Transcriptomic analysis of wild type and Del(Hotair)-/- mouse tissues

Despite decades of interest, the mechanisms that control Hox gene expression are not yet fully understood. It was recently proposed that Hotair, a lncRNA transcribed from the HoxC cluster, regulates HoxD gene expression via Polycomb targeting and thus is important for correct skeletal development. However, genetic manipulations of the locus led to conflicting results regarding the roles of Hotair. Here, we analyze the molecular and phenotypic consequences of deleting the Hotair locus in vivo. In contradiction with previous findings, we show that deleting Hotair has no detectable effect on HoxD gene expression in vivo. We could not observe any morphological alteration in mice lacking the Hotair locus. However, we find a significant impact of deleting Hotair on the expression of neighboring genes Hoxc11 and Hoxc12. Our results do not support an RNA-dependent role for Hotair in vivo, but argue in favor of a DNA-dependent effect of Hotair deletion on the transcriptional landscape in cis. Overall design: We micro-dissected wild type and Del(Hotair)-/- E12.5 embryos into 6 segments: forelimbs (FL), hindlimbs (HL), genital tubercle (GT), trunk section corresponding to the lumbar/sacral region (T1); trunk section corresponding to the sacral/caudal region (T2) and trunk section corresponding to the caudal region (T3). We generated strand-specific RNA-seq data for each segment, in two biological replicates and we performed differential expression analyses for each tissue. Furthermore, we analyzed the impact of deleting the Hotair locus on the local transcriptional landscape, in the HoxC cluster.