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M D Weston

Publications and source records attributed to M D Weston.

At least 19 recordsLinked to original sources
PubMed1998

Mutation of a gene encoding a protein with extracellular matrix motifs in Usher syndrome type IIa.

Usher syndrome type IIa (OMIM 276901), an autosomal recessive disorder characterized by moderate to severe sensorineural hearing loss and progressive retinitis pigmentosa, maps to the long arm of human chromosome 1q41 between markers AFM268ZD1 and AFM144XF2. Three biologically important mutations in Usher syndrome type IIa patients were identified in a gene (USH2A) isolated from this critical region. The USH2A gene encodes a protein with a predicted size of 171.5 kilodaltons that has laminin epidermal growth factor and fibronectin type III motifs; these motifs are most commonly observed in proteins comprising components of the basal lamina and extracellular matrixes and in cell adhesion molecules.

Amino Acid Sequence↗
PubMed1998

Identification of three novel mutations in human EYA1 protein associated with branchio-oto-renal syndrome.

The Branchio-oto-renal (BOR) syndrome is an autosomal dominant disorder characterized by branchial clefts, preauricular sinuses, hearing loss, and renal anomalies. Recent studies have shown that mutations in EYA1 are associated with BOR. However, the underlying molecular mechanisms by which mutations in the EYA1 gene cause BOR syndrome are unknown. We have investigated 12 unrelated Caucasian families for mutations by heteroduplex analysis and direct sequencing of products from the polymerase chain reaction. In this study, we identified two novel frameshift deletions and a single base substitution that introduces a stop codon mutation in the C-terminal region of the EYA1 gene. No obvious relationships were observed between the nature of the mutations and the variable clinical features associated with BOR syndrome.

Amino Acid Sequence↗
PubMed1997

Isolation of a novel human homologue of the gene coding for echinoderm microtubule-associated protein (EMAP) from the Usher syndrome type 1a locus at 14q32.

Usher syndrome type 1 (USH1) is an autosomal recessive, genetically heterogeneous disorder causing severe congenital deafness, retinitis pigmentosa, and vestibular dysfunction. The USHla locus located on 14q32 has been linked to the genetic markers D14S250 and D14S78. Using D14S250 and D14S78, we have isolated two nonchimeric YACs, 878g10 and 844g2, and a single BAC (135i20) and PAC (194e17) clone and have arranged them into a contig spanning over the D14S250 and D14S78 markers. The analysis of the YACs, BAC, and PAC revealed that the physical distance between D14S250 and D14S78 is less than 25 kb. Iterative cDNA library screening initiated with the EST 219670 found in the vicinity of the D14S78 marker yielded a cDNA contig. The nucleotide sequence of the cDNA encodes a protein of 717 amino acids in length, showing a high level of homology to the Echinoderm 77-kDa microtubule-associated protein (EMAP). The human homologue of Echinoderm microtubule-associated protein defines a novel human gene. We propose that the human EMAP is a strong candidate for the USH1a gene based on its genomic location and the proposed function of the protein.

Animals↗
PubMed1997

The genomic structure of the gene defective in Usher syndrome type Ib (MYO7A).

Usher syndrome type Ib is a recessive autosomal disorder manifested by congenital deafness, vestibular dysfunction, and progressive retinal degeneration. Mutations in the human myosin VIIa gene (MYO7A) have been reported to cause Usher type Ib. Here we report the genomic organization of MYO7A. An STS content map was determined to discover the YAC clones that would cover the critical region for Usher syndrome type Ib. Three of the YACs (802A5, 966D6, and 965F10) were subcloned into cosmids and used to assemble a preliminary cosmid contig of the critical region. Part of the gene encoding human myosin VIIa was found in the preliminary cosmid contig. A cosmid, P1, PAC, and long PCR contig that contained the entire MYO7A gene was assembled. Primers were designed from the composite cDNA sequence and used to detect intron-exon junctions by directly sequencing cosmid, P1, PAC, and genomic PCR DNA. Alternatively spliced products were transcribed from the MYO7A gene: the largest transcript (7.4 kb) contains 49 exons. The MYO7A gene is relatively large, spanning approximately 120 kb of genomic DNA on chromosome 11q13.

Abnormalities, Multiple↗
PubMed1996

The construction of a yeast artificial chromosome (YAC) contig in the vicinity of the Usher syndrome type IIa (USH2A) gene in 1q41.

