title: Genetic and functional evaluation of the role of DLL1 in susceptibility to visceral leishmaniasis in India.
abstract: Chromosome 6q26-27 is linked to susceptibility to visceral leishmaniasis (VL) in Brazil and Sudan. DLL1 encoding the Delta-like 1 ligand for Notch 3 was implicated as the etiological gene. DLL1 belongs to the family of Notch ligands known to selectively drive antigen-specific CD4 T helper 1 cell responses, which are important in protective immune response in leishmaniasis. Here we provide further genetic and functional evidence that supports a role for DLL1 in a well-powered population-based study centred in the largest global focus of VL in India. Twenty-one single nucleotide polymorphisms (SNPs) at PHF10/C6orf70/DLL1/FAM120B/PSMB1/TBP were genotyped in 941 cases and 992 controls. Logistic regression analysis under an additive model showed association between VL and variants at DLL1 and FAM120B, with top associations (rs9460106, OR=1.17, 95%CI 1.01-1.35, P=0.033; rs2103816, OR=1.16, 95%CI 1.01-1.34, P=0.039) robust to analysis using caste as a covariate to take account of population substructure. Haplotype analysis taking population substructure into account identified a common 2-SNP risk haplotype (frequency 0.43; P=0.028) at FAM120B, while the most significant protective haplotype (frequency 0.18; P=0.007) was a 5-SNP haplotype across the interval 5' of both DLL1 (negative strand) and FAM120B (positive strand) and extending to intron 4 of DLL1. Quantitative RT/PCR was used to compare expression of 6q27 genes in paired pre- and post-treatment splenic aspirates from VL patients (N=19). DLL1 was the only gene to show differential expression that was higher (P<0.0001) in pre- compared to post-treatment samples, suggesting that regulation of gene expression was important in disease pathogenesis. This well-powered genetic and functional study in an Indian population provides evidence supporting DLL1 as the etiological gene contributing to susceptibility to VL at Chromosome 6q27, confirming the potential for polymorphism at DLL1 to act as a genetic risk factor across the epidemiological divides of geography and parasite species.
authors.affiliation: Institute of Medical Sciences, Banaras Hindu University, Varanasi, OS 221 005, India. anniebhu19@gmail.com
authors.forename: Sanjana
authors.initials: S
authors.lastname: Mehrotra
authors.forename: Michaela
authors.initials: M
authors.lastname: Fakiola
authors.forename: Anshuman
authors.initials: A
authors.lastname: Mishra
authors.forename: Medhavi
authors.initials: M
authors.lastname: Sudarshan
authors.forename: Puja
authors.initials: P
authors.lastname: Tiwary
authors.forename: Deepa Selvi
authors.initials: DS
authors.lastname: Rani
authors.forename: Kumarasamy
authors.initials: K
authors.lastname: Thangaraj
authors.forename: Madhukar
authors.initials: M
authors.lastname: Rai
authors.forename: Shyam
authors.initials: S
authors.lastname: Sundar
authors.forename: Jenefer M
authors.initials: JM
authors.lastname: Blackwell
mesh_terms: D000293:Adolescent; D000328:Adult; D002135:Calcium-Binding Proteins; D016022:Case-Control Studies; D005260:Female; D020022:Genetic Predisposition to Disease; D006239:Haplotypes; D006801:Humans; D007194:India / Q000453:epidemiology; D036341:Intercellular Signaling Peptides and Proteins / Q000235:genetics* / Q000378:metabolism; D007898:Leishmaniasis, Visceral / Q000453:epidemiology / Q000235:genetics*; D015810:Linkage Disequilibrium; D016015:Logistic Models; D008297:Male; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism; D008875:Middle Aged; D008957:Models, Genetic; D020641:Polymorphism, Single Nucleotide; D051880:Receptors, Notch / Q000235:genetics / Q000378:metabolism; D013154:Spleen / Q000737:chemistry / Q000378:metabolism
chemical_list: D002135:Calcium-Binding Proteins; C512941:DLK1 protein, human; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D051880:Receptors, Notch