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Biomedical subjects

D Weil

Publications and source records attributed to D Weil.

At least 55 records · Page 3Linked to original sources
PubMed1997

Clustering of mutations responsible for branchio-oto-renal (BOR) syndrome in the eyes absent homologous region (eyaHR) of EYA1.

Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder, characterised by the association of branchial, otic and renal anomalies with variable degrees of severity. We have recently identified EYA1 , a human homologue of the Drosophila eyes absent gene, as the gene underlying this syndrome. The products of both genes share a highly conserved 271 amino acid C-terminal region (eyaHR). The eyaHR was also found in the products of two other human genes (EYA2 and EYA3), demonstrating the existence of a novel gene family. We report here on the complete genomic structure of EYA1. This gene consists of 16 coding exons and extends over 156 kb. It encodes various alternatively spliced transcripts differing only in their 5' regions. Sequence analysis of the entire EYA1 coding region was performed for 20 unrelated patients affected by BOR syndrome, and six novel mutations were identified. Among these mutations, two are missense mutations, highlighting amino acid residues essential for the function of the EYA1 protein, and one mutation comprises a de novo Alu insertion into an exon. This insertion presumably occurs by retrotransposition, and the mobile Alu element has a poly(A) tail that is unstable throughout generations. To date, 14 mutations have been detected in BOR patients, all of which are different. However, all the mutations are located within or in the immediate vicinity of the eyaHR; the significance of this clustering is discussed.

Amino Acid Sequence↗
PubMed1996

Human myosin VIIA responsible for the Usher 1B syndrome: a predicted membrane-associated motor protein expressed in developing sensory epithelia.

The gene encoding human myosin VIIA is responsible for Usher syndrome type III (USH1B), a disease which associates profound congenital sensorineural deafness, vestibular dysfunction, and retinitis pigmentosa. The reconstituted cDNA sequence presented here predicts a 2215 amino acid protein with a typical unconventional myosin structure. This protein is expected to dimerize into a two-headed molecule. The C terminus of its tail shares homology with the membrane-binding domain of the band 4.1 protein superfamily. The gene consists of 48 coding exons. It encodes several alternatively spliced forms. In situ hybridization analysis in human embryos demonstrates that the myosin VIIA gene is expressed in the pigment epithelium and the photoreceptor cells of the retina, thus indicating that both cell types may be involved in the USH1B retinal degenerative process. In addition, the gene is expressed in the human embryonic cochlear and vestibular neuroepithelia. We suggest that deafness and vestibular dysfunction in USH1B patients result from a defect in the morphogenesis of the inner ear sensory cell stereocilia.

Alternative Splicing↗
PubMed1995

A YAC contig and an EST map in the pericentromeric region of chromosome 13 surrounding the loci for neurosensory nonsyndromic deafness (DFNB1 and DFNA3) and limb-girdle muscular dystrophy type 2C (LGMD2C).

Two forms of inherited childhood nonsyndromic deafness (DFNB1 and DFNA3) and a Duchenne-like form of progressive muscular dystrophy (LGMD2C) have been mapped to the pericentromeric region of chromosome 13. To clone the genes responsible for these diseases we constructed a yeast artificial chromosome (YAC) contig spanning an 8-cM region between the polymorphic markers D13S175 and D13S221. The contig comprises 24 sequence-tagged sites, among which 15 were newly obtained. This contig allowed us to order the polymorphic markers centromere-D13S175-D13S141-D13S143-D13S115-AF M128yc1-D13S292-D13S283-AFM323vh5- D13S221-telomere. Eight expressed sequence tags, previously assigned to 13q11-q12 (D13S182E, D13S183E, D13S502E, D13S504E, D13S505E, D13S837E, TUBA2, ATP1AL1), were localized on the YAC contig. YAC screening of a cDNA library derived from mouse cochlea allowed us to identify an alpha-tubulin gene (TUBA2) that was subsequently precisely mapped within the candidate region.

