PubMed Health⌕ Search

Biomedical subjects

Emma Roberts

Publications and source records attributed to Emma Roberts.

11 recordsLinked to original sources
PubMed2006

An SCN9A channelopathy causes congenital inability to experience pain.

The complete inability to sense pain in an otherwise healthy individual is a very rare phenotype. In three consanguineous families from northern Pakistan, we mapped the condition as an autosomal-recessive trait to chromosome 2q24.3. This region contains the gene SCN9A, encoding the alpha-subunit of the voltage-gated sodium channel, Na(v)1.7, which is strongly expressed in nociceptive neurons. Sequence analysis of SCN9A in affected individuals revealed three distinct homozygous nonsense mutations (S459X, I767X and W897X). We show that these mutations cause loss of function of Na(v)1.7 by co-expression of wild-type or mutant human Na(v)1.7 with sodium channel beta(1) and beta(2) subunits in HEK293 cells. In cells expressing mutant Na(v)1.7, the currents were no greater than background. Our data suggest that SCN9A is an essential and non-redundant requirement for nociception in humans. These findings should stimulate the search for novel analgesics that selectively target this sodium channel subunit.

Base Sequence↗
PubMed2006

MORM syndrome (mental retardation, truncal obesity, retinal dystrophy and micropenis), a new autosomal recessive disorder, links to 9q34.

A consanguineous pedigree is described where 14 individuals are affected with a novel autosomal recessive disorder, which causes static moderate mental retardation, truncal obesity, a congenital nonprogressive retinal dystrophy and micropenis in males. We have tentatively named this condition MORM syndrome. It shows similarities to Bardet-Biedl syndrome and Cohen syndrome, but can be distinguished by clinical features; the age of onset and nonprogressive nature of the visual impairment, the lack of characteristic facies, skin or gingival infection, microcephaly, 'mottled retina', polydactyly and small penis without testicular anomalies. Furthermore, linkage to the known Bardet-Biedl (BBS1-8) and Cohen syndrome loci was excluded. Autozygosity mapping identified a single homozygous subtelomeric region shared by all affecteds on chromosome 9q34.3, with a maximum LOD score of 5.64. We believe this to be the first example of the identification of a subtelomeric recessive locus by autozygosity mapping.

Chromosome Mapping↗
PubMed2006

Effects of TSH receptor mutations on binding and biological activity of monoclonal antibodies and TSH.

The effects of an extensive series of mutations in the TSH receptor (TSHR) leucine-rich domain (LRD) on the ability of thyroid-stimulating monoclonal antibodies (TSMAbs) and TSH to bind to the receptor and stimulate cyclic AMP production in TSHR-transfected CHO cells has been investigated. In addition, the ability of a mouse monoclonal antibody with blocking (i.e., antagonist) activity (RSR-B2) to interact with mutated receptors has been studied. Several amino acids distributed along an extensive part of the concave surface of the LRD were found to be important for binding and stimulation by the thyroid-stimulating human MAb M22 but did not appear to be important for TSH binding and stimulation. Most of these amino acids important for M22 interactions were also found to be important for the stimulating activity of six different mouse TSMAbs and a hamster TSMAb. Furthermore, most of these same amino acids were important for stimulation by TSHR autoantibodies in a panel of sera from patients with Graves' disease. Amino acid R255 was the only residue found to be unimportant for TSH stimulation but critical for stimulation by all thyroid-stimulating antibodies tested (23 patient serum TSHR autoantibodies, M22, and all seven animal TSMAbs). About half the amino acids (all located in the N-terminal part of the LRD) found to be important for M22 activity were also important for the blocking activity of RSR-B2 and although the epitopes for the two MAbs overlap they are different. As the two MAbs have similar affinities, their epitope differences are probably responsible for their different activities. Overall our results indicate that different TSMAbs and different patient sera thyroid-stimulating autoantibodies interact with the same region of the TSHR, but there are subtle differences in the actual amino acids that make contact with the different stimulators.

Animals↗
PubMed2005

A sensitive non-isotopic assay for acetylcholine receptor autoantibodies.

BACKGROUND: Detection and measurement of serum acetylcholine receptor autoantibodies (AChRAb) are useful in the diagnosis and management of myasthenia gravis (MG). An immunoprecipitation assay (IPA) based on AChR labelled with 125I-alpha bungarotoxin is widely used for measurement of AChRAb, but a non-isotopic assay of sensitivity and specificity comparable to IPA is not available as yet. METHODS: A new AChRAb ELISA, which is based on the ability of AChRAb to compete with 3 different AChR monoclonal antibodies (MAbs 1-3) for binding sites on affinity purified fetal and adult-type AChR preparations, is described. The sensitivity and specificity of the ELISA were assessed by comparing assay results with a conventional IPA. RESULTS: There was good agreement between the IPA and the ELISA for measurement of AChRAb (r = 0.85; n = 83; p <0.001). 76/83 MG sera were positive in the ELISA, whilst 72/83 were positive by IPA. Eight sera were positive in the ELISA (inhibition range 18%-46%) but negative by IPA (0.33-0.47 nmol/L toxin bound) and 4 sera were negative in the ELISA (inhibition range -1% to15%) whilst positive by IPA (0.56-2.9 nmol/L toxin bound). Overall 80/83 (96%) of the MG sera were AChRAb positive in one or both assays. In addition, all 191 control serum samples which were negative for AChRAb by IPA were below or equal to 16% of inhibition in our ELISA. The AChRAb ELISA also showed good inter-assay and intra-assay precision. CONCLUSION: The AChRAb ELISA we have described has sensitivity and specificity at least as high as our current radioactive IPA. It has good precision and good handling characteristics making it suitable for routine use.

Adult↗
PubMed2005

A centrosomal mechanism involving CDK5RAP2 and CENPJ controls brain size.

Autosomal recessive primary microcephaly is a potential model in which to research genes involved in human brain growth. We show that two forms of the disorder result from homozygous mutations in the genes CDK5RAP2 and CENPJ. We found neuroepithelial expression of the genes during prenatal neurogenesis and protein localization to the spindle poles of mitotic cells, suggesting that a centrosomal mechanism controls neuron number in the developing mammalian brain.

Animals↗
PubMed2004

Baseline assessment for addressing acute malnutrition by public-health staff in Cambodia.

The objective of this study was to formulate appropriate responses by the public-health sector to reduce acute malnutrition among children in Cambodia. A cross-sectional survey to identify wasting together with a simple wealth-ranking exercise was conducted. Thereafter, separate focus-group discussions were also conducted with mothers of malnourished and non-malnourished children, who belonged to the poorest strata, to identify coping mechanisms and to assess feeding and hygiene practices. There was no statistical correlation between wasting and socioseconomic status (df=3, p=0.06). Reported feeding practices were poor, including not giving of colostrum, too early introduction of weaning, low feeding frequency, and late introduction of nutritious foods. Healthcare-seeking behaviour appeared inadequate, and hand-washing with soap was not practised. Acute malnutrition was mainly related to these factors rather than to food insecurity. An education campaign in tandem with peer-counselling would be the most appropriate option.

Acute Disease↗
PubMed2003

Protein-truncating mutations in ASPM cause variable reduction in brain size.

Mutations in the ASPM gene at the MCPH5 locus are expected to be the most common cause of human autosomal recessive primary microcephaly (MCPH), a condition in which there is a failure of normal fetal brain development, resulting in congenital microcephaly and mental retardation. We have performed the first comprehensive mutation screen of the 10.4-kb ASPM gene, identifying all 19 mutations in a cohort of 23 consanguineous families. Mutations occurred throughout the ASPM gene and were all predicted to be protein truncating. Phenotypic variation in the 51 affected individuals occurred in the degree of microcephaly (5-11 SDs below normal) and of mental retardation (mild to severe) but appeared independent of mutation position.

Amino Acid Sequence↗
PubMed2003

Fraser syndrome and mouse blebbed phenotype caused by mutations in FRAS1/Fras1 encoding a putative extracellular matrix protein.

Fraser syndrome (OMIM 219000) is a multisystem malformation usually comprising cryptophthalmos, syndactyly and renal defects. Here we report autozygosity mapping and show that the locus FS1 at chromosome 4q21 is associated with Fraser syndrome, although the condition is genetically heterogeneous. Mutation analysis identified five frameshift mutations in FRAS1, which encodes one member of a family of novel proteins related to an extracellular matrix (ECM) blastocoelar protein found in sea urchin. The FRAS1 protein contains a series of N-terminal cysteine-rich repeat motifs previously implicated in BMP metabolism, suggesting that it has a role in both structure and signal propagation in the ECM. It has been speculated that Fraser syndrome is a human equivalent of the blebbed phenotype in the mouse, which has been associated with mutations in at least five loci including bl. As mapping data were consistent with homology of FRAS1 and bl, we screened DNA from bl/bl mice and identified a premature termination of mouse Fras1. Thus, the bl mouse is a model for Fraser syndrome in humans, a disorder caused by disrupted epithelial integrity in utero.

Animals↗
PubMed2002

ASPM is a major determinant of cerebral cortical size.

One of the most notable trends in mammalian evolution is the massive increase in size of the cerebral cortex, especially in primates. Humans with autosomal recessive primary microcephaly (MCPH) show a small but otherwise grossly normal cerebral cortex associated with mild to moderate mental retardation. Genes linked to this condition offer potential insights into the development and evolution of the cerebral cortex. Here we show that the most common cause of MCPH is homozygous mutation of ASPM, the human ortholog of the Drosophila melanogaster abnormal spindle gene (asp), which is essential for normal mitotic spindle function in embryonic neuroblasts. The mouse gene Aspm is expressed specifically in the primary sites of prenatal cerebral cortical neurogenesis. Notably, the predicted ASPM proteins encode systematically larger numbers of repeated 'IQ' domains between flies, mice and humans, with the predominant difference between Aspm and ASPM being a single large insertion coding for IQ domains. Our results and evolutionary considerations suggest that brain size is controlled in part through modulation of mitotic spindle activity in neuronal progenitor cells.

Anthropometry↗
PubMed2002

Identification of microcephalin, a protein implicated in determining the size of the human brain.

Primary microcephaly (MIM 251200) is an autosomal recessive neurodevelopmental condition in which there is a global reduction in cerebral cortex volume, to a size comparable with that of early hominids. We previously mapped the MCPH1 locus, for primary microcephaly, to chromosome 8p23, and here we report that a gene within this interval, encoding a BRCA1 C-terminal domain-containing protein, is mutated in MCPH1 families sharing an ancestral 8p23 haplotype. This gene, microcephalin, is expressed in the developing cerebral cortex of the fetal brain. Further study of this and related genes may provide important new insights into neocortical development and evolution.

Adolescent↗