PDF《SPERM CHROMATIN》

Full Terms &

Conditions of access and use can be found at https://www.

tandfonline.com/action/journalInformation?journalCode=iaan20 Archives of Andrology Journal of Reproductive Systems ISSN: 0148-5016 (Print) (Online) Journal homepage: https://www.tandfonline.com/loi/iaan19 SPERM CHROMATIN G. Fuentes-Mascorro, H. Serrano, A. Rosado To cite this article: G. Fuentes-Mascorro, H. Serrano, A. Rosado (2000) SPERM CHROMATIN, Archives of Andrology, 45:3, 215-225, DOI: 10.1080/01485010050193995 To link to this article: https://doi.org/10.1080/01485010050193995 Published online:

09 Jul 2009. Submit your article to this journal Article views:

284 Citing articles:

74 View citing articles

215 ARCHIVES OF ANDROLOGY 45:215C225 (2000) Copyright ?

2000 Taylor &

Francis 0148-5016 /00 $12.00 + .00 SPERM CHROMATIN G. FUENTES-MASCORRO H. SERRANO A. ROSADO Division de Ciencias Biológicas y de la Salud, Universidad Autónoma Metropolitana, Unidad Iztapalapa, México DF, Mexico Available data on dry and hydrated nuclear volume of mammalian spermatozoa indicate that available volume is clearly insufficient to contain sperm chromatin packed in nucleosome-like structures. There- fore, sperm DNACprotein complexes must be packed differently than somatic DNACprotein complexes. Packing of DNA in fixed, dehydrated mammalian sperm approaches the physical limits of molecular compaction, making mammalian sperm chromatin the most condensed eukaryotic DNA known. The fundamental packaging unit of sperm chromatin is a toroid ~900-? outer diameter, 200-? thickness, and 150-? diameter hole. Each toroid contains

60 kilobases of DNA and is linked to other toroids by uncoiled DNA stretches. The factors that contribute to mammalian chromatin structuration are still under study. The role of protamines in sperm chromatin condensation and nuclear shaping has been overstressed to the exclusion of other possible factors. Chromatin organization in sperm nuclei is main- tained during sperm condensation by tight interactions with the nuclear matrix at fixed sites, inducing the formation of individual toroid-shaped DNA loop stuctures. Observations that abnormal manchettes affect sperm head shape and chromatin organization inducing sterility speak about manchette impor- tance during chromatin organization. The presence in sperm chromatin of regions packaged in specific ways with several types of protamines or even with histones, indicates that nuclear shaping and chroma- tin organization must be under DNA control. The structural properties that distinguish sperm DNA from somatic DNA may play the most important role in chromatin organization. Keywords chromatin structure, nucleosomes, sperm DNA Sperm chromatin has been the subject of extensive research. DNA in the sperm of some animal species, such as the sea urchin [33] and frog [34], appears to be packed in nucleosomes in a similar way to somatic chromatin. In most fishes, certain insects, echinoderms and mam- mals, sperm DNA is packed with a special type of small, basic proteins, into a tight, almost crystalline status, that is at least

6 times more condensed than in mitotic chromosomes. For practical purposes sperm DNA seems to be biochemically inert. During spermiogenesis round spermatids undergo dramatic changes giving rise to cells, sperm, completely different from the We acknowledge the help of Gerónimo Cruz García for line drawing elaboration. Address correspondence to Gisela Fuentes-Mascorro Departamento de Biología de la Reproducción, área de Re- producción Animal Asistida, Universidad Autónoma Metropolitana, Unidad Iztapalapa, Av. Michoacán y La Purísima Iztapalapa 09340, México D.F. A.P. 55-535, Mexico. E-mail: protamina@starmedia.com