Synaptonemal complex

Fig. 2.6 The moqjhological events of sporulation in Saccharomyces cerevisiae. (a) starved cell V, vacuole LG, lipid granule ER, endoplasmic reticulum CW, cell wall M, mitochondrion S, spindle pole SM, spindle microtubules N, nucleus NO, nucleolus, (b) Synaptonemal complex (SX) and development of polycomplex body (PB) along with division of spindle pole body in (c). (d) First meiotic division which is completed in (e). (f) Prepararation for meiosis II. (g) Enlargement of prospore wall, culminating in enclosure of separate haploid nuclei (h). (i) Spore coat (SC) materials produced and deposited, giving rise to the distinct outer spore coat (OSC) seen in the completed spores of the mature ascus (j). Reproduced from the review by Dickinson (1988) with permission from Blackwell Science Ltd.

Maguire MP, Paredes AM, Riess RW 1991 The desynaptic mutant of maize as a combined defect of synaptonemal complex and chiasma maintenance. Genome 34 879-887 May GS, McGoldrick CA, Holt CL, Denison SH 1992 The bimB3 mutation of Aspergillus nidulans uncouples DNA replication from the completion of mitosis. J Biol Chem 267 15737-15743... 

Cawood, A.D. and Breckon, G. (1983). Synaptonemal complexes as indicators of induced structural change in chromosomes after irradiation of spermatogonia. Mutation Res. 122 149-154. 

Upper Left A pair of mitotic sister chromatids in a section stained with an antibody to topoisomerase II. Notice that the two chromatids are coiled with opposite helical handedness. Lower Left Meiotic chromosomes of a lily at the pachytene stage in which sister chromatids are connected along their length in a synaptonemal complex. From Kleckner, N. (1996) Proc. Natl. Acad, Sci U.S.A. 93, 8167-8174... 

During the prophase of the first meiotic division (meiosis I) two homologous pairs of partially "condensed" chromosomes must find each other and pair with appropriate orientation. A protein in the telomeres of the chromosomes seems to be involved.269 277 The key structure in meiotic crossing-over is the ribbonlike synaptonemal complex formed by the pairs of homologous chroma fids.271/278 2791 This complex, in which a proteinaceous core or axial element separates the greatly extended chromatid pairs (Fig. 26-13), is fully formed in the pachytene stage of meiosis. Formation of the synaptonemal complex is preceded by development of a few double-stranded breaks in... 

Figure 26-13 Synaptonemal complexes. (A) Aligned pairs of homologous chromatids lying 0.4 pm apart in Allium cepa. Arrows indicate "recombination nodules" which may be involved in initiating formation of crossovers. Portions of meiotic chromosomes of lily are shown at successive stages (B) Pachytene. (C) Portion of diplotene nucleus. (D) A bivalent at diplo-tene. (E) Two bivalents at diakinesis. Pairs of sister chromatids are coiled with appropriate handedness. (F) Sister chromatid cores are far apart in preparation for separation. A chiasma is present between the two central strands. (B) through (F) courtesy of Stephen Stack.279,279d (G) Pair of sister chromatids coiled with opposite handedness at metaphase. These are immun-ostained with anti-topoisomerase II antibodies. From Boy de la Tour and Laemmli.280 Courtesy of U. K. Laemmli.

Cells of patients with Bloom syndrome (BS) have many chromosome breaks and a high frequency of sister chromatid exchanges, perhaps in an effort to correct these breaks. The body is small but well-proportioned.kk A somewhat similar disease, the Werner syndrome (WS), is associated with premature aging.11 The Bloom s protein BLM and the WS gene product WRN are both helicases related to E.coli RecQ. Protein BLM colocalizes with replication protein A as discrete foci in the meiotic synaptonemal complex.1 3 Protein WRN also seems to be associated with DNA replication. Defects... 

Egel-Mitani M, Olson LW, Egel R Meiosis in Aspergillus nidulans Another example for lacking synaptonemal complexes in the absence of crossover interference. Hereditas 1982 97 179-187. 

Schmekel. K., Wahrman, J., Skoglund, U.. and Daneholt, B. (1993a). The central region of the synaptonemal complex in Blaps cribrosa studied by electron microscope tomography. Chromosoma 102,669-681. 

Structural Analysis of Meiotic Chromosomes and Synaptonemal Complexes in Higher Vertebrates ... 

Definitions and Dimensions of the Synaptonemal Complex II. Selection and Handling of Materials... 

V. Spreading and Drying-Down Methods for Synaptonemal Complexes... 

C. Procedure for Microspreads of Synaptonemal Complexes from Human and... 

D. Drying-Down Techniques for Synaptonemal Complexes VI. Methods for Recombination Nodules... 

The synaptonemal complex, a flattened, ribbonlike structure usually formed by three parallel components (two lateral elements and a central element), is found along the axes of bivalents during meiotic prophase (Fig. 1). Measurements of SC dimensions in different species have been compiled by Westergaard and von Wettstein (1972). It is generally accepted that the width of the ribbonlike SC is quite constant, about 0.2 pm (von Wettstein et al., 1984). This regularity is due to the constancy of the central region width, about 100 nm in a wide... 

Albini, S., and Jones, G. (1988). Synaptonemal complex spreading in Allium cepa and Allium fistulosum. II. Pachytene observations The SC karyotype and the correspondence of late recombination nodules and chiasmata. Genome 30, 399-410. 

Croft, J. A., and Jones, G. H. (1986). Surface spreading of synaptonemal complexes in locusts. 1. Pachytene observations. Chromosoma 93, 483-488. 

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