Animals↗
PubMed1995

Prevalence and molecular analysis of two hot spots for ectopic recombination leading to XX maleness.

Two hot spots of ectopic Xp-Yp recombination have previously been shown to be at the origin of XX maleness (Weil et al., 1994, Nature Genet. 7:414-419). To get more insight into the molecular basis of the abnormal interchange, 25 Y(+) class 3 XX male patients were studied. The two hot spots were found to account for the aberrant exchange in more than 50% of the cases. In addition, there is a correlation between the prevalence of each hot spot and the degree of X-Y homology between the corresponding fragments. Sequencing of the X-Y junctions in six patients, who carried a breakpoint mapping in either of these two hot spot fragments, showed that their precise locations were different from one individual to the other. In particular, the results obtained here in four new patients exclude the possibility that the repeated elements, present in these X-Y homologous fragments, are responsible for the high incidence of X-Y interchanges observed. Moreover, the breakpoints of all 25 class 3 XX males were found to be arranged in the same order on the X and Y chromosomes. This suggests that most ectopic recombinations leading to class 3 XX maleness involve X-Y homologous sequences persisting from an ancestral larger block of homology on the short arms of both sex chromosomes.

Base Sequence↗
PubMed1995

Regulation of pre-mRNA processing by src.

BACKGROUND: Changes in gene expression in response to external signals provide a key mechanisms for the regulation of higher eukaryotic cell functions. The importance of transcriptional control in the response of cells to growth factors and cytokines has been extensively documented, but gene expression has also been shown to be controlled at other levels, such as the stability of mRNA in the cytoplasm, its localization and translation. By contrast to transcriptional control, little is known of the contribution of pre-mRNA nuclear processing to the regulation of gene expression, as most of our knowledge of pre-mRNA processing in vivo is indirect, being inferred from comparisons of transcription rates and levels of mRNA accumulation. RESULTS: In this study, we have used as a model the well-characterized maturation pathway of transcripts of the cytokine, tumour necrosis factor beta (TNF beta). We have used the murine TNF beta gene as a reporter for pre-mRNA processing, using a co-transfection approach to investigate whether overproduction of proteins involved in signal transduction influences the processing of TNF beta transcripts. Although transfection of both activated ras and src genes led to an increase in RNA accumulation in the nuclear and cytoplasmic compartments, as expected from their transactivation of the TNF beta expression vector, only src induced a modification of RNA processing. Comparison of several modes of src activation indicated that two distinct effects of src on pre-mRNA processing can be coupled: one involves slowing down splicing and the other allows the export of partially spliced transcripts. These effects can be observed not only on the three introns of TNF beta but also on transcripts from a beta globin expression vector. DISCUSSION: We have characterized how the processing of transcripts of TNF beta and beta globin is regulated by the signal transduction pathway that includes the Src protein, establishing that external signals have the capacity to regulate gene expression at a post-transcriptional level within the nucleus. Src seems to act on a general mechanism of splicing and/or mRNA transport, but its biologically relevant targets are likely to be restricted to genes for which either alternative processing pathways are in competition, or the kinetics of splicing is critical. This regulation could reflect a modulation by Src of the activity of components of the splicing and transport machineries, but could also involve RNA-binding proteins, which have been shown to interact with Src.

3T3 Cells↗
PubMed1995

Defective myosin VIIA gene responsible for Usher syndrome type 1B.

