title: Thermal manipulation of the chicken embryo triggers differential gene expression in response to a later heat challenge.
abstract: Meat type chickens have limited capacities to cope with high environmental temperatures, this sometimes leading to mortality on farms and subsequent economic losses. A strategy to alleviate this problem is to enhance adaptive capacities to face heat exposure using thermal manipulation (TM) during embryogenesis. This strategy was shown to improve thermotolerance during their life span. The aim of this study was to determine the effects of TM (39.5 °C, 12 h/24 vs 37.8 °C from d7 to d16 of embryogenesis) and of a subsequent heat challenge (32 °C for 5 h) applied on d34 on gene expression in the Pectoralis major muscle (PM). A chicken gene expression microarray (8 × 60 K) was used to compare muscle gene expression profiles of Control (C characterized by relatively high body temperatures, Tb) and TM chickens (characterized by a relatively low Tb) reared at 21 °C and at 32 °C (CHC and TMHC, respectively) in a dye-swap design with four comparisons and 8 broilers per treatment. Real-time quantitative PCR (RT-qPCR) was subsequently performed to validate differential expression in each comparison. Gene ontology, clustering and network building strategies were then used to identify pathways affected by TM and heat challenge.
  
  
  
  Among the genes differentially expressed (DE) in the PM (1.5 % of total probes), 28 were found to be differentially expressed between C and TM, 128 between CHC and C, and 759 between TMHC and TM. No DE gene was found between TMHC and CHC broilers. The majority of DE genes analyzed by RT-qPCR were validated. In the TM/C comparison, DE genes were involved in energy metabolism and mitochondrial function, cell proliferation, vascularization and muscle growth; when comparing heat-exposed chickens to their own controls, TM broilers developed more specific pathways than C, especially involving genes related to metabolism, stress response, vascularization, anti-apoptotic and epigenetic processes.
  
  
  
  This study improved the understanding of the long-term effects of TM on PM muscle. TM broilers displaying low Tb may have lower metabolic intensity in the muscle, resulting in decreased metabolic heat production, whereas modifications in vascularization may enhance heat loss. These specific changes could in part explain the better adaptation of TM broilers to heat.
authors.affiliation: URA, INRA, 37380, Nouzilly, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Loyau
authors.affiliation: URA, INRA, 37380, Nouzilly, France.
authors.forename: Christelle
authors.initials: C
authors.lastname: Hennequet-Antier
authors.affiliation: URA, INRA, 37380, Nouzilly, France.
authors.forename: Vincent
authors.initials: V
authors.lastname: Coustham
authors.affiliation: URA, INRA, 37380, Nouzilly, France.
authors.forename: Cécile
authors.initials: C
authors.lastname: Berri
authors.affiliation: URA, INRA, 37380, Nouzilly, France.
authors.forename: Marie
authors.initials: M
authors.lastname: Leduc
authors.affiliation: URA, INRA, 37380, Nouzilly, France.
authors.forename: Sabine
authors.initials: S
authors.lastname: Crochet
authors.affiliation: URA, INRA, 37380, Nouzilly, France.
authors.forename: Mélanie
authors.initials: M
authors.lastname: Sannier
authors.affiliation: URA, INRA, 37380, Nouzilly, France.
authors.forename: Michel Jacques
authors.initials: MJ
authors.lastname: Duclos
authors.affiliation: URA, INRA, 37380, Nouzilly, France.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Mignon-Grasteau
authors.affiliation: URA, INRA, 37380, Nouzilly, France.
authors.forename: Sophie
authors.initials: S
authors.lastname: Tesseraud
authors.affiliation: URA, INRA, 37380, Nouzilly, France.
authors.forename: Aurélien
authors.initials: A
authors.lastname: Brionne
authors.affiliation: URA, INRA, 37380, Nouzilly, France.
authors.forename: Sonia
authors.initials: S
authors.lastname: Métayer-Coustard
authors.affiliation: CRB GADIE, INRA, Domaine de Vilvert, 78350, Jouy-en-Josas, France.
authors.forename: Marco
authors.initials: M
authors.lastname: Moroldo
authors.affiliation: CRB GADIE, INRA, Domaine de Vilvert, 78350, Jouy-en-Josas, France.
authors.forename: Jérôme
authors.initials: J
authors.lastname: Lecardonnel
authors.affiliation: GABI, INRA, Plateforme de Microgénomique Iso Cell Express (ICE), 78350, Jouy-en-Josas, France.
authors.forename: Patrice
authors.initials: P
authors.lastname: Martin
authors.affiliation: PEGASE, INRA, Agrocampus Rennes, 35590, Saint-Gilles, France.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Lagarrigue
authors.affiliation: Institute of Animal Science, The Volcani Center, Bet Dagan, P.O. Box 6, 50250, Israel.
authors.forename: Shlomo
authors.initials: S
authors.lastname: Yahav
authors.affiliation: URA, INRA, 37380, Nouzilly, France. Anne.Collin@tours.inra.fr.
authors.forename: Anne
authors.initials: A
authors.lastname: Collin
mesh_terms: D000818:Animals; D002642:Chick Embryo; D002645:Chickens / Q000235:genetics / Q000254:growth & development*; D047108:Embryonic Development; D020869:Gene Expression Profiling / Q000379:methods*; D018507:Gene Expression Regulation, Developmental; D053263:Gene Regulatory Networks; D006358:Hot Temperature; D024510:Muscle Development; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D010369:Pectoralis Muscles / Q000196:embryology*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods