Analysis of a nanoparticle-enriched fraction of plasma reveals miRNA candidates for Down syndrome pathogenesis

Down syndrome (DS) is caused by the presence of part or all of a third copy of
chromosome 21. DS is associated with several phenotypes, including intellectual disability,
congenital heart disease, childhood leukemia and immune defects. Specific microRNAs
(miRNAs/miR) have been described to be associated with DS, although none of them so far have

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been unequivocally linked to the pathology. The present study focuses to the best of our knowledge
for the first time on the miRNAs contained in nanosized RNA carriers circulating in the blood.
Fractions enriched in nanosized RNA-carriers were separated from the plasma of young
participants with DS and their non-trisomic siblings and miRNAs were extracted. A microarray-
based analysis on a small cohort of samples led to the identification of the three most abundant
miRNAs, namely miR-16-5p, miR-99b-5p and miR-144-3p. These miRNAs were then profiled for
15 pairs of DS and non-trisomic sibling couples by reverse transcription-quantitative polymerase
chain reaction (RT-qPCR).
Results identified a clear differential expression trend of these miRNAs in DS with respect
to their non-trisomic siblings and gene ontology analysis pointed to their potential role in a number
of typical DS features, including “nervous system development”, “neuronal cell body” and certain
forms of “leukemia”. Finally, these expression levels were associated with certain typical
quantitative and qualitative clinical features of DS.
These results contribute to the efforts in defining the DS-associated pathogenic mechanisms
and emphasize the importance of properly stratifying the miRNA fluid vehicles in order to probe
biomolecules that are otherwise hidden and/or not accessible to (standard) analysis.