RTL1 (retrotransposon Gag like 1) is a paternally expressed, imprinted gene that plays essential roles in placental development, skeletal muscle development, and neurological function 1. The gene is derived from retrotransposon sequences and is crucial for maintaining fetal capillary networks in the placenta during gestation 2. RTL1 is also essential for fetal and neonatal skeletal muscle development, with both deficiency and overexpression causing severe muscle defects and neonatal lethality in mouse models 2. In the nervous system, RTL1 is widely expressed in the central nervous system, including the limbic system, and regulates neuronal excitability in the locus coeruleus 3. The gene mediates anxiety-like behaviors, social behaviors, fear-related learning, and locomotor activity 34. RTL1 expression is controlled by complex imprinting mechanisms involving the DLK1-DIO3 domain, with the maternal allele silenced by the long non-coding RNA MEG3 5. Dysregulation of RTL1 is implicated in Temple syndrome and Kagami-Ogata syndrome, genomic imprinting disorders that affect placental, muscle, and neurological development 16. Additionally, RTL1 expression has been observed in immune cells and is aberrantly expressed in breast cancer tissues 78.