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Biomedical subjects

G Wistow

Publications and source records attributed to G Wistow.

At least 19 recordsLinked to original sources
PubMed2000

Usher syndrome 1D and nonsyndromic autosomal recessive deafness DFNB12 are caused by allelic mutations of the novel cadherin-like gene CDH23.

Genes causing nonsyndromic autosomal recessive deafness (DFNB12) and deafness associated with retinitis pigmentosa and vestibular dysfunction (USH1D) were previously mapped to overlapping regions of chromosome 10q21-q22. Seven highly consanguineous families segregating nonsyndromic autosomal recessive deafness were analyzed to refine the DFNB12 locus. In a single family, a critical region was defined between D10S1694 and D10S1737, approximately 0.55 cM apart. Eighteen candidate genes in the region were sequenced. Mutations in a novel cadherin-like gene, CDH23, were found both in families with DFNB12 and in families with USH1D. Six missense mutations were found in five families with DFNB12, and two nonsense and two frameshift mutations were found in four families with USH1D. A northern blot analysis of CDH23 showed a 9.5-kb transcript expressed primarily in the retina. CDH23 is also expressed in the cochlea, as is demonstrated by polymerase chain reaction amplification from cochlear cDNA.

Alleles↗
PubMed1992

Absence of MHC gene expression in lens and cloning of dbpB/YB-1, a DNA-binding protein expressed in mouse lens.

The status of major histocompatibility complex (MHC) class I and II gene expression in the normal mouse lens was examined. No mRNA for either class I or II genes was detectable in mouse lens, while the expression of MHC genes in other tissues generally matched immunohistochemical data from human tissues. However it was observed that MHC class I mRNA is present in the mouse lens-derived cell line alpha TN4-1. From a new-born mouse lens cDNA library a clone was obtained for the murine homologue of the DNA-binding protein dbpB/YB-1, a protein originally identified in human lymphocytes and proposed to be a negative regulator of MHC class II gene expression. Northern blots detect dbpB/YB-1 mRNA in all mouse tissues and cells examined, including both mouse lens and alpha TN4-1 cells, suggesting that dbpB/YB-1 has a general and widespread role.

Amino Acid Sequence↗
PubMed1992

The product of unr, the highly conserved gene upstream of N-ras, contains multiple repeats similar to the cold-shock domain (CSD), a putative DNA-binding motif.

We show that the open reading frame transcribed from the unr gene (immediately upstream of N-ras) in mammals consists of multiple repeats similar to the cold-shock domain (CSD), a putative DNA-binding motif found in prokaryotic cold-shock proteins, and eukaryotic DNA-binding proteins. Alignment of the CSD sequences of unr with those from other proteins reveals a core of similarity for which a consistent secondary structure prediction can be derived. This prediction suggests that the CSD consists primarily of beta-sheet, in contrast to most known eukaryotic DNA-binding proteins. Sequence analysis of the 3' end of the guinea pig unr gene shows that the core of one CSD repeat is encoded in a single exon, consistent with the modular assembly of the gene from ancestral CSD-coding units.

Amino Acid Sequence↗
PubMed1991

Lens protein expression in mammals: taxon-specificity and the recruitment of crystallins.

Vertebrate lenses show remarkably taxon-specific patterns of protein composition, most obviously in the recruitment of enzymes as major crystallins. Phylogenetic relationships are particularly apparent in mammals. Here we describe eta-crystallin, which is probably identical to cytosolic aldehyde dehydrogenase, lens-specifically expressed at high abundance in the elephant shrews, primitive eutherians of the family Macroscelidae, and mu-crystallin, a novel lens protein expressed in some marsupials. We have also observed that enzymes that have been recruited as crystallins in some species are also moderately abundant in the lenses of other species. This hints that the origins of enzyme-crystallins may lie in a pool of enzymes widely expressed in lenses at fairly high levels, perhaps because they have important developmental or functional roles in the tissue.

