Presence of abnormal synaptonemal complexes in heterothallic species of Neurospora

Genome ◽  
1988 ◽  
Vol 30 (5) ◽  
pp. 697-709 ◽  
Author(s):  
Maja Bojko
Keyword(s):  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Low Frequency ◽  
Chiasma Formation ◽  
Lateral Component ◽  
Late Pachytene ◽  
Synaptonemal Complexes ◽  
Neurospora Intermedia ◽  
Heterothallic Species ◽  
Type Strains

Synaptonemal complex abnormalities are frequent in reconstructed meiotic prophase nuclei of Neurospora crassa and Neurospora intermedia. Three kinds of synaptonemal complex anomalies were seen: lateral component splits, lateral component junctions, and multiple complexes. The anomