Abstract:

Objective To identify the  novel microRNA(miRNA) gene  located at the chromosome 21 by  Solexa high-throughput sequencing technology,and to provide basis for clarifying function of the chromosome 21 and investingating the new therapeutic target of Down syndrome(DS) patients.Methods Thecord blood of  5 DS fetues verified by chromosome karyotype  analysis and 3 normal fetuses  were collected.Total RNA was extracted from mononuclear cells of cord blood in DS fetuses to construct the small RNA library.Then the miRNA gene was identified by Solexa high-throughput sequencing,computer analysis and Stem-loop RT-PCR,and its biological function was analyzed.Results The chromosome karyotype analysis showed that the  karyetypes in cord blood of DS fetuses were standard DS karyotypes,and those in normal fetuses were normal karyotypes. A total of 21 novel miRNAs were identified in cord blood of DS fetuses.But only one candidat miRNA was located on the “DS critical region” of the chromosome 21,named as “miRnov21”, and its expression level in  mononuclear cells of cord bood in DS fetuses was higher than that in normal fetuses.Biological funcation analysis revealed that  miR-nov21  could regulate 211 conserved target genes containing 215 conserved sites,which were involved in gene expression,regulation of cell differentiation,embryonic morphogenesis,and heart development.Conclusion There is a novel miRNA gene  in  “DS critical region” of the chromosome 21.

Key words: microRNA, Down syndrome, high-throughput sequence technology, cord blood