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Biomedical subjects

Christine Hall

Publications and source records attributed to Christine Hall.

17 recordsLinked to original sources
PubMed2006

Clinical phenotype associated with homozygosity for a HOXD13 7-residue polyalanine tract expansion.

Synpolydactyly (SPD) is an autosomal dominant malformation of the distal limbs caused by mutations in the homeobox gene HOXD13 located on chromosome 2q31. We detail the clinical findings in a consanguineous Pakistani family segregating a HOXD13 7-residue polyalanine tract expansion. Three members of this pedigree were heterozygotes with features typical of SPD. Two further members demonstrate a more severe phenotype consistent with homozygosity for the familial mutation. We also report a child from a consanguineous Somali family homozygous for the same molecular lesion. Characteristic changes include a complex central polydactyly in the hands, abnormal modelling of the metacarpals and metatarsals, an increased number of carpal bones with abnormal shapes, hypoplasia or absence of the fifth digital rays in the feet, hypoplasia of the middle phalanges and abnormally long proximal phalanges in hands and feet. These cases illustrate the distinct phenotype associated with homozygosity for a HOXD13 mutation and also highlight the importance of considering homozygosity for a dominant mutation in consanguineous pedigrees.

Consanguinity↗
PubMed2005

IQGAP1 promotes neurite outgrowth in a phosphorylation-dependent manner.

In eukaryotic cells IQGAP1 binds to and alters the function of several proteins, including actin, E-cadherin, beta-catenin, Cdc42, and Rac1. Yeast IQGAP1 homologues have an important role in cytoskeletal organization, suggesting that modulation of the cytoskeleton is a fundamental role of IQGAP1. Phosphorylation is a common mechanism by which cells regulate protein function. Here we demonstrate that endogenous IQGAP1 is highly phosphorylated in MCF-7 human breast epithelial cells. Moreover, incubation of cells with phorbol 12-myristate 13-acetate (PMA) stimulated phosphate incorporation into IQGAP1. By using mass spectrometry, Ser-1443 was identified as the major site phosphorylated on IQGAP1 in intact cells treated with PMA. Ser-1441 was also phosphorylated but to a lesser extent. In vitro analysis with purified proteins documented that IQGAP1 is a substrate for protein kinase Cepsilon, which catalyzes phosphorylation on Ser-1443. Consistent with these findings, inhibition of cellular protein kinase C via bisindolymaleimide abrogated Ser-1443 phosphorylation in response to PMA. To elucidate the biological sequelae of phosphorylation, Ser-1441 and Ser-1443 were converted either to alanine, to create a nonphosphorylatable construct, or to glutamic acid and aspartic acid, respectively, to generate a phosphomimetic IQGAP1. Although overexpression of wild type IQGAP1 promoted neurite outgrowth in N1E-115 neuroblastoma cells, the nonphosphorylatable IQGAP1 S1441A/S1443A had no effect. In contrast, the S1441E/S1443D mutation markedly enhanced the ability of IQGAP1 to induce neurite outgrowth. Our data disclose that IQGAP1 is phosphorylated at multiple sites in intact cells and that phosphorylation of IQGAP1 will alter its ability to regulate the cytoskeleton of neuronal cells.

Amino Acid Sequence↗
PubMed2005

C1, see them all.

Recent structural analysis of crystalline beta2-chimaerin shows the central protein kinase C-like, diacylglycerol (DAG)-binding C1 domain to be masked by its intramolecular interactions with the N-terminal SH2 and GAP domains, and linker regions. A mechanism of activation has been derived from modelling of a GAP-Rac GTPase complex--the auto-inhibitory constraints are released via membrane engagement, unmasking the C1 domain to enable DAG binding and subsequent GAP stimulation of Rac GTPase catalytic activity.

Animals↗
PubMed2005

Outgrowth of neurites from NIE-115 neuroblastoma cells is prevented on repulsive substrates through the action of PAK.

In the central nervous system (CNS), damaged axons are inhibited from regeneration by glial scars, where secreted chondroitin sulfate proteoglycan (CSPG) and tenascin repulse outgrowth of neurites, the forerunners of axons and dendrites. During differentiation, these molecules are thought to form boundaries for guiding neurons to their correct targets. In neuroblastoma NIE-115 cells, outgrowth of neurites on laminin could be induced by serum starvation or inhibition of RhoA by Clostridium botulinum C3 toxin. The outgrowing neurites avoided crossing onto the repulsive substrate CSPG or tenascin. This avoidance response was partially overcome on expression of membrane-targeted and kinase-inactive forms of PAK. In these cells, the endogenous PAK isoforms colocalized with actin in distinctive sites, alphaPAK in the cell center as small clusters and along the neurite shaft and betaPAK and gammaPAK in areas with membrane ruffles and filopodia, respectively. When isoform-specific N-terminal PAK sequences were introduced to interfere with PAK function, substantially more neurites crossed onto CSPG when cells contained a gammaPAK-derived peptide but not the corresponding alphaPAK- or betaPAK-derived peptide. Thus, while neurite outgrowth can be promoted by RhoA inhibition, overcoming the accompanying repulsive guidance response will require modulation of PAK activity. These results have therapeutic implications for CNS repair processes.

ADP Ribose Transferases↗
PubMed2004

Alpha2-chimaerin, cyclin-dependent Kinase 5/p35, and its target collapsin response mediator protein-2 are essential components in semaphorin 3A-induced growth-cone collapse.

Neurite outgrowth is influenced by positive and negative signals that include the semaphorins, an important family of axonal outgrowth inhibitors. Here we report that the Rac GTPase activating protein (GAP)alpha2-chimaerin is involved in Semaphorin 3A (Sema 3A) signaling. In dorsal root ganglion neurons, Sema 3A-induced growth cone collapse was inhibited by alpha2-chimaerin mutated to eliminate GAP activity or interaction with phosphotyrosine. Activation of alpha2-chimaerin by phorbol ester caused growth cone collapse. Active alpha2-chimaerin interacts with collapsin response mediator protein-2 (CRMP-2) and cyclin-dependent kinase (Cdk) 5/p35 kinase through its SH2 and GAP domains, respectively. Cdk5 phosphorylates CRMP-2 at serine 522, possibly facilitating phosphorylation of serine 518 and threonine 514 by glycogen synthase kinase 3beta (GSK3beta), a kinase previously implicated in Sema 3A signaling. Phosphorylation of CRMP-2 serine 522 was essential for Sema 3A-induced growth cone collapse, which is dependent on Cdk5 but not Rho kinase activity. alpha2-chimaerin, like CRMP-2, can associate with the Sema 3A receptor. These results indicate that active alpha2-chimaerin Rac GAP, Cdk5/p35, and its substrate CRMP-2, are implicated in the dynamics of growth cone guidance initiated through Sema 3A signaling.

Animals↗
PubMed2004

Kantaputra mesomelic dysplasia: a second reported family.

We present the clinical and radiographic findings in a mother and son with a dominantly inherited mesomelic skeletal dysplasia almost identical to that described in a large Thai family by Kantaputra et al., in which ankle, carpal and tarsal synostoses were noted. The proband in the family is a 48-year-old woman with mesomelic limb shortening, most pronounced in the upper limbs. Her parents were of normal stature and build. Her 15-year-old son has similar mesomelic limb shortening, and in addition talipes equinovarus. Radiological examination showed severe shortening of the radius and ulna with bowing of the radius and dislocation of the radial head. Multiple carpal and tarsal synostoses were present and in addition, the talus and calcaneum were fused. In the original Thai family, linkage to chromosome 2q24-q32, which contains the HOXD cluster has been reported, and it is postulated that the phenotype may result from a disturbance of regulation of the HOXD cluster. Although linkage analysis was not possible in our family, molecular analysis was undertaken and HOXD11 was sequenced, however, no mutations were detected. This is only the second reported family affected with Kantaputra mesomelic dysplasia (MIM 156232), a distinct mesomelic skeletal dysplasia.

Adolescent↗
PubMed2004

Central osteosclerosis with trichothiodystrophy.

Trichothiodystrophy (TTD) is a rare, autosomal recessive, multisystem disorder associated with defects in nucleotide excision repair. We report a 7-year-old boy with TTD due to mutation in the XPD gene. The patient has classic features of this condition, including brittle, sulphur-deficient hair, ichthyosis, growth retardation and developmental delay. In addition, he has radiological evidence of progressive central osteosclerosis. Although similar radiological findings have previously been reported in a small number of patients, this association is not widely recognised. We review the radiological findings in this and other similar cases and discuss the natural history of these bony changes.

Abnormalities, Multiple↗
PubMed2003

Phenotypic characterization of overexpression or deletion of the Escherichia coli crcA, cspE and crcB genes.

The authors have previously shown that overexpression of the Escherichia coli K-12 crcA, cspE and crcB genes protects the chromosome from decondensation by camphor. In this study they examine the phenotypic consequences of deleting or overexpressing crcA, cspE and crcB. Overexpressing crcA, cspE and crcB increases supercoiling levels of plasmids in wild-type cells and in temperature-sensitive (Ts) gyrase mutants, suppresses the sensitivity of gyrase and topoisomerase IV (topo IV) Ts mutants to nalidixic acid, makes gyrase and topo IV Ts mutants more resistant to camphor and corrects the nucleoid morphology defects in topo IV Ts mutants. Overexpression of crcA, cspE and crcB results in a slight (2.2-fold) activation of the rcsA gene. Deleting crcA, cspE and crcB is not lethal to cells but results in an increase in sensitivity to camphor. Deletion of crcA, cspE and crcB exacerbates the nucleoid morphology defects of the topo IV Ts mutants. When the individual crcA, cspE or crcB genes were tested for their effects on camphor resistance and regulation of rcsA, cspE alone conferred 10-fold camphor resistance and 1.7-fold activation of rcsA. These activities were augmented when crcB was overexpressed with cspE (100-fold camphor resistance and 2.1-fold induction of rcsA).

Base Sequence↗
PubMed2002

p80 ROKalpha binding protein is a novel splice variant of CRMP-1 which associates with CRMP-2 and modulates RhoA-induced neuronal morphology.

Using antibody against the Rho binding domain of ROKalpha, two neuronal phosphoproteins of 62 and 80 kDa were co-immunoprecipitated from brain extracts. Peptide analysis revealed their identity as collapsin response mediator proteins (CRMPs); p62 was CRMP-2 whereas p80 was a novel splice form of CRMP-1 with an extended N-terminus. p80 CRMP-1 was able to complex with CRMP-2, suggesting that p80 CRMP-1 and CRMP-2 form oligomers. CRMP-2 was the major substrate of ROK. p80 CRMP-1 interacted with the kinase domain of ROKalpha, resulting in inhibition of the catalytic activity towards other substrates. Over-expression of p80 CRMP-1 and CRMP-2 together counteracted the effects of RhoA on neurite retraction, an effect enhanced by mutation of the ROK phosphorylation site in CRMP-2. p80 CRMP-1 and CRMP-2 may be modulators of RhoA-dependent signaling, through interaction with and regulation of ROKalpha.

Alternative Splicing↗
PubMed2002

Constitutional deletion of chromosome 20q in two patients affected with albright hereditary osteodystrophy.

Albright hereditary osteodystrophy (AHO) results from heterozygous inactivation of G(s)alpha, encoded by the GNAS1 locus on the distal long arm of chromosome 20. This autosomal dominant condition is characterized by short stature, obesity, shortening of the metacarpals and metatarsals, and variable mental retardation and may also include end-organ resistance to multiple hormones. Small insertions and deletions or point mutations of GNAS1 are found in approximately 80% of patients with AHO. The remainder may be accounted for by larger genomic rearrangements, but none have been reported to date. We now describe two patients with constitutional 20q deletions and features of AHO. Such deletions are rare in the published literature and have not previously been associated with AHO. Molecular genetic analysis confirmed complete deletion of GNAS1 in both patients. Parental origin could be determined in both cases and provides further support for the parent-of-origin effect on the biochemical status of patients with AHO.

Adolescent↗
PubMed2002

Characterization of RhoA-binding kinase ROKalpha implication of the pleckstrin homology domain in ROKalpha function using region-specific antibodies.

Rho-binding kinase alpha (ROKalpha) is a serine/threonine kinase with multiple functional domains involved in actomyosin assembly. It has previously been documented that the C terminus part of ROKalpha interacts with the N-terminal kinase domain and thereby regulates its catalytic activity. Here we used antibodies against different domains of ROKalpha and were able to reveal some structural aspects that are essential for the specific functions of ROKalpha. Antibodies against the kinase domain revealed that this part of the protein is highly complex and inaccessible. Further experiments confirmed that this domain could undergo inter- and intramolecular interactions in a complex manner, which regulates the kinase catalytic activity. Other antibodies that raised against the coiled-coil domain, Rho binding domain, and the pleckstrin homology (PH) domain were all effective in recognizing the native proteins in an immunoprecipitation assay. Only the anti-Rho binding domain antibodies could activate the kinase independent of RhoA. The PH antibodies had no apparent effects on the catalytic activity but were effective in blocking actomyosin assembly and cell contractility. Likewise, mutations of the PH domains can abrogate its dominant negative effects on actin morphology. The subsequent disruption of endogenous ROK localization to the actomyosin network by overexpressing the PH domain is supportive of a role of the PH domain of ROK in targeting the kinase to these structures.

Animals↗
PubMed2002

Osteocraniostenosis in a fetus with a 46,XX/46,XY karyotype.

Osteocraniostenosis is a disorder characterized by thin tubular bones, dymorphic facies and splenic hypoplasia/aplasia in some cases. We report a further case of this rare skeletal dysplasia in a 31 week male fetus with ambiguous external genitalia and asymmetry in whom a 46,XX/46,XY karyotype was demonstrated in both cartilage and skin.

Abnormalities, Multiple↗
PubMed2002

Gene expression analysis using oligonucleotide arrays produced by maskless photolithography.

Microarrays containing 195,000 in situ synthesized oligonucleotide features have been created using a benchtop, maskless photolithographic instrument. This instrument, the Maskless Array Synthesizer (MAS), uses a digital light processor (DLP) developed by Texas Instruments. The DLP creates the patterns of UV light used in the light-directed synthesis of oligonucleotides. This digital mask eliminates the need for expensive and time-consuming chromium masks. In this report, we describe experiments in which we tested this maskless technology for DNA synthesis on glass surfaces. Parameters examined included deprotection rates, repetitive yields, and oligonucleotide length. Custom gene expression arrays were manufactured and hybridized to Drosophila melanogaster and mouse samples. Quantitative PCR was used to validate the gene expression data from the mouse arrays.

Animals↗
PubMed2002

Transcriptional activation of the Rhodobacter sphaeroides cytochrome c(2) gene P2 promoter by the response regulator PrrA.

Anoxygenic photosynthetic growth of Rhodobacter sphaeroides, a member of the alpha subclass of the class Proteobacteria, requires the response regulator PrrA. PrrA and the sensor kinase PrrB are part of a two-component signaling pathway that influences a wide range of processes under oxygen-limited conditions. In this work we characterized the pathway of transcription activation by PrrB and PrrA by purifying these proteins, analyzing them in vitro, and characterizing a mutant PrrA protein in vivo and in vitro. When purified, a soluble transmitter domain of PrrB (cPrrB) could autophosphorylate, rapidly transfer phosphate to PrrA, and stimulate dephosphorylation of phospho-PrrA. Unphosphorylated PrrA activated transcription from a target cytochrome c(2) gene (cycA) promoter, P2, which contained sequences from -73 to +22 relative to the transcription initiation site. However, phosphorylation of PrrA increased its activity since activation of cycA P2 was enhanced up to 15-fold by treatment with the low-molecular-weight phosphodonor acetyl phosphate. A mutant PrrA protein containing a single amino acid substitution in the presumed phosphoacceptor site (PrrA-D63A) was not phosphorylated in vitro but also was not able to stimulate cycA P2 transcription. PrrA-D63A also had no apparent in vivo activity, demonstrating that aspartate 63 is necessary both for the function of PrrA and for its phosphorylation-dependent activation. The cellular level of wild-type PrrA was negatively autoregulated so that less PrrA was present in the absence of oxygen, conditions in which the activities of many PrrA target genes increase. PrrA-D63A failed to repress expression of the prrA gene under anaerobic conditions, suggesting that this single amino acid change also eliminated PrrA function in vivo.

Bacterial Proteins↗
PubMedDate not supplied

Sagittal plane compensations for artificially induced limitation of the first metatarsophalangeal joint: a preliminary study.

This study was undertaken to establish whether reduced dorsiflexion at the first metatarsophalangeal joint affects sagittal plane kinematics at the ankle, knee, and hip. Twenty individuals with symptom-free metatarsophalangeal joints were studied as they walked with and without an insole designed to restrict first metatarsophalangeal joint dorsiflexion. Sagittal plane kinematics at the ankle, knee, and hip were compared in the two conditions. When walking with the insole, the ankle was more dorsiflexed during late midstance and less plantarflexed during propulsion, the knee was more flexed during midstance, and the hip was less extended during late midstance. This evidence of a link between the first metatarsophalangeal joint and the kinematics of the proximal joints demonstrates the potential for the clinical entities of hallux rigidus and hallux limitus to influence gait and justifies more detailed study of this relationship.

Adult↗