title: Genetically haploid spermatids are phenotypically diploid.
abstract: Because chromosomal homologues segregate from one another during meiosis, spermatids are genetically different. Post-meiotic gene expression could lead to gametic differences, some of which might lead to preferential transmission of certain alleles over others. In both insects and mammals, however, all the cells derived from a single spermatogonial cell develop within a common syncytium formed as a result of incomplete cytokinesis at each of the mitotic and meiotic cell divisions. It has been proposed that the intercellular bridges connecting the cells, which are about 1 micron in diameter, permit the sharing of cytoplasmic constituents, thus ensuring the synchronous development of a clone of cells and gametic equivalence between haploid spermatids. By analysing the product of a transgene which is expressed exclusively in post-meiotic germ cells in hemizygous transgenic mice, we have shown that genetically distinct spermatids share the product of the transgene and hence can be phenotypically equivalent.
authors.affiliation: Howard Hughes Medical Institute, University of Washington, Seattle 98195.
authors.forename: R E
authors.initials: RE
authors.lastname: Braun
authors.forename: R R
authors.initials: RR
authors.lastname: Behringer
authors.forename: J J
authors.initials: JJ
authors.lastname: Peschon
authors.forename: R L
authors.initials: RL
authors.lastname: Brinster
authors.forename: R D
authors.initials: RD
authors.lastname: Palmiter
mesh_terms: D000818:Animals; D005796:Genes; D013006:Growth Hormone / Q000235:genetics; D006238:Haploidy; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009693:Nucleic Acid Hybridization; D010641:Phenotype; D011479:Protamines / Q000235:genetics; D013087:Spermatids / Q000166:cytology / Q000502:physiology*; D013091:Spermatogenesis
chemical_list: D011479:Protamines; D013006:Growth Hormone