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Biomedical subjects

D J Elliott

Publications and source records attributed to D J Elliott.

At least 19 recordsLinked to original sources
PubMed1999

T-STAR/ETOILE: a novel relative of SAM68 that interacts with an RNA-binding protein implicated in spermatogenesis.

RBM is an RNA-binding protein encoded on the Y chromosome in mammals and is expressed only in the nuclei of male germ cells. Genetic evidence from infertile men implicates it in spermatogenesis, but its function is unknown. Of a number of potential partners for RBM identified by a yeast two-hybrid screen with testis cDNA, the most frequent isolates encoded a novel RNA-binding protein, termed T-STAR, that is closely related to SAM68, an Src-associated protein of unknown function. The mouse homologue was also cloned and designated étoile. It mapped to chromosome 15, while T-STAR mapped to the syntenic region on human chromosome 8. T-STAR/étoile is expressed primarily in the testis; in rat germ cells, the expression of both T-STAR/étoile and SAM68 is regulated during meiosis. Transfection of T-STAR/étoile fused with green fluorescent protein into HeLa cells caused an accumulation of protein in a novel compartment of the nucleus, adjacent to the nucleolus but distinct from the peri-nucleolar compartment. RBM and other hnRNP G family members are candidate downstream targets for regulation by T-STAR/ETOILE and SAM68.

3T3 Cells↗
PubMed1998

Understanding the genes involved in spermatogenesis: a progress report.

OBJECTIVE: To review the current literature on genes known to affect fertility in the human and mouse. DESIGN: A literature review was performed and key articles were chosen for focus in the areas of genes with effects only on spermatogenesis and oogenesis, with an emphasis on Y-chromosome-encoded gene families and spermatogenesis. In addition, studies describing genes deleted in transgenic mice were incorporated. RESULT(S): Several gene families on the Y chromosome are implicated in spermatogenic failure, but the link between the genetic lesion and the resulting defect is unclear. Many mouse genes involved in repair and DNA damage monitoring have specific effects on gametogenesis in and around meiosis. CONCLUSION(S): Many genes are involved only in gametogenesis, and some of these are beginning to be understood in terms of their functions. An even larger number of genes is required for gametogenesis, and other functions and mouse models give insights important for human disease.

Animals↗
PubMed1998

Mouse homologues of the human AZF candidate gene RBM are expressed in spermatogonia and spermatids, and map to a Y chromosome deletion interval associated with a high incidence of sperm abnormalities.

An RNA-binding motif (RBM) gene family has been identified on the human Y chromosome that maps to the same deletion interval as the 'azoospermia factor' (AZF). We have identified the homologous gene family (Rbm) on the mouse Y with a view to investigating the proposal that this gene family plays a role in spermatogenesis. At least 25 and probably >50 copies of Rbm are present on the mouse Y chromosome short arm located between Sry and the centromere. As in the human, a role in spermatogenesis is indicated by a germ cell-specific pattern of expression in the testis, but there are distinct differences in the pattern of expression between the two species. Mice carrying the deletion Yd1, that maps to the proximal Y short arm, are female due to a position effect resulting in non-expression of Sry ; sex-reversing such mice with an Sry transgene produces males with a high incidence of abnormal sperm, making this the third deletion interval on the mouse Y that affects some aspect of spermatogenesis. Most of the copies of Rbm map to this deletion interval, and the Yd1males have markedly reduced Rbm expression, suggesting that RBM deficiency may be responsible for, or contribute to, the abnormal sperm development. In man, deletion of the functional copies of RBM is associated with meiotic arrest rather than sperm anomalies; however, the different effects of deletion are consistent with the differences in expression between the two species.

Amino Acid Sequence↗
PubMed1998

Dynamic changes in the subnuclear organisation of pre-mRNA splicing proteins and RBM during human germ cell development.

RBM is a germ-cell-specific RNA-binding protein encoded by the Y chromosome in all mammals, implying an important and evolutionarily conserved (but as yet unidentified) function during male germ cell development. In order to address this function, we have developed new antibody reagents to immunolocalise RBM in the different cell types in the human testis. We find that RBM has a different expression profile from its closest homologue hnRNPG. Despite its ubiquitous expression in all transcriptionally active germ cell types, RBM has a complex and dynamic cell biology in human germ cells. The ratio of RBM distributed between punctate nuclear structures and the remainder of the nucleoplasm is dynamically modulated over the course of germ cell development. Moreover, pre-mRNA splicing components are targeted to the same punctate nuclear regions as RBM during the early stages of germ cell development but late in meiosis this spatial association breaks down. After meiosis, pre-mRNA splicing components are differentially targeted to a specific region of the nucleus. While pre-mRNA splicing components undergo profound spatial reorganisations during spermatogenesis, neither heterogeneous ribonucleoproteins nor the transcription factor Sp1 show either developmental spatial reorganisations or any specific co-localisation with RBM. These results suggest dynamic and possibly multiple functions for RBM in germ cell development.

