotype frequencies, so that the haplotype frequencies can be compared between the cases and controls; however, this traditional method is limited to a binary trait (case vs. control), and it does not provide a method of testing the statistical significance of specific haplotypes. To address these limitations, we developed new methods of testing the statistical association between haplotypes and a wide variety of traits, including binary, ordinal, and quantitative traits. Our methods allow adjustment for nongenetic covariates, which may be critical when analyzing genetically complex traits. Furthermore, our methods provide several different global tests for association, as well as haplotype-specific tests, which give a meaningful advantage in attempts to understand the roles of many different haplotypes. The statistics can be computed rapidly, making it feasible to evaluate the associations between many haplotypes and a trait. To illustrate the use of our new methods, they are applied to a study of the association of haplotypes (composed of genes from the human-leukocyte-antigen complex) with humoral immune response to measles vaccination. Limited simulations are also presented to demonstrate the validity of our methods, as well as to provide guidelines on how our methods could be used.

The molecular biology, biochemistry, and physiology of human steroidogenesis and its disorders.

Abstract: Steroidogenesis entails processes by which cholesterol is converted to biologically active steroid hormones. Whereas most endocrine texts discuss adrenal, ovarian, testicular, placental, and other steroidogenic processes in a gland-specific fashion, steroidogenesis is better understood as a single process that is repeated in each gland with cell-type-specific variations on a single theme. Thus, understanding steroidogenesis is rooted in an understanding of the biochemistry of the various steroidogenic enzymes and cofactors and the genes that encode them. The first and rate-limiting step in steroidogenesis is the conversion of cholesterol to pregnenolone by a single enzyme, P450scc (CYP11A1), but this enzymatically complex step is subject to multiple regulatory mechanisms, yielding finely tuned quantitative regulation. Qualitative regulation determining the type of steroid to be produced is mediated by many enzymes and cofactors. Steroidogenic enzymes fall into two groups: cytochrome P450 enzymes and hydroxysteroid dehydrogenases. A cytochrome P450 may be either type 1 (in mitochondria) or type 2 (in endoplasmic reticulum), and a hydroxysteroid dehydrogenase may belong to either the aldo-keto reductase or short-chain dehydrogenase/reductase families. The activities of these enzymes are modulated by posttranslational modifications and by cofactors, especially electron-donating redox partners. The elucidation of the precise roles of these various enzymes and cofactors has been greatly facilitated by identifying the genetic bases of rare disorders of steroidogenesis. Some enzymes not principally involved in steroidogenesis may also catalyze extraglandular steroidogenesis, modulating the phenotype expected to result from some mutations. Understanding steroidogenesis is of fundamental importance to understanding disorders of sexual differentiation, reproduction, fertility, hypertension, obesity, and physiological homeostasis.

Androgen Receptor in Prostate Cancer

Abstract: The normal development and maintenance of the prostate is dependent on androgen acting through the androgen receptor (AR). AR remains important in the development and progression of prostate cancer. AR expression is maintained throughout prostate cancer progression, and the majority of androgen-independent or hormone refractory prostate cancers express AR. Mutation of AR, especially mutations that result in a relaxation of AR ligand specificity, may contribute to the progression of prostate cancer and the failure of endocrine therapy by allowing AR transcriptional activation in response to antiandrogens or other endogenous hormones. Similarly, alterations in the relative expression of AR coregulators have been found to occur with prostate cancer progression and may contribute to differences in AR ligand specificity or transcriptional activity. Prostate cancer progression is also associated with increased growth factor production and an altered response to growth factors by prostate cancer cells. The kinase signal transduction cascades initiated by mitogenic growth factors modulate the transcriptional activity of AR and the interaction between AR and AR coactivators. The inhibition of AR activity through mechanisms in addition to androgen ablation, such as modulation of signal transduction pathways, may delay prostate cancer progression.