Liver fat deposition related to systemic insulin resistance defines non-alcoholic fatty liver disease (NAFLD) which, when associated with oxidative hepatocellular damage, inflammation, and activation of fibrogenesis, i.e. non-alcoholic steatohepatitis (NASH), can progress towards cirrhosis and hepatocellular carcinoma. Due to the epidemic of obesity, NAFLD is now the most frequent liver disease and the leading cause of altered liver enzymes in Western countries. Epidemiological, familial, and twin studies provide evidence for an element of heritability of NAFLD. Genetic modifiers of disease severity and progression have been identified through genome-wide association studies. These include the Patatin-like phosholipase domain-containing 3 (PNPLA3) gene variant I148M as a major determinant of inter-individual and ethnicity-related differences in hepatic fat content independent of insulin resistance and serum lipid concentration. Association studies confirm that the I148M polymorphism is also a strong modifier of NASH and progressive hepatic injury. Furthermore, a few large multicentre case-control studies have demonstrated a role for genetic variants implicated in insulin signalling, oxidative stress, and fibrogenesis in the progression of NAFLD towards fibrosing NASH, and confirm that hepatocellular fat accumulation and insulin resistance are key operative mechanisms closely involved in the progression of liver damage. It is now important to explore the molecular mechanisms underlying these associations between gene variants and progressive liver disease, and to evaluate their impact on the response to available therapies. It is hoped that this knowledge will offer further insights into pathogenesis, suggest novel therapeutic targets, and could help guide physicians towards individualised therapy that improves clinical outcome.

We explored potential genetic risk factors implicated in nonalcoholic fatty liver disease (NAFLD) within a Caribbean-Hispanic population in New York City. A total of 316 individuals including 40 subjects with biopsy-proven NAFLD, 24 ethnically matched non-NAFLD controls, and a 252 ethnically mixed random sampling of Bronx County, New York were analyzed. Genotype analysis was performed to determine allelic frequencies of 74 known single-nucleotide polymorphisms (SNPs) associated with NAFLD risk based on previous genome-wide association study (GWAS) and candidate gene studies. Additionally, the entire coding region of PNPLA3, a gene showing the strongest association to NAFLD was subjected to Sanger sequencing. Results suggest that both rare and common DNA variations in PNPLA3 and SAMM50 may be correlated with NAFLD in this small population study, while common DNA variations in CHUK and ERLIN1, may have a protective interaction. Common SNPs in ENPP1 and ABCC2 have suggestive association with fatty liver, but with less compelling significance. In conclusion, Hispanic patients of Caribbean ancestry may have different interactions with NAFLD genetic modifiers; therefore, further investigation with a larger sample size, into this Caribbean-Hispanic population is warranted.

Stroke is a devastating complication of sickle cell anemia (SCA), occurring in 11% of patients before age 20 years. Previous studies of sibling pairs have demonstrated a genetic component to the development of cerebrovascular disease in SCA, but few candidate genetic modifiers have been validated as having a substantial effect on stroke risk. We performed an unbiased whole-genome search for genetic modifiers of stroke risk in SCA. Genome-wide association studies were performed using genotype data from single-nucleotide polymorphism arrays, whereas a pooled DNA approach was used to perform whole-exome sequencing. In combination, 22 nonsynonymous variants were identified and represent key candidates for further in-depth study. To validate the association of these mutations with the risk for stroke, the 22 candidate variants were genotyped in an independent cohort of control patients (n = 231) and patients with stroke (n = 57) with SCA. One mutation in GOLGB1 (Y1212C) and another mutation in ENPP1 (K173Q) were confirmed as having significant associations with a decreased risk for stroke. These mutations were discovered and validated by an unbiased whole-genome approach, and future studies will focus on how these functional mutations may lead to protection from stroke in the context of SCA.

Pseudoxanthoma elasticum (PXE) is a rare hereditary disorder characterized by progressive calcification and fragmentation of elastic fibers. Because of the great clinical variability between PXE patients the involvement of modifier genes was recently suggested. Therefore, we investigated the association of single nucleotide variants (SNVs) in selected candidate genes known to regulate cellular pyrophosphate metabolism.