Study provides molecular insight into sexual dimorphism in chicken feathers

Birds have unique skin appendages called feathers that are derived from the outermost layer of skin cells. Feathers are important for several functions, including flight, temperature regulation, protection from external stimuli, and mating behavior. The development of feathers according to gender in birds and the vivid plumage patterns that distinguish males from females (also known as sexual dimorphism) are of interest to the global research community.

Previous scientific reports have suggested a role for estrogen and thyroid hormones in feather formation. However, the underlying molecular mechanisms and the relationship between the two hormones remain unclear. To elucidate the hormonal interactions underlying sexual dimorphism in chicken feathers, a Japanese research team has now conducted a series of advanced and innovative gene expression experiments.

The research team was led by Professor Sakae Takeuchi of the Graduate School of Environmental, Life and Natural Sciences, Okayama University, with appropriate support from Dr. Hibiki Fukuchi. Student at Okayama University Graduate School of Environmental, Life and Natural Sciences. Their findings were published in the journal General and Comparative Endocrinology on October 1, 2024.

Regarding the motivation behind this research, Professor Takeuchi said, “Melanocyte-stimulating hormone (MSH), which is secreted from the middle lobe of the pituitary gland, regulates body color in most vertebrates. It is believed that they lack MSH for a reason.” Our research team has documented and shown that birds produce and utilize MSH to regulate feather development. ”

First, the researchers administered estrogen (E2) capsules to male chickens, which induced the formation of female-type feathers with distinct barbules. Furthermore, we investigated the role of the thyroid hormone activation/inactivation system in the sexual dimorphism observed in saddle feathers.

To achieve this goal, Takeuchi et al. used RT-PCR analysis to detect the thyroid hormone activator DIO2 (type 2 deiodinase) and the thyroid hormone inactivator DIO3 (type 2 deiodinase) from RNA. We studied the expression of specific genes such as deiodinase (type deiodinase). (ribonucleic acid) of regenerated feather follicles. Additionally, expression of the barbule-specific marker BlSK1 (barbule-specific keratin 1) and the red/yellow melanin inducer ASIP (agouti signaling protein) was also observed.

The results showed that E2 treatment suppressed the expression of DIO3 and ASIP, while stimulating the expression of BlSK1, thus affecting the overall fringe structure and color of the wing. Finally, the researchers evaluated the influence of the thyroid on sexual dimorphism through the administration of thyroxine (T4) and triiodothyronine (T3).

They found that administering T4 to chickens increased the expression of BlSK1 and POMC (proopiomelanocortin), a precursor of MSH, inducing black/brown melanin and producing black feathers. . Treatment of cultured dental pulp cells (isolated from wings) with T3 increased POMC expression.

Professor Takeuchi said, “By understanding sexual dimorphism and sex differences caused by hormones, we not only strengthen our understanding of biological diversity, but also make sexual diversity more inclusive and accepting.” We have also contributed to contributing to a better society.” sexual minorities. ” Needless to say, this understanding benefits society as a whole by fostering empathy, promoting social cohesion, and fostering tolerance and understanding of diversity.

In summary, these findings not only highlight the cultural importance attached to chickens since ancient times in Japanese society, but also reveal a hormone-dependent molecular mechanism that causes sexual dimorphism in chicken feathers. .