Genetic analysis of familial lupus in Omani population

Background: Systemic lupus erythematosus (SLE) is the archetypal systemic autoimmune disease. The clinical presentations are diverse, ranging from mild poly-arthralgia to fatal multisystemic disease. There is no known cure, and management hinges on chronic immunosuppression. Lupus is most common in women of productive age (15-40 years old), but sometimes begins earlier. In most cases, the cause of SLE remains unknown, although two lines of evidence indicate that there is a substantial genetic component. First, the rate of concordance for lupus between monozygotic twins is approximately 50%, compared with 2-3% for dizygotic twins. Second, rare cases of simple Mendelian lupus have been described. Environmental factors such as exposure to ultraviolet light, infection and hormones are likely to contribute as well, since the rate of concordance between MZ twins is not 100%. Familial lupus is defined as any case in which more than one person affected with SLE in the same family due to acquisition of certain genetic traits. Familial cases tend to occur more in areas where the rate of consanguineous marriage is high such as in the Middle East including the Sultanate of Oman. Genetically specified cases have provided important insights into the causal mechanisms of lupus. These cases have revealed that several different types of fundamental defects can cause a clinical lupus phenotype. Disease heterogeneity can be resolved partially by analysis of the derangement of immunity in lupus. Examples of the involved immune components are expansion of specific subsets of T cells (T follicular helper cells) and B cell auto-reactivity causing abnormal production of autoantibodies and deposition of immune complexes giving rise to tissue damage at different organs. Understanding pathophysiology of SLE is crucial since current nonspecific immunosuppressive medications with many side effects are in use to control and prevent further tissue damage in patients with SLE. There is no literature available about clinical and laboratory phenotype of familial lupus in adult population coming from Arab countries in general and from Oman in particular to compare with published literature from other ethnic groups. Moreover, despite the availability of familial lupus cases in Oman which might be due to the high consanguinity rate, so far these cases have not been thoroughly investigated. As a result, all Omani lupus cases are treated in similar ways with no attempt toward personalized or targeted therapy. Objective, material and methods: Utilizing our familial cases, our main objective is better understanding of SLE pathophysiology that can be used for earlier diagnosis and more personalized management of the disease. This will be done through examination of certain genetic variations, associated cellular phenotypes and the involved pathway. Material and methods: The study aimed to recruit up to 30 familial lupus pedigrees. So far, 16 pedigrees were recruited for genetic analysis into this ethically approved project. Further detailed clinical phenotyping and available family tree examination for 12 pedigrees has helped in selection of 7 pedigrees with a total of 18 affected individuals. These 18 individuals were then subjected to (NGS) at the Centre for Personalized Immunology (CPI). At this stage we have results of bioinformatics analysis on 7 from the 18 affected individuals. These results have confirmed presence of known SLE causing gene (DNASE1L3) only in one family (3 affected siblings of paediatric onset SLE). We have also discovered two very interesting genes that might be the cause of familial lupus in some of our pedigrees. One of them is involved in T regulatory ( Tregs, in 2 affected siblings) pathway formation and function in addition to another gene that is involved in the NF-?B signalling pathway (in 2 affected individuals, mother and daughter) Therefore, the main objectives of this project are: -Further recruiting the remaining 14 families out of initial proposed 30 families for NGS. -Bioinformatics analysis of the remaining cohort, which will be done by the local team. -Flowcytometric examination and analysis of the associated cellular phenotype of the recruited cohort which will be done by the local team. -Identification of more plausible novel genes/ pathways in the remaining cohort through re-examination of the NGS genetic data based on the clinical, laboratory and cellular findings, which will be done by the local team in collaboration with the external collaborator Prof Cook. -Confirmation of the mutation(s) novelty across same ethnic group by analysing existing normal Omani control cohort for the absence of the same mutation, which will be done by the local team. -Familial segregation and Sanger sequencing of the novel mutation(s), which will be done by the local team. -Functional assessment of the discovered mutations, which will be done by the local team. -Mouse model with the discovered mutations to examine effects of these mutations, which will be done by the external collaborator team. Blood will be drawn from recruited members for detailed cellular phenotypic analysis (10 colour flow cytometry) in order to characterize abnormal cellular signatures. In addition, DNA will be extracted from the newly recruited families and will be sent for NGS. Bioinformatics analysis will be done locally. Identified mutations will be confirmed using Sanger sequencing and novelty across race will be confirmed using existing normal controls genetic data base. Functional studies will be done to prove causation in a given pathway of the proposed gene. Expected outcomes are the first description of reference clinical and laboratory data about familial lupus in Omani adult patients to compare with published data for other ethnic groups. In addition, this project will enable discovery of more novel genetic variants and their associated cellular signatures is our Omani cohort. This has the potential to illuminate pathophysiology of SLE. Understanding the involved pathway is always the first step toward improving diagnostic and personalizing treatment options.