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A Tunnacliffe

Publications and source records attributed to A Tunnacliffe.

At least 19 recordsLinked to original sources
PubMed2000

Intracellular trehalose improves osmotolerance but not desiccation tolerance in mammalian cells.

Trehalose has been shown to play a role in osmotolerance or desiccation tolerance in some microorganisms, anhydrobiotic invertebrates and resurrection plants. To test whether trehalose could improve stress responses of higher eukaryotes, a mouse cell line was genetically engineered to express bacterial trehalose synthase genes. We report that the resulting levels of intracellular trehalose ( approximately 80 mM) are able to confer increased resistance to the partial dehydration resulting from hypertonic stress, but do not enable survival of complete desiccation due to air drying.

Animals↗
PubMed2000

Stabilisation of Salmonella vaccine vectors by the induction of trehalose biosynthesis.

The growth of an aroA mutant of Salmonella typhimurium (SL3261) in minimal medium containing 0.5 M NaCl resulted in the intracellular accumulation of 2.2 micromol trehalose/mg total protein. The vacuum drying of these bacteria in the presence of trehalose allowed the recovery of 35% of the viable cells that were present before drying. In contrast, bacteria cultured in control medium accumulated 0.4 micromol trehalose/mg total protein and only 5% of the viable cells were recovered after vacuum drying with trehalose. Similar results were obtained when S. typhimurium SL3261, expressing the vaccine antigen (F1-antigen) of Yersinia pestis, was cultured in minimal medium with or without 0.5 M NaCl and dried in the presence of trehalose. Although these results indicate the potential for trehalose stabilisation of vaccine strains of S. typhimiurium, growth in minimal medium containing 0.5 M NaCl resulted in the loss of invasion competence of the bacteria.

Animals↗
PubMed2000

Cloning and chromosomal localization of the human BARX2 homeobox protein gene.

The human BARX2 gene encodes a homeodomain-containing protein of 254 amino acids, which binds optimally to the DNA consensus sequence YYTAATGRTTTTY. BARX2 is highly expressed in adult salivary gland and is expressed at lower levels in other tissues, including mammary gland, kidney, and placenta. The BARX2 gene consists of four exons, and is located on human chromosome 11q25. This chromosomal location is within the minimal deletion region for Jacobsen syndrome, a syndrome including craniosynostosis and other developmental abnormalities. This chromosomal location, along with the reported expression of murine barx2 in craniofacial development, suggests that BARX2 may be causally involved in the craniofacial abnormalities in Jacobsen syndrome.

Amino Acid Sequence↗
PubMed2000

Co-localisation of CCG repeats and chromosome deletion breakpoints in Jacobsen syndrome: evidence for a common mechanism of chromosome breakage.

Folate-sensitive fragile sites are associated with the expansion and hypermethylation of CCG-repeats. The fragile site in 11q23.3, FRA11B, has been shown to cause chromosome deletions in vivo, its expression being associated with Jacobsen (11q-) syndrome. However, the majority of Jacobsen deletions are distal to FRA11B and are not related to its expression. To test the hypothesis that other unidentified fragile sites might be located in 11q23.3-24 and may cause these deletions, we have identified and characterised CCG-trinucleotide repeats within a 40 Mb YAC contig spanning distal chromosome 11q. Only eight CCG-repeats were identified within the entire YAC contig (not including FRA11B ), six of which map to the region of 11q23.3-24 that includes Jacobsen deletions. We have previously collated the deletion mapping data of 24 Jacobsen patients with the physical map of chromosome 11q, and accurately localised six breakpoints to short intervals corresponding to individual YAC clones. We now show that in each of these cases, YAC clones found to contain a deletion breakpoint also contain a CCG-repeat. The improved analysis of one of these deletions, together with those of several new Jacobsen cases, further strengthens this association by localising five breakpoints to individual PAC clones containing CCG-repeats. These data provide strong evidence for the non-random clustering of chromosome deletion breakpoints with CCG-repeats, and suggests that they may play an important role in a common mechanism of chromosome breakage.

Abnormalities, Multiple↗
PubMed2000

Fli-1 is required for murine vascular and megakaryocytic development and is hemizygously deleted in patients with thrombocytopenia.