Alcohol Dehydrogenase↗
PubMed1991

Anomalous behavior of beta B1-crystallin subunits from avian lenses.

In soluble extracts of bird lenses, crystallin subunits of apparent sizes between 30kDa and 40kDa show considerable variability in both abundance and mobility in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS PAGE). This is only partly due to the taxon-specific distribution of lactate dehydrogenase-B (LDH-B)/epsilon-crystallin. Here we show that, in spite of high conservation in primary sequence, beta B1-crystallin subunits of avian lenses have a markedly slower migration in SDS PAGE than those of mammals and that the apparent subunit size of beta B1-crystallin varies among birds. This may be at least partly due to unusual post-translational modifications, since beta B1-crystallins of adult birds react strongly in a glycan detection procedure. No other crystallins in birds or mammals share this strong reaction. Modification of beta B1-crystallin could have interesting consequences for the formation of high molecular weight beta-crystallin aggregates in bird lenses.

Amino Acid Sequence↗
PubMed1991

Lens protein gene expression: alpha-crystallins and MIP.

The crystallin genes encode the major soluble proteins of the lens. Some of the crystallin genes are expressed exclusively in the lens while others are also expressed in different tissues. The two alpha-crystallin genes, alpha A and alpha B, differ in their tissue specificity. Transcription of the alpha A-crystallin gene occurs only in the lens, while the alpha B-crystallin gene is also expressed in other tissues, including heart, skeletal muscle, kidney, lung and brain. MIP (also called MP26), the major intrinsic protein of the lens fiber membranes, is also expressed exclusively in the lens. Correct expression of both alpha-crystallin and MIP are required for normal lens function. Here we review our studies on the molecular basis of expression of the alpha-crystallin and MIP genes in the lens. The 5' flanking sequences containing the initiation site of transcription of the alpha A-crystallin, alpha B-crystallin and MIP genes were fused to the bacterial chloramphenicol acetyltransferase (CAT) gene, and the expression of this reporter gene was studied in transient assays and transgenic mice. DNA sequences flanking the 5' end of the alpha A-crystallin gene contain regulatory elements responsible for the lens-specific expression and developmental regulation of the CAT gene in transgenic mice. Interestingly, although some of the murine alpha A-crystallin regulatory sequences are conserved in the human and chicken genes, different functional regulatory elements appear to control the expression of the murine and chicken alpha A-crystallin genes. The 5' flanking sequence of the alpha B-crystallin gene preferentially directs expression of the CAT gene to the lens and to skeletal muscle. Different regulatory elements of the alpha B-crystallin gene appear to be responsible for its transcription in various tissues. The 5' flanking sequence of the MIP gene also contains regulatory elements that direct expression of the CAT gene to lens cells; these sequences are not functional in transfected non-lens cells and are different from the cis regulatory elements controlling alpha-crystallin gene expression. The multiplicity of cis-regulatory elements controlling the transcription of these three genes indicates the complexity of the mechanisms that regulate gene expression in the lens.

Animals↗
PubMed1990

Evolution of a protein superfamily: relationships between vertebrate lens crystallins and microorganism dormancy proteins.

A search of sequence databases shows that spherulin 3a, an encystment-specific protein of Physarum polycephalum, is probably structurally related to the beta- and gamma-crystallins, vertebrate ocular lens proteins, and to Protein S, a sporulation-specific protein of Myxococcus xanthus. The beta- and gamma-crystallins have two similar domains thought to have arisen by two successive gene duplication and fusion events. Molecular modeling confirms that spherulin 3a has all the characteristics required to adopt the tertiary structure of a single gamma-crystallin domain. The structure of spherulin 3a thus illustrates an earlier stage in the evolution of this protein superfamily. The relationship of beta- and gamma-crystallins to spherulin 3a and Protein S suggests that the lens proteins were derived from an ancestor with a role in stress-response, perhaps a response to osmotic stress.

Amino Acid Sequence↗
PubMed1990

Evidence for neutral and selective processes in the recruitment of enzyme-crystallins in avian lenses.

