SNP g.1007A>G within the Porcine DNAL4 Gene Affects Sperm Motility and Percentage of Midpiece Abnormalities

Morphology and motility are essential criteria for the assessment of an ejaculate’s fertilizing ability. Flagellar beating of a spermatozoon is generated by activation and inactivation of dynein molecules of the axoneme. The DNAL4 gene (dynein, axonemal, light chain 4) encodes a subunit of dyneins and is therefore a candidate gene for sperm motility. We re-sequenced the porcine DNAL4 and identified 23 SNPs. Associations between the SNPs and spermatological traits (n=8,833) of 82 AI boars (i.e. Pietrain, German Large White, and German Landrace) as well as morphological measurements (n=1,173) were estimated by single marker regression analysis. The same model was applied to estimate additive and dominance effects of alleles. Significances were calculated using a t-test after Bonferroni correction. Six DNAL4 polymorphisms were associated with motility (p<0.05). There was an effect of SNP g.1007A>G (p<0.0001) on motility after 24h (MOT1) and 48h (MOT2), resulting in a marked reduction by 10.33% respectively 19.37% and a loss of motility in undiluted ejaculate (MOTUD) by 4.59%. Applying the dominant-recessive model, genotypic values for MOTUD, given as LSmeans, differed significantly (p=0.05): 67.67% (AA), 64.16% (AG) and 53.91% (GG). In addition, associations between four SNPs and malformed sperm midpieces were observed (p=0.05). The average effect of gene substitution was 1.59% for g.1007A>G. Genotypic values were 0.018 for wildtype- and 0.087 for heterozygous variants. Observations available for homozygous mutant genotypes were missing. Considering its physical localization, we propose that DNAL4 is a second QTL for sperm motility and morphology on SSC5 in addition to CD9.