title: Further studies on knockout mice lacking a functional dynein heavy chain (MDHC7). 1. Evidence for a structural deficit in the axoneme.
abstract: Male mice had previously been generated in which the inner dynein arm heavy chain 7 gene (MDHC7) was inactivated by the substitution of four exons encoding the ATP-binding site (P1-loop) with the neomycin resistance gene, giving a putative non-functional gene product. We have used additional techniques of electron microscopy to determine what effect the truncated, non-functional heavy chain has on the assembly of the inner dynein arm complex. From a comparison of MDHC7-/- with the wild-type morphology, we have found that the expected loss of a C-terminal (globular) domain is associated with inner dynein arm 3, a change from two visible "heads" to one. This deficit was seen in replicas of rapidly-frozen, deeply-etched spermatozoa, and was confirmed in filtered images of 20-nm-thin sections, cut in longitudinal planes. Assembly of the other IDAs appeared unaffected. This study is the first to reveal the location of a specific dynein heavy chain within the 96-nm repeat pattern of the inner dynein arms of the mammalian axoneme.
authors.affiliation: Department of Physiology, School of Medical Sciences, University of Bristol, Bristol, United Kingdom.
authors.forename: Geraint G
authors.initials: GG
authors.lastname: Vernon
authors.forename: Juergen
authors.initials: J
authors.lastname: Neesen
authors.forename: David M
authors.initials: DM
authors.lastname: Woolley
mesh_terms: D000818:Animals; D004398:Dyneins / Q000737:chemistry / Q000235:genetics*; D005407:Flagella / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D005613:Freeze Etching; D046911:Macromolecular Substances; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D046529:Microscopy, Electron, Transmission; D009154:Mutation / Q000235:genetics; D017434:Protein Structure, Tertiary / Q000235:genetics; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics*; D013081:Sperm Motility / Q000235:genetics*; D013094:Spermatozoa / Q000002:abnormalities* / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D046911:Macromolecular Substances; D021122:Protein Subunits; D004398:Dyneins