First Report of a Novel Pathogenic Variant in the RREB1 Gene Associated With Obesity and Metabolic Syndrome.

Ras-responsive element binding protein 1 (RREB1) is a zinc finger transcription factor that is crucial in regulating cell growth, gene expression, and DNA repair. It functions as both a repressor and an activator, with its activity controlled by the MAPK signaling pathway. RREB1 has been implicated in various conditions such as type 2 diabetes (T2D), obesity, and cancer, suggesting its potential as both a biomarker and a therapeutic target for these diseases. While several cases of 6p terminal deletions in the RREB1 gene and one case of Noonan-like RASopathy due to a loss-of-function variant have been reported, this study presents the first case of a pathogenic loss-of-function variant in RREB1 associated with morbid obesity and metabolic disturbances. Our patient, a 16-year-old male, exhibited morbid obesity, metabolic disorders, moderate intellectual disability, and atypical autism symptoms. He was referred to our clinic by the pediatric endocrinology department for genetic evaluation. Initial genetic testing included karyotype analysis and SNP array testing with 700 000 probes. Whole exome sequencing (WES) was then performed on the patient and his family, revealing a de novo novel variant, c.3178_3179del, p.(Glu1060Argfs*37) in the RREB1 gene, which was confirmed by Sanger sequencing. This novel variant underscores the critical role of RREB1 in regulating metabolic processes, particularly obesity. Additionally, the patient's neurodevelopmental delay aligns with previously reported findings of RREB1 loss-of-function variants. These results highlight the need for further research to fully understand the metabolic implications of RREB1 gene loss, with this study providing valuable insights for future investigations.