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ThesisItem Open Access IDENTIFICATION OF POLYMORPHISM AND EPIGENETIC MODIFICATION OF PARTIAL PROMOTER OF ACACB GENE VIS-A-VIS EFFECT OF POLYMORPHISM ON EGG PRODUCTION AND QUALITY TRAITS IN LAYERS(SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA, 2021-03) SHIVAPRASAD, C.H; Vinoo, R (MAJOR); Chatterjee, R.N; Muralidhar, M; Narendranath, D; Aswani kumar, KPoultry eggs are rich source of inexpensive, high-quality protein, vitamins namely A, B2, B6, B12, D, E and K, minerals like zinc, iron selenium, and copper etc. Egg yolk contains more calories and fat. In the recent past, there is demand for consumption of food sources of poly unsaturated fatty acids like dodecanoic acid, nonadecanoic acid, myristoleic acid, alpha linoleic acid and omega-3 fatty acids. The fatty acid composition depends on type of diet and genetic composition. Among the candidate genes, the acetyl-coenzyme A carboxylase beta (ACACB) is a candidate gene that can influence fatty acid composition. Perusal of literature revealed that the identification of partial promoter of ACACB gene was not done in chicken. Hence the present study is aimed at identification of partial promoter region, genetic polymorphism, gene expression and epigenetic regulation of ACACB gene in chicken. Further, the study also aimed at unraveling the association of the genetic polymorphism with body weight, egg production and egg quality traits in the two-layer lines, IWI and IWK. The study could successfully predict the minimal promoter region which is in the upstream 0.5 kb region. The region included certain transcription factors like CEBP, COUP, HNF4, PPARA, SREBP1, and T3R which are known to be involved in lipid metabolism. The minimal promoter region could potentially translate the gene in chicken embryo fibroblasts. Further, the minimal promoter region is polymorphic with 12 haplotypes and 18 haplogroups based on SSCP analysis. The haplotype h5 is least frequent in both IWI and IWK lines while h11 haplotype is most frequent in IWI line and h4 haplotype is the most frequent one in IWK line. Sequencing of the haplotypes revealed indels and substitutes in these haplotypes. The h8h8 haplogroup is associated with higher body weight at 8th, 16th and 20th week in IWI line. The haplogroup h12h12 is strongly associated with higher egg production in IWI line up to 52 weeks of age. The egg weight didn’t vary significantly within the line in any of the age except h1h2 haplogroup in IWI line at 72nd week, which is associated with higher egg weight. The shell weight is not particularly associated with any of the haplotypes in IWI line, but within IWK line, the h6h6, h9h9 haplogroups showed higher shell weight. The h9h9 and h9h10 haplogroups are associated with higher shell weight in IWK line compared to IWI line. The total egg fat% is significantly higher within IWI line, when they have h10h10 haplogroup. The same haplogroup also showed higher total fat% in IWI line compared to IWK line. There is no significant association is observed between haplogroups and HDL concentration in IWI line. But, in IWK line, the h8h8 haplogroup is associated with high serum HDL cholesterol concentration. Temporal expression pattern of the ACACB gene indicated that the gene expresses in all stages in the skeletal muscle of chicken during pre and post-hatch period. Epigenetic profile of the minimal promoter indicated that there are seven CpG islands in this region. There is negative relationship between highest and lowest expressed birds with the percent methylation in both the genetic groups. The present study suggests that the ACACB gene plays a crucial role in pre and post- hatch period in IWI and IWK lines. Further studies with spatial expression pattern of the gene and experiments aiming at precise functional analysis would provide additional insights into the role of ACACB gene in chicken in providing healthy eggs and meat.
