title: Active digestion of sperm mitochondrial DNA in single living sperm revealed by optical tweezers.
abstract: In almost all eukaryotes, mitochondrial (mt) genes are transmitted to progeny mainly from the maternal parent. The most popular explanation for this phenomenon is simple dilution of paternal mtDNA, because the paternal gametes (sperm) are much smaller than maternal gametes (egg) and contribute a limited amount of mitochondria to the progeny. Recently, this simple explanation has been challenged in several reports that describe the active digestion of sperm mtDNA, down-regulation of mtDNA replication in sperm, and proteolysis of mitochondria triggered by ubiquitination. In this investigation, we visualized mt nucleoids in living sperm by using highly sensitive SYBR green I vital staining. The ability to visualize mt nucleoids allowed us to clarify that the elimination of sperm mtDNA upon fertilization is achieved through two steps: (i) gradual decrease of mt nucleoid numbers during spermatogenesis and (ii) rapid digestion of sperm mtDNA just after fertilization. One notable point is that the digestion of mtDNA is achieved before the complete destruction of mitochondrial structures, which may be necessary to avoid the diffusion and transmission of potentially deleterious sperm mtDNA to the progeny.
authors.affiliation: Department of Biological Sciences, Graduate School of Science, University of Tokyo, Hongo 7-3-1, Tokyo 113-0033, Japan. yn37@cornell.edu
authors.forename: Yoshiki
authors.initials: Y
authors.lastname: Nishimura
authors.forename: Tomoya
authors.initials: T
authors.lastname: Yoshinari
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Naruse
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamada
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Sumi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Mitani
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Higashiyama
authors.forename: Tsuneyoshi
authors.initials: T
authors.lastname: Kuroiwa
mesh_terms: D000818:Animals; D052160:Benzothiazoles; D002460:Cell Line; D004247:DNA / Q000737:chemistry; D017931:DNA Primers / Q000737:chemistry; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism; D003959:Diamines; D004531:Eggs / Q000382:microbiology; D005306:Fertilization; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000235:genetics; D009930:Organic Chemicals / Q000494:pharmacology; D009990:Oryzias; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D011804:Quinolines; D011995:Recombination, Genetic; D013091:Spermatogenesis; D013094:Spermatozoa / Q000378:metabolism* / Q000648:ultrastructure*
chemical_list: D052160:Benzothiazoles; D017931:DNA Primers; D004272:DNA, Mitochondrial; D003959:Diamines; D009930:Organic Chemicals; D011804:Quinolines; C098022:SYBR Green I; D004247:DNA; D009245:NADH Dehydrogenase