Recombination nodule

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.

Croft, J.A. and Jones, C.H. (1989) Meiosis in Mesostoma ehrenbergii ehrenbergii. iv. Recombination nodules in spermatocytes and a test of the correspondence of late recombination nodules and chiasmata. Genetics 121, 255-262. 

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

B. Method for Recombination Nodules from Avian Oocytes... 

C. Silver Staining of Recombination Nodules from Plants... 

The recombination nodules (RNs) were recognized as definite structures associated with SCs in Drosophila oocytes (Carpenter, 1975). Data on RNs continue to be accumulated (Rahn and Solari, 1986 Stack et al., 1989 Zickler et al., 1992 Sherman and Stack, 1995). 

Fig. 1 Schematic drawing of the SC components. LE, Lateral element CE, central element TF, transverse libers RN. recombination nodule CHR, chromatin loops attached to the lateral elements.

Fig. 2 Electron micrograph of a microspread mouse spermatocyte, stained with phosphotungstic acid. The axis of the X and Y chromosomes show a short synaptic region in the lower part of the figure. A nucleolar body (asterisk) is close to the XY pair. The autosomal bivalent (up) shows a recombination nodule (arrowhead). xSOOO.

Staining with PTA. This procedure leads to a substantial amount of information on SCs (kinetochores, LEs, attachment plaques) and on recombination nodules. Some weaknesses of PTA staining are the variability in the degree of staining, low contrast in the EM, and the requirement for fresh spreads. 

Recombination nodules are the most variable structures associated with SCs. For unknown reasons nodules from some vertebrate species, are not readily apparent, whereas in other species, such as in humans, RNs may be conspicuous... 

Fig. 4 (a) Thin section of a human spermatocyte nucleus showing an SC piece with a recombination nodule (arrowhead). Uranyl acetate and lead citrate staining X45.000. (b) Microspread human spermatocyte showing three SCs with recombination nodules (arrowheads) x 14,000. 

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. 

Carpenter, A. T. C. (1975). Electron microscopy of meiosis in Drosophila melanogaster females. II. The recombination nodule—A recombination associated structure at pachytene Proc. Natl. Acad. Sci. U.S.A. 72, 3186-3189. 

Glamann, J. (1986). Crossing over in the male mouse as analysed by recombination nodules and bars. Carlsberg Res. Commiin. 51, 14.1-162. 

Rahn, M. 1 and Solari, A. J. (1986). Recombination nodules in the oocytes of the chicken, Gallus domesticus. Cytogenet. Cell Genet. 43, 187-193. 

Sherman, J. D., and Stack, S. M. (1995). Two-dimensional spreads of synaptonemal complexes from solanaceous plants. VI. High-rcsolution recombination nodule map for tomato (Lycopersicon esculentum). Genetics 141, 683-708. 

Zickler, D., Moreau, P. J. F., Huynh, A. D., and Slezec, A. (1992). Correlation between pairing initiation sites, recombination nodules and meiotic recombination in Sordaria macrospora. Genetics 132, 135 148. 

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