Usher syndrome represents the association of a hearing impairment with retinitis pigmentosa and is the most frequent cause of deaf-blindness in humans. It is inherited as an autosomal recessive trait which is clinically and genetically heterogeneous. Some patients show abnormal organization of microtubules in the axoneme of their photoreceptors cells (connecting cilium), nasal ciliar cells and sperm cells, as well as widespread degeneration of the organ of Corti. Usher syndrome type 1 (USH1) is characterized by a profound congenital sensorineural hearing loss, constant vestibular dysfunction and prepubertal onset of retinitis pigmentosa. Of three different genes responsible for USH1. USH1B maps to 11q13.5 (ref. 10) and accounts for about 75% of USH1 patients. The mouse deafness shaker-1 (sh1) mutation has been localized to the homologous murine region. Taking into account the cytoskeletal abnormalities in USH patients, the identification of a gene encoding an unconventional myosin as a candidate for shaker-1 (ref. 14) led us to consider the human homologue as a good candidate for the gene that is defective in USH1B. Here we present evidence that a gene encoding myosin VIIA is responsible for USH1B. Two different premature stop codons, a six-base-pair deletion and two different missense mutations were detected in five unrelated families. In one of these families, the mutations were identified in both alleles. These mutations, which are located at the amino-terminal end of the motor domain of the protein, are likely to result in the absence of a functional protein. Thus USH1B appears as a primary cytoskeletal protein defect. These results implicate the genes encoding other unconventional myosins and their interacting proteins as candidates for other genetic forms of Usher syndrome.

Adult↗
PubMed1994

Torsion of the gallbladder in children.

Two cases of torsion of the gallbladder in children (ages 5 and 7) are reported, and the relevant literature is reviewed. The condition is extremely rare in the pediatric population, and the correct diagnosis is rarely made preoperatively. However, the clinical presentation may be evocative of the diagnosis. Ultrasonography is helpful for the diagnosis, but ultrasonographic modifications of the gallbladder occur after the onset of the pain. The treatment of this condition is early cholecystectomy.

Child↗
PubMed1994

Highly homologous loci on the X and Y chromosomes are hot-spots for ectopic recombinations leading to XX maleness.

In 80% of XX males, maleness is due to the presence of Y-specific DNA including the SRY gene and results from an abnormal terminal X-Y interchange during paternal meiosis. Here we address the molecular basis of this ectopic recombination through the analysis of the X-Y junction in two class 3 XX males. We show that each of the rearrangements has involved X-Y highly homologous loci on the sex-specific part of these chromosomes (98.7% and 96% sequence identity over 1.2 and 1.1 kb respectively). Moreover in five out of six other XX males, the X-Y junctions are located in the same rearranged restriction fragment as in either of these patients. These fragments thus define two hot-spots of ectopic recombination which together could account for about one third of XX males. Evolution of these loci in primates is discussed.

Animals↗
PubMed1993

A 45,X male with an X;Y translocation: implications for the mapping of the genes responsible for Turner syndrome and X-linked chondrodysplasia punctata.

In a male patient with a 45,X karyotype, the terminal part of the Y chromosome short arm was translocated as a single block on to the X chromosome. This rearranged X chromosome was, in every regard, the same as that present in XX males resulting from an abnormal X-Y interchange. Correlations between the phenotype of this patient and the extent of the deletions on the X and Y chromosomes allowed us to map the genes responsible for most features of the Turner syndrome between DXS432 and Xqter on the X chromosome, and the homologous Y genes either on Yp in interval 4 or on Yq. The molecular analysis of this X-Y translocation allowed us also to reduce the interval for the X-linked recessive chondrodysplasia punctata gene to a 1.5 Mb interval between DXS432 and DXS31.

Adolescent↗
PubMed1993

In vivo cooperation between introns during pre-mRNA processing.

In higher eukaryotes the large number of introns present in most genes implies that the pre-mRNA processing machinery should be efficient and accurate. Although this could be achieved at the level of each intron, an attractive alternative would be that interactions between introns improve the performance of this machinery. In this study we tested this hypothesis by comparing the processing of transcripts of the tumor necrosis factor beta gene, which differ only by their number of introns. We took advantage of the ordered splicing of the three introns present in this gene to design constructs that should generate, as primary transcripts, molecules that are normally produced by splicing. We established that the apparent splicing rate of intron 3 is increased 2.5- and 3.5-fold by the presence of one or two other introns on the primary transcript, respectively. Similarly, the apparent splicing rate of intron 2 is increased by the presence of intron 1. As these effects involve the splice sites of the upstream intron, these observations support the existence of cooperative interactions between introns during pre-mRNA processing.

