miR-101 and 5’-isomiR-101 are abundant in different cells and tissues. A. Relative frequencies of different miR-101 isomiRs in the frontal cortex (FC) and striatum (ST) of a control individual  and prefrontal cortex (pFC, 98 years and 2 days old) . The summed frequency of all sequences mapping onto miR-101 was considered as the 100%. B. Percentage of each of the two main seed regions in human brain (4 individuals) and blood (4 individuals), and human cell lines . A scheme is included showing miR-101 precursor and mature forms (in red). The arrows point to the major cleavage sites producing the most abundant mature miR-101 variants. The seed regions in each variant are contained in a blue box. C. Abundance of miR-101 in human blood and brain (amygdala –am- of 4 individuals and frontal cortex –fc- of two individuals aging 25 and 66 years ) and in cell lines . In each sample, the percentage of sequences mapping onto miR-101 is calculated with respect to the total of sequences mapping onto miRNA database. D-F. miR-101 and 5’-isomiR-101 expression in the frontal cortex and the striatum of control individuals (C) and patients with HD ; in undifferentiated and differentiated SH-SY5Y cells and in the frontal cortex of individuals at different ages . In D, E, F normalized counts are expressed as the ratio: (frequency of sequences presenting miR-101 or 5’isomiR-101 seed regions) / (frequency of sequences mapping onto miRNAs) * 10E6. When more than a biological replica is available (B and C) data are presented as the mean ± standard deviation. SH: SH-SY5Y human neuroblastoma cell line, Fibro: Fibrocytes, HEK: human embryonic kidney 293 cells, 143B: human bone osteosarcoma 143B cell line, H520: human squamous cell carcinoma H520 cell line, MCF7: human breast cancer MCF7 cell line, U2S: human osteosarcoma U2S cell line, HeLa: human cervical cancer HeLa cell line.