In apparent contrast to most other tissues, the ocular lenses in vertebrates show striking differences in protein composition between taxa, most notably in the recruitment of different enzymes as major structural proteins. This variability appears to be the result of at least partially neutral evolutionary processes, although there is also evidence for selective modification in molecular structure. Here we describe a bird, the chimney swift (Chaetura pelagica), that lacks delta-crystallin/argininosuccinate lyase, usually the major crystallin of avian lenses. Clearly, delta-crystallin is not specifically required for a functionally effective avian lens. Furthermore the lens composition of the swift is more similar to that of the related hummingbirds than to that of the barn swallow (Hirundo rustica), suggesting that phylogeny is more important than environmental selection in the recruitment of crystallins. However differences in epsilon-crystallin/lactate dehydrogenase-B sequence between swift and hummingbird and other avian and reptilian species suggest that selective pressures may also be working at the molecular level. These differences also confirm the close relationship between swifts and hummingbirds.

Amino Acid Sequence↗
PubMed1989

A superfamily of NADPH-dependent reductases in eukaryotes and prokaryotes.

Aldose reductase (AR) is implicated in some of the disabling complications of diabetes, including neuropathy, retinopathy and cataracts. Our studies are aimed at further clarifying the role of AR in diabetes and facilitating the design of new classes of potent, specific AR inhibitors by gaining an understanding of the protein structure of AR. To this end, we have determined the complete protein sequence of rat lens AR using cDNA analysis and primer extension of mRNA. By comparing protein sequences, we have found that the structural relatedness (41% to 57%) among the vertebrate proteins, aldose reductase, aldehyde reductase, prostaglandin F synthase and the frog lens protein rho-crystallin can now be extended to prokaryotes by the inclusion of Corynebacterium 2,5-diketo-D-gluconate reductase. This more distantly related protein shares 30-40% identity with the vertebrate enzymes. Sequence alignments reveal that 18% of the amino acids are completely conserved in all members of the superfamily, many of them in clusters, suggesting that they mark important structural features such as the nucleotide binding site and substrate binding site. rho-Crystallin, which is structurally related to this superfamily of NADPH-dependent reductases, does not appear to reduce PGH2, PGD2, xylose or glyceraldehyde to any appreciable extent. It does, however, bind NADPH.

Aldehyde Oxidoreductases↗
PubMed1987

Aldose reductase and p-crystallin belong to the same protein superfamily as aldehyde reductase.

Aldose reductase (EC 1.1.1.21) has been implicated in a variety of diabetic complications. Here we present the first primary sequence data for the rat lens enzyme, obtained by amino acid and cDNA analysis. We have found structural similarities with another NADPH-dependent oxidoreductase: human liver aldehyde reductase (EC 1.1.1.2). The identity between these two enzymes is 50%. Both enzymes share approx. 40-50% homology with p-crystallin, a major lens protein present only in the frog, Rana pipiens. We propose that aldose reductase, aldehyde reductase and p-crystallin are members of a superfamily of related proteins.

Alcohol Dehydrogenase↗
PubMed1987

Recruitment of enzymes as lens structural proteins.

Crystallins, the principal components of the lens, have been regarded simply as soluble, structural proteins. It now appears that the major taxon-specific crystallins of vertebrates and invertebrates are either enzymes or closely related to enzymes. In terms of sequence similarity, size, and other physical characteristics delta-crystallin is closely related to argininosuccinate lyase, tau-crystallin to enolase, and SIII-crystallin to glutathione S-transferase; moreover, it has recently been demonstrated that epsilon-crystallin is an active lactate dehydrogenase. Enzymes may have been recruited several times as lens proteins, perhaps because of the developmental history of the tissue or simply because of evolutionary pragmatism (the selection of existing stable structures for a new structural role).

Amino Acid Sequence↗
PubMed1987

Primary and secondary structure of bovine retinal S antigen (48-kDa protein).

