Date of Graduation

12-2017

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Cell & Molecular Biology (PhD)

Degree Level

Graduate

Department

Biological Sciences

Advisor

Douglas Rhoads

Committee Member

Suresh Thallapuranam

Second Committee Member

Yuchun Du

Third Committee Member

David McNabb

Keywords

GWAS, Poultry, Primordial Germ Cells, RNA Seq, Sperm Mobility

Abstract

Sperm mobility is a major determinant of male fertility in chicken. In spite of low heritability of reproductive traits, sperm mobility has high heritability index which suggests presence of quantitative trait loci (QTLs) governing the trait. Our research focused on three objectives: i) to identify the QTLs affecting low mobility phenotype in chicken, ii) to understand the impact of Sertoli-cells and germ cells interactions in influencing the mobility phenotype and iii) to identify the genes and gene networks differentially expressed in male and female PGCs. To detect the QTLs, genome wide association studies (GWAS) was conducted which revealed the presence of multiple minor alleles influencing the trait and indicated the role of epistasis. The second section of research involved isolation, culture and transfer of primordial germ cells (PGCs) to create high line germ line chimera chicken carrying low line PGCs. We established the culture of chicken PGCs isolated from the embryonic blood in a feeder free culture conditions but could not detect the presence of low line genotype in the semen of transgenic males. Our final study involved RNA-sequencing (RNAseq) of male and female PGCs to identify differentially expressed genes from their transcriptomes. We identified five candidate genes: 3-hydroxy-3-methylglutaryl CoA reductase (HMGCA), germ cell-less (GCL), SWIM (zinc finger SWIM domain containing transcription factor), SLC1A1 (solute carrier family 1 member 1), UBE2R2L (ubiquitin conjugating enzyme) and validated their expression level in male and female PGCs by RT-qPCR. GCL was exclusively expressed in males while SLC1A1 & UBE2R2L were expressed only in female cPGCs. This present study provides novel gender specific germ cell markers in the broiler chicken. These results will help in elucidating the genetic programming of gender specific germ line development in broilers.

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