title: High-pressure freezing of spermiogenic nuclei supports a dynamic chromatin model for the histone-to-protamine transition.
abstract: In this study, we present for the first time a description of the dynamic chromatin changes that occur during spermiogenesis in the internally fertilizing caenogastropod mollusc Nucella lamellosa. Chromatin condensation in developing sperm cells in some animals, such as the model biological system used here, involves the histone-to-protamine transition and proceeds through a patterning stage from granules to fibers to lamellae. This may be due to the physicochemical phenomenon of phase separation by spinodal decomposition, a dynamic mechanism known to generate pattern. This hypothesis is based entirely on published transmission electron microscopy photomicrographs using conventional fixation technology. We now report that spermatid nuclear patterning and subsequent condensation in testis of Nucella lamellosa fixed by high-pressure freezing and freeze substitution (HPF/FS) is similar to that in glutaraldehyde-fixed testis, and can be related to the processing of sperm nuclear basic proteins (SNBPs).
authors.affiliation: BioImaging Facility, Department of Botany, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4.
authors.forename: Garnet
authors.initials: G
authors.lastname: Martens
authors.forename: Elaine C
authors.initials: EC
authors.lastname: Humphrey
authors.forename: Lionel G
authors.initials: LG
authors.lastname: Harrison
authors.forename: Begonia
authors.initials: B
authors.lastname: Silva-Moreno
authors.forename: Juan
authors.initials: J
authors.lastname: Ausió
authors.forename: Harold E
authors.initials: HE
authors.lastname: Kasinsky
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism*; D005615:Freezing; D049851:Gastropoda / Q000378:metabolism; D006651:Histocytochemistry; D006657:Histones / Q000378:metabolism*; D008297:Male; D046529:Microscopy, Electron, Transmission; D011479:Protamines / Q000378:metabolism*; D013087:Spermatids / Q000378:metabolism; D013091:Spermatogenesis
chemical_list: D002843:Chromatin; D006657:Histones; D011479:Protamines