Cyclic AMP Response Element Modulator↗
PubMed1997

Expression of RBM in the nuclei of human germ cells is dependent on a critical region of the Y chromosome long arm.

The association of abnormal spermatogenesis in men with Y chromosome deletions suggests that genes important for spermatogenesis have been removed from these individuals. Recently, genes encoding two putative RNA-binding proteins (RBM and DAZ/SPGY) have been mapped to two different regions of the human Y chromosome. Both of these genes encode proteins that contain a single RNA recognition motif and a (different) internally repeating sequence. Y-linked RBM homologues are found in all mammalian species. We have raised an antiserum to RBM and used it to show that RBM is a nuclear protein expressed in fetal, prepubertal, and adult male germ cells. The distribution of RBM protein in the adult correlates with the pattern of transcriptional activity in spermatogenesis, suggesting that RBM is involved in the nuclear metabolism of newly synthesized RNA. RBM sequences are found on both arms of the Y chromosome making genotype-phenotype correlations difficult for this gene family. To address the location of the functional genes and the consequences of their deletion, we examined a panel of men with Y chromosome deletions and known testicular pathologies using this antiserum. This approach enabled us to map a region of the Y chromosome essential for RBM expression. In the absence of detectable RBM expression we see stages of germ cell development up to early meiosis, but not past this point into the haploid phase of spermatogenesis.

Adult↗
PubMed1997

The molecular genetics of male infertility.

Spermatogenesis is an elaborate process involving both cell division and differentiation, and cell-cell interactions. Defects in any of these processes can result in infertility, and in some cases these can be genetic in cause. Mapping experiments have defined at least three regions of the human Y chromosome that are required for normal spermatogenesis. Two of these contain the genes encoding the RNA binding proteins RBM and DAZ, suggesting that the control of RNA metabolism is likely to be an important control point for human spermatogenesis. A similar analysis in mice has shown that at least two regions of the mouse Y chromosome are essential for spermatogenesis. Both genetic and reverse genetic approaches have been used to identify mouse autosomal genes required for spermatogenesis. These studies have shown that genes in a number of different pathways are essential for normal spermatogenesis, and also provide putative models of human infertility.

Animals↗
PubMed1996

Yeast pre-mRNA is composed of two populations with distinct kinetic properties.

As an approach to the study of yeast pre-mRNA splicing in vivo, we have examined properties of transcripts derived from a gal-UAS intron-containing fusion gene encoding RP51A and a series of its derivatives. RNA half-life measurements were carried out after transcription initiation was blocked by the addition of glucose. Pre-mRNA encoded by GalRP51A decayed with a half-life of approximately 6 min and was substantially polyadenylated, and transcripts derived from a nonspliced version of the same gene decayed with a similar half-life ( approximately 4 min). A comparison of the steady-state levels of these two transcripts suggests that the bulk of GalRP51A pre-mRNA is processed much more rapidly, with an average lifetime of about 2 s. We propose that this inferred population of rapidly processed molecules is spliced cotranscriptionally and that it is the principal precursor to GalRP51A mRNA. Although the pre-mRNA molecules detected are therefore unlikely to be the major splicing precursors, an in vivo assay suggests that they are likely to have bound splicing factors. They must then be spliced much more slowly than most primary transcripts, or not spliced at all and then degraded through a different cellular pathway. As a result of its comparatively long lifetime, this minor fraction of the pre-mRNA population makes up the majority of the steady-state level of GalRP51A pre-mRNA.

Base Sequence↗
PubMed1996

An RBM homologue maps to the mouse Y chromosome and is expressed in germ cells.

