Tatsuhiko Goto

Aggression is an essential animal behavior for survival, particularly in situations where fighting cannot be avoided. In such situations, the choice of fighting strategy (eg biting, charging, or defending) is critical. Although the molecular bases of fighting and aggressiveness have been previously studied, how genetic, transcriptional, and neurobiological mechanisms contribute to the choice of fighting strategy remains largely unknown. Here, we use two subpopulations of chickens bred for cockfighting that show markedly different fighting strategies: offensive and defensive attack. A genome-wide screen comparing individuals from the two subpopulations indicated a polygenic background and we identified 15 candidate genes, five of which are implicated in neuronal development. Among these, the transcription factor gene FOXP1 was notable. FOXP1 is essential for neuronal development in the brain and has been implicated in the regulation of motor circuits. Transcriptomic analysis of the diencephalon also revealed differential expressions of genes involved in neurodevelopment, as well as in the synthesis and release of neurotransmitters. RNA-sequencing and immunohistochemistry suggested that activation of the indirect pathway of the brain motor circuit promotes the defensive fighting strategy. This was further supported by behavioral pharmacological experiments targeting dopaminergic signaling. Taken together, our results indicate that genomic variation and altered expression of neurodevelopment-related genes underlie differences in fighting strategies, and that the neuroendocrine changes in brain circuits further modulate these behavioral outcomes.

Japanese indigenous chickens potentially produce good‐quality eggs. This study aims to analyze egg quality traits using four Japanese indigenous breeds: Tosa‐jidori (TSJ), Ko‐Shamo (KSM), Minohikichabo (MHC), and Chabo (CHB). Eleven egg quality traits were measured from 73 hens in total. One‐way ANOVA, correlation analysis, and principal component analysis (PCA) were conducted. Significant breed effects were observed for nine egg traits, except for the length of the short axis of the egg and eggshell yellowness. TSJ and KSM have significantly higher egg weight and albumen weight than MHC and CHB. The weights of yolk and eggshell in KSM were significantly higher than those of the others. MHC indicated significantly higher eggshell strength and thickness than CHB. MHC showed significantly redder eggshells than the others. PC1 (size and weight of egg components), PC2 (eggshell quality and color), and PC3 (thickness, weight, and redness of the eggshell) explained 76.9% of the total variance. Significant breed effects were observed for PC1 and PC2, revealing breed‐specific characteristics in egg traits in this study. Moderate to strong correlations were found both among size and weight traits and among eggshell color traits. These results suggest the importance of characterizing untapped genetic resources in egg quality traits.

Eggs are good sources of animal proteins. Methods for creating designer eggs are attractive to scientists and producers of the eggs, in order to fulfill customers’ demands. We review and summarize the current understanding of how genetic and environmental factors influence chicken egg components, specifically, amino acid contents of yolk and albumen. Genetically diverse breeds of chicken enable us to obtain a wide variety of egg amino acids. Moreover, the use of fermented feed and different rearing systems (barn and deep litter) has impacts on egg amino acids, which may be mediated through changes in the intestinal environment, including the microbiota. To overcome the future food crisis, the combinations of breeds, feeds, and rearing systems will be important for producing designer eggs. In the future, not only long-term selected layer strains will be required, but also many kinds of indigenous chicken breeds, which have already adapted to each local environment in the world, should be investigated under the continental levels of climate environment using different fermented feed materials. To better understand the interplay between genetic and environmental factors, we will offer valuable insights for both egg producers and consumers, potentially guiding future efforts to optimize egg amino acid contents in chickens.

Equol is a microbial metabolite from daidzein, an isoflavone, in the animal intestine. This study aimed to identify equol‐producing bacteria in the intestines of chickens. Sixteen 181‐day‐old Hy‐Line Brown laying hens were given a basal diet formulated excluding soy products for 2 weeks and subsequently given the diets supplemented with 0‐, 100‐, 1000‐, and 10,000‐ppm daidzein for 10 days. Plasma and egg yolk equol concentration was significantly increased with dietary daidzein supplementation. Gene abundance of two major bacterial enzymes catalyzing the conversion of daidzein to equol, dihydrodaidzein reductase, and tetrahydro daidzein reductase was measured using polymerase chain reaction (PCR) analysis, with the abundance increasing with dietary daidzein supplementation ( p < 0.05). After sequencing the PCR amplicons, six possible bacteria were identified, and they were further identified and quantified using a specific primer for each bacterial gene. As a result, Adlercreutzia equolifaciens and Slackia equolifaciens were identified, and their bacterial relative abundance increased with dietary daidzein concentration and plasma equol levels ( p < 0.05). A. equolifaciens and S. equolifaciens are known as equol‐producing bacteria, and the present study was the first to show that these bacteria could also contribute to equol production in chickens.

