353 research outputs found
Scalp fibroblasts have a shared expression profile in monogenic craniosynostosis
BACKGROUND: Craniosynostosis can be caused by both genetic and environmental factors, the relative contributions of which vary between patients. Genetic testing identifies a pathogenic mutation or chromosomal abnormality in ∼ 21% of cases, but it is likely that further causative mutations remain to be discovered. OBJECTIVE: To identify a shared signature of genetically determined craniosynostosis by comparing the expression patterns in three monogenic syndromes with a control group of patients with non-syndromic sagittal synostosis. METHODS: Fibroblasts from 10 individuals each with Apert syndrome (FGFR2 substitution S252W), Muenke syndrome (FGFR3 substitution P250R), Saethre-Chotzen syndrome (various mutations in TWIST1) and non-syndromic sagittal synostosis (no mutation detected) were cultured. The relative expression of ∼ 47,000 transcripts was quantified on Affymetrix arrays. RESULTS: 435, 45 and 46 transcripts were identified in the Apert, Muenke and Saethre-Chotzen groups, respectively, that differed significantly from the controls. Forty-six of these transcripts were shared between two or more syndromes and, in all but one instance, showed the same direction of altered expression level compared with controls. Pathway analysis showed over-representation of the shared transcripts in core modules involving cell-to-cell communication and signal transduction. Individual samples from the Apert syndrome cases could be reliably distinguished from non-syndromic samples based on the gene expression profile, but this was not possible for samples from patients with Muenke and Saethre-Chotzen syndromes. CONCLUSIONS: Common modules of altered gene expression shared by genetically distinct forms of craniosynostosis were identified. Although the expression profiles cannot currently be used to classify individual patients, this may be overcome by using more sensitive assays and sampling additional tissues
Severe obesity and diabetes insipidus in a patient with PCSK1 deficiency.
Non-synonymous mutations affecting both alleles of PCSK1 (proprotein convertase 1/3) are associated with obesity and impaired prohormone processing. We report a proband who was compound heterozygous for a maternally inherited frameshift mutation and a paternally inherited 474kb deletion that encompasses PCSK1, representing a novel genetic mechanism underlying this phenotype. Although pro-vasopressin is not a known physiological substrate of PCSK1, the development of central diabetes insipidus in this proband suggests that PCSK1 deficiency can be associated with impaired osmoregulation.ISF and SOR were supported by the Wellcome Trust, the MRC Centre for Obesity and Related Disorders and the UK NIHR Cambridge Biomedical Research Centre.This is the final published version. It first appeared at http://www.sciencedirect.com/science/article/pii/S1096719213001145#
Simultaneous polychromatic flow cytometric detection of multiple forms of regulated cell death
Queen Mary University London.GS
Identification and characterization of an inhibitory fibroblast growth factor receptor 2 (FGFR2) molecule, up-regulated in an Apert Syndrome mouse model
AS (Apert syndrome) is a congenital disease composed of skeletal, visceral and neural abnormalities, caused by dominant-acting mutations in FGFR2 [FGF (fibroblast growth factor) receptor 2]. Multiple FGFR2 splice variants are generated through alternative splicing, including PTC (premature termination codon)-containing transcripts that are normally eliminated via the NMD (nonsense-mediated decay) pathway. We have discovered that a soluble truncated FGFR2 molecule encoded by a PTC-containing transcript is up-regulated and persists in tissues of an AS mouse model. We have termed this IIIa–TM as it arises from aberrant splicing of FGFR2 exon 7 (IIIa) into exon 10 [TM (transmembrane domain)]. IIIa–TM is glycosylated and can modulate the binding of FGF1 to FGFR2 molecules in BIAcore-binding assays. We also show that IIIa–TM can negatively regulate FGF signalling in vitro and in vivo. AS phenotypes are thought to result from gain-of-FGFR2 signalling, but our findings suggest that IIIa–TM can contribute to these through a loss-of-FGFR2 function mechanism. Moreover, our findings raise the interesting possibility that FGFR2 signalling may be a regulator of the NMD pathway
Resistance to thyroid hormone caused by a mutation in thyroid hormone receptor (TR)alpha 1 and TR alpha 2: clinical, biochemical, and genetic analyses of three related patients
Background
The thyroid hormone receptor α gene (THRA) transcript is alternatively spliced to generate either thyroid hormone receptor (TR)α1 or a non-hormone-binding variant protein, TRα2, the function of which is unknown. Here, we describe the first patients identified with a mutation in THRA that affects both TRα1 and TRα2, and compare them with patients who have resistance to thyroid hormone owing to a mutation affecting only TRα1, to delineate the relative roles of TRα1 and TRα2.
Methods
We did clinical, biochemical, and genetic analyses of an index case and her two sons. We assessed physical and radiological features, thyroid function, physiological and biochemical markers of thyroid hormone action, and THRA sequence.