The ETS gene Fli-1 is involved in the induction of erythroleukemia in mice by Friend murine leukemia virus and Ewings sarcoma in children. Mice with a targeted null mutation in the Fli-1 locus die at day 11.5 of embryogenesis with loss of vascular integrity leading to bleeding within the vascular plexus of the cerebral meninges and specific downregulation of Tek/Tie-2, the receptor for angiopoietin-1. We also show that dysmegakaryopoiesis in Fli-1 null embryos resembles that frequently seen in patients with terminal deletions of 11q (Jacobsen or Paris-Trousseau Syndrome). We map the megakaryocytic defects in 14 Jacobsen patients to a minimal region on 11q that includes the Fli-1 gene and suggest that dysmegakaryopoiesis in these patients may be caused by hemizygous loss of Fli-1.

Animals↗
PubMed2000

Anhydrobiotic engineering of gram-negative bacteria.

Anhydrobiotic engineering aims to improve desiccation tolerance in living organisms by adopting the strategies of anhydrobiosis. This was achieved for Escherichia coli and Pseudomonas putida by osmotic induction of intracellular trehalose synthesis and by drying from trehalose solutions, resulting in long-term viability in the dried state.

Biotechnology↗
PubMed1999

Localization of Jacobsen syndrome breakpoints on a 40-Mb physical map of distal chromosome 11q.

Jacobsen syndrome is a haploinsufficiency disorder caused, most frequently by terminal deletion of part of the long arm of chromosome 11, with breakpoints in 11q23.3-11q24.2. Inheritance of an expanded p(CCG)n trinucleotide repeat at the folate-sensitive fragile site FRA11B has been implicated in the generation of the chromosome breakpoint in several Jacobsen syndrome patients. The majority of such breakpoints, however, map distal to this fragile site and are not linked with its expression. To characterize these distal breakpoints and ultimately to further investigate the mechanisms of chromosome breakage, a 40-Mb YAC contig covering the distal long arm of chromosome 11 was assembled. The utility of the YAC contig was demonstrated in three ways: (1) by rapidly mapping the breakpoints from two new Jacobsen syndrome patients using FISH; (2) by demonstrating conversion to high resolution PAC contigs after direct screening of PAC library filters with a YAC clone containing a Jacobsen syndrome breakpoint; and (3) by placing 23 Jacobsen syndrome breakpoints on the physical map. This analysis has suggested the existence of at least two new Jacobsen syndrome breakpoint cluster regions in distal chromosome 11.

Abnormalities, Multiple↗
PubMed1998

Most Jacobsen syndrome deletion breakpoints occur distal to FRA11B.

Recent studies have identified a (CCG)n repeat in the 5' untranslated region of the CBL2 protooncogene (11q23.3) and have demonstrated that expansion of this repeat causes expression of the folate-sensitive fragile site FRA11B. It has also been demonstrated that FRA11B is the site of breakage in some cases of Jacobsen syndrome (JS) involving terminal deletions of chromosome 11q. We report on 2 patients with JS and a 46,XX,del(11)(q23.3) karyotype. In both cases, microsatellite and fluorescence in situ hybridization analyses indicated that the deletion breakpoint was approximately 1.5-3 Mb telomeric to FRA11B. There was no evidence of expansion of the CBL2 (CCG)n repeat in the parents of either patient. The deleted chromosome was of paternal origin in both cases, although it was of maternal origin in the cases reported to be caused by FRA11B. These findings and those in previously reported patients suggest that the breakpoint for most 11q deletions in JS patients is telomeric to FRA11B, which raises the possibility that there may be other fragile sites in 11q23.3 in addition to FRA11B. These findings also support previous evidence that there may be a propensity for breakpoints to differ depending on the parental origin of the deleted chromosome.

Abnormalities, Multiple↗
PubMed1995

Association of a chromosome deletion syndrome with a fragile site within the proto-oncogene CBL2.

The fragile site FRA11B has been localized to the p(CCG)n repeat of the CBL2 proto-oncogene. A proportion of Jacobsen (11q-) syndrome patients inherited a chromosome carrying a CBL2 p(CCG)n expansion, which was truncated close to FRA11B. These results have broad implications for the role of p(CCG)n repeat expansion in the aetiology of genetic disease involving chromosome rearrangements.

