Using RNA-Seq to Characterize Brain Development in the Maturing Domesticated Turkey

The turkey is a major protein source with little known about the early development of key organs including the brain.  Here we report on the first use of RNA-Seq to gain insight into the transcriptional profiles associated with brain development in the domesticated turkey.  Brain tissues were collected from 4 males and 4 females at five early age points.  Total RNA was extracted and RNA-Seq libraries were prepared and sequenced on an Illumina HiSeq 1000 (101-cycle single-end).  After trimming and filtering, approximately 488M sequencing reads remained, of which 239M reads from females and 249M reads from males.  Total reads were assembled and clustered using a combination of Velvet/Oases suite and PASA using the newly updated turkey genome build (Ver. 5.0), resulting in 22,022 and 21, 875 clusters for females and males, respectively.  HTSeq/DESeq analyses showed over 90% and 87% of clusters were constitutively expressed across all ages in females and males, respectively; whereas less than 1.6% and 2.0% of clusters were uniquely expressed at each age in female and male brains, respectively.  In addition, the ten most highly expressed clusters at each age contributed roughly 12–20% of clusters.  Comparing female and male brain transcriptomes, patterns of differentially expressed clusters and abundance of highly expressed clusters were similar within each age, except for day 14 males, which exhibited the highest number of unique clusters.  As further analyses are completed, this comprehensive overview of gene expression will provide detailed insight into transcriptomic changes of the brain during turkey development.