A premature acrosome reaction is programmed by mouse t haplotypes during sperm differentiation and could play a role in transmission ratio distortion.
Mouse t haplotypes are variant forms of chromosome 17 that can be transmitted at non-Mendelian ratios by heterozygous +/t males. The accumulated genetic data indicate that '+-sperm' and 't-sperm' are produced in equal numbers but that most '+-sperm' are rendered dysfunctional, so that 't-sperm' have a relative advantage at fertilization. To date, the basis for this t-induced sperm dysfunction has remained unknown. Here we demonstrate that a high proportion of sperm obtained from certain strains of +/t mice undergo a premature acrosome reaction under in vitro capacitation conditions. The simplest interpretation of these data, in conjunction with previous results, is that developing '+-spermatids' are preprogrammed by 't-spermatids' to undergo this premature reaction. Since acrosome-reacted sperm are unable to participate in the process of fertilization, this defect could account for the extreme distortion of transmission ratio observed from mice heterozygous for a class of complete t haplotypes.
Brown
J
J
Department of Biology, Princeton University, New Jersey 08544.
Cebra-Thomas
J A
JA
Bleil
J D
JD
Wassarman
P M
PM
Silver
L M
LM
D000177:Acrosome / Q000502:physiology*; D000818:Animals; D002454:Cell Differentiation; D002874:Chromosome Mapping; D003433:Crosses, Genetic; D005260:Female; D005799:Genes, Dominant; D005804:Genes, Lethal; D006239:Haplotypes; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D013075:Sperm Capacitation; D013094:Spermatozoa / Q000166:cytology* / Q000502:physiology