Articles written in Journal of Genetics

    • Genetics of ulcerative colitis: putting into perspective the incremental gains from Indian studies


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      Ulcerative colitis (UC), one of the two clinical subtypes of inflammatory bowel disease is perceived as a potential 'sleeping giant' in the Indian subcontinent. Clinical manifestation is overall believed to be the same across ethnic groups but overwhelming genetics from large European and fewer non-European studies have revealed shared as well as unique disease susceptibly signaturesbetween them, pointing to population specific differences at genomic and environmental levels. A systematic recount of the four major eras in UC genetics spanning earliest linkage analysis, cherry picked candidate gene association studies, unbiased genomewide association studies, their logical extension in trans-ethnic setting (Immunochip study), lastly whole exome sequencing efforts forrare variant burden; and lessons learnt thereof in context of genetically distinct Indian population was attempted in this review. Genetic heterogeneity manifesting at allelic/locus level across these approaches has been the consistent finding through the range of pan India studies. On the other hand, these salient findings also highlight the limitations of even the best of these genetic leadsfor prognostic/clinical application. The imminent need, therefore, for the UC research community to adopt newer approaches/tools with improved study design to (i) gain better insight into genetic/mechanistic basis of disease; (ii) identify biomarkers of immediate translational value; and (iii) develop new/alternate therapeutic options is emphasized at the end.

    • Celiac disease-associated loci show considerable genetic overlap with neuropsychiatric diseases but with limited transethnic applicability


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      Clinical and public health research has revealed the co-occurrence of several neuropsychiatric diseases among patients with celiac disease (CD). The significant presence of CD-specific autoantibodies in patients with neuropsychiatric diseases and vice versa are often reported. To explain the genetic basis of such frequent disease co-occurrence and investigate the underlying common pathways/processes, we performed an extensive cross-disease association study followed by supporting in silico functional validation of the leads. Genomewide association study (GWAS) data for CD and eight commonly co-occurring neuropsychiatric diseases from Caucasian populations were analysed, and the shared loci were determined.We performed Immunochip-based fine mapping of these overlapping association signals in anindependent European CD data and tested their cross-ethnic transferability using CD association data from the genetically distinct north Indian population. This study identified 12 shared loci between the two diseases with genomewide significance (P ≤ 5e-8). Of these five loci, namely NFIA, KIA1109, NOTCH4-TSBP1-PBX2, HLA-DQA1 and CSK replicated in an independent Dutch cohort representing European ancestry. Three of these loci, namely NFIA, NOTCH4-TSBP1-PBX2 and HLA-DQA1 that are common between CD, anxiety, migraine and schizophrenia respectively withstood locus transferability test in north Indians. Tissue-specific eQTL analysis of SNPs from transferable loci revealedexpression QTL effects in brain tissue besides the small intestine and whole blood. Pathway analysis and evidence of epigenetic regulation highlighted the potential contribution of these SNPs to disease pathology. The replicable and transferable association of genetic variants from MHC locus and their functional implications suggest the process of antigen presentation and adaptive/innate immune response regulated by non-HLA genes in the locus may dominate the shared pathogenesis of CD and neuropsychiatric diseases. Functional validation of the shared candidate genes is warranted to unravel the molecular mechanism for the co-occurrence of CD and specific neuropsychiatric diseases.

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