The gene for Usher syndrome type II (USH2A), an autosomal recessive syndromic deafness, has been mapped to a region of 1q41 flanked proximally by D1S217 and distally by D1S439. Using sequence-tagged sites (STSs) within the region, a total of 21 yeast artificial chromosome (YAC) clones were isolated and ordered into a single contig that spans approximately 11.0 Mb. The order of microsatellite and STS markers in this region was established as D1S505-D1S425-DXS217-D1S556-D1S237-D1S4 74-EB1-EB2-KB6-AFM144XF2-KB1-K B4-D1S229-D1S490-D1S227-TGFbeta2-D1S439. Analysis of newly positioned polymorphic markers in recombinant individuals in two Usher syndrome type IIa families has enabled us to identify DXS474 and AFM144XF2 as two flanking markers for the Usher type IIa locus. The physical distance between the two markers is 1.0 Mb. This region is covered by eight YACs from the CEPH library: 945f7, 867g9, 762a6, 919h3, 794b8, 785h4, 848b9, and 841g2. A long-range physical map of the Usher type IIa critical region, using MluI, BssHII, NotI, EagI, and SacII, has been developed.

Base Sequence↗
PubMed1996

Myosin VIIA mutation screening in 189 Usher syndrome type 1 patients.

Usher syndrome type 1b (USH1B) is an autosomal recessive disorder characterized by congenital profound hearing loss, vestibular abnormalities, and retinitis pigmentosa. The disorder has recently been shown to be caused by mutations in the myosin VIIa gene (MYO7A) located on 11q14. In the current study, a panel of 189 genetically independent Usher I cases were screened for the presence of mutations in the N-terminal coding portion of the motor domain of MYO7A by heteroduplex analysis of 14 exons. Twenty-three mutations were found segregating with the disease in 20 families. Of the 23 mutations, 13 were unique, and 2 of the 13 unique mutations (Arg212His and Arg212Cys) accounted for the greatest percentage of observed mutant alleles (8/23, 31%). Six of the 13 mutations caused premature stop codons, 6 caused changes in the amino acid sequence of the myosin VIIa protein, and 1 resulted in a splicing defect. Three patients were homozygotes or compound heterozygotes for mutant alleles; these three cases were Tyr333Stop/Tyr333Stop, Arg212His-Arg302His/Arg212His-Arg302His, and IVS13nt-8c-->g/Glu450Gln. All the other USH1B mutations observed were simple heterozygotes, and it is presumed that the mutation on the other allele is present in the unscreened regions of the gene. None of the mutations reported here were observed in 96 unrelated control samples, although several polymorphisms were detected. These results add three patients to single case reported previously where mutations have been found in both alleles and raises the total number of unique mutations in MYO7A to 16.

Alleles↗
PubMed1995

Construction and characterization of a NotI linking library from human chromosome region 1q25-qter.

Chromosome 1q25-qter-specific NotI linking clones have been isolated from a NotI linking library that was constructed using DNA from MCH206.1 somatic cell hybrid cells. These cells contain chromosome 1q25-qter translocated to human chromosome Xp22 as the only human genetic material in mouse background. Sixty-eight NotI linking clones have been mapped by a combination of fluorescence in situ hybridization and R-banding to cytogenetic bands on the long arm of chromosome 1. The relative order of 11 NotI clones and their relation to known chromosome 1 markers have also been determined in 1q32 and 1q41, where the genes of Van der Woude and Usher syndrome type IIa have been previously mapped: cen-chr1.14-chr1.79-chr1.56-chr1.11-chr1.9 5- chr1.58 (chr1.74)-D1S70-chr1.15-chr1.82 (chr1.143)-chr1.62-D1S81-tel. The 1q32- and 1q41-specific NotI linking clones were sequenced in the vicinity of the NotI site. They were analyzed in terms of nucleotide composition, G+C content, frequency of CpG dinucleotides, and protein coding potentials. Most of the 1q32-q41-specific NotI linking clones were derived from CpG islands. Sequences of three NotI linking clones proved to be identical with known genes. Six of the remaining eight had a high potential for coding regions and shared short homologous regions with sequences in the GenBank database. The NotI linking clones and the identified CpG islands will provide valuable resources for constructing a long-range restriction map of chromosome 1q25-q44 and for the eventual isolation of disease genes of Van der Woude syndrome (1q32-q41) and Usher syndrome type IIa (1q41).

