Protein arginine N-methyltransferase 5 is an enzyme that in humans is encoded by the PRMT5 gene. PRMT5 symmetrically dimethylates H2AR3, H4R3, H3R2, and H3R8 in vivo, all of which are linked to a range of transcriptional regulatory events. PRMT5 is a highly conserved arginine methyltransferase that translocated from the cytoplasm to the nucleus at embryonic day ~E8.5, and during preimplantation development at the ~4-cell stage. Model organisms have been used in the study of PRMT5 function. Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion. Twenty five tests were carried out on mutant mice and two significant abnormalities were observed. No homozygous mutant embryos were identified during gestation, and therefore none survived until weaning. The remaining tests were carried out on heterozygous mutant adult mice but no further abnormalities were observed. A conditional allele of Prmt5 in the mouse limb shows that it is essential for maintaining a progenitor population, as conditional mutants have limb defects.