Jaanam Lalchandani

Individuals with Alpha-1 antitrypsin deficiency (AATD) PiZZ genotype, have an increased risk of developing lung and/or liver disease, although not all of them develop the same manifestations, which suggests the presence of modifier genetic variants that favor a specific phenotype. These genetic factors are mostly unknown, but they could help to identify patients with a higher risk of developing AATD-associated lung or liver disease. In order to identify modifier genetic variants, we have sequenced the complete exome (Twist Human Core Exome Plus) of a group of 72 patients with AATD, all of them with the PiZZ genotype. Among these patients, 13 had liver disease (ZZ-HEP) and 59 had lung disease only (ZZ-PUL). After annotating the variants, an association analysis was performed comparing the frequencies in both groups ZZ-PUL and ZZ-HEP. We found 537 genes with variants significantly associated with lung or liver disease (OR between 3-25, p>0.05), 412 variants presented higher frequency in ZZ-HEP and 125 variants were more frequent in ZZ-PUL. Among these variants, 14% produce amino acid changes in proteins, and 86% were non-coding intronic variants. The functional annotations of genes with significant variants were related to different pathways such as transport, bile acid synthesis, apoptosis, biological oxidations, metabolism, proteases, PTEN regulation, or macroautophagy. Our results identified genetic variants that confer specific risk of lung or liver damage in PiZZ patients, and that could contribute to stratify patients identifying those at higher risk of suffering AATD lung or liver associated disease.

Different mutations in the SERPINA1 gene result in alpha-1 antitrypsin (AAT) deficiency and in an increased risk for the development of liver diseases. More than 90% of severe deficiency patients are homozygous for Z (Glu342Lys) mutation. This mutation causes Z-AAT polymerization and intrahepatic accumulation which can result in hepatic alterations leading to steatosis, fibrosis, cirrhosis, and/or hepatocarcinoma. We aimed to investigate lipid status in hepatocytes carrying Z and normal M alleles of the SERPINA1 gene. Hepatic organoids were developed to investigate lipid alterations. Lipid accumulation in HepG2 cells overexpressing Z-AAT, as well as in patient-derived hepatic organoids from Pi*MZ and Pi*ZZ individuals, was evaluated by Oil-Red staining in comparison to HepG2 cells expressing M-AAT and liver organoids from Pi*MM controls. Furthermore, mass spectrometry-based lipidomics analysis and transcriptomic profiling were assessed in Pi*MZ and Pi*ZZ organoids. HepG2 cells expressing Z-AAT and liver organoids from Pi*MZ and Pi*ZZ patients showed intracellular accumulation of AAT and high numbers of lipid droplets. These latter paralleled with augmented intrahepatic lipids, and in particular altered proportion of triglycerides, cholesterol esters, and cardiolipins. According to transcriptomic analysis, Pi*ZZ organoids possess many alterations in genes and cellular processes of lipid metabolism with a specific impact on the endoplasmic reticulum, mitochondria, and peroxisome dysfunction. Our data reveal a relationship between intrahepatic accumulation of Z-AAT and alterations in lipid homeostasis, which implies that liver organoids provide an excellent model to study liver diseases related to the mutation of the SERPINA1 gene.