Biomedical subjects

Roseline Godbout

Publications and source records attributed to Roseline Godbout.

9 recordsLinked to original sources

PubMed2005

Dynamic nature of cleavage bodies and their spatial relationship to DDX1 bodies, Cajal bodies, and gems.

DDX1 bodies, cleavage bodies, Cajal bodies (CBs), and gems are nuclear suborganelles that contain factors involved in RNA transcription and/or processing. Although all four nuclear bodies can exist as distinct entities, they often colocalize or overlap with each other. To better understand the relationship between these four nuclear bodies, we examined their spatial distribution as a function of the cell cycle. Here, we report that whereas DDX1 bodies, CBs and gems are present throughout interphase, CPSF-100-containing cleavage bodies are predominantly found during S and G2 phases, whereas CstF-64-containing cleavage bodies are primarily observed during S phase. All four nuclear bodies associate with each other during S phase, with cleavage bodies colocalizing with DDX1 bodies, and cleavage bodies/DDX1 bodies residing adjacent to gems and CBs. Although inhibitors of RNA transcription had no effect on DDX1 bodies or cleavage bodies, inhibitors of DNA replication resulted in loss of CstF-64-containing cleavage bodies. A striking effect on nuclear structures was observed with latrunculin B, an inhibitor of actin polymerization, resulting in the formation of needlelike nuclear spicules made up of CstF-64, CPSF-100, RNA, and RNA polymerase II. Our results suggest that cleavage body components are highly dynamic in nature.

Actins↗

PubMed2005

CECR2, a protein involved in neurulation, forms a novel chromatin remodeling complex with SNF2L.

Chromatin remodeling complexes play critical roles in development. Here we describe a transcription factor, CECR2, which is involved in neurulation and chromatin remodeling. CECR2 shows complex alternative splicing, but all variants contain DDT and bromodomain motifs. A mutant mouse line was generated from an embryonic stem cell line containing a genetrap within Cecr2. Reporter gene expression demonstrated Cecr2 expression to be predominantly neural in the embryo. Mice homozygous for the Cecr2 genetrap-induced mutation show a high penetrance of the neural tube defect exencephaly, the human equivalent of anencephaly, in a strain-dependent fashion. Biochemical isolation of CECR2 revealed the presence of this protein as a component of a novel heterodimeric complex termed CECR2-containing remodeling factor (CERF). CERF comprises CECR2 and the ATP-dependent chromatin remodeler SNF2L, a mammalian ISWI ortholog expressed predominantly in the central nervous system. CERF is capable of remodeling chromatin in vitro and displays an ATP hydrolyzing activity that is stimulated by nucleosomes. Together, these data identify a novel chromatin remodeling complex with a critical role in neurulation.

Adenosine Triphosphatases↗

PubMed2004

A DEAD box protein facilitates HIV-1 replication as a cellular co-factor of Rev.

HIV-1 Rev escorts unspliced viral mRNAs out of the nucleus of infected cells, which allows formation of infectious HIV-1 virions. We have identified a putative DEAD box (Asp-Glu-Ala-Asp) RNA helicase, DDX1, as a cellular co-factor of Rev, through yeast and mammalian two-hybrid systems using the N-terminal motif of Rev as "bait". DDX1 is not a functional homolog of HIV-1 Rev, but down-regulation of DDX1 resulted in an alternative splicing pattern of Rev-responsive element (RRE)-containing mRNA, and attenuation of Gag p24 antigen production from HLfb rev- cells rescued by exogenous Rev. Co-transfection of a DDX1 expression vector with HIV-1 significantly increased viral production. DDX1 binding to Rev, as well as to the RRE, strongly suggest that DDX1 affects Rev function through the Rev-RRE axis. Moreover, down-regulation of DDX1 altered the steady state subcellular distribution of Rev, from nuclear/nucleolar to cytoplasmic dominance. These findings indicate that DDX1 is a critical cellular co-factor for Rev function, which maintains the proper subcellular distribution of this lentiviral regulatory protein. Therefore, alterations in DDX1-Rev interactions could induce HIV-1 persistence and targeting DDX1 may lead to rationally designed and novel anti-HIV-1 strategies and therapeutics.

Animals↗

PubMed2004

Alternative splicing modulates Disabled-1 (Dab1) function in the developing chick retina.

The Reelin-Disabled 1 (Dab1)-signaling pathway plays a critical role in neuronal cell positioning in the brain. We have isolated two alternatively spliced variants of Dab1 from chick retina, an early form (chDab1-E) expressed in undifferentiated cells and a late form (chDab1-L) expressed in amacrine and ganglion cells. A key difference between the two forms is the exclusion in chDab1-E of two Src-related tyrosine kinase recognition sites implicated in Reelin-mediated Dab1 tyrosine phosphorylation. Retinal cultures transfected with a chDab1-L expression construct undergo a dramatic change in morphology, accompanied by the formation of numerous thin elongated processes, increased tyrosine phosphorylation, activation of Src family kinase(s) and increased levels of the axonal outgrowth protein growth-associated protein-43. In contrast, chDab1-E transfectants retain an undifferentiated morphology. Mutational analysis implicates a specific tyrosine (tyr-198) in the morphological and biochemical alterations associated with chDab1-L expression. We propose that alternative splicing of chDab1 represents an effective and flexible way of regulating the Reelin-Dab1-signaling pathway in a mixed cell population, by ensuring that secreted Reelin activates the signaling cascade only in target neuronal cells.

