Mutations In CD40 Ligand Gene Research Articles

SAT-669 CD40 Ligand Gene Mutation in Type 1 Diabetes Mellitus in a Saudi Consanguineous Family

Introduction:Type 1 Diabetes Mellitus (T1D) is a common autoimmune disorder. Investigating genetic factors that could turn the immune cells to auto-reactive are critical to our understanding of T1D. In this study genetic factors and the affected autoimmunity related molecular mechanisms in familial T1D with parental consanguinity were studied.Materials and Method:Whole Exome Sequencing (WES) was performed in a family with familial T1D. Sanger Sequencing was done to analyze segregation in affected and non-affected. Clinical and molecular aspects were also evaluated. Protein modeling and other in silico tools were used to identify probable impact of genetic abnormalities on the structure and function of protein.Result:We identified a novel homozygous substitution mutation at “c.379A>T:p.Iso127Val” in CD40 Ligand (CD40LG) gene in diabetic siblings by WES. This change was found to be segregating in the affected and non-affected individuals by Sanger sequencing. Parents and non-diabetic siblings were found to be heterozygous carriers of the nucleotide change. The c.379A>T is located within evolutionarily conserved locus of human genome. Functional prediction by Gene Ontology term analysis suggested that immune functions of CD40LG are compromised by this genetic change. Further, by protein-modeling analysis we identified that structure of ligand-binding domain of CD40LG protein, with which it interacts with other immune cells, may also be affected. In silico analysis revealed significantly reduced spatial inter amino acid distance between the site of genetic change and the ligand binding domain in mutant CD40LG.Discussion:Apoptotic elimination of developing auto-reactive T-cells, having the potential to generate an autoimmune response against pancreatic cells, is critical to prevent T1D. This apoptotic removal mechanisms, occurs in thymus and is dependent on highly specific interaction of cell surface molecules as CD40LG on developing T-cells, and the corresponding cell surface molecules on Antigen Presenting Cells (APC). In the diabetic individuals investigated in our study, the mutation in CD40LG gene, caused significant structural damage to its protein, due to which these interactions between mutant CD40LG (present on T-cells) and the corresponding CD40 (present on APC) were probably affected. This loss of interaction between CD40LG bearing T-cells and APC, probably led to escape of auto-reactive T-cells in to immune system, which further generated autoimmune response against the pancreatic tissue, precipitating to T1D among these individuals.ConclusionGenetic investigation of cell surface proteins in autoimmune cells and understanding their mechanism for development of autoimmunity offers prospects for the development of new therapeutic strategies in the approach to probable early diagnosis of T1D.

A Novel CD40L Mutation Associated with X-Linked Hyper IgM Syndrome in a Chinese Family

ABSTRACTBackground: Mutations in CD40 ligand gene (CD40L) affecting immunoglobulin class-switch recombination and somatic hypermutation can result in X-Linked Hyper IgM Syndrome (HIGM1, XHIGM), a kind of rare serious primary immunodeficiency disease (PID) characterized by the deficiency of IgG, IgA and IgE and normal or increased serum concentrations of IgM. The objective of this study is to explain genotype-phenotype correlation and highlight the mutation responsible for a Chinese male patient with XHIGM.Methods: Whole exome sequencing (WES) and Sanger sequencing validation were performed to identify and validate the likely pathogenic mutation in the XHIGM family.Results: The results of the sequencing revealed that a new causative mutation in CD40L (c.714delT in exon 5, p.F238Lfs*4) which leads to the change in amino acids (translation terminates at the third position after the frameshift mutation) appeared in the proband. As his mother in the family was carrier with this heterozygous mutation, the hemizygous mutation in this patient came from his mother indicating that genetic mode of XHIGM is X-linked recessive inheritance.Conclusion: This study broadens our knowledge of the mutation in CD40L and lays a solid foundation for prenatal diagnosis and genetic counseling for the XHIGM family.

Clinical and molecular features of X-linked hyper IgM syndrome – An experience from North India

X-linked hyper IgM Syndrome (XLHIGM), the most frequent form of the Hyper IgM syndromes is a primary immune deficiency resulting from a mutation in the CD40 ligand gene (CD40LG). We analyzed the clinical and laboratory features of ten patients with XLHIGM, who were diagnosed at a tertiary care hospital in North India. Most common infections were sinopulmonary infections (80%) and diarrhea (50%). Sclerosing cholangitis and necrotising fasciitis were noted in one patient each. Three novel mutations in CD40LG (c.429_429 delA, p. G144DfsX5; c.500 G > A, p.G167E and c.156 G > C, p.K52 N) were detected. In addition, we found one missense mutation, two splice site mutations and two large deletions, which have been previously reported. Four (4) patients had expired at the time of analysis. We report the first series of XLHIGM from North India where we have documented unique features such as pulmonary alveolar proteinosis and infections with Mycobacterium sp.

Epstein-Barr virus can establish infection in the absence of a classical memory B-cell population.

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus that persists in the body for life after primary infection. The primary site of EBV persistence is the memory B lymphocyte, but whether the virus initially infects naïve or memory B cells is still disputed. We have analyzed EBV infection in nine cases of X-linked hyper-immunoglobulin M (hyper-IgM) syndrome who, due to a mutation in CD40 ligand gene, do not have a classical, class-switched memory B-cell population (IgD(-) CD27(+)). We found evidence of EBV infection in 67% of cases, which is similar to the infection rate found in the general United Kingdom population (60 to 70% for the relevant age range). We detected EBV DNA in peripheral blood B cells and showed in one case that the infection was restricted to the small population of nonclassical, germinal center-independent memory B cells (IgD(+) CD27(+)). Detection of EBV small RNAs, latent membrane protein 2, and EBV nuclear antigen 3C expression in peripheral blood suggests full latent viral gene expression in this population. Analysis of EBV DNA in serial samples showed variability over time, suggesting cycles of infection and loss. Our results demonstrate that short-term EBV persistence can occur in the absence of a germinal center reaction and a classical memory B-cell population.

A novel mutation in CD40 ligand gene in a sporadic patient with hyper-IgM syndrome

Hyper-IgM syndrome is a rare immunodeficiency disease characterized by low or absent IgG, IgA, and IgE levels but normal or elevated level of IgM. It can occur as an acquired form or X-linked or autosomal mode of inheritance. The X-linked form (HIGM1) is a result of mutations in the CD40L ligand (CD40L) gene. We investigate the expression of CD40L on activated T cells from a sporadic male case of HIM with no family history and the B cell function in response to anti-CD40L mAb and cytokines. Staining of CD40L on activated T cells from the patient is negative with recently developed anti-human CD40L mAb, M90 and M92. The low expression of CD40L on activated T cells from the patient’s mother is also detected. Sequencing of CD40L coding region reveals a 4 bp deletion within the CD40L binding domain. These results indicate that the patient has X-linked inheritance pattern (XIGM1). CD40L mAb alone could induce the patient’s PBMCs to secret markedly IgG. Our data suggest that the detection of CD40L expression on ativated T cells may be used to identify sporadic cases of HIM as HIGM1.