Mature miR-99a Upregulation in the Amniotic Fluid Samples from Female Fetus Down Syndrome Pregnancies: A Pilot Study.

Background and Objective: Although Down syndrome is the most frequent aneuploidy, its pathogenic molecular mechanisms are not yet fully understood. The aim of our study is to quantify-by qRT-PCR-the expression levels of both the mature forms and the pri-miRNAs of the microRNAs resident on chromosome 21 (miR(21)) in the amniotic fluid samples from Down syndrome singleton pregnancies and to estimate the impact of the differentially expressed microRNAs on Down syndrome fetal heart and amniocytes transcriptomes. Materials and methods: We collected amniotic fluid samples harvested by trained obstetricians as part of the second trimester screening/diagnostic procedure for aneuploidies to assess the trisomy 21 status by QF-PCR and karyotyping. Next, we evaluated-by Taqman qRT-PCR-the expression levels of both the mature forms and the pri-miRNA precursors of the microRNAs resident on chromosome 21 in amniotic fluid samples from singleton Down syndrome and euploid pregnancies. Further, we combined miRWalk 3.0 microRNA target prediction with GEO DataSets analysis to estimate the impact of hsa-miR-99a abnormal expression on Down syndrome heart and amniocytes transcriptome. Results: We found a statistically significant up-regulation of the mature form of miR-99a, but not pri-miR-99a, in the amniotic fluid samples from Down syndrome pregnancies with female fetuses. GATHER functional enrichment analysis of miRWalk3.0-predicted targets from Down syndrome amniocytes and fetal hearts transcriptome GEODataSets outlined both focal adhesion and cytokine-cytokine receptor interaction signaling as novel signaling pathways impacted by miR-99a and associated with cardiac defects in female Down syndrome patients. Conclusions: The significant overexpression of miR-99a, but not pri-miR-99a, points towards an alteration of the post-transcriptional mechanisms of hsa-miR-99a maturation and/or stability in the female trisomic milieu, with a potential impact on signaling pathways important for proper development of the heart.

A pilot study on the expression of microRNAs resident on chromosome 21 in laser microdissected FFPE prostate adenocarcinoma samples.

The tremendous research effort of the last decades added a new, epigenetic layer of complexity to the already complex image of prostate cancer pathogenesis. Here we use quantitative real-time polymerase chain reaction (qRT-PCR) to investigate the expression of the microRNAs resident on chromosome 21 (miR-ch21) in laser capture microdissected (LCM) tissues from formalin-fixed paraffin-embedded (FFPE) archived, prostate adenocarcinoma samples. We show a strong, specific down-regulation of miR-ch21 in tumoral epithelia and stromae as compared to normal counterparts, results at odd with the current paradigm on the involvement of these microRNAs in prostate oncogenesis. By comparing this result with the expression of two well-known pluripotency associated microRNA, hsa-miR-372 and miR-373, we suggest that miR-ch21 down-regulation might be the result of specific silencing of miR genes mapped to chromosome 21. Further studies, of larger sample size are needed to confirm our preliminary data.