IDENTIFICATION AND FUNCTIONAL VALIDATION OF RARE MISSENSE VARIANTS IN PLXNA1 AS A CANDIDATE GENE FOR SEVERE EARLY-ONSET OBESITY

Abstract

Childhood obesity is a pressing issue in Qatar, with a reported prevalence of 49% among school-aged children and adolescents. This complex problem involves a combination of genetic and environmental factors. Monogenic obesity (MO) is a rare form of obesity caused by mutations in a single gene, making it an interesting area for study, especially in populations with high rates of consanguinity like Qatar. Despite this, the genetic basis of MO in Arab countries, including Qatar, remains poorly understood. Our research, conducted in collaboration with Sidra Medicine, aims to identify new genetic factors contributing to severe childhood obesity using whole genome sequencing. We then investigated the functional implications of these genetic variants using human cells and zebrafish embryos as models. This work has the potential to improve the understanding of severe childhood obesity, leading to better genetic testing, counseling, and potentially new treatment options for affected individuals. One promising candidate gene discovered in this context is PLXNA1. In our research project, we have identified three rare missense variants in the PLXNA1 gene (c.3510C>G, p.I1170M; c.4127A>C, p.E1376A; c.2476T>C, p.F826L) among children with severe early-onset obesity inherited in compound heterozygous pattern. Upon in vitro functional validation using T-cell enrichment, PLXNA1 and adiposity markers gene expression levels in the patient were increased as compared to lean control. While in vivo zebrafish knockdown of PLXNA1 orthologs gave statistically significant increases in adiposity phenotypes such as increased yolk sac size, increased lipid content, increased leptin, triglycerides, and cAMP levels, and increased overall metabolic rate. In conclusion, we have identified rare variants in PLXNA1 in severely obese children with early onset obesity, and we have functionally validated the role of the gene in zebrafish model to show an adiposity phenotype with gene knockdown. Our research lays the groundwork for exploring the role of PLXNA1 in obesity development paving the way for targeted interventions and improved management strategies.