The CREPT(cell cycle-related and expression elevated protein in tumor,also known as RPRD1B)and p15RS(p15INK4b-related sequence,also known as RPRD1A)genes,which are highly related in regulating cell proliferation and cycling,have been shown to regulate cell proliferation and alter the cell cycle through transcription of Wnt/βcatenin pathway downstream genes in humans.Although some studies have identified the mechanism of CREPT and p15RS regulation of cell proliferation in humans and mammals,it is still unclear how does these genes regulate cell proliferation in poultry.In order to determine the function of CREPT and pl5RS in chickens,we examined the expression of CREPT and p15RS in a variety of chicken tissues and DF-1 cells.Then,we transiently transfected chicken DF-1 cells with overexpression and short hairpin RNA(shRNA)vectors to determine the effect of overexpression or knockdown of CREPT or p15RS,respectively,on the regulation of cell proliferation.We found that CREPT and pl5RS had different expression patterns and opposite effects on the cell cycle and cell proliferation.Knockdown of p15RS expression or overexpression of CREPT facilitated cell proliferation by promoting the cell-,cycle transition from G0/G1 to the S-phase,whereas knockdown of CREPT expression or overexpression of p15RS inhibited cell proliferation.Mechanistically,CREPT and p15RS regulate DF-1 cell proliferation by the regulating the expression of Wnt/β-catenin pathway downstream regulatory genes,includingβ-catenin,TCF4,and Cyclin Dl.Our results demonstrate that CREPT and p15RS regulate cell proliferation and the cell-cycle transition in chicken DF-1 cells by regulating the transcription of Wnt/β-catenin pathway downstream regulatory genes.