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Abe H.,Kyoto University | Abe H.,University of Otago | Nagao K.,Animal Husbandry Research Division | Inoue-Murayama M.,Kyoto University
PLoS ONE | Year: 2013

Introduction: Tonic immobility (TI) is fear-induced freezing that animals may undergo when confronted by a threat. It is principally observed in prey species as defence mechanisms. In our preliminary research, we detected large inter-individual variations in the frequency and duration of freezing behavior among newly hatched domestic chicks (Gallus gallus). In this study we aim to identify the copy number variations (CNVs) in the genome of chicks as genetic candidates that underlie the behavioral plasticity to fearful stimuli. Methods: A total of 110 domestic chicks were used for an association study between TI responses and copy number polymorphisms. Array comparative genomic hybridization (aCGH) was conducted between chicks with high and low TI scores using an Agilent 46180 custom microarray. We specifically focused on 3 genomic regions (>60 Mb) of chromosome 1 where previous quantitative trait loci (QTL) analysis showed significant F-values for fearful responses. Results: ACGH successfully detected short CNVs within the regions overlapping 3 QTL peaks. Eleven of these identified loci were validated by real-time quantitative polymerase chain reaction (qPCR) as copy number polymorphisms. Although there wkas no significant p value in the correlation analysis between TI scores and the relative copy number within each breed, several CNV loci showed significant differences in the relative copy number between 2 breeds of chicken (White Leghorn and Nagoya) which had different quantitative characteristics of fear-induced responses. Conclusion: Our data shows the potential CNVs that may be responsible for innate fear response in domestic chicks. © 2013 Abe et al.

Tadano R.,Hiroshima University | Nakamura A.,Animal Husbandry Research Division | Kino K.,Animal Husbandry Research Division
Poultry Science | Year: 2012

The aim of the present study was to characterize genetic diversity within and differentiation between 5 closely related lines of Japanese-native chickens, the Nagoya breed, based on microsatellite polymorphisms. For 5 Nagoya lines, the mean number of alleles per locus, the observed heterozygosity, the expected heterozygosity, and the inbreeding coefficient within a line ranged from 2.35 to 2.85, from 0.385 to 0.507 (average = 0.438), from 0.404 to 0.480 (average = 0.433), and from -0.056 to 0.074, respectively. These results indicated that Nagoya lines have moderate levels of genetic diversity and no severe inbreeding signatures. Genetic differentiations between pairs of lines (pairwise F ST) ranged from 0.0224 to 0.2500. The lowest differentiation was found between 2 lines that were divided into distinct lines about 10 years ago. Genetic clustering analyses, the neighbor-joining tree constructed from genetic distances of the proportion of shared alleles and the Bayesian model-based clustering, were carried out based on multilocus genotypes of individuals. The results suggested that Nagoya lines were genetically distinct from commercial gene pools (broilers and white and brown-egg layers) and that the Nagoya breed is a unique genetic resource. The results from the present study have the potential to contribute to future breeding and management of lines of the Nagoya breed. © 2012 Poultry Science Association Inc.

Abe H.,Kyoto University | Takeuchi H.-Aki.,University of Shizuoka | Yamada S.,University of Shizuoka | Nakamura A.,Animal Husbandry Research Division | And 4 more authors.
Animal Science Journal | Year: 2013

Polymorphisms in the neurotransmitter-related genes can be a major source of behavioral variations. We searched for polymorphic sites in chicken neurotransmitter-related genes and identified two variable number of tandem repeat (VNTR) loci encompassing the paralog of chicken serotonin transporter gene (5-HTT). Both intronic VNTR were highly polymorphic across chicken breeds and the other Galliformes species, even though predominant alleles were considerably different among breeds. One VNTR locus contained sequences complementary to a conserved motif of CCCTC-binding factor (CTCF) within each repetitive unit, indicating that transcription of chicken 5-HTT paralog may be regulated by the CTCF protein. It is of great interest to contrast these results with previous knowledge on the human 5-HTT that also has CTCF binding sites in the repetitive units of intronic VNTR. Additionally, we measured the degree of impulsiveness in domestic chicks for their preference of immediate/small to large/delayed rewards. A significant difference in the impulsiveness score was detected between two chicken breeds (White Leghorn vs. Boris Brown; P<0.01), as well as between White Leghorn chicks with different 5-HTT genotypes. These findings imply the possibility that 5-HTTVNTR genotypes may have some impact on chicks' impulsive choice by modifying the serotonergic neurotransmission. © 2012 Japanese Society of Animal Science.

Kansaku N.,Azabu University | Guemene D.,French National Institute for Agricultural Research | Nakamura A.,Animal Husbandry Research Division | Uchida M.,Animal Husbandry Research Division
Journal of Poultry Science | Year: 2011

The avian endogenous virus gene (ev21) and dominant sex-linked late feathering (LF) gene (K) are closely associated on the Z chromosome of LF chickens. The K gene is linked to two large repeats: ev21-unoccupied repeat region (URa) and ev21-occupied repeat region (OR). On the other hand, the recessive allele (early feathering, EF: k +) is linked to ev21-unoccupied region (URb). These three regions show high similarity but due to minor sequence differences, restriction enzyme treatment distinguishes URa and URb in White Leghorn. However, the applicability of the PCR-RFLP technique or the association between ev21 and K gene are not well investigated in the other breeds or strains. In this study, ev21 loci were detected in White Leghorn, Nagoya, Silky, Geline but not Gifujidori breeds of chickens, and the URa and URb from the various breeds were sequenced. Four types of sequence (URa-1 and URa-2 from LF or ev21 positive, URb-1 and URb-2 from EF or ev21 negative) were identified. At position 1072-1075, URa-2, URb-1 and URb-2 had "GGCC" whereas URa-1 had "AGCC". The transition at 1072 clearly indicates that the PCR-RFLP technique used for White Leghorn is not applicable to Nagoya. Interestingly, both URa-1 and URa-2 were obtained from the ev21 positive sample of Geline. Presence of different sequence of URa in the Geline may explain that fixation of one of sequences to White Leghorn or Nagoya had occurred during breed establishment. © Japan Poultry Science Association.

Abe H.,Kyoto University | Nagao K.,Animal Husbandry Research Division | Nakamura A.,Animal Husbandry Research Division | Inoue-Murayama M.,Kyoto University
Behavioural Processes | Year: 2013

Freezing responses to fearful stimuli are crucial for survival among all animal species within a prey-predator system. Generally, the degree of fearfulness correlates with intensity, duration, and frequency of freezing behaviours in response to fear-relevant stimuli. The present study examines innate fear responses to human handling in 144 newly hatched chicks through a tonic immobility (TI) test. Two fear responses-freezing duration and number of TI inductions-were examined. Individual variations in innate fear were investigated in chicks 1-2 days post-hatching when the restraint procedure was successively repeated 3 times within each day. Chicks showed sensitivity to fearful stimuli and considerable inter-individual variation in freezing duration and number of attempts required to induce TI. Moreover, differences were observed between breeds; White Leghorn chicks showed relatively low fear levels with gradual increases in TI duration, whereas Nagoya chicks showed extended TI duration and habituation to fearful stimuli. Our results suggest that TI reactions among newly hatched chicks are an innately determined behaviour specific to a breed or strain of chicken. Further, fearful responses among newborn chicks are not simple, but complex behaviours that involve multiple factors, such as breed-specific contextual fear learning and habituation/sensitisation processes. © 2013 Elsevier B.V.

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