The complete amino acid sequence of bovine S antigen (48-kDa protein) has been determined by cDNA and partial amino acid sequencing. A 1623-base-pair (bp) cDNA contains an open reading frame coding for a protein of 404 amino acids (45,275 Da). Tryptic peptides and cyanogen bromide peptides of native bovine S antigen were purified and partially sequenced. All of these peptides were accounted for in the long open reading frame. Searching of the National Biomedical Research Foundation data bank revealed no extensive sequence homology between S antigen and other proteins. However, there are local regions of sequence similarity with alpha transducin, including the sites subject to ADP-ribosylation by Bordetella pertussis and cholera toxins and the phosphoryl binding-sites. Secondary structure prediction and circular dichroic spectroscopy show that S antigen is composed predominantly of beta-sheet conformation. Acid-catalyzed methanolysis suggests the presence of low levels of carbohydrate in the molecule.

Amino Acid Sequence↗
PubMed1987

Joint finance: promoting a new balance of care and responsibilities in England?

British government policy has long aimed at substituting local government community services for centrally-funded long-stay hospital services. Thus, the health service has depended on the willingness of locally administered and financed services to accept a shift in the balance of care. A special financial programme--joint finance--was introduced in 1976 to provide local authorities with an incentive to implement this shift. The programme apparently provided health authorities with the power to ensure that joint finance spending met their own priorities for service development. In practice, a number of influences combined to ensure that local authority interests and priorities prevailed. The principal lesson of this initiative, and its successor, is the importance of devising balanced incentives which prevent either party from exercising a veto over inter-agency transactions.

Community Mental Health Services↗
PubMed1987

The structure of bovine retinal S-antigen: sequence analysis and identification of monoclonal antibody epitopes and uveitogenic site.

cDNA clones for bovine retinal S-antigen (48K protein) have been isolated and sequenced. Secondary structure prediction for the deduced amino acid sequence suggest that the protein has predominantly beta-conformation with a helical region at the C-terminus. Local regions of sequence similarity with alpha-transducin have been observed, including the sites subject to ADP-ribosylation by pertussis and cholera toxins. Thirty-nine tryptic peptides and ten CNBr peptides of native S-antigen were purified and partially sequenced, showing good agreement with the sequence deduced from the cDNA analysis. The locations of two monoclonal epitopes have been determined by different methods. Furthermore, one synthetic peptide corresponding to the determined amino acid sequence was found to be highly pathogenic for the induction of experimental autoimmune uveitis (EAU). Native S-antigen has further been shown to be glycosylated, which has implications for its antigenicity.

Amino Acid Sequence↗
PubMed1986

cDNA and deduced protein sequence for the beta B1-crystallin polypeptide of the chicken lens. Conservation of the PAPA sequence.

The nucleotide sequence of two cDNA clones corresponding to the beta B1-crystallin mRNA (formerly beta 35) of the chicken eye lens has been determined. The derived amino acid sequence of the chicken beta B1 polypeptide fits well with the two-domain, four "Greek Key" motif structure common to the beta gamma-crystallin superfamily of proteins. The calculated molecular weight of the encoded chicken beta B1 protein is 27,267. The beta B1 polypeptide has both an N- and C-terminal extension and is highly homologous to the mammalian beta B1-crystallin polypeptide. There is a 72% homology between the core regions of the chicken and bovine beta B1 polypeptides; by contrast, there is only 27% homology between the N-terminal extensions of these polypeptides. The N-terminal extension of chicken beta B1 contains a short alternating proline-alanine (PAPA) sequence, like that in the mammalian beta B1, and has some homology with the N-terminal region of histone H1.4, myosin light chain, prokaryotic outer membrane protein A, and adenovirus 24/28-kDa early protein. At the nucleic acid level, the chicken beta B1 crystallin gene has an atypical polyadenylation signal, AATTAAA. This appears to be associated with microheterogeneity of the polyadenylation site by comparison of two cDNA clones, suggesting an additional level at which diversity in crystallin gene expression may arise.

Amino Acid Sequence↗