Properties, Genetics and Innate Immune Function of the Cuticle in Egg-Laying Species Kulshreshtha, Garima Rodríguez Navarro, Alejandro Eggshell cuticle Egg-laying birds Bacterial pathogens Food safety Microbiome Genetics Evolution The authors would like to thank Jianqun Wang from the Nano Imaging Facility at Carleton University for help with energydispersive X-ray spectroscopy and scanning electron microscopy. LD’A would like to thank grant support by FWO-G0A7921N. AR research was funded by PID2020-116660GB-I00, RNM-938 group (Junta de Andalucı́a) and UCE PP 2016.05 (Universidad de Granada). MH and SR-G thank “LE STUDIUM Institute for advanced studies—Loire Valley” for supporting the residency of MH at DOVE, BOA, INRAE Centre Val de Loire, France. Salary support for GK was provided by a MITACS Accelerate Fellowship (Application Ref. IT13653/Funding Request Ref. FR35012). We are thankful to Dr. Vincent Guyonnet for his insight on global egg washing regulations. FUNDING This work was supported by funding from the Egg Farmers of Canada (EFC), Livestock Research Innovation Corporation (LRIC) and Canadian Natural Sciences and Engineering Research Council (NSERC, Discovery program RGPIN-2016- 04410) to MH. ID was funded by the BBSRC, Lohmann Tierzucht and Aviagen through the BBSRC LINK grants BB/ K0070921/1 and BB/K006096/1 ‘Cute-Egg’. The Roslin Institute is funded by a BBSRC Institute strategic program grant BB/ P013759/1. Cleidoic eggs possess very efficient and orchestrated systems to protect the embryo from external microbes until hatch. The cuticle is a proteinaceous layer on the shell surface in many bird and some reptile species. An intact cuticle forms a pore plug to occlude respiratory pores and is an effective physical and chemical barrier against microbial penetration. The interior of the egg is assumed to be normally sterile, while the outer eggshell cuticle hosts microbes. The diversity of the eggshell microbiome is derived from both maternal microbiota and those of the nesting environment. The surface characteristics of the egg, outer moisture layer and the presence of antimicrobial molecules composing the cuticle dictate constituents of the microbial communities on the eggshell surface. The avian cuticle affects eggshell wettability, water vapor conductance and regulates ultraviolet reflectance in various ground-nesting species; moreover, its composition, thickness and degree of coverage are dependent on species, hen age, and physiological stressors. Studies in domestic avian species have demonstrated that changes in the cuticle affect the food safety of eggs with respect to the risk of contamination by bacterial pathogens such as Salmonella and Escherichia coli. Moreover, preventing contamination of internal egg components is crucial to optimize hatching success in bird species. In chickens there is moderate heritability (38%) of cuticle deposition with a potential for genetic improvement. However, much less is known about other bird or reptile cuticles. This review synthesizes current knowledge of eggshell cuticle and provides insight into its evolution in the clade reptilia. The origin, composition and regulation of the eggshell microbiome and the potential function of the cuticle as the first barrier of egg defense are discussed in detail. We evaluate how changes in the cuticle affect the food safety of table eggs and vertical transmission of pathogens in the production chain with respect to the risk of contamination. Thus, this review provides insight into the physiological and microbiological characteristics of eggshell cuticle in relation to its protective function (innate immunity) in egg-laying birds and reptiles. 2022-04-07T10:10:24Z 2022-04-07T10:10:24Z 2022-02-25 journal article Kulshreshtha G, D’Alba L, Dunn IC, Rehault-Godbert S, Rodriguez-Navarro AB and Hincke MT (2022) Properties, Genetics and Innate Immune Function of the Cuticle in Egg-Laying Species. Front. Immunol. 13:838525. [doi: 10.3389/fimmu.2022.838525] http://hdl.handle.net/10481/74214 10.3389/fimmu.2022.838525 eng http://creativecommons.org/licenses/by/3.0/es/ open access Atribución 3.0 España Frontiers Media