MiRNAs can be located within their own open reading frame (ORF) or within the intron of a host gene. Those miRNAs that are located within an intron are dependent on the transcriptional regulation of its host gene. In the human genome, miR-126 is found on chromosome 9 within intron 7 of the EGFL7 gene. An alternative miR-126 transcript from this region has also been reported and is designated miR-126*. Notably, EGFL7 expression is undetectable in normal brain tissue but is deregulated in malignant glioblastoma tumor cells as well as vascular endothelium cells within the tumor (Huang et al., 2010). EGFL7 is also secreted by endothelium and regulates angiogenesis. Recent studies demonstrate that both miR-126 and its host gene EGFL-7 harbor CpG islands invoking epigenetic regulation as one potential mechanism for the observed deregulation of miR-126 in both solid and hematologic malignancies (Saito et al., 2009).

MiRNAs are transcribed as a longer primary mRNA transcript which is called a pri-miR. The pri-miRs are processed mRNA molecules containing a 5 cap and a poly A tail and can range from hundred to thousand nucleotides (Nana-Sinkam et al., 2009). Currently the pri-miR for miR-126 is unknown. In the nucleus, the processing of the pri-miRs by the RNase enzyme, Drosha, to a smaller pre-miR molecule occurs (Nana-Sinkam et al., 2009). The pre-miR forms a stem loop structure to facilitate its transport to the nucleus. For miR-126, it is processed to an 85 nucleotide pre-miR that is then transported to the cytoplasm. Once in the cytoplasm, the pre-miR is incorporated in the RNA-inducible silencing complex (RISC). The RISC contains an RNase III endonuclease, Dicer, which further cleaves the pre-miR to the mature miRNA and minor antisense miRNA.
The pre-miR sequence for miR-126 is 5-GCTGGCGACGGGACATTATTACTTTTGGTACGCGCTGTGACACTTCAAACTCGTACCGTGAGTAATAATGCGCCGTCCACGGCA-3.
The mature sequence for miR-126 is 52-ucguaccgugaguaauaaugcg-73.

Minor miRNA sequence:
In some cases, the antisense sequence to the mature miRNA in the hairpin structure is also processed to a minor miRNA. A minor miRNA sequence has been identified for miR-126 and is designated MiR-126*.
- ID: hsa-miR-126*,
- miRBASE Accession #: MI0000444,
- Sequence: The mature sequence for miR-126* is 14-cauuauuacuuuugguacgcg-35.

MicroRNAs are not translated to protein.