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W Engel

Publications and source records attributed to W Engel.

At least 73 records · Page 4Linked to original sources
PubMed1997

Specific binding of a 47-kilodalton protein to the 3' untranslated region of rat transition protein 2 messenger ribonucleic acid.

The synthesis of transition protein (TNP) 2, one of the predominant nuclear proteins of mammalian spermatids, was shown to be posttranscriptionally regulated, by storing the untranslated mRNA for about 3-5 days in the cytoplasm of differentiating spermatids. It has been proposed that binding of a cytoplasmic protein to a conserved motif of 8 nucleotides (nt) in the 3' untranslated region (3'UTR) of TNP2 mRNA is involved in this translational control mechanism. In this report, we show that deletion or variation of the conserved 8-nt motif (GCCAT-CAC) in rat TNP2-3'UTR abolishes the capacity of the in vitro-transcribed RNA to reconstitute specific RNA-protein complexes in RNA bandshift assays. Using Northwestern analysis, we identified specific binding to the TNP2-3'UTR of four proteins of 45, 47, 49, and 60 kDa, all of which are stage-specifically regulated in male germ cell differentiation. Deletion of the 8-nt motif in the 3'UTR specifically prevented binding of the 47-kDa protein, the interaction of which is thought to be mediated by the RNA secondary structure. Analysis of the RNA secondary structure revealed that the 8-nt motif is an essential element of a specific stem-loop structure that is predicted for rat wild-type TNP2-3'UTR. Therefore we assume that the 47-kDa protein plays an important role in specific RNA-protein complex formation of rat TNP2-3'UTR that may be a central event in the translational control of rat TNP2 mRNA.

Ammonium Sulfate↗
PubMed1996

Isolation, characterization, and organ-specific expression of two novel human zinc finger genes related to the Drosophila gene spalt.

The region-specific homeotic gene spalt (sal) of Drosophila specifies head and tail as opposed to trunk segments. During later stages of ontogenesis, sal is also expressed and required in a small number of tissues and organs in the developing embryo. sal encodes a zinc finger protein of unusual but characteristic structure. We made use of these unique features to isolate sal-like genes from humans. Here we report the isolation and molecular characterization of two sal-like transcription units, termed Hsal1 and Hsal2, which are located on chromosomes 16q12.1 and 14q11.1-q12.1, respectively. Their transcripts are expressed in a limited number of adult organs, including the brain. While Hsal2 is evenly expressed in different brain areas, Hsal1 transcripts preferentially accumulate in the corpus callosum and the substantia nigra. In the fetal brain, transcripts of both genes were detected in neurons. The arrangement of sal-like zinc finger domains and their high degree of sequence similarity suggest a novel and conserved subfamily of human zinc finger transcription factors that is closely related to the Drosophila gene product encoded by the gene sal.

Adult↗
PubMed1996

BIBP 3226, the first selective neuropeptide Y1 receptor antagonist: a review of its pharmacological properties.

Based on the assumption that the pharmacophoric groups interacting with the Y1 receptor are located in the C-terminal part of neuropeptide Y, low molecular weight compounds with high affinity and selectivity for the Y1 receptor were designed and synthesized. The prototype BIBP 3226 possesses affinity for the Y1 receptor in the nanomolar range. In addition, this compound is selective displaying rather low affinity for Y2, Y3, Y4 and a set of 60 other receptors. Both biochemical and pharmacological studies showed that BIBP 3226 behaves as a competitive antagonist. Using BIBP 3226 it was possible to investigate the role of NPY and/or Y1 receptors in blood pressure regulation. The interesting observation was that antagonism to Y1 receptors had no major influence on the basal blood pressure but attenuated stress induced hypertension. This strongly supports the hypothesis that NPY is mainly released during stress involving intense sympathetic nervous system activation. Moreover, BIBP 3226 can be used to characterize NPY receptor subtypes. For instance, we were able to show that presynaptic NPY receptors mediating catecholamine release do not solely belong to the Y2 subtype, but that presynaptic Y1 receptors also exist. In conclusion, BIBP 3226 has been shown to be an important tool for the elucidation of the physiological role of Y1 receptors in the cardiovascular system.

