To identify the methylation pattern of the porcine MKRN3 promoter CpG island in the embryo heart,embryos of days 65 and 100 of gestation from the reciprocal crosses of Yorkshire-Meishan pig were collected.Firstly,CpG island in the promoter region of MKRN3 was predicted by utilizing bio-informatics method,and primers was designed based on this predicted CpG island.Bisulfite sequencing (BSP) was utilized to detect methylation level in the embryo heart from Yorkshire-Meishan reciprocal crosses.Results showed that,in the heart from embryo of days 65,the CpG island of porcine MKRN3 showed high level of methylation,with 75.6% from Yorkshire×Meishan and 76.4% from Meishan×Yorkshire.In the heart from embryo of 100 days,the CpG island of target gene showed high level of methylation (80%) from Yorkshire×Meishan,while low level of methylation (35.6%) from Meishan×Yorkshire crosses.Results above indicated that the methylation pattern of the porcine MKRN3 promoter CpG island would change according to the change of reciprocal crosses and developmental stages.For embryo of 65 days,reciprocal crosses of Yorkshire-Meishan represented high methylationlevel,but for embryos of 100 days,high methylation from Yorkshire×Meishan but low methylation from Meishan×Yorkshire were observed,indicating that de-methylation might take place in the paternal or maternal allele,during the late stage of embryonic development.