Base Sequence↗
PubMed1995

The human archain gene, ARCN1, has highly conserved homologs in rice and Drosophila.

A novel human gene, ARCN1, has been identified in chromosome band 11q23.3. It maps approximately 50 kb telomeric to MLL, a gene that is disrupted in a number of leukemia-associated translocation chromosomes. cDNA clones representing ARCN1 hybridize to 4-kb mRNA species present in all tissues tested. Sequencing of cDNAs suggests that at least two forms of mRNA with alternative 5' ends are present within the cell. The mRNA with the longest open reading frame gives rise to a protein of 57 kDa. Although the sequence reported is novel, remarkable similarity is observed with two predicted protein sequences from partial DNA sequences generated by rice (Oryza sativa) and fruit fly (Drosophila melanogaster) genome projects. The degree of sequence conservation is comparable to that observed for highly conserved structural proteins, such as heat shock protein HSP70, and is greater than that of gamma-tubulin and heat shock protein HSP60. A more distant relationship to the group of clathrin-associated proteins suggests a possible role in vesicle structure or trafficking. In view of its ancient pedigree and a potential involvement in cellular architecture, we propose that the ARCN1 protein be named archain.

Amino Acid Sequence↗
PubMed1994

The two genes generating RET/PTC3 are localized in chromosomal band 10q11.2.

PCR analysis of DNA from a selected panel of human-rodent somatic cell hybrids and fluorescent in situ hybridization (FISH) analysis allowed us to localize the human ELE1 gene. This previously uncharacterized gene is fused with the tyrosine kinase (tk) domain of the RET proto-oncogene to generate the oncogenic sequence RET/PTC3, thus providing a third example of RET oncogenic activation in papillary thyroid carcinomas. ELE1 was localized to band 10q11.2, the subband where RET also maps, at a minimum distance of more than 500 kb from the proto-oncogene. The fusion event corresponding to the rearrangement reciprocal to that leading to the formation of RET/PTC3 was also identified and characterized. The karyotype of two RET/PTC3 positive tumors did not show any evidence of chromosome 10 abnormalities. The data indicate that a cytogenetically undetectable paracentric inversion within 10q11.2 generates RET/PTC3.

Base Sequence↗
PubMed1994

A multiple interval physical map of the pericentromeric region of human chromosome 10.

Five intervals in the pericentromeric region of human chromosome 10 have been defined using a panel of somatic cell hybrids carrying portions of the chromosome. The map positions of twelve markers, consisting of four genes and eight anonymous DNA segments, have been localized by assignment to one of the five intervals. Several other markers could be placed in specific intervals by genetic linkage to assigned loci. When previously published data are incorporated, the summary map of the pericentromeric region encompasses thirty-two loci in bands 10p11.2-q11.2.

Base Sequence↗
PubMed1994

Physical linkage of the fragile site FRA11B and a Jacobsen syndrome chromosome deletion breakpoint in 11q23.3.

Autosomal fragile sites, unlike their X-linked counterparts, are not known to be associated with disease. However, one case report has highlighted a possible relationship between the inheritance of a rare folate-sensitive fragile site in band 11q23.3 (FRA11B) and the chromosome 11q23-->qter deletion in Jacobsen (11q-) syndrome. The mother and brother of the reported Jacobsen syndrome child are FRA11B carriers, suggesting that in vivo breakage at the fragile site during early development could have given rise to the chromosome deletion. We have tested this hypothesis by high resolution physical mapping of FRA11B and of the deletion chromosome breakpoint in the Jacobsen syndrome patient. A detailed restriction map of 600 kb of human chromosome band 11q23.3 has been assembled which covers the PBGD, CBL2 and THY1 genes. FISH experiments with YACs and cosmids from this region have localised FRA11B to an interval of approximately 100 kb containing the 5' end of the CBL2 gene, which includes a CCG trinucleotide repeat. This class of repeat is expanded in the four cloned examples of fragile site and therefore the CBL2 repeat is a candidate for the location of FRA11B. Further, it is shown that the chromosomal deletion breakpoint of the Jacobsen syndrome child maps within the same interval as the fragile site. The breakpoint has apparently been repaired and stabilised by the de novo addition of a telomere. These data are consistent with a role for an inherited fragile site in the aetiology of a chromosome deletion syndrome.

Abnormalities, Multiple↗
PubMed1994

Point mutation within the tyrosine kinase domain of the RET proto-oncogene in multiple endocrine neoplasia type 2B and related sporadic tumours.

The susceptibility loci for the three multiple endocrine neoplasia (MEN) type 2 syndromes have been mapped to the region of chromosome 10q11.2 containing the RET proto-oncogene, which codes for a receptor tyrosine kinase. The majority of MEN 2A and familial medullary thyroid carcinoma results from missense mutations within one of five cysteine codons in the extracellular domain of the RET proto-oncogene. We now report a missense mutation, resulting in the substitution of a threonine for a methionine at codon 918 in the tyrosine kinase catalytic domain, in the germline of 26 of 28 apparently distinct families with MEN 2B. DNA from five of 13 apparently sporadic MTC and one of 12 apparently sporadic phaeochromocytomas harboured a similar mutation, but the corresponding germline DNA was wildtype in each case.

Adenoma↗
PubMed1993

In vivo persistence of expanded clones specific for bacterial antigens within the human T cell receptor alpha/beta CD4-8- subset.

We analyzed the T cell receptor (TCR) rearrangements of 100 TCR-alpha/beta CD4-CD8- (double negative [DN]) T cell clones from normal individuals. We found that in four out of six donors this subset contains expanded clones that often account for 0.5% and, in one individual, even 7% of all peripheral blood lymphocytes. By combining limiting dilution analysis and N region oligotyping of polymerase chain reaction amplified TCR cDNA, we could measure the clonal size and show that two of these expanded clones remain stable in size for up to 4 yr in peripheral blood. The expanded clones analyzed ex vivo are not cycling and CD45 RAhi ROlo, but express high levels of alpha 4/beta 1 integrins, suggesting that they may have reverted to resting cells after activation. One of these expanded DN clones proliferates in vitro in response to Escherichia coli presented by monocytes cultured in GM-CSF plus IL-4 and kills CD1a+ Molt-4 cells. In contrast to what was found in the alpha/beta DN subset, alpha/beta CD4+ T cell clones specific for a tetanus toxin epitope showed a very small clonal size (< 1 in 10(7)) and could not be reisolated after 2 yr. Taken together, these results indicate that large clonal size and persistence are distinctive features of alpha/beta DN cells specific for bacterial antigens. These cells may use antigen-presenting cells, restriction molecules, and selection routes different from those used by antigen-specific CD4+ T cells.

Amino Acid Sequence↗
PubMed1993

Duplicated KOX zinc finger gene clusters flank the centromere of human chromosome 10: evidence for a pericentric inversion during primate evolution.

Two related zinc finger (ZNF) gene clusters from the pericentromeric region of human chromosome 10, defined by cDNAs of the KOX series, have been cloned in yeast artificial chromosomes (YACs). The two clusters evolved by duplication of an ancestral gene cluster before the divergence of the human and great ape lineages. Included in cluster A are the ZNF gene sequences ZNF11A, ZNF33A, and ZNF37A, while cluster B comprises the related sequences ZNF11B, ZNF33B and ZNF37B. Genes from both clusters are expressed: cDNAs KOX2, KOX31 and KOX21 derive from ZNF11B, ZNF33A and ZNF37A, respectively. Further YACs have been isolated which link ZNF11A and ZNF33A to another gene, ZNF25, defined by cDNA clone KOX19. Therefore ZNF25 also forms part of cluster A, but has no counterpart in cluster B. Surprisingly, the KOX ZNF gene clusters are located on opposite sides of the centromere: cluster A maps to 10p11.2, while cluster B is in 10q11.2. This suggests the occurrence during primate evolution of a previously undescribed pericentric inversion subsequent to the cluster duplication. The evolution of this subset of KOX ZNF genes has therefore involved three types of genetic event: local gene duplication, gene cluster duplication, and chromosome rearrangement.

Amino Acid Sequence↗