Mutations in the NHEJ component XRCC4 cause primordial dwarfism.
Am J Hum Genet. 2015 Mar 5;96(3):412-24
Authors: Murray JE, van der Burg M, IJspeert H, Carroll P, Wu Q, Ochi T, Leitch A, Miller ES, Kysela B, Jawad A, Bottani A, Brancati F, Cappa M, Cormier-Daire V, Deshpande C, Faqeih EA, Graham GE, Ranza E, Blundell TL, Jackson AP, Stewart GS, Bicknell LS
Non-homologous end joining (NHEJ) is a key cellular process ensuring genome integrity. Mutations in several components of the NHEJ pathway have been identified, often associated with severe combined immunodeficiency (SCID), consistent with the requirement for NHEJ during V(D)J recombination to ensure diversity of the adaptive immune system. In contrast, we have recently found that biallelic mutations in LIG4 are a common cause of microcephalic primordial dwarfism (MPD), a phenotype characterized by prenatal-onset extreme global growth failure. Here we provide definitive molecular genetic evidence supported by biochemical, cellular, and immunological data for mutations in XRCC4, encoding the obligate binding partner of LIG4, causing MPD. We report the identification of biallelic mutations in XRCC4 in five families. Biochemical and cellular studies demonstrate that these alterations substantially decrease XRCC4 protein levels leading to reduced cellular ligase IV activity. Consequently, NHEJ-dependent repair of ionizing-radiation-induced DNA double-strand breaks is compromised in XRCC4 cells. Similarly, immunoglobulin junctional diversification is impaired in cells. However, immunoglobulin levels are normal, and individuals lack overt signs of immunodeficiency. Additionally, in contrast to individuals with LIG4 mutations, pancytopenia leading to bone marrow failure has not been observed. Hence, alterations that alter different NHEJ proteins give rise to a phenotypic spectrum, from SCID to extreme growth failure, with deficiencies in certain key components of this repair pathway predominantly exhibiting growth deficits, reflecting differential developmental requirements for NHEJ proteins to support growth and immune maturation.
PMID: 25728776 [PubMed - indexed for MEDLINE]
Achieving High Signal-to-Noise in Cell Regulatory Systems: Spatial Organization of Multiprotein Transmembrane Assemblies of FGFR and MET Receptors.
Prog Biophys Mol Biol. 2015 May 5;
Authors: Blaszczyk M, Harmer NJ, Chirgadze DY, Ascher DB, Blundell TL
How is information communicated both within and between cells of living systems with high signal to noise? We discuss transmembrane signaling models involving two receptor tyrosine kinases: the fibroblast growth factor receptor (FGFR) and the MET receptor. We suggest that simple dimerization models might occur opportunistically giving rise to noise but cooperative clustering of the receptor tyrosine kinases observed in these systems is likely to be important for signal transduction. We propose that this may be a more general prerequisite for high signal to noise in transmembrane receptor signaling.
PMID: 25957048 [PubMed - as supplied by publisher]
Germline Mutations in the CDKN2B tumor suppressor gene predispose to renal cell carcinoma.
Cancer Discov. 2015 Apr 14;
Authors: Jafri M, Wake NC, Ascher DB, Pires DE, Gentle D, Morris MR, Rattenberry E, Simpson MA, Trembath RC, Weber A, Woodward ER, Donaldson A, Blundell TL, Latif F, Maher ER
Familial renal cell carcinoma (RCC) is genetically heterogeneous and may be caused by mutations in multiple genes, including VHL, MET, SDHB, FH, FLCN, PTEN and BAP1. However, most individuals with inherited RCC do not have a detectable germline mutation. To identify novel inherited RCC genes we undertook exome resequencing studies in a familial RCC kindred and identified a CDKN2B nonsense mutation that segregated with familial RCC status. Targeted resequencing of CDKN2B in individuals (n=82) with features of inherited RCC then revealed three candidate CDKN2B missense mutations (p.Pro40Thr, (p.Ala23Glu, p.Asp86Asn). In silico analysis of the three-dimensional structures indicated that each missense substitution was likely pathogenic through reduced stability of the mutant or reduced affinity for CDK4 and CDK6 and in vitro studies demonstrated that each of the mutations impaired CDKN2B-induced suppression of proliferation in a RCC cell line. These findings identify germline CDKN2B mutations as a novel cause of familial RCC.
PMID: 25873077 [PubMed - as supplied by publisher]