Animals↗
PubMed1996

Isolation, expression, and chromosomal localization of the human mitochondrial capsule selenoprotein gene (MCSP).

The mitochondrial capsule selenoprotein (MCS) (HGMW-approved symbol MCSP) is one of three proteins that are important for the maintenance and stabilization of the crescent structure of the sperm mitochondria. We describe here the isolation of a cDNA, the exon-intron organization, the expression, and the chromosomal localization of the human MCS gene. Nucleotide sequence analysis of the human and mouse MCS cDNAs reveals that the 5'- and 3 '-untranslated sequences are more conserved (71%) than the coding sequences (59%). The open reading frame encodes a 116-amino-acid protein and lacks the UGA codons, which have been reported to encode the selenocysteines in the N-terminal of the deduced mouse protein. The deduced human protein shows a low degree of amino acid sequence identity to the mouse protein (39%). The most striking homology lies in the dicysteine motifs. Northern and Southern zooblot analyses reveal that the MCS gene in human, baboon, and bovine is more conserved than its counterparts in mouse and rat. The single intron in the human MCS gene is approximately 6 kb and interrupts the 5'-untranslated region at a position equivalent to that in the mouse and rat genes. Northern blot and in situ hybridization experiments demonstrate that the expression of the human MCS gene is restricted to haploid spermatids. The human gene was assigned to q21 of chromosome 1.

Amino Acid Sequence↗
PubMed1996

Sequence analysis of the conserved protamine gene cluster shows that it contains a fourth expressed gene.

Structural data are presented on the protamine gene cluster (PGC) of human, mouse, rat, and bull. By restriction mapping we demonstrate that the organization of the protamine cluster is conserved throughout all four species, i.e., the genes are situated in a head to tail arrangement in the order: protamine 1-protamine 2-transition protein 2. Further, we established the nucleotide sequence of the entire human PGC (25 kb in total) and the 3' portion of the rat protamine cluster (PRM2 and TNP2 genes and intergenic region). In addition, a 1 kb fragment of the bovine and murine protamine cluster, situated between PRM2 and TNP2, was sequenced. This fragment is conserved regarding sequence, position, and orientation in all species examined, and was classified as likely coding region by gene recognition program GRAIL. Using the rat fragment as a probe in RNA blots, we detected a testis-specific signal of about 0.5 kb. Finally, we demonstrate a high density of Alu elements, both full and fragmented copies, in the human PGC and discuss their localization with respect to evolutionary and functional aspects.

Animals↗
PubMed1996

Cloning, expression, and chromosomal localization of the rat mitochondrial capsule selenoprotein gene (MCS): the reading frame does not contain potential UGA selenocysteine codons.

The mitochondrial capsule selenoprotein (MCS) is a selenium-containing polypeptide. It is one of three proteins that are important for the maintenance and stabilization of the crescent structure of the sperm mitochondria. In this paper, we report the isolation and characterization of the rat MCS cDNA and gene. The cDNA contains a reading frame for a 145-amino-acid protein and it lacks the UGA codons, which have been found in the reading frame of the mouse MCS cDNA and have been presumed to encode the selenocysteine in the amino terminal of the deduced mouse amino acid sequence. The deduced amino acid sequence of the rat and mouse MCS shows a high level of homology (79%). The rat MCS gene contains two exons; the intron sequence interrupts the 5' untranslated sequence at the same position as in the mouse MCS gene. The transcription start site is located 184 bp upstream of the translation start site. Alignment of the 5'-flanking regions of the mouse and rat genes reveals that the first 400 nucleotides upstream of the transcription start site exhibit an overall sequence similarity of 73%. This conserved region contains no TATA or CAAT box motifs. Northern blot analysis indicates that the MCS mRNA is detectable only in the testis after day 30 of postnatal development. Moreover, in situ hybridization revealed that the rat MCS gene is mainly expressed in round spermatids. From the analysis of mouse-rat cell hybrids that segregate rat chromosomes, the MCS gene was assigned to rat chromosome 2.

Amino Acid Sequence↗
PubMed1996

Human Y chromosome azoospermia factors (AZF) mapped to different subregions in Yq11.

