Integrative genetic and genomic networks identify microRNA associated with COPD and ILD

Chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD) are clinically and molecularly heterogeneous diseases. We utilized clustering and integrative network analyses to elucidate roles for microRNAs (miRNAs) and miRNA isoforms (isomiRs) in COPD and ILD pathogenesis. Short RNA sequencing was performed on 351 lung tissue samples of COPD (n=145), ILD (n=144) and controls (n=64). Five distinct subclusters of samples were identified including 1 COPD-predominant cluster and 2 ILD-predominant clusters which associated with different clinical measurements of disease severity. Utilizing 262 samples with gene expression and SNP microarrays, we built disease-specific genetic and expression networks to predict key miRNA regulators of gene expression. Members of miR-449/34 family, known to promote airway differentiation by repressing the Notch pathway, were among the top connected miRNAs in both COPD and ILD networks. Genes associated with miR-449/34 members in the disease networks were enriched among genes that increase in expression with airway differentiation at an air-liquid interface. A highly expressed isomiR containing a novel seed sequence was identified at the miR-34c-5p locus. 47% of the anticorrelated predicted targets for this isomiR were distinct from the canonical seed sequence for miR-34c-5p. Overexpression of the canonical miR-34c-5p and the miR-34c-5p isomiR with an alternative seed sequence down-regulated NOTCH1 and NOTCH4. However, only overexpression of the isomiR down-regulated genes involved in Ras signaling such as CRKL and GRB2. Overall, these findings elucidate molecular heterogeneity inherent across COPD and ILD patients and further suggest roles for miR-34c in regulating disease-associated gene-expression. Overall design: Libraries for 45 samples were prepared with the Illumina Small RNA Sample Prep Kit v1.5 and sequenced on the Genome Analyzer IIx. 6 of these libraries were also sequenced on the HiSeq 2000. The libraries for an additional 320 samples were prepared with the Illumina TruSeq Small RNA Sample Prep Kit and sequenced on the Illumina HiSeq 2000 with multiplexing 10 samples per lane. One additional sample was found to be a biological duplicate. Samples were clustered using the distribution of read lengths after trimming and alignment. 13 samples were excluded for being outliers based on the clustering of read length distributions. After exclusion of 7 replicate samples and 13 poor-quality samples, 351 samples were included in the final analysis set.