CR1 variants contribute to FSGS susceptibility across multiple populations

Focal segmental glomerulosclerosis (FSGS) is a leading cause of nephrotic syndrome, with an annual incidence of 24 cases per million among African-Americans and 5 per million among European-Americans in the United States. It ranks as the second most common glomerular disease in Europe and Latin America and the fifth in Asia. We conducted a case-control study involving 726 FSGS cases and 13,994 controls from diverse ethnic backgrounds, using panel sequencing of ∼2,500 podocyte-expressed genes. Rare variant association tests confirmed known risk genes (KANK1, COLAPOL1) and identified a significant association with the CR1 gene. The CR1 variant rs17047661, which encodes the Sl1/Sl2 (R1601G) allele, was previously linked to cerebral malaria protection and is now identified as a risk variant for FSGS. This highlights an evolutionary trade-off between infectious disease resistance and kidney disease susceptibility, emphasizing the role of adaptive immunity in FSGS pathogenesis and potential therapeutic targets.

Serum C3 and Renal Outcome in Patients with Primary Focal Segmental Glomerulosclerosis

The role of complement (C) in the pathogenesis or progression of focal segmental glomerulosclerosis (FSGS) is uncertain. The present study assessed the relationship between serum C3, the baseline characteristics, and the progression of FSGS in the cohort and identified the clinical implications of serum C3 levels in patients with FSGS. Compared to the patients with C3 ≥ 85 mg/dL (N = 474), those with C3 < 85 mg/dL (N = 117) presented a higher level of serum creatinine, lower levels of eGFR, hemoglobin, proteinuria, triglyceride, cholesterol, IgA, as well as, severe tubulointerstitial injury (TI). Of the 221 patients with a mean follow-up of 53.3 months, the risk of reaching end-stage renal disease (ESRD) was significantly higher in patients with low serum C3 level (p < 0.001). An additional 40 patients with primary FSGS revealed a significant correlation between MAC and AP (p = 0.003), MAC and serum C3 (p = 0.018), and AP and serum C3 (p = 0.028). Compared to patients with none-to-mild TI, those with moderate-to-severe TI exhibited a lower level of serum C3 and AP, and a higher level of serum MAC. In conclusion, complement activation occurring in patients with FSGS is associated with clinical and histological severities. Low serum C3 was an independent risk factor for poor renal outcome in patients with FSGS.