In a large collaborative screening project, 370 men with idiopathic azoospermia or severe oligozoospermia were analysed for deletions of 76 DNA loci in Yq11. In 12 individuals, we observed de novo microdeletions involving several DNA loci, while an additional patient had an inherited deletion. They were mapped to three different subregions in Yq11. One subregion coincides to the AZF region defined recently in distal Yq11. The second and third subregion were mapped proximal to it, in proximal and middle Yq11, respectively. The different deletions observed were not overlapping but the extension of the deleted Y DNA in each subregion was similar in each patient analysed. In testis tissue sections, disruption of spermatogenesis was shown to be at the same phase when the microdeletion occurred in the same Yq11 subregion but at a different phase when the microdeletion occurred in a different Yq11 subregion. Therefore, we propose the presence of not one but three spermatogenesis loci in Yq11 and that each locus is active during a different phase of male germ cell development. As the most severe phenotype after deletion of each locus is azoospermia, we designated them as: AZFa, AZFb and AZFc. Their probable phase of function in human spermatogenesis and candidate genes involved will be discussed.

Chromosome Mapping↗
PubMed1996

Are there genetic risks associated with microassisted reproduction?

Of all the techniques available for microassisted reproduction, the direct injection of individual sperm cells or spermatids into the cytoplasm of the oocyte (ICSI) is the most invasive, through which any possible selection against sperm cells with genomic defects would be excluded. It has, however, been shown that such a possible selection is present neither in the female genital tract nor at the zona pellucida. Selection against genetic-based defects occurs after the fertilization of the oocyte, during both embryonic and fetal development. Based on the data to date, it can be assumed that ICSI would not result in either a significant increase in genetic-based diseases, or in an increase in the number of infertile males. If, however, mutations of X-chromosomal or Y-chromosomal genes should play a major role in male fertility disorders, one could expect, over generations, an increase, though probably very slight, in the number of males with such disorders.

Animals↗
PubMed1996

Interphase chromosome arrangement in Sertoli cells of adult mice.

Sertoli cells of adult male laboratory mice were examined with a number of banding techniques and by nonradioactive in situ hybridization applying different repetitive DNA probes. All banding methods revealed the typical features of mouse Sertoli cells, i.e., a central nucleolus, usually with two chromocenters associated at diametrically opposed sides in which the centromeric regions of the chromosomes are clustered. Silver staining as well as in situ hydridization with rDNA labeled part of the chromocenters and the nucleolus, indicating transcriptional activity of at least some of the nucleolus organizer regions. In situ hybridization with X- and Y-specific DNA probes showed both sex chromosomes to be undercondensed in Sertoli cells This decondensation suggests expression of sex chromosomal genes in Sertoli cells. While the X chromosome appeared to occupy a central position near one of the chromocenters, the Y chromosome was found at the periphery of the nucleus in the majority of cells. Hybridization with telomeric sequences resulted in strong labeling of the chromocenters and dispersed signals at the nuclear periphery.

Animals↗
PubMed1996

Five novel mutations in the L1CAM gene in families with X linked hydrocephalus.

Five novel mutations have been identified in the gene encoding L1CAM, a neural cell adhesion protein, in families with X linked hydrocephalus (XHC). Interestingly, all five mutations are in the evolutionarily highly conserved Ig-like domains of the protein. The two frameshift mutations (52insC and 955delG) and the nonsense mutation (Trp276Ter) most probably result in functional null alleles and complete absence of L1CAM at the cell surface. The two missense mutations (Tyr194Cys and Pro240Leu) may considerably alter the structure of the L1CAM protein. These data provide convincing evidence that XHC is genetically extremely heterogeneous.

Abnormalities, Multiple↗
PubMed1996

Neuropeptide Y and the nonpeptide antagonist BIBP 3226 share an overlapping binding site at the human Y1 receptor.

Neuropeptide Y (NPY) is a 36-amino acid peptide that exhibits actions on the cardiovascular system and the central nervous system. NPY can regulate blood pressure, psychomotor function, anxiety, food intake, and endocrine secretions. BIBP 3226, the first potent and selective nonpeptide antagonist at the NPY Y1 receptor, was designed by mimicking the carboxyl-terminal structure of NPY. We investigated the interaction of NPY and BIBP 3226 with the human Y1 receptor at the molecular level. Alanine mutants at positions Y100, D104, W288, and H298 of the human Y1 receptor showed no or significantly reduced binding for NPY but were not affected in their ability to bind BIBP 3226. Receptors with alanine mutations at positions W163, F173, Q219, N283, F286, and D287 showed reduced binding for both NPY and BIBP 3226. Mutations at other positions were tested (H105, S170, L174, V178, D200, D205, S206, H207, S210, T212, T280, T284, N289, H290, and Q291) and did not affect the binding of NPY or BIBP 3226. The human Y1 receptor mutant Y211A showed no affinity for BIBP 3226 but retained wild-type affinity for NPY. Based on these experimental results, a detailed model for the interaction of BIBP 3226 with the human Y1 receptor was developed using a Y1 receptor model and a three-dimensional model of BIBP 3226. The experimental results, supported by modeling studies, clearly suggest that the native ligand (NPY) and the antagonist (BIBP 3226) share an overlapping binding site.

Amino Acid Sequence↗
PubMed1996

Stage and developmental specific gene expression during mammalian spermatogenesis.

Spermatogenesis is a complex developmental process which involves amplification of germinal stem cells, their differentiation into spermatocytes, meiotic division and finally transformation into mature spermatozoa. Therefore, spermatogenesis provides an interesting system for examining the regulation of gene expression during development and differentiation. The genes expressed during spermatogenesis can be divided into two main groups: diploid and haploid expressed genes. In this review, we report about the regulation of expression of a diploid expressed gene, namely the proacrosin gene, and that of a haploid expressed gene, the transition protein 2 gene.

Acrosin↗
PubMed1996

The structures of the bovine and porcine proacrosin genes and their conservation among mammals.

Sperm acrosin is a serine protease that is involved in the recognition, binding and penetration of the sperm of the zona pellucida of the ovum. The bovine and porcine genes were cloned and characterized. Alignment of the intron/exon structure of both genes with the previously characterized human, rat and mouse genes and with other serine protease genes reveals that the coded sequence of the mammalian proacrosin is distributed in 5 exons and the splice junction types are identical to the exons encoding the catalytic domain of other serine protease genes. A comparison of the bovine, porcine, human, guinea pig, rabbit, rat and mouse preproprotein sequences shows that the catalytic domain is highly conserved, while the sequence of the proline rich domain is very variable among the species, ranging from 28.9% to 68.8%.

Acrosin↗
PubMed1995

Labeling of neuropeptide Y receptors in SK-N-MC cells using the novel, nonpeptide Y1 receptor-selective antagonist [3H]BIBP3226.

The binding of tritium-labelled BIBP3226, N2-(diphenylacetyl)-N-[(4-hydroxy-phenyl)methyl]-D-arginine amide, to human neuroblastoma SK-N-MC cells was investigated. [3H]BIBP3226 reversibly binds to neuropeptide Y receptors of the Y1 subtype expressed in SK-N-MC cells with a KD of 2.1 +/- 0.3 nM (mean +/- S.E.M., n = 3) and a Bmax of 58,400 +/- 1100 sites/cell. Non-specific binding did not exceed 30% of the total radioactivity bound at KD. In competition experiments [3H]BIBP3226 is concentration-dependently displaced by neuropeptide Y and its peptide analogues with an affinity pattern neuropeptide Y = [Leu31, Pro34]neuropeptide Y >> neuropeptide Y-(18-36). This rank order of potencies is consistent with the interaction of [3H]BIBP3226 with neuropeptide Y receptors of the Y1 subtype. Therefore, [3H]BIBP3226 can be used as selective ligand to study neuropeptide Y Y1 receptors.

Arginine↗
PubMed1995

Translational control in spermatogenesis.

Translational silencing phenomena during spermatogenesis in the two model systems Drosophila and mouse are reviewed. Cis-acting sequences were identified in both species that are necessary for translational repression. While in Drosophila these elements so far have only been found in the 5' untranslated region (5' UTR), in the mammals such regions were identified both in the 5' as well as in the 3' UTR. In all cases, RNA-binding proteins interact with these regions, yet their specific role in the observed negative regulation of translation has to be established.

Animals↗