 The excised region or, mature product, of the miR-138 precursor is the microRNA mir-138.miR-138 has been used as an example of the post-transcriptional regulation of miRNA, due to the finding that while the precursor is expressed ubiquitously, the mature product is found only in specific cell types.The presence of miR-138 has been detected experimentally in humans ("Homo sapiens") and in different animals including house mouse ("Mus musculus"), brown rat ("Rattus norvegicus"), platypus ("Ornithorhynchus anatinus"), Carolina anole("Anolis carolinensis"), cattle ("Bos taurus"), common carp ("Cyprinus carpio"), dog ("Canis familiaris"), Chinese hamster ("Cricetulus griseus"), zebrafish ("Danio rerio"), red junglefowl ("Gallus gallus"), western gorilla ("Gorilla gorilla"), gray short-tailed opossum ("Monodelphis domestica"), "Oryzias latipes", sea lamprey ("Petromyzon marinus"), Tasmanian devil ("Sarcophilus harrisii"), wild boar ("Sus scrofa") and zebra finch ("Taeniopygia guttata").