In silico Northern blot, an automated method to determine expression patterns from EST databases, reveals tissue specificity of murine 17beta-hydroxysteroid dehydrogenase type 11

Evolution of Gene Expression Balance Among Homeologs of Natural Polyploids

Polyploidy is a major evolutionary process in eukaryotes, yet the expression balance of homeologs in natural polyploids is largely unknown. To study this expression balance, the expression patterns of 2180 structurally well-characterized genes of wheat were studied, of which 813 had the expected three copies and 375 had less than three. Copy numbers of the remaining 992 ranged from 4 to 14, including homeologs, orthologs, and paralogs. Of the genes with three structural copies corresponding to homeologs, 55% expressed from all three, 38% from two, and the remaining 7% expressed from only one of the three copies. Homeologs of 76-87% of the genes showed differential expression patterns in different tissues, thus have evolved different gene expression controls, possibly resulting in novel functions. Homeologs of 55% of the genes showed tissue-specific expression, with the largest percentage (14%) in the anthers and the smallest (7%) in the pistils. The highest number (1.72/3) of homeologs/gene expression was in the roots and the lowest (1.03/3) in the anthers. As the expression of homeologs changed with changes in structural copy number, about 30% of the genes showed dosage dependence. Chromosomal location also impacted expression pattern as a significantly higher proportion of genes in the proximal regions showed expression from all three copies compared to that present in the distal regions.

Immune gene discovery by expressed sequence tag (EST) analysis of hemocytes in the ridgetail white prawn Exopalaemon carinicauda

The ridgetail white prawn Exopalaemon carinicauda is one of the most important commercial species in eastern China. However, little information of immune genes in E. carinicauda has been reported. To identify distinctive genes associated with immunity, an expressed sequence tag (EST) library was constructed from hemocytes of E. carinicauda. A total of 3411 clones were sequenced, yielding 2853 ESTs and the average sequence length is 436 bp. The cluster and assembly analysis yielded 1053 unique sequences including 329 contigs and 724 singletons. Blast analysis identified 593 (56.3%) of the unique sequences as orthologs of genes from other organisms (E-value < 1e-5). Based on the COG and Gene Ontology (GO), 593 unique sequences were classified. Through comparison with previous studies, 153 genes assembled from 367 ESTs have been identified as possibly involved in defense or immune functions. These genes are categorized into seven categories according to their putative functions in shrimp immune system: antimicrobial peptides, prophenoloxidase activating system, antioxidant defense systems, chaperone proteins, clottable proteins, pattern recognition receptors and other immune-related genes. According to EST abundance, the major immune-related genes were thioredoxin (141, 4.94% of all ESTs) and calmodulin (14, 0.49% of all ESTs). The EST sequences of E. carinicauda hemocytes provide important information of the immune system and lay the groundwork for development of molecular markers related to disease resistance in prawn species.

The mouse as a model to investigate sex steroid metabolism in the normal and pathological prostate

Metabolism of sex steroids within the prostate is an important factor affecting its growth and pathology. Mouse models with genetic gain- and especially loss-of-function have characterised different steroid metabolic pathways and their contribution to prostate pathology. With reference to the human prostate, this review aims to summarize the steroidogenic pathways in the mouse prostate as the basis for using the mouse as a model for intraprostatic steroid signalling. In this review we summarize the current information for three main components of the steroid signalling pathway in the mouse prostate: circulating steroids, steroid receptors and steroidogenic enzymes with regard to signalling via androgen, estrogen, progesterone and glucocorticoid pathways. This review reveals many opportunities for characterisation steroid metabolism in various mouse models. The knowledge of steroid metabolism within prostate tissue and in a lobe (rodent)/region (human) specific manner, will give valuable information for future, novel hypotheses of intraprostatic control of steroid actions. This review summarizes knowledge of steroid metabolism in the mouse prostate and its relevance to the human.

