C11orf21 is a gene located in the imprinted domain of chromosome 11.5 that encodes a 132-amino acid cytoplasmic protein 1. The gene shows tissue-restricted expression, being predominantly expressed in human heart 1, and displays biallelic (non-imprinted) expression patterns 1. Functionally, C11orf21 is a transcriptional target of RUNX1, a critical transcription factor in hematopoiesis 2. In t(8;21) acute myeloid leukemia, the oncogenic RUNX1-ETO fusion protein suppresses C11orf21 transcription through direct promoter binding, suggesting that C11orf21 depletion may contribute to leukemogenesis 2. Beyond hematologic malignancies, C11orf21 variants are associated with chr11 lymphocytic leukemia susceptibility in genome-wide association studies 3. Epigenetically, C11orf21/TSPAN32 shows differential methylation patterns in autism spectrum disorder, with hypomethylated CpGs identified in autistic brain tissue 4, and has been repeatedly identified as an epigenetic marker in autism 5. The gene's location within the Beckwith-Wiedemann syndrome region on 11p15.5 suggests potential involvement in genomic imprinting disorders 1. Overall, C11orf21 appears to play roles in leukemogenesis, neurodevelopmental function, and possibly imprinting-related diseases.