Comparative Transcriptome Analysis of Milk Somatic Cells During Lactation Between Two Intensively Reared Dairy Sheep Breeds.

Sofia Michailidou,Athanasios Gelasakis,Georgios Banos,Anagnostis Argiriou,George Arsenos

doi:10.3389/fgene.2021.700489

Abstract

In dairy sheep industry, milk production dictates the value of a ewe. Milk production is directly related to the morphology and physiology of the mammary gland; both being designated targets of breeding strategies. Although within a flock breeding parameters are mutual, large differences in milk production among individual ewes are usually observed. In this work, we tested two of the most productive dairy sheep breeds reared intensively in Greece, one local the Chios breed and one foreign the Lacaune breed. We used transcriptome sequencing to reveal molecular mechanisms that render the mammary gland highly productive or not. While highly expressed genes (caseins and major whey protein genes) were common among breeds, differences were observed in differentially expressed genes. ENSOARG00000008077, as a member of ribosomal protein 14 family, together with LPCAT2, CCR3, GPSM2, ZNF131, and ASIP were among the genes significantly differentiating mammary gland’s productivity in high yielding ewes. Gene ontology terms were mainly linked to the inherent transcriptional activity of the mammary gland (GO:0005524, GO:0030552, GO:0016740, GO:0004842), lipid transfer activity (GO:0005319) and innate immunity (GO:0002376, GO:0075528, GO:0002520). In addition, clusters of genes affecting zinc and iron trafficking into mitochondria were highlighted for high yielding ewes (GO:0071294, GO:0010043). Our analyses provide insights into the molecular pathways involved in lactation between ewes of different performances. Results revealed management issues that should be addressed by breeders in order to move toward increased milk yields through selection of the desired phenotypes. Our results will also contribute toward the selection of the most resilient and productive ewes, thus, will strengthen the existing breeding systems against a spectrum of environmental threats.

Highlights

In the Mediterranean basin, dairy sheep have been milked since time immemorial to produce special dairy products
Several sampling methods have been proposed for transcriptome sequencing of ruminant’s mammary gland, since the udder is a complex and heterogeneous gland that is comprised of multiple cell lineages (Van Keymeulen et al, 2011; Cánovas et al, 2014)
We sequenced the mammary gland transcriptome using RNA extracted from milk somatic cells (MSCs)

Summary

INTRODUCTION

In the Mediterranean basin, dairy sheep have been milked since time immemorial to produce special dairy products. Transcriptome sequencing in sheep targets mainly the mammary gland and in particular, the discovery of highly or differentially expressed genes among breeds or time-points of lactation (Paten et al, 2015; Suárez-Vega et al, 2015, 2017a; Hao et al, 2019; Farhadian et al, 2020; Wang et al, 2020) These studies have explored the expression profile of sheep’s mammary gland during different stages of lactation, little is known about the underlying mechanisms that render the mammary gland highly productive or not within breed in terms of milk yield. Lacaune sheep are well-adapted in Greece and demonstrate high lactation persistency It is common, to observe ewes of the same breed reared in the same flock with extreme differences in milk yield. The aim is to reveal the biological mechanisms that support milk production and to explore whether such clusters of genes can be used as potential markers to improve performance and facilitate selective breeding strategies

MATERIALS AND METHODS

RESULTS AND DISCUSSION

DATA AVAILABILITY STATEMENT

ETHICS STATEMENT