Genetic analysis of DDR1 polymorphisms as robust markers for milk yield in Simmental cattle

This study aimed to determine new polymorphisms in 15 exon regions of the discoidin domain receptor tyrosine kinase 1 (DDR1) gene. A total of 72 Simmental cattle were used in this study. Single nucleotide polymorphisms (SNPs) of gene regions were performed using polymerase chain reaction (PCR) high-resolution melting (HRM) analysis followed by sequence analysis. The identified DDR1 gene regions include the g.28183947 G/T polymorphic region for the 1^' exon region of the DDR1 gene, g.28183480 G/C and g.28183434 C/A-G polymorphic regions for the 3^' exon region of the DDR1 gene, g.28181525 C/A polymorphic region for the 5^' exon region of the DDR1 gene, g.28180846 G/C polymorphic region for the 6^' exon region of the DDR1 gene, g.28180437 C/G polymorphic region for the 7^' exon region of the DDR1 gene, g.28178065 G/C polymorphic region for the 10^' exon region of the DDR1 gene, g.28175989 G/T polymorphic region for the 12^' exon region of the DDR1 gene and g.28173956 T/G and g.28173954 T/C polymorphic regions for the 16^' exon region of the DDR1 gene. As a result of the statistical analysis, a significant relationship was found between the g.28183947 G/T polymorphic region in the 1^' exon region of the DDR1 gene and the 305 d milk yield ( $P<0.05$ ). A significant relationship was found between the g.28181525 C/A polymorphic region in the 5^' exon region of the DDR1 gene and daily average milk yields, lactation milk yields and the 305 d milk yield ( $P<0.05$ ). No significant relationship was found between the other polymorphic regions detected and milk yields ( $P>0.05$ ). Consequently, the genotype and allele gene frequencies of the detected new polymorphic regions were determined. This study suggests that DDR1 gene polymorphic regions found to affect milk yield in Simmental cattle can be used as new candidate molecular markers in animal breeding and selection.