Disclosed herein are novel compositions, methods, and systems for determining whether a subject has, or is at risk of developing, or is at a given stage of a condition afflicting a tissue of interest, or determining the tissue or cell provenance of a biological sample, based on expression level of one or more of the novel miRNA and isomiR sequences disclosed herein. The compositions, methods, and systems described herein can be used to diagnose a disease or disorder, or prognose a given stage and/or progression of the disease or disorder, or determine the identity of the tissue or cell in a sample. In some embodiments, the compositions, methods, and systems described herein can be used to develop a treatment for the disease or disorder. For example, in some embodiments, the novel miRNAs can be used as therapeutics for treatment of a disease or disorder.