Early-life environment has a long-lasting effect on later life, though its estimation is often prevented in the wild because of a lack of available methods. Recently, isotope analysis of eye lenses has attracted considerable interest as a means to reconstruct the environmental conditions experienced by animals during the developmental period. This analysis has mostly been confined to fish for practical reasons and remains to be resolved for application to other animals. In this study, we broadened its applicability by developing a novel approach and verifying its usability for the reconstruction of early-life environments. We performed a feeding experiment using Japanese quail ( Coturnix japonica ), in which we administered two diets: one composed mainly of C3 plants (low δ ¹³ C and high δ ¹⁵ N) and the other of C4 plants (high δ ¹³ C and low δ ¹⁵ N). Quails in the control group were continuously fed a C3-based diet from hatching until 200 days old, whereas those in the treatment groups (T10, T15, T20, and T40) were switched from the C3 to the C4-based diet at 10, 15, 20, and 40 days after hatching, respectively. We found that the δ ¹³ C in the eye lenses of the treatment groups decreased from the center layer to the middle layer of the lens and then increased toward the outer layer, thus reflecting the diet change. In contrast, those of the control group exhibited a decreasing trend and equilibrated at the middle layer of the eye lens, with no increase thereafter. This novel approach revealed the postnatal feeding histories of the diet-shift experiment. The high δ ¹³ C values observed in the center of the eye lenses would reflect the prenatal feeding environment, i.e., the C4-based diet consumed by their mothers, which is further reinforced by higher δ ¹⁵ N values at this position due to the consumption of egg yolk-derived nutrition. These results indicate that the avian eye lens can be used as an “isotopic chronicle,” which is a useful tool for reconstructing chronological isotopic information about their early-life history.

Genomic information must be faithfully transmitted into two daughter cells during mitosis. To ensure the transmission process, interphase chromatin is further condensed into mitotic chromosomes. Although protein factors like condensins and topoisomerase IIα are involved in the assembly of mitotic chromosomes, the physical bases of the condensation process remain unclear. Depletion attraction/macromolecular crowding, an effective attractive force that arises between large structures in crowded environments around chromosomes, may contribute to the condensation process. To approach this issue, we investigated the “chromosome milieu” during mitosis of living human cells using an orientation-independent-differential interference contrast module combined with a confocal laser scanning microscope, which is capable of precisely mapping optical path differences and estimating molecular densities. We found that the molecular density surrounding chromosomes increased with the progression from prophase to anaphase, concurring with chromosome condensation. However, the molecular density went down in telophase, when chromosome decondensation began. Changes in the molecular density around chromosomes by hypotonic or hypertonic treatment consistently altered the condensation levels of chromosomes. In vitro, native chromatin was converted into liquid droplets of chromatin in the presence of cations and a macromolecular crowder. Additional crowder made the chromatin droplets stiffer and more solid-like. These results suggest that a transient rise in depletion attraction, likely triggered by the relocation of macromolecules (proteins, RNAs, and others) via nuclear envelope breakdown and by a subsequent decrease in cell volumes, contributes to mitotic chromosome condensation, shedding light on a different aspect of the condensation mechanism in living human cells.

Fancy breeds of Japanese indigenous chicken display extensive morphological diversity, particularly in tail feathers. Although marked differences in tail and bone traits have been reported between Tosa‐jidori (wild type) and Minohikichabo (rich type) breeds, little is known about the pattern of genetic inheritance in cross experiments. Therefore, this study aimed to investigate the strain and sex effects, and inheritance patterns, in the morphometric variation of pygostyle bones among Tosa‐jidori, Minohikichabo, and their F₁ hybrids. Five morphological traits, angle of the apex of the pygostyle, pygostyle length, margo cranialis length, tail feather number, and body weight, were evaluated at the adult stage. A significant strain difference was detected in all traits, whereas significant sex differences were observed in only three traits, but not in the angle of the apex of the pygostyle and tail feather number. In F₁ hybrids, the angle of the apex of the pygostyle was significantly different to that of Tosa‐jidori but not that of Minohikichabo, whereas the pygostyle length and tail number of F₁ hybrids were significantly different from those of Minohikichabo but not those of Tosa‐jidori. A significant heterosis effect was found in the margo cranialis length and body weight. All five traits showed nonadditive inheritance patterns but varied in each trait between partial dominance (angle of the apex of pygostyle), full dominance (pygostyle length and tail feather number), and over‐dominance (margo cranialis length and body weight). Interestingly, different patterns of genetic inheritance in the F₁ hybrid were observed at different locations, even within the same pygostyle bone. Using the Japanese indigenous chicken model, these results provide a substantial step toward understanding the genetic architecture of morphology in chickens.

It is well known in the poultry industry that fear and stress experienced during the handling of day-old chicks in commercial hatcheries can have long-lasting effects on their behavior later in life. These hatchery-related stresses are more intense and complex than those encountered in traditional behavioral tests. Consequently, a single behavioral test may not be sufficient to measure hatchery stresses and chicken temperament. In this study, we developed a new behavioral handling test for day-old chickens, which incorporated concepts from established behavioral tests used with both young and adult birds. The new test assessed 10 behavioral traits, including vocalization frequency and responses to human interaction. It was conducted on 96 two-day-old chicks from seven breeds of native Japanese and Western chickens. The results of the principal component analysis classified chicken temperaments into three distinct categories: bustle, aggression, and timidity. Using these categories, the seven breeds were classified into five groups, each with distinct temperaments. This study highlights the reliability and value of the new handling test in characterizing the temperaments of various chicken breeds and provides insights into the complex behaviors of chickens.