Dominant-negative HNF1α mutant promotes liver steatosis and inflammation by regulating hepatic complement factor D.

Patients with HNF1A variants may develop liver steatosis, while the underlying mechanism is still unclear. Here, we established a mouse model carrying the dominant-negative HNF1α P291fsinsC mutation (hHNF1Amut/-) and found that the mutant mice developed liver steatosis spontaneously under the normal chow diet. Transcriptome analysis showed significant upregulation of Cfd and other genes related to innate immune response in the liver of hHNF1Amut/- mice. The changes in lipid metabolism and complement pathways were also confirmed by proteomics. We demonstrated that HNF1α inhibited CFD expression in hepatocytes, and the P291fsinsC mutant could reverse this inhibitory effect. Furthermore, the suppression of CFD with specific inhibitor or siRNAs reduced triglyceride levels in hepatocytes, suggesting that CFD regulated hepatocyte lipid deposition. Our results demonstrate that the HNF1α P291fsinsC mutant promotes hepatic steatosis and inflammation by upregulating CFD expression, and targeting CFD may delay the progression of nonalcoholic fatty liver disease.

R158Q and G212S, novel pathogenic compound heterozygous variants in SLC12A3 of Gitelman syndrome.

The dysfunction of Na+-Cl- cotransporter (NCC) caused by mutations in solute carrier family12, member 3 gene (SLC12A3) primarily causes Gitelman syndrome (GS). In identifying the pathogenicity of R158Q and G212S variants of SLC12A3, we evaluated the pathogenicity by bioinformatic, expression, and localization analysis of two variants from a patient in our cohort. The prediction of mutant protein showed that p.R158Q and p.G212S could alter protein's three-dimensional structure. Western blot showed a decrease of mutant Ncc. Immunofluorescence of the two mutations revealed a diffuse positive staining below the plasma membrane. Meanwhile, we conducted a compound heterozygous model-Ncc R156Q/G210S mice corresponding to human NCC R158Q/G212S. NccR156Q/G210S mice clearly exhibited typical GS features, including hypokalemia, hypomagnesemia, and increased fractional excretion of K+ and Mg2+ with a normal blood pressure level, which made NccR156Q/G210S mice an optimal mouse model for further study of GS. A dramatic decrease and abnormal localization of the mutant Ncc in distal convoluted tubules contributed to the phenotype. The hydrochlorothiazide test showed a loss of function of mutant Ncc in NccR156Q/G210S mice. These findings indicated that R158Q and G212S variants of SLC12A3 were pathogenic variants of GS.