We have isolated a murine homologue of the human Y-linked RBM genes (previously termed YRRM), a gene family implicated in spermatogenesis and which encodes proteins containing an RNA recognition motif. A number of very similar copies of this gene (called Rbm) are present in the mouse. These mouse homologues are also Y-encoded, mapping on the short arm of the chromosome, proximal to Sry. Expression is confined to the testis, specifically the germ line on the basis of lack of expression in the germ-line negative testes of adult sex-reversed mice. The timing of Rbm transcription is regulated, with fetal message levels reaching a peak at 15 d.p.c. Transcripts are clearly detectable by 4 days after birth and reach their highest level at 14 d.p.p. which is the time at which the Y chromosome condenses during meiotic prophase. These results suggest that Rbm is functionally involved in germline RNA metabolism.

Amino Acid Sequence↗
PubMed1995

Spatial consequences of defective processing of specific yeast mRNAs revealed by fluorescent in situ hybridization.

This work introduces the first use of fluorescent in situ hybridization (FISH) to detect the distribution of specific transcripts in Saccharomyces cerevisiae. We have applied this technique to analysis of reporter transcripts from a single, integrated copy, or multicopy plasmids. We have evaluated the effect of splice site deletions or the presence or absence of a terminator/cleavage site and demonstrated that both splicing and polyadenylation affect the export of these transcripts from the nucleus to the cytoplasm. Moreover, we show that the exported pre-mRNAs are substrates for nonsense codon-mediated decay through the UPF1 pathway. The work presented here demonstrates that the spatial distribution of transcripts will also be an important component of yeast RNA metabolism.

Base Sequence↗
PubMed1994

mRNA nuclear export.

The export of mRNA from the nucleus to the cytoplasm is an essential step in the expression of genetic information in eukaryotes. It is an energy-dependent process and involves transport across the nuclear pores. It requires both cis-acting ribonucleoprotein particle signals and specific trans-acting factors. Although much remains to be learned, recent information has begun to define this pathway at both the cellular and biochemical levels and indicates that it is used as a key regulatory step by several viruses.

Animals↗
PubMed1992

A yeast splicing factor is localized in discrete subnuclear domains.

Digital imaging microscopy has been used to visualize the splicing protein PRP6p and three other yeast nuclear proteins. The results show that PRP6p is uniquely localized to discrete subnuclear regions. A combination of cytological and biochemical assays suggests that these sites can be saturated when the protein is overexpressed and likely correspond to the location of U4/U6 snRNPs. The observations indicate that some splicing components are located in discrete subregions of the yeast nucleus, similar to the situation described for the mammalian nucleus.

Blotting, Western↗
PubMed1990

Importance of alignment between local DC magnetic field and an oscillating magnetic field in responses of brain tissue in vitro and in vivo.

The frequency dependence of the electric and magnetic (EM)-field-induced release of calcium ions from an in vitro brain tissue preparation has been shown to be a function of the density of the local DC magnetic field (Bdc). In this study, we demonstrate that the relative orientation of the Bdc and the magnetic component (Bac) of a 315-Hz EM signal (15 Vrms/m and 61 nTrms) are crucial for the induced release to be observed. The induced release occurs only when the Bdc and the Bac are perpendicular, and not when they are parallel. This finding is consistent with a magnetic resonance-like transduction mechanism for the conversion of EM energy into a physicochemical change, and contrasts with the requirement for parallel Bdc and Bac components in the diatom-mobility experiments of Smith et al. A review of the exposure conditions in the rat behavioral experiments conducted by Thomas et al. identifies unhydrated calcium and zinc ions as alternatives to lithium ions as candidates for interaction under parallel magnetic-field orientations but fails to reject perpendicular orientations as an alternative basis for the phenomenon. Investigators that attempt to confirm the rat behavioral experiments should be aware of the conflicting exposure conditions that can be assumed to be operative, and they should design their experiments to test all conditions accordingly.

Animals↗
PubMed1990

Depressive characteristics of sexually abused children.

Allen and Tarnowski (1988) identified a pattern of depressive characteristics that distinguished physically abused from nonabused children. The present study attempted to extend the generality of these findings to sexually abused children. Sexually abused and nonabused children were compared on measures of depression, hopelessness, and self-esteem. Results indicated that while sexually abused children self-reported more depressive symptoms in comparison to nonabused controls, that these differences were not statistically significant and failed to replicate the findings noted for physically abused children.

Child↗
PubMed1989

Mutually exclusive synthetic pathways for sea urchin mitochondrial rRNA and mRNA.

The structure and abundance of mitochondrial transcripts in sea urchin embryos were investigated by a combination of RNA blot-hybridization, S1 mapping, and primer extension assays. Between the egg and blastula stages, the relative abundance of mitochondrial rRNAs declined slightly, while that of mitochondrial mRNAs increased up to 10-fold. Fine mapping of the termini of the rRNAs and of the adjacent transcripts indicated that, although they appeared to be butt-joined at their 5' ends to the upstream transcripts, tRNA-Phe 5' to the small subunit (12S) rRNA and NADH dehydrogenase subunit 2 mRNA 5' to the large subunit (16S) rRNA, respectively, their 3' ends were found to overlap the 5' ends of the downstream transcripts. 12S rRNA was found to extend 7 to 13 nucleotides into the sequence of tRNA-Glu; 16S rRNA was shown to terminate 3 to 5 nucleotides inside the coding region of cytochrome oxidase subunit 1 (COI) and 8 to 10 nucleotides from the mapped 5' end of COI mRNA. The rRNAs and the downstream transcripts must therefore be synthesized by distinct pathways, either by alternative processing of the same primary transcript(s) or by processing of different precursors. In either case, the events which select the ribosomal 3' ends preclude the production of functional transcripts of the downstream genes from the same precursor molecule. No developmental alterations in transcript structure were detected. We propose that mitochondrial RNA levels are regulated in early development by the selection of alternate and mutually exclusive RNA-processing pathways.

Animals↗
PubMed1988

Nucleotide sequence and gene organization of sea urchin mitochondrial DNA.

The 15,650 base-pair mitochondrial genome of the sea urchin Strongylocentrotus purpuratus has been cloned and sequenced. It exhibits a novel organization that suggests the primacy of post-transcriptional gene regulation. The same 13 polypeptides, two rRNAs and 22 tRNAs are encoded as in other animal mitochondrial DNAs, but are organized with extreme economy; non-coding information between genes is almost completely absent, some stop codons are generated post-transcriptionally and tRNA sequences are interspersed between only a minority of other structural genes. The genome uses a variant genetic code, in which AAA specifies asparagine, ATA isoleucine, TGA tryptophan and AGN serine, and has an unusual pattern of codon bias. The order of genes shows several differences from that of vertebrates. The genes for the large (16 S) ribosomal RNA and for NADH dehydrogenase subunit 4L (ND4L) are in different positions, located respectively between those encoding ND2 and cytochrome oxidase subunit I (COI) and between COI and COII. This organization is conserved amongst at least four regular echinoids diverging by some 225 million years. Most tRNA genes are also in different positions. The only long unassigned sequence in the genome (121 base-pairs) is located within a cluster of 15 tRNA genes. It contains elements resembling some of those found in the displacement (D) loop of vertebrate mtDNAs, notably polypurine/polypyrimidine tracts that may play a role in regulating transcription and the initiation of replication. The separation of the ribosomal RNA genes from each other and from the putative control region imposes special demands on the transcription of the genome.

Animals↗
PubMed1988

Influence of electromagnetic fields on the efflux of calcium ions from brain tissue in vitro: a three-model analysis consistent with the frequency response up to 510 Hz.

The frequency dependence of electromagnetic field-induced calcium-ion efflux from chicken brain tissues has been examined at 15-Hz intervals over the range 1-510 Hz. The electric field component was 15 Vrms/m and the magnetic component varied between 59 and 69 nTrms. No patterns of response as a function of frequency could be readily discerned when the differences in mean efflux values between exposed and sham samples were compared. However, the calculated P-value, a function that combines at each frequency the difference between the means of the exposed and sham groups with the variance of each group, does provide a basis for hypothesizing the existence of three frequency-dependent patterns in the data. One pattern includes all the highly significant (P less than .01) responses which occur between 15 and 315 Hz, at 30-Hz intervals; two independent trials at 165 Hz, giving nonsignificant responses (P greater than .5), break this pattern into two groups of five frequencies each, which is contrary to the expected result for a simple Lorentz-force interaction. However, another pattern of significant results at 60, 90, and 180 Hz, but not at 300 Hz, is consistent with a Lorentz-force model. A third pattern, composed of only one significant response at 405 Hz, is very close to the resonance predicted on a linear extrapolation from high-frequency data for 13carbon atoms. This hypothetical ordering of the frequency-response profile provides the basis for future experimental designs to test each possible interaction model and for their connection to the calcium-ion efflux endpoint.

Animals↗