In contrast, downregulation of TFAM by hsa-miR-155-5p did not decrease mtDNA content in fibroblasts derived from a donor with Down syndrome (DS, trisomy 21).
MiR-155-5p is one of the best characterized miRNAs and recent data indicate that miR-155-5p plays a critical role in various physiological and pathological processes such as hematopoietic lineage differentiation, immunity, inflammation, viral infections, cancer, cardiovascular disease, and Down syndrome.
In these studies, a screening of micro-RNA (miRNA) from Down's syndrome brain and peripheral tissues indicated an upregulation of a chromosome 21-encoded miRNA-155 and a decrease in the abundance of the miRNA-155 mRNA target complement factor H (CFH), an important repressor of the innate immune response.
Since hsa-miR-155 is on chromosome 21, we hypothesize that the observed lower blood pressure in trisomy 21 is partially caused by the overexpression of hsa-miR-155 leading to allele-specific underexpression of AGTR1.