TMEM50A (transmembrane protein 50A), encoded by the SMP1 gene located in the intergenic region between RHD and RHCE on chromosome 1.11, functions primarily as a regulator of RH blood group gene expression. TMEM50A modulates RHCE and RHD gene activity through mRNA stability mechanisms involving splicing functions 1. Overexpression of TMEM50A significantly increases RHCE expression (63.56%), while inhibition decreases both RHCE (41.82%) and RHD expression (27.35%) 1. The protein localizes to the endoplasmic reticulum and is involved in late endosome-to-vacuole transport pathways. TMEM50A is clinically relevant in the context of rare Rh blood group phenotypes; complex RH gene structural inversions involving TMEM50A breakpoints have been identified as a major molecular mechanism underlying the extremely rare D-- phenotype in Chinese populations, with significant implications for transfusion safety 2. Additionally, genetic studies in African ancestry populations identified TMEM50A as a genetically regulated gene expression associate with lung cancer susceptibility 3. Preliminary evidence suggests TMEM50A may also play a role in embryonic nervous system development 1.