3T3 Cells↗
PubMed1991

Endemic and epidemic aspergillosis associated with in-hospital replication of Aspergillus organisms.

When a new hospital opened in 1983, environmental culturing for Aspergillus organisms and surveillance for nosocomial aspergillosis cases were begun to characterize the relationship between environmental contamination and infection. Monthly air sampling demonstrated increasing concentrations of Aspergillus flavus and Aspergillus fumigatus to mean levels greater than 1 cfu/m3 during 1986-1987, accompanied by a progressive increase in incidence of aspergillosis to 1.2% in immunocompromised patients. This prompted an inspection that revealed heavy growth of Aspergillus organisms on air filters. Subsequent inspections of hospital wards showed small foci of A. flavus growth on other materials. Removal of the contaminated filters and improved environmental maintenance were associated with reduction in A. flavus and A. fumigatus to 0.01 cfu/m3 and a fourfold decline in aspergillosis incidence during the next 2 years. These findings, together with laboratory studies that showed aspergilli could proliferate on common hospital materials when moistened, indicate a need for careful environmental maintenance.

Air Microbiology↗
PubMed1990

Structural and functional characterization of a splicing mutation in the pro-alpha 2(I) collagen gene of an Ehlers-Danlos type VII patient.

A splicing mutation in the pro-alpha 2(I) collagen gene of a patient with Ehlers-Danlos syndrome type VII has been characterized. Protein microsequencing of peptides prepared from the patient's dermal collagen identified an interstitial deletion of 18 residues. The deleted segment corresponds to the amino-terminal telopeptide junction domain encoded by the sixth exon of the pro-alpha 2(I) collagen gene. Sequencing of specifically primed cDNA clones confirmed the presence of two distinct populations of pro-alpha 2(I) mRNAs, a normal one and another which lacks the sequences of exon 6. Limited sequencing of genomic clones showed that one of the pro-alpha 2(I) alleles displays a conservative change in the seventh codon of exon 6 (GAC for GAT), and a base substitution at position +1 of intron 6 (A for G). Since the normal transcript contains the GAT codon, the intronic change was associated with the allele that gives rise to the shortened pro-alpha 2(I) collagen mRNA. The two allelic fragments were subcloned into an expression vector and the pattern of splice-site selection for exons 5-8 was assessed for each of the constructs after transfection into COS cells. This documented skipping of exon 6 sequences only in transcripts of the minigene construct that harbors the G to A transition. Expression of allelic cross-constructs confirmed that the single-base substitution at position +1 of intron 6 is the mutation responsible for the abnormal joining of exons 5 and 7 sequences in the patient's shortened pro-alpha 2(I)mRNA.

Alleles↗
PubMed1990

RNA processing is a limiting step for murine tumor necrosis factor beta expression in response to interleukin-2.

We have previously reported that tumor necrosis factor beta (TNF beta) expression is induced by interleukin-2 (IL-2) in the murine lymphocytic T-cell line CTLL-2. In this study, we have characterized the nuclear and cytoplasmic TNF beta transcript and assessed their role in TNF beta gene expression. A unique feature of TNF beta expression was the accumulation of nuclear precursors, which reflected a slow nuclear RNA processing. As a consequence, there was a delay in the appearance of cytoplasmic messengers after the transcriptional induction of TNF beta by IL-2. We also found that two messengers, the fully spliced messenger and an intron 3-retaining messenger, were exported to the cytoplasm and actively translated. The same pattern of expression was observed in concanavalin A-stimulated splenocytes, although the level of expression was much lower than in CTLL-2 cells. The simple genetic structure and the high level of accumulation of nuclear precursors make TNF beta a particularly attractive model system to use for studies of RNA processing and cytoplasmic transport of partially spliced messengers.

Amino Acid Sequence↗