Cloning, characterization, and expression analysis of a putative 17 beta-hydroxysteroid dehydrogenase 11 in the abalone, Haliotis diversicolor supertexta

The 17-beta-hydroxysteroid dehydrogenases (17β-HSDs) are key enzymes for sex steroid biosynthesis. To date, relatively little is known about the presence and function of 17β-HSDs in marine gastropods. In the present study, a cDNA sequence encoding putative 17β-HSD type 11 (17β-HSD-11) was identified in marine abalone (Haliotis diversicolor supertexta). The full-length cDNA contains 1058bp, including an open reading frame (ORF) of 900bp that encodes a protein of 299 amino acids. Comparative structural analysis revealed that abalone 17β-HSD-11 shares relatively high homology with other 17b-HSD-11 hormologues, and a lesser degree of amino acid identity with other forms of 17b-HSD, especially in the functional domains, including the cofactor binding domain (TGxxxGxG) and catalytic site (YxxSK). Phylogenetic analysis showed that abalone 17β-HSD-11 belongs to the short-chain dehydrogenase/reductase (SDR) family. Functional analysis following transient transfection of the ORF into human embryonic kidney-293 (HEK-293) cells indicated that abalone 17β-HSD-11 has the ability to convert 5α-androstane-3α,17β-diol (3α-diol) to androsterone (A) and testosterone (T) to androstenedione (4A). Expression analysis in vivo demonstrated that abalone 17β-HSD-11 is differentially expressed during three stages (non-reproductive, reproductive, and post-reproductive). Taken together, these results indicate that ab-17β-HSD-11 is an SDR family member with a potential role in steroid regulation during the reproductive stage.

Human and zebrafish hydroxysteroid dehydrogenase like 1 (HSDL1) proteins are inactive enzymes but conserved among species

Hydroxysteroid dehydrogenase like 1 protein (HSDL1) is an uncharacterized member of short-chain dehydrogenase/reductase (SDR) protein family. In search for functional assignment of both human and zebrafish HSDL1 we characterized the subcellular localization as well as the tissue distribution and performed a screen for putative substrates of HSDL1 enzymes. Surprisingly, human HSDL1 shows exchange of an amino acid in the active center (Sx(12)FSxxK instead of Sx(12)YSxxK) that is considered critical for catalysis. Native human HSDL1 expressed in cells did not show enzymatic activity with any of the substrates tested. Expression of the point mutation F218Y HSDL1 though, resulted in the detection of weak dehydrogenase activity towards steroid and retinoid substrates. The role of this inactivating mutation is uncertain but was found to be conserved in many other vertebrate species, including zebrafish. Identification of protein interaction partners by yeast two-hybrid system suggests that despite the potential lack of enzymatic activity HSDL1 might retain regulatory functions in the cell.

RDH12, a retinol dehydrogenase causing Leber's congenital amaurosis, is also involved in steroid metabolism

Three retinol dehydrogenases (RDHs) were tested for steroid converting abilities: human and murine RDH 12 and human RDH13. RDH12 is involved in retinal degeneration in Leber's congenital amaurosis (LCA). We show that murine Rdh12 and human RDH13 do not reveal activity towards the checked steroids, but that human type 12 RDH reduces dihydrotestosterone to androstanediol, and is thus also involved in steroid metabolism. Furthermore, we analyzed both expression and subcellular localization of these enzymes.

Bioinformatic identification and characterization of new members of short-chain dehydrogenase/reductase superfamily

With about 60 genes known in the human genome, short-chain dehydrogenases/reductases (SDRs) form a large gene family with important implications for medicine. They are known to be involved in carcinogenesis (e.g. breast and prostate cancer) as well as in metabolic and degenerative defects such as the pathogenesis of Alzheimer's disease, osteoporosis and diabetes. Uncharacterized SDRs are thus potential candidates for many monogenic and multifactorial human diseases. The identification and functional analysis of such SDR enzymes is therefore the primary goal of the study leading to new targets for drug development. In all taxa (bacteria, plants, insects, vertebrates), members of SDR superfamily are known. Up to now, there are several thousand members annotated many of which have not been characterized biochemically with regard to enzymatic activity, substrate specificity, or subcellular localization. We bioinformatically identified 250 vertebrate candidate genes belonging to the SDR superfamily using the BioNetWorks software SDR finder. The number was reduced to 95 after continuative analysis, including manual SDR motif verification and focus on human, rat and murine enzymes. Here, we present several new mammalian SDRs that were clustered into several enzymatically different groups by detailed phylogenetic analyses. Furthermore, characteristic mRNA expression patterns were identified for some of these genes by a recently developed in silico Northern blot method supporting their putative functions in retinoid, steroid, sugar and other metabolic pathways.