W579 Sperm Mobility

Date: Saturday, January 14, 2012
Time: 2:00 PM
Room: Sunset
David P. Froman , Oregon State University, Corvallis, OR
Sperm mobility is a quantitative trait (h2 = 0.30 in the chicken).  An exclusively maternal additive genetic effect was observed when heritability was estimated.  Initially, this effect was attributed to the mitochondrial genome.  However, genome-wide SNPlotyping has identified a locus of interest on the Z chromosome (Rhoads and Froman, unpublished data).  The trait’s name denotes the net movement of sperm from one place to another.  It is noteworthy that such movement is against resistance at body temperature.  The trait is measured in vitro by sperm penetration of a 6% (w/v) Accudenz solution from an overlaid sperm suspension.  The size of the mobile subpopulation is proportional to the absorbance of the Accudenz layer after a 5-min incubation interval.  Mobile sperm have a straight line velocity > 30 μm per second.  Thus, whereas all mobile sperm are motile, not all motile sperm are mobile.  This is a key distinction that imparts biological significance to phenotype.  In essence, a sperm mobility measurement denotes an effective insemination dose.  In fact, male fertility in the chicken is a function of sperm mobility phenotype.  Phenotypic variation appears to arise from a genetic disposition that puts sperm cells at risk of mitochondrial failure while sperm pass through the excurrent ducts of the testis.  In other words, premature mitochondrial failure stems from conditions that interact to affect sperm in a stochastic manner.  Two critical variables are currently under investigation:  (1) sperm cell glycolytic ability, and (2) deferent duct  transit time.  To date, the study of sperm mobility has:  (1) helped explain variation in fertility among males, (2) revealed the most likely explanation for in vivo semen storage in the hen, (3) provided an approach to semen preservation based on sperm cell energetics, (4) enabled semen quality in the chicken to defined in a quantitative manner, i.e. the number of mobile sperm produced per testis per day, and (5) has revealed loci of interest on several autosomes in addition to the Z chromosome.  The gene networks responsible for phenotypic variation are being sought in collaboration with Douglas Rhoads and Shane Burgess.