Transciptomic profiling of the magnum of laying and non-laying hens using RNA-seq

Purpose: With the advent of Next-generation sequencing (NGS), several novel genes/proteins and cellular pathways in wide varitey of tissues has discovered. The aim of this study are to perform transcriptome profiling (RNA-seq) of magnum to determine differently expressed genes in laying and non-laying hens and to further validate the expression of candidate genes using real-time quantitative reverse transcription polymerase chain reaction (qRT–PCR) in laying, non-laying and molting hens. Methods: Magnum mRNA profiles of 35-60 weeks-old laying and non-laying hens, three each, were generated with NextSeq 500 sequencer in single-end mode with a read length of 1x76 bp. Raw sequencing reads were cleaned and trimmmed with Prinseq tool and good reads were aligned against the chicken reference gemone (Galgal 5.0) in Array Studio. Differential gene expression analysis was performed by the DESeq2 algorithm as implemented in Array Studio. The genes with at least three-fold change (FC) and Benjamini and Hochberg q-value < 0.05 were called differentially expressed. Results: Using an optimized data analysis workflow, we mapped about 30.5 million reads from layers and 33.4 million reads from non-layers to the chicken genome. A total of 19,152 gene transcripts were annotated from Ensembl alignment which represents 50.24% of the chicken genome assembly. Differential gene expression analysis showed 540 were differentially expressed between layer and non-layer hens. 152 DEGs were significantly up-regulated and 388 were significantly down-regulated in the laying hens when compared to the non-laying hens. Conclusions: Our study reports the expression of several pre-discovered and many novel genes that may be involved in the transport of precurosor molecules for biosynthesis and secretion of the egg-white proteins in the magnum. These genes can be used as quantitative basis of selecting hens with an improved egg quality. Overall design: Magnum mRNA profile of three 35-60 weeks old laying and non-laying hens was genereted using Illumina NextSeq 500