Multi-ancestry GWAS analysis identifies two novel loci associated with diabetic eye disease and highlights APOL1 as a high risk locus in patients with diabetic macular edema.

Diabetic retinopathy (DR) is a common complication of diabetes. Approximately 20% of DR patients have diabetic macular edema (DME) characterized by fluid leakage into the retina. There is a genetic component to DR and DME risk, but few replicable loci. Because not all DR cases have DME, we focused on DME to increase power, and conducted a multi-ancestry GWAS to assess DME risk in a total of 1,502 DME patients and 5,603 non-DME controls in discovery and replication datasets. Two loci reached GWAS significance (p<5x10-8). The strongest association was rs2239785, (K150E) in APOL1. The second finding was rs10402468, which co-localized to PLVAP and ANKLE1 in vascular / endothelium tissues. We conducted multiple sensitivity analyses to establish that the associations were specific to DME status and did not reflect diabetes status or other diabetic complications. Here we report two novel loci for risk of DME which replicated in multiple clinical trial and biobank derived datasets. One of these loci, containing the gene APOL1, is a risk factor in African American DME and DKD patients, indicating that this locus plays a broader role in diabetic complications for multiple ancestries. Trial Registration: NCT00473330, NCT00473382, NCT03622580, NCT03622593, NCT04108156.

A UGT2B10 splicing polymorphism common in african populations may greatly increase drug exposure.

RO5263397 [(S)-4-(3-fluoro-2-methyl-phenyl)-4,5-dihydro-oxazol-2-ylamine], a new compound that showed promising results in animal models of schizophrenia, is mainly metabolized in humans by N-glucuronidation. Enzyme studies, using the (then) available commercial uridine 5'-diphosphate-glucuronosyltransferases (UGTs), suggested that UGT1A4 is responsible for its conjugation. In the first clinical trial, in which RO5263397 was administered orally to healthy human volunteers, a 136-fold above-average systemic exposure to the parent compound was found in one of the participants. Further administration in this trial identified two more such poor metabolizers, all three of African origin. Additional in vitro studies with recombinant UGTs showed that the contribution of UGT2B10 to RO5263397 glucuronidation is much higher than UGT1A4 at clinically relevant concentrations. DNA sequencing in all of these poor metabolizers identified a previously uncharacterized splice site mutation that prevents assembly of full-length UGT2B10 mRNA and thus functional UGT2B10 protein expression. Further DNA database analyses revealed the UGT2B10 splice site mutation to be highly frequent in individuals of African origin (45%), moderately frequent in Asians (8%) and almost unrepresented in Caucasians (<1%). A prospective study using hepatocytes from 20 individual African donors demonstrated a >100-fold lower intrinsic clearance of RO5263397 in cells homozygous for the splice site variant allele. Our results highlight the need to include UGT2B10 when screening the human UGTs for the enzymes involved in the glucuronidation of a new compound, particularly when there is a possibility of N-glucuronidation. Moreover, this study demonstrates the importance of considering different ethnicities during drug development.

Effect of IL28B genotype on early viral kinetics during interferon-free treatment of patients with chronic hepatitis C.

BACKGROUND & AIMS: Although interleukin 28B (interferon, lambda 3) (IL28B) genotype affects the response of patients with chronic hepatitis C to peginterferon and ribavirin, little is known regarding its effect on response to direct-acting antivirals in interferon-free combinations. We analyzed the effects of IL28B genotype on the viral kinetic (VK) response to an interferon-free combination of the nucleoside polymerase inhibitor mericitabine (RG7128) and the hepatitis C virus (HCV) protease inhibitor danoprevir. METHODS: We performed a double-blind, dose-escalation study of patients with chronic HCV genotype 1 infection who were interferon treatment naive or had not responded to previous therapy with peginterferon and ribavirin. Patients were sequentially assigned to 1 of 7 cohorts then randomly assigned to groups that received up to 13 days of treatment with mericitabine (500 or 1000 mg, twice daily) plus danoprevir (100 or 200 mg, every 8 hours, or 600 or 900 mg, twice daily) or placebo. Eighty-three of 87 patients were genotyped for the IL28B single-nucleotide polymorphism rs12979860. VKs were analyzed only in patients who received 13 days of treatment, at optimal doses, using a biphasic model to describe first- and second-phase slopes of viral decay during therapy. RESULTS: At day 14 (the end of interferon-free treatment), the mean reduction in the serum level of HCV RNA was slightly greater in patients with the CC polymorphism (5.01 log(10) IU/mL) than those without (4.59 log(10) IU/mL). Modeling revealed that patients with the CC polymorphism had slightly better early VKs, most apparent in the ß-phase of viral decay. A mixed effect on the α-phase was observed, which was reduced in magnitude but prolonged in patients with CC, who also had better on-treatment response to peginterferon and ribavirin during follow up. CONCLUSIONS: IL28B genotype appears to affect early VKs in patients with chronic hepatitis C receiving interferon-free treatment.

High molecular weight RNAs and small interfering RNAs induce systemic posttranscriptional gene silencing in plants.

Posttranscriptional gene silencing (PTGS) in transgenic plants is an epigenetic form of RNA degradation related to PTGS and RNA interference (RNAi) in fungi and animals. Evidence suggests that transgene loci and RNA viruses can generate double-stranded RNAs similar in sequence to the transcribed region of target genes, which then undergo endonucleolytic cleavage to generate small interfering RNAs (siRNA) that promote degradation of cognate RNAs. The silent state in transgenic plants and in Caenorhabditis elegans can spread systemically, implying that mobile silencing signals exist. Neither the chemical nature of these signals nor their exact source in the PTGS pathway is known. Here, we use a positive marker system and real-time monitoring of green fluorescent protein expression to show that large sense, antisense, and double-stranded RNAs as well as double-stranded siRNAs delivered biolistically into plant cells trigger silencing capable of spreading locally and systemically. Systemically silenced leaves show greatly reduced levels of target RNA and accumulate siRNAs, confirming that RNA can induce systemic PTGS. The induced siRNAs represent parts of the target RNA that are outside of the region of homology with the triggering siRNA. Our results imply that siRNAs themselves or intermediates induced by siRNAs could comprise silencing signals and that these signals induce self-amplifying production of siRNAs.