Characterization of the Expression Profile and Genetic Polymorphism of the Cellular Retinol-Binding Protein (CRBP IV) Gene in Erlang Mountainous Chickens

Relative mRNA expression of CRBP IV gene and its association with layer economic traits in Rhode Island Red chicken

Cellular retinol-binding protein (CRBP) IV gene plays an important role in absorption, transport, metabolism and homeostasis of retinol (Vitamin A) and its derivatives. Vitamin A plays vital role in ovarian follicular growth, oviduct and uterine environments, embryo and its development, and oocyte maturation. Present investigation was carried out in Rhode Island Red (RIR) chicken to assess relative mRNA expression of CRBP IV gene in kidney, liver and oviduct tissues, collected from 12 birds at 40 weeks of age from four different egg production-body weight groups, viz. high egg production-high body weight (HEP-HBW), high egg production-low body weight (HEP-LBW), low egg production-high body weight (LEP-HBW) and low egg production-low body weight (LEPLBW), using qRT-PCR method. Data on body weight at 20 weeks of age (BW20) and layer traits, viz. age at sexual maturity (ASM), egg weight at 28 (EW28) and 40 (EW40) weeks and egg production up to 40 weeks of age (EP40) were analyzed by LS ANOVA taking sire as random and hatch as fixed effects. LS means of ASM, BW20, EW28, EW40 and EP40 were 135.19±1.15 days, 1347.13±15.28 g, 42.49±0.27 g, 48.19±0.42 g and 124.55±1.94 eggs, respectively. Expression data was analyzed by LS ANOVA using SAS. The basal mRNA expression of CRBP IV gene differed significantly among different egg production-body weight groups in kidney only. The 40-ΔCt values of mRNA expression levels of CRBP IV gene in the four groups were 35.81±1.60, 29.49±1.60, 32.16±1.60 and 39.02±1.60, respectively. Significantly lower expression was observed in HEP-LBW group. Similarly, tissues differed significantly for the CRBP IV gene expression. The 40-ΔCt values of mRNA expression levels of CRBP IV gene in kidney, liver and oviduct were 34.12±0.87, 31.67±0.87 and 37.97±0.87, respectively. Highest expression was observed in oviduct. The study generated significant information on basal mRNA expression of CRBP IV gene in poultry which may have great potential for use in selection for higher reproductive efficiencies.

Genetic effects of polymorphisms in myogenic regulatory factors on chicken muscle fiber traits

The myogenic regulatory factors is a family of transcription factors that play a key role in the development of skeletal muscle fibers, which are the main factors to affect the meat taste and texture. In the present study, we performed candidate gene analysis to identify single-nucleotide polymorphisms in the MyoD, Myf5, MyoG, and Mrf4 genes using polymerase chain reaction-single strand conformation polymorphism in 360 Erlang Mountain Chickens from three different housing systems (cage, pen, and free-range). The general linear model procedure was used to estimate the statistical significance of association between combined genotypes and muscle fiber traits of chickens. Two polymorphisms (g.39928301T>G and g.11579368C>T) were detected in the Mrf4 and MyoD gene, respectively. The diameters of thigh and pectoralis muscle fibers were higher in birds with the combined genotypes of GG-TT and TT-CT (p<0.05). Moreover, the interaction between housing system and combined genotypes has no significant effect on the traits of muscle fiber (p>0.05). Our findings suggest that the combined genotypes of TT-CT and GG-TT might be advantageous for muscle fiber traits, and could be the potential genetic markers for breeding program in Erlang Mountain Chickens.

Characterization of the expression profile of CRBP1 and CRBP3 gene in chicken

In this study, we quantified the expression of CRBP1 and CRBP3 in Roman layer (R) and Erlang mountainous chickens (SD02 and SD03), to discern the tissue, breed and age-related expression patterns in order to discover potential involvement in egg production and other related reproduction traits. Real-time quantitative PCR assays were developed for accurate measurement of CRBP1 and CRBP3 mRNA levels in different tissues from chickens at four ages (12, 20, 32 and 45 weeks). We found that the CRBP1 and CRBP3 were expressed in all six tissues examined in all three breeds of chicken at 32 weeks. CRBP1 mRNA levels in SD02 kidneys were slightly higher than those in SD03 and R at 12 weeks, whereas, at the other three time points, the expression levels of CRBP1 in SD03 were higher than those in SD02 and R. In addition, there was higher hepatic expression of CRBP3 mRNA in layers (R) compared to broilers (SD02 and SD03) at 20 and 32 weeks. An age-related expression pattern of CRBP1 gene was evident in liver (P < 0.01), but not in pituitary (P > 0.05). Overall, the expression level of CRBP1 gene in kidney, ovary and oviduct at the different ages had a "decline-rise-decline" trend in all three breeds. In contrast, in pituitary, hypothalamus, liver and kidney CRBP3 mRNA expression levels were significantly different at various ages (P < 0.05) and exhibited a "rise-decline-rise" pattern in all three breeds. Our results show that the expression of CRBP1 and CRBP3 in chicken tissues exhibit specific developmental changes and age-related patterns.

Expression Profiles of Cellular Retinol-binding Protein, Type II (CRBP II) in Erlang Mountainous Chickens

Cellular retinol-binding protein II (CRBP II) belongs to the family of cellular retinol-binding proteins and plays a major role in absorption, transport, and metabolism of vitamin A. In addition, because vitamin A is correlated with reproductive performance, we measured CRBP II mRNA abundance in erlang mountainous chickens by real-time PCR using the relative quantification method. The expression of CRBP II showed a tissue-specific pattern and egg production rate-dependent changes. The expression was very high (p<0.05) in jejunum and liver, intermediate in kidney, ovary, and oviduct, and lowest (p<0.05) in heart, hypothalamus, and pituitary. In the hypothalamus, oviduct, ovary, and pituitary, CRBP II mRNA abundance were correlated to egg production rate, which increased from 12 wk to 32 wk, peaked at 32 wk relative to the other time points, and then decreased from 32 wk to 45 wk. In contrast, the expression of CRBP II mRNA in heart, jejunum, kidney, and liver was not different at any of the ages evaluated in this study. These data may help to understand the genetic basis of vitamin A metabolism, and suggest that CRBP II may be a candidate gene to affect egg production traits in chickens.