cel-mir-248: Cel-mir-248 is a spike-in oligo commonly used for normalization in RNA extraction and miRNA expression analysis experiments [PMC8005714] [PMC7204029] [PMC5952410] [PMC9691121] [PMC5349967] [PMC7423998] [PMC4673232] [PMC7281602] [PMC7293253] [PMC8584247] [PMC7465670]. It is often used alongside other spike-in oligos such as cel-miR-254, ath-miR-159a, osa-miR-414, and osa-miR-442 to ensure accurate normalization in various experiments and assays involving miRNA expression analysis and RNA extraction from exosomes or plasma samples [PMC8005714] [PMC7204029] [PMC5952410] [PMC9691121] [PMC5349967] [PMC7423998] [PMC4673232] [PMC7281602] [PMC7293253] [PMC8584247] [PMC7465670]. Cel-mir-248 is typically added to samples at a concentration of 200 pM or 1000 attomoles/spike-in, depending on the specific experiment or assay being conducted [PMC8005714]. It serves as a reference gene to normalize the expression of mature single miRNAs in various samples, including exosomal pellets and plasma samples [PMC5952410]. The normalization process involves adding cel-mir-248 to each sample either before or after lysis, depending on the specific protocol being followed [PMC7204029]. Different methods, such as the TaqMan Stem-loop miRNA assay or Nanostring nCounter Human v3a miRNA Expression Assay, are used to assess the expression of miRNAs, with cel-mir-248 being used as the reference gene for normalization purposes [PMC5952410] [PMC8584247]. Cel-mir-248 is part of a panel of spike-in probes that also includes other non-endogenous miRNAs from different species, such as ath-miR159a, cel-miR254, osa-miR414, and osa-miR442, which are incorporated into code sets used for analysis alongside positive and negative controls to ensure accurate measurement of miRNA expression levels in the samples [PMC7423998] [PMC8584247].