Elucidating fish oil-induced milk fat depression in dairy sheep: Milk somatic cell transcriptome analysis

Aroa Suárez-Vega,Juan José Arranz,Pablo G Toral,Gonzalo Hervás,Beatriz Gutiérrez-Gil,Pilar Frutos

doi:10.1038/srep45905

Aroa Suárez-Vega, Juan José Arranz + Show 4 more

Open Access

https://doi.org/10.1038/srep45905

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Abstract

In this study, RNA sequencing was used to obtain a comprehensive profile of the transcriptomic changes occurring in the mammary gland of lactating sheep suffering from fish oil-induced milk fat depression (FO-MFD). The milk somatic cell transcriptome analysis of four control and four FO-MFD ewes generated an average of 42 million paired-end reads per sample. In both conditions, less than 220 genes constitute approximately 89% of the total counts. These genes, which are considered as core genes, were mainly involved in cytoplasmic ribosomal proteins and electron transport chain pathways. In total, 117 genes were upregulated, and 96 genes were downregulated in FO-MFD samples. Functional analysis of the latter indicated a downregulation of genes involved in the SREBP signaling pathway (e.g., ACACA, ACSL, and ACSS) and Gene Ontology terms related to lipid metabolism and lipid biosynthetic processes. Integrated interpretation of upregulated genes indicated enrichment in genes encoding plasma membrane proteins and proteins regulating protein kinase activity. Overall, our results indicate that FO-MFD is associated with the downregulation of key genes involved in the mammary lipogenesis process. In addition, the results also suggest that this syndrome may be related to upregulation of other genes implicated in signal transduction and codification of transcription factors.

Highlights

In this study, RNA sequencing was used to obtain a comprehensive profile of the transcriptomic changes occurring in the mammary gland of lactating sheep suffering from fish oil-induced milk fat depression (FO-MFD)
The transcriptome analysis presented provides a thorough view of differentially expressed genes (DEGs), biological processes and pathways associated with FO-MFD
This study presents for the first time in the scientific literature a comprehensive profile of the transcriptomic changes occurring in the mammary gland of lactating sheep suffering from FO-induced MFD

Summary

Introduction

RNA sequencing was used to obtain a comprehensive profile of the transcriptomic changes occurring in the mammary gland of lactating sheep suffering from fish oil-induced milk fat depression (FO-MFD). The milk somatic cell transcriptome analysis of four control and four FO-MFD ewes generated an average of 42 million paired-end reads per sample In both conditions, less than 220 genes constitute approximately 89% of the total counts. Diet supplementation with marine lipids (namely, fish oil, FO) is an effective tool to modify the milk FA profile by increasing the content of certain bioactive lipids, such as n-3 PUFA and conjugated linoleic acid (CLA)[7,8,10]. This type of supplementation has been associated with milk fat depression (MFD) syndrome[11]. Generation RNA sequencing technology (RNA-Seq) offers valuable methodology to unravel previously challenging transcriptomic complexities as it allows complete characterization of the transcriptome and provides the opportunity to quantify transcripts and identify differential regulation between two or more conditions[15,16]

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