Animals↗
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↗
PubMed1995

Gene mapping of Usher syndrome type IIa: localization of the gene to a 2.1-cM segment on chromosome 1q41.

Usher syndrome type II is associated with hearing loss and retinitis pigmentosa but not with any vestibular problems. It is known to be genetically heterogeneous, and one locus (termed USH2A) has been linked to chromosome 1q41. In an effort to refine the localization of USH2A, the genetic map of the region between and adjacent to the marker loci previously recognized as flanking USH2A (D1S70 and PPOL) is updated. Analysis of marker data on 68 Usher II families places the USH2A gene into a 2.1-cM region between the markers D1S237 and D1S229. The gene for transforming growth factor beta 2 (TGFB2) and the gene for the homeodomain box (HLX1) are both eliminated as candidates for USH2A, by virtue of their localization outside these flanking markers. The earlier finding of genetic heterogeneity was confirmed in six new families, and the proportion of unlinked Usher II families is estimated at 12.5%. The placement of the USH2A gene into this region will aid in the physical mapping and isolation of the gene itself.

Chromosome Mapping↗
PubMed1994

Mivacurium in the myasthenic patient.

We have used mivacurium in four myasthenic patients presenting for thymectomy. Supramaximal single twitch stimulation was applied to the ulnar nerve at the wrist and the force of contraction of the adductor pollicis was measured. After an initial bolus dose of 30 micrograms kg-1 (approximately one-fifth of the normal intubating dose), we observed a mean 37.5 (SEM 5.6)% reduction in evoked twitch tension. Neuromuscular block was increased with incremental doses and maintained with repeat bolus doses of 15 micrograms kg-1 at 25% recovery. The interval between maintenance bolus doses remained constant (mean 5.9 (0.7) min). Spontaneous offset was rapid with a mean recovery index (T25-T75) of 11.9 (2.1) min. Provided anticholinesterase therapy is withheld in the immediate preoperative period, mivacurium would appear to be a safe and appropriate neuromuscular blocker in this variably sensitive group of patients. The cumulative dose required to establish full neuromuscular block varied between 60 and 90 micrograms kg-1. A maintenance infusion, commencing at 3 micrograms kg-1 min-1, is recommended, guided by neuromuscular monitoring.

Adult↗
PubMed1993

Genetic heterogeneity of Usher syndrome type II.

Usher syndrome is an autosomal recessive disorder characterised by retinitis pigmentosa and congenital sensorineural hearing loss. A gene for Usher syndrome type II (USH2) has been localised to chromosome 1q32-q41. DNA from a family with four of seven sibs affected with clinical characteristics of Usher syndrome type II was genotyped using markers spanning the 1q32-1q41 region. These included D1S70 and D1S81, which are believed to flank USH2. Genotypic results and subsequent linkage analysis indicated non-linkage of this family to these markers. The A test analysis for heterogeneity with this family and 32 other Usher type II families was statistically significant at p < 0.05. Further clinical evaluation of this family was done in light of the linkage results to determine if any phenotypic characteristics would allow for clinical identification of the unlinked type. No clear phenotypic differences were observed; however, this unlinked family may represent a previously unreported subtype of Usher type II characterised by a milder form of retinitis pigmentosa and mild vestibular abnormalities. Heterogeneity of Usher syndrome type II complicates efforts to isolate and clone Usher syndrome genes using linkage analysis and limits the use of DNA markers in early detection of Usher type II.

Adolescent↗
PubMed1992

Linkage of Usher syndrome type I gene (USH1B) to the long arm of chromosome 11.

Usher syndrome is the most commonly recognized cause of combined visual and hearing loss in technologically developed countries. There are several different types and all are inherited in an autosomal recessive manner. There may be as many as five different genes responsible for at least two closely related phenotypes. The nature of the gene defects is unknown, and positional cloning strategies are being employed to identify the genes. This is a report of the localization of one gene for Usher syndrome type I to chromosome 11q, probably distal to marker D11S527. Another USH1 gene had been previously localized to chromosome 14q, and this second localization establishes the existence of a new and independent locus for Usher syndrome.

Base Sequence↗