Insulin-like growth factor (IGF) family plays important roles in regulating the development of various organ systems through stimulating cell proliferation and differentiation. Photoperiod is an important factor affecting growth and development in the chicken, yet the effect of constant light exposure in early life on IGF1 and IGF2 expression in the chicken remains unclear. In this study, one-day-old chickens were kept in either constant light (24L:0D, LL) or natural photoperiod (12L:12D, LD) for the first week of life and then maintained in constant light from 8 to 21 d of age. Constant light exposure in early life reduced mRNA expression of IGF gene family, including mRNA expression of IGF1, IGF2, and IGF2 binding proteins, in the hippocampus, hypothalamus, and liver of chickens at both 7 and 21 d of age. Moreover, constant light exposure increased mRNA expression of genes involved in RNA methylation N6-methyladenosine (m6A) in a tissue-specific manner. Interestingly, higher m6A on 3'UTR of IGF2 mRNA coincides with lower IGF2 mRNA, indicating a possible role of m6A in the post-transcriptional regulation of IGF2 expression in the hippocampus, hypothalamus, and liver of chickens. These findings suggest a m6A-mediated gene regulation of IGF gene family in different organs of chicken and expand our knowledge on mechanism of gene regulation in response to early life experience.
Keywords: IGF2; IGF2BPs; chicken; constant light; m6A.
Light pollution has become a potential risk factor for the health of animals and humans. Aberrant light exposure (such as light at night and super-intensity light) induces sleep disturbances and mood disorders, as well as major depressive disorder. In poultry, photoperiod is an important factor affecting the growth and behavior of broiler chickens. The hippocampus is critical for the regulation of spatial memory and depression-like behaviors in birds and mammals. Insulin-like growth factor (IGF) family plays important roles in regulating the development of various organ systems through stimulating cell proliferation and differentiation in a tissue-specific manner. At present, broiler chickens are commonly reared under constant light (24 h light) in the first week after hatching, yet the effect of constant light exposure in early life on the expression of IGF family in the chicken remains unclear. In this study, 1-d-old Yellow-footed broiler chickens were kept in either constant light (24L:0D, LL) or natural photoperiod (12L:12D, LD) for the first week of life and then maintained in natural photoperiod from 8 to 21 d of age. We analyzed the mRNA expression and the post-transcriptional regulation of IGF2 expression in the hippocampus, hypothalamus, and liver of chickens. Constant light exposure in early life reduced mRNA expression of IGF gene family, including mRNA expression of IGF1, IGF2, and IGF2 binding proteins (IGF2BPs), in the hippocampus, hypothalamus, and liver of chickens at both 7 and 21 d of age. Our findings demonstrate the expression of IGF gene family in different organs of chickens and expand our knowledge on the mechanism of gene regulation in response to early-life experience.
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