Alternative Splicing↗

PubMed2003

The Simpson-Golabi-Behmel gene, GPC3, is not involved in sporadic Wilms tumorigenesis.

Many genes have been implicated in Wilms tumor; however, only one gene, WT1, has a proven role in the development of this embryonal tumor. Wilms tumor occurs in a number of congenital syndromes including the Simpson-Golabi-Behmel syndrome (SGBS) which has phenotypic overlap with another Wilms tumor-predisposing syndrome Wiedemann-Beckwith syndrome. The putative function and expression pattern of the SGBS gene, glypican 3 (GPC3), makes it an attractive candidate Wilms tumor gene. We, therefore, hypothesized that Wilms tumors from non-SGBS patients may harbor somatic mutations of GPC3. Mutation analysis of 64 Wilms tumors was performed. One case of a tumor-specific deletion of the entire GPC3 gene and several polymorphisms were identified. GPC3 expression was evaluated in 36 Wilms tumors and 29/36 expressed GPC3. Surprisingly, we did not find evidence of functional mutations of GPC3 in sporadic Wilms tumor suggesting that GPC3 is not often directly involved in Wilms tumorigenesis.

DNA Mutational Analysis↗

PubMed2003

Isolation of a novel cDNA enriched in the undifferentiated chick retina and lens.

By using a differential screening strategy, we have identified a previously uncharacterised gene that is preferentially expressed in chick retinal precursor cells as well as in the anterior epithelial cells of the lens at early stages of development. The EURL transcript has an open reading frame of 293 amino acids and a 3' untranslated region of >850 nucleotides. The only recognizable feature in the EURL (early undifferentiated retina and lens) amino acid sequence is a putative coiled-coil domain located at the C-terminus of the protein. The human EURL orthologue maps to chromosome 21q21. Northern blot analysis, in situ hybridization of tissue sections, and whole-mount hybridization indicate elevated levels of EURL mRNA in the embryonic dorsal retina from stage 14 (day 2) to stage 18 (day 3). At day 3.5, when >90% of the retinal cells are in the proliferative stage, EURL transcripts are found primarily in the peripheral dorsal retina, i.e., the most undifferentiated part of the dorsal retina. EURL transcripts are also detected in the lens at stage 18 and remain abundant in the proliferating epithelial cells of the lens until at least day 11. The distribution pattern of EURL in the developing retina and lens suggest a role before the events leading to cell determination and differentiation.

3' Untranslated Regions↗

PubMed2003

Leiomyosarcoma of the bladder in a retinoblastoma patient.

We report a rare case of leiomyosarcoma in the bladder which occurred in an 18-year-old female with a prior history of retinoblastoma (RB). Molecular characterization of this tumor displayed a homozygous RB deletion and a reduced P53 expression. These results suggest that the loss of RB and P53 may have contributed to the initiation and/or progression of the leiomyosarcoma of the bladder in this patient.

Adolescent↗

PubMed2002

Cloning and expression analysis of the chicken DEAD box gene DDX1.

DEAD box proteins are putative RNA unwinding proteins found in organisms ranging from mammals to bacteria. While some DEAD box genes expressed in higher eukaryotes are ubiquitous, others have distribution profiles that suggest a cell-, tissue-, or developmental-specific role. The DEAD box gene, DDX1, was identified by differential screening of a subtracted retinoblastoma cDNA library. A limited survey of human fetal tissues indicated that DDX1 mRNA has a widespread distribution but is not uniformly expressed in all tissues. To further document the spatial and temporal distribution of DDX1 during embryonic development, we cloned the chicken DDX1 cDNA. The predicted amino acid sequence of chicken DDX1 was 93% identical to that of human DDX1. All DEAD box motifs, as well as a SPRY domain, were present in chicken DDX1. Northern and Western blot analyses showed highest levels of DDX1 at early stages of development. Tissue maturation was generally accompanied by a decrease in expression, although DDX1 levels remained elevated in late embryonic retina and brain. In situ hybridization of retinal tissue sections revealed widespread distribution of DDX1 mRNA at early developmental stages with preferential expression in amacrine and ganglion cells of the differentiated tissue. Preferential expression of DDX1 was also observed in specific areas of the brain in older embryos, such as the external granule layer of the cerebellum. These results suggest a specific role for DDX1 in subsets of differentiated cells as well as a more general role in undifferentiated cells.

Amino Acid Sequence↗

PubMed2002

Expression of spermidine/spermine N(1)-acetyltransferase in the Müller glial cells of the developing chick retina.

A number of genes have been found to be asymmetrically expressed along the three axes of the retina: central-peripheral, dorsal-ventral, temporal-nasal. Some of the asymmetrically expressed genes have been shown to play a role in the establishment of boundaries required for guiding retinal axons to their correct targets in the brain. Asymmetric expression during development can also be a consequence of the different rates of differentiation along the three retinal axes. The authors have used a differential-display-PCR approach to identify genes asymmetrically expressed along the dorsal-ventral axis in the chick retina. One of the selected genes, spermidine/spermine N(1)-acetyltransferase (SSAT), was preferentially expressed in the dorsal-temporal quadrant of the developing retina. There was a sharp increase in retinal SSAT mRNA levels during the transition stage from proliferation (E7) to early differentiation (E10). SSAT mRNA was found in Müller glial cells and its distribution pattern in these cells closely followed the three differentiation axes of the developing retina, with a central-dorsal-temporal preference. The elevated levels of SSAT mRNA in Müller glial cells may reflect a requirement for acetylated spermine/spermidine or putrescine in the differentiating neuronal cells of the retina.

Acetyltransferases↗