Differences in cAMP levels in tn- and non-tn-bearing mouse spermatozoa

Fertility of sperm from t/+ mice: evidence that +-bearing sperm are dysfunctional

Male mice carrying one complete t haplotype transmit it to virtually all offspring. This implies that either the sperm carrying the t haplotype have an advantage in fertilization, or that the sperm not carrying a t haplotype are dysfunctional. To distinguish between these possibilities, epididymal sperm from tw32/ + and congenic + / + males were artificially inseminated into the uterus of T / + females, and the transmission ratio determined from the phenotype of the offspring. After artificial insemination (AI) of sperm from tw32/ + males, the mean ratio was 0·95 (3 experiments, 5 litters), demonstrating that the transmission ratio remains high after AI into the uterus. After AI of a mixture of equal numbers of motile sperm from tw32/ + and congenic + / + males, the mean ratio was 0·22 (6 experiments, 8 litters). These results suggest that sperm carrying a t haplotype from t/ + males are not superior to sperm from + / + males, and therefore imply that sperm not carrying a t haplotype from t/ + males are dysfunctional.

Genetic background affects expression of t haplotype in mouse sperm

Two aspects of sperm phenotype were examined for tw32/+ males of the inbred strains C3H and C57BL/6 (B6). Sperm from fertile C3H-tw32/+ males very rarely achieved fertilization in vitro, while sperm from congenie C3H-+/+ males had no such difficulties. The presence of tw32 had no effect on ability of B6 sperm to undergo fertilization in vitro. In fertile hybrid males produced from crosses of B6 and C3H strains, tw32 significantly reduced, but did not inhibit completely, the sperms' ability to fertilize in vitro. The presence of tw32 decreased by a factor of two the frequency of abnormal sperm heads in males of the B6 strain, but doubled the frequency in the C3H strain. Hybrid males resembled the C3H strain in this respect. The presence of T or T2J had no effect on the level of sperm abnormalities in any strain. These results emphasize the importance of genetic background in expression of t haplotypes in sperm, and suggest that tw32 can influence a range of sperm characteristics, by interacting with products of other loci.

Is Haploid gene expression possible for sperm antigens?

The development of spermatozoon (sperm) from a spermatid involves a complex process of differentiation during which a variety of new gene products appear. It has been generally assumed that no genetic transcription occurs after meiosis and, if this were so, that all the new sperm proteins would have to to be transcribed from stored messenger RNA. However, the biochemical evidence suggests that there is no abrupt change in the rate of RNA synthesis during meiosis and that qualitative changes in RNA synthesis, to the extent that they are known, favor the likelihood of continuing messenger RNA synthesis. Experimental analyses of distorted transmission ratios of t-alleles and unbalanced chromosomal states in makes also suggest that genes are expressed in haploid nuclei after meiosis. It is probable that spermatozoa are functionally equivalent in most respects because of intercellular bridges that create a continuous cytoplasm between developing spermatozoa, facilitating an exchange of most postmeiotic gene products. Plasma membrane proteins which are potential antigens might not be shared across the intercellular bridges but the evidence to date for haploid expression of sperm antigens is poor.