Comparison of the transcriptome in circulating leukocytes in early lactation between primiparous and multiparous cows provides evidence for age-related changes
Authors: Buggiotti Laura , Cheng Zhangrui , Salavati Mazdak , Wathes Claire D. ,   the Genotype plus Environment Consortium, Fahey Alan , Crisà Alessandra , Fouladi Ali , Wylie Alistair , Vanlierde Amelie , Fogh Anders , Santoro Andreia , Cromie Andrew , Van Laere Anne-Sophie , Pearn Armin , Evertson Arnold , Laine Aurelie , Bernardo Beatriz Sanz , Moioli Bianca , Vanranst Bonny , Bastin Catherine , Gaillard Charlotte , Tan Chen , Elsik Chris , Marchitelli Cinzia , Wathes Claire , Grelet Clement , Byrne Colin , Ferris Conrad , Matthews Daragh , Triant Deborah , Werling Dirk , Matthews Elizabeth , Meyer Else , Froidmont Eric , Signorelli Federica , Carter Fiona , Napolitano Francesco , Kearney Francis , Becker Frank , Colinet Frederic , Dehareng Frederic , Conant Gavin , Opsomer Geert , Pollott Geoff , Wang Guiqiang , Hua Guohua , Bogaert Hannes , Takeda Haruko , Hammami Hedi , Chen Huanchun , Vandepitte Jan , Rothmann Janne , Ettema Jehan , De Koster Jenne , McClure Jennifer , Taylor Jerry , Hoglund Johanna , Zhao Junlong , Ingvartsen Klaus , Hermans Kristof , Vandevelde Leila , Foldager Leslie , Yang Liguo , Kosten Linda , Buttazzoni Luca , Pamplona Marilou Ramos , Crowe Mark , Sciarretta Marlène , Schulze Martin , Sorensen Martin Tang , Bell Matt , McClure Matt , Lucy Matthew , Salavati Mazdak , Bonneau Michel , Georges Michel , Vaneetvelde Mieke , Hostens Miel , Krogh Mogens , McLoughlin Niamh , Gengler Nicolas , Rudd Pauline , Mota Rodrigo , O’Flaherty Roisin , Darbagshahi Saied Naderi , Moerman Sander , Vera Sergio Palma , Zhang Shujun , Hallinan Sinead , Ostergaard Soren , Dahl Susanne , Andersen Thomas , Rousing Tine , Larsen Torben , Silva de Oliveira Victor H. , Chen Xing , Cheng Zhangrui 
Published: September 2021

Abstract
Background
Previous studies have identified many immune pathways which are consistently altered in humans and model organisms as they age. Dairy cows are often culled at quite young ages due to an inability to cope adequately with metabolic and infectious diseases, resulting in reduced milk production and infertility. Improved longevity is therefore a desirable trait which would benefit both farmers and their cows. This study analysed the transcriptome derived from RNA-seq data of leukocytes obtained from Holstein cows in early lactation with respect to lactation number.

Results
Samples were divided into three lactation groups for analysis: i) primiparous (PP, n = 53), ii) multiparous in lactations 2–3 (MP 2–3, n = 121), and iii) MP in lactations 4–7 (MP > 3, n = 55). Leukocyte expression was compared between PP vs MP > 3 cows with MP 2–3 as background using DESeq2 followed by weighted gene co-expression network analysis (WGCNA). Seven modules were significantly correlated (r ≥ 0.25) to the trait lactation number. Genes from the modules which were more highly expressed in either the PP or MP > 3 cows were pooled, and the gene lists subjected to David functional annotation cluster analysis. The top three clusters from modules more highly expressed in the PP cows all involved regulation of gene transcription, particularly zinc fingers. Another cluster included genes encoding enzymes in the mitochondrial beta-oxidation pathway. Top clusters up-regulated in MP > 3 cows included the terms Glycolysis/Gluconeogenesis, C-type lectin, and Immunity. Differentially expressed candidate genes for ageing previously identified in the human blood transcriptome up-regulated in PP cows were mainly associated with T-cell function (CCR7, CD27, IL7R, CAMK4, CD28), mitochondrial ribosomal proteins (MRPS27, MRPS9, MRPS31), and DNA replication and repair (WRN). Those up-regulated in MP > 3 cows encoded immune defence proteins (LYZ, CTSZ, SREBF1, GRN, ANXA5, ADARB1).

Conclusions
Genes and pathways associated with lactation number in cows were identified for the first time to date, and we found that many were comparable to those known to be associated with ageing in humans and model organisms. We also detected changes in energy utilization and immune responses in leukocytes from older cows.