The proposed pathogenesis of the cardiac manifestations of neonatal lupus (cardiac-NL) involves maternal autoantibodies to the ribonucleoproteins SSA/Ro and SSB/La enhanced by as yet unknown factors likely to involve the dysregulation of both inflammatory and fibrotic fetal responses. This study was designed to improve the power to detect specific associations in genes with candidate biological functions.
Using data from our genome-wide association study (GWAS) in 116 cardiac-NL Caucasian children and 3,351 Caucasian controls, we tested for enrichment of SNP associations in genes with candidate biological functions related to fibrosis, immune, apoptosis, T cell function, cell infiltration, innate immune cell function, interferon, Toll like receptors and calcium channels. After linkage disequilibrium pruning and exclusion of the extended HLA region, a total of 15,103 SNPs in 3,068 genes remained.
A highly significant enrichment of P-values was observed in genes related to fibrosis (P=2.27×10−9), apoptosis (P=7.67×10−7), innate immune cell (P=2.53×10−6), immune (P=5.01×10−4), T cell (P=2.23×10−4), and interferon functions (P=1.64×10−3). The most significant non-HLA associations included the sialyltransferase ST8SIA2 (rs1487982, P=3.38×10−5, OR [95%CI]=2.20 [1.52–3.19]), the integrin ITGA1 (rs2432143, P=4.54×10−5, OR [95%CI]=2.31 [1.54–3.45]), and the complement regulator CSMD1 (rs7002001, P=6.33×10−5, OR [95%CI]=2.41 [1.57–3.72]).
This study identified novel candidate genes associated with cardiac-NL and highlights the value of this cohort in advancing our knowledge regarding the genetic etiology of this syndrome. Identification of causal alleles is expected to provide critical insight into the molecular mechanisms responsible for linking maternal autoantibodies to cardiac scarring in these fetuses/neonates.