ESPE Abstracts

Objectives: Prader–Willi syndrome (PWS) is the most common genetic obesity disorder and results from lack of gene expression on paternally inherited chromosome 15q11.2-q13. However, the factors regulating obesity in PWS are poorly understood. We aimed to characterize genetic alterations in PWS using whole genome microarrays to analyze gene expression, and to understand the molecular mechanisms of obesity in PWS patients.

Methods: We performed microarray using RNA isolated from whole blood from 25 PWS subjects and 25 age matched control. Gene expression data was obtained by Affymetrix Whole Transcript Expression array (GeneChip Whole Transcript PLUS reagent Kit). After preprocessing of data to reduce heterogeneity, differentially expressed genes (DEGs) between groups were identified using a linear regression model package. Gene ontology and of genes and genome pathway enrichment analyses were conducted using R package ‘limma’. The heat map for the gene expression data was generated using a pheatmap in R package. Separate KEGG pathway analysis using EnrichR for up-regulated and down-regulated genes was performed.

Results: Of 21,488 probes examined in the microarray, 4,156 were detectable. Twenty-five genes had significantly different expression in the obese relative to non-obese PWS patients (12 genes upregulated and 13 downregulated). All of these genes were not located in chromosome 15q11.2. S100A12, KCNJ15, and HCAR2 were most significantly upregulated in obese PWS patients. Most significantly downregulated genes were ARL17B, PRKY, and USP9Y. The upregulated genes were associated with sulfur metabolism, nitrogen metabolism, and fatty acid biosynthesis.

Conclusions: This study reveals 25 genes associated with obesity in PWS patients. These genes could suggest new therapeutic targets or potential biomarkers for obesity in PWS.