Transcriptomic Changes in Broiler Chicken Hypothalamus during Growth and Development

The hypothalamus plays an overarching role that is reflected in the physiological processes observed in the entire organism. The hypothalamus regulates selected metabolic processes and activities of the autonomic nervous system. The avian hypothalamus due to the structural complexity is not well described and has a slightly different function than the mammalian hypothalamus that is the subject of numerous studies. The present study evaluated activities of hypothalamic genes in fast-growing chickens during development (at the 1^st day and 3^rd and 6^th weeks after hatching). The hypothalamic transcriptomes for 3- and 6-week-old cockerels were analysed using an RNA sequencing method in next-generation sequencing (NGS) technology. The differentially expressed gene analysis was conducted using DESeq2 software. In younger 22-day-old cockerels, 389 genes showed higher expression (fold change > 1.5) than that in 45-day-old birds. These genes played a role in several biological processes because they encoded proteins involved in integrin signalling, regulation of hormone levels, camera-type eye development, and blood vessel development. Moreover, surprisingly in the hypothalamus of 3-week-old cockerels, transcripts were identified for proteins involved in both anorexigenic (POMC, NMU) and orexigenic (PMCH, ALDH1A1, LPL, and GHRH) pathways. The RNA-seq results were confirmed by qPCR methods. In summary, the intensive growth of 3-week-old chickens was reflected in hypothalamic activities because the genes associated with the somatotropin axis and regulation of satiety centre showed increased expression.