A Comprehensive Transcriptome Profiling Across Six Wool Follicle Developmental Stages of Chinese Merino Sheep

Merino sheep is the most well-known fine wool-producing breed. In order to fully understand molecular mechanisms of unique wool follicle development at the transcriptome level, total RNAs of skin tissues derived from 6 typically developmental stages of wool follicle (fetuses at day 55, 75, 85, 105, 135 of gestation and adult Chinese merino sheep) were sampled and sequenced by RNA-seq approach. These samples represent the critical windows of wool follicle developmental stage, including initiation of primary and secondary wool follicle, branching of originally secondary follicles of merino sheep. Hereby we generated mRNA and microRNA libraries for biopsies from 6 different stage skin tissues. More than 2.6 X10⁷ clean reads of each mRNA library and 9.3 X10⁶ clean reads of each miRNA library were obtained. Based on the reads mapping to ovine reference genome, total of 23854 genes and 794 miRNAs were profiled. Among them, 653,85,1002,360 and 229 differentially expressed genes within successive stages ( day 55 to 75, 75 to 85, 85 to 105, 105 to 135 of gestation, and day 135 to adult, respectively) were determined. Moreover, 39, 1, 14, 35 and 50 differentially expressed microRNAs correspondent to each adjacent stages were also identified. Among of the mRNAs and miRNAs, EDAR, BMP7, Hox13, FGF2R, miR - Let7, miR - 23B, miR - 143 and miR – 21, which are known to be involved in hair follicle morphogenesis, hair growth and cell differentiation, were evidenced. Meanwhile, a few of novel transcripts were identified putatively to be associated with hair follicle morphogenesis. Our study provides fundamental transcriptome profiling to characterize molecular activities and mechanisms for prenatal wool follicle development and even postnatal fiber growth.