Chicken Hypothalamic and Ovarian DNA Methylome Alteration in Response to Forced Molting

SIMPLE SUMMARY: Forced molting refers to the systemic stress response of laying hens caused by some externally imposed artificial measures (such as starvation), resulting in production suspension, weightlessness, and molting of laying hens. After the stress is restored to normal feeding conditions, the chickens will recover their physical fitness so that the egg-laying rate can be restored to the second peak of egg production and egg quality can be improved. Previously, we thought that only genes regulate this reversible biological process at the transcriptome level, but further studies showed that environmentally induced epigenetic inheritance could also regulate this process, and there is an interspersed effect between them. ABSTRACT: Epigenetic modifications play an important role in regulating animal adaptation to external stress. To explore how DNA methylation regulates the expression levels of related genes during forced molting (FM) of laying hens, the hypothalamus and ovary tissues were analyzed at five periods using Whole-Genome Bisulfite Sequencing. The results show that methylation levels fluctuated differently in the exon, intron, 5′UTR, 3′UTR, promoter, and intergenic regions of the genome during FM. In addition, 16 differentially methylated genes (DMGs) regulating cell aging, immunity, and development were identified in the two reversible processes of starvation and redevelopment during FM. Comparing DMGs with differentially expressed genes (DEGs) obtained in the same periods, five hypermethylated DMGs (DSTYK, NKTR, SMOC1, SCAMP3, and ATOH8) that inhibited the expression of DEGs were found. Therefore, DMGs epigenetically modify the DEGs during the FM process of chickens, leading to the rapid closure and restart of their reproductive function and a re-increase in the egg-laying rate. Therefore, this study further confirmed that epigenetic modifications could regulate gene expression during FM and provides theoretical support for the subsequent optimization of FM technology.