Findings
The patients presented in childhood with growth failure, developmental delay, and constipation, which improved after treatment with thyroxine, despite normal concentrations of circulating thyroid hormones. They had similar clinical (macrocephaly, broad faces, skin tags, motor dyspraxia, slow speech), biochemical (subnormal ratio of free thyroxine:free tri-iodothyronine [T3], low concentration of total reverse T3, high concentration of creatine kinase, mild anaemia), and radiological (thickened calvarium) features to patients with TRα1-mediated resistance to thyroid hormone, although our patients had a heterozygous mis-sense mutation (Ala263Val) in both TRα1 and TRα2 proteins. The Ala263Val mutant TRα1 inhibited the transcriptional function of normal receptor in a dominant-negative fashion. By contrast, function of Ala263Val mutant TRα2 matched its normal counterpart. In vitro, high concentrations of T3 restored transcriptional activity of Ala263Val mutant TRα1, and reversed the dominant-negative inhibition of its normal counterpart. High concentrations of T3 restored expression of thyroid hormone-responsive target genes in patient-derived blood cells.
Interpretation
TRα1 seems to be the principal functional product of the THRA gene. Thyroxine treatment alleviates hormone resistance in patients with mutations affecting this gene, possibly ameliorating the phenotype. These findings will help the diagnosis and treatment of other patients with resistance to thyroid hormone resulting from mutations in THRA.
Funding
Wellcome Trust, NIHR Cambridge Biomedical Research Centre, Marie Curie Actions, Foundation for Development of Internal Medicine in Europe
A Transcriptomic Signature of the Hypothalamic Response to Fasting and BDNF Deficiency in Prader-Willi Syndrome.
Transcriptional analysis of brain tissue from people with molecularly defined causes of obesity may highlight disease mechanisms and therapeutic targets. We performed RNA sequencing of hypothalamus from individuals with Prader-Willi syndrome (PWS), a genetic obesity syndrome characterized by severe hyperphagia. We found that upregulated genes overlap with the transcriptome of mouse Agrp neurons that signal hunger, while downregulated genes overlap with the expression profile of Pomc neurons activated by feeding. Downregulated genes are expressed mainly in neuronal cells and contribute to neurogenesis, neurotransmitter release, and synaptic plasticity, while upregulated, predominantly microglial genes are involved in inflammatory responses. This transcriptional signature may be mediated by reduced brain-derived neurotrophic factor expression. Additionally, we implicate disruption of alternative splicing as a potential molecular mechanism underlying neuronal dysfunction in PWS. Transcriptomic analysis of the human hypothalamus may identify neural mechanisms involved in energy homeostasis and potential therapeutic targets for weight loss
Functional characterization of obesity-associated variants involving the α and β isoforms of human SH2B1.
We have previously reported rare variants in sarcoma (Src) homology 2 (SH2) B adaptor protein 1 (SH2B1) in individuals with obesity, insulin resistance, and maladaptive behavior. Here, we identify 4 additional SH2B1 variants by sequencing 500 individuals with severe early-onset obesity. SH2B1 has 4 alternatively spliced isoforms. One variant (T546A) lies within the N-terminal region common to all isoforms. As shown for past variants in this region, T546A impairs SH2B1β enhancement of nerve growth factor-induced neurite outgrowth, and the individual with the T546A variant exhibits mild developmental delay. The other 3 variants (A663V, V695M, and A723V) lie in the C-terminal tail of SH2B1α. SH2B1α variant carriers were hyperinsulinemic but did not exhibit the behavioral phenotype observed in individuals with SH2B1 variants that disrupt all isoforms. In in vitro assays, SH2B1α, like SH2B1β, enhances insulin- and leptin-induced insulin receptor substrate 2 (IRS2) phosphorylation and GH-induced cell motility. None of the variants affect SH2B1α enhancement of insulin- and leptin-induced IRS2 phosphorylation. However, T546A, A663V, and A723V all impair the ability of SH2B1α to enhance GH-induced cell motility. In contrast to SH2B1β, SH2B1α does not enhance nerve growth factor-induced neurite outgrowth. These studies suggest that genetic variants that disrupt isoforms other than SH2B1β may be functionally significant. Further studies are needed to understand the mechanism by which the individual isoforms regulate energy homeostasis and behavior.This work was supported by the Wellcome Trust (098497/Z/
12/Z; 077016/Z/05/Z; 096106/Z/11/Z) (to I.S. Farooqi and L.R.
Pearce), by the Medical Research Council Metabolic Diseases Unit and NIHR Cambridge Biomedical Research Centre (to I.S.
Farooqi, I. Barroso, and S. O’Rahilly) and the Bernard Wolfe
Health Neuroscience Fund (I.S. Farooqi); and by NIH grants
RO1-DK54222 (to C. Carter-Su), RO1-DK065122 and RO1-
DK073601 (to L. Rui), a predoctoral fellowship from the Systems and Integrative Biology Training Grant NIH–T32-GM008322 (to M.E. Doche) and a Rackham Merit Fellowship
from the University of Michigan (to R. Joe). Confocal microscopy was performed using the Morphology and Image Analysis
Core of the Michigan Diabetes Research Center (NIH grant
P60-DK20572).This is the final published version distributed under a Creative Commons Attribution License, which can also be found on the publisher's website at: http://press.endocrine.org/doi/abs/10.1210/en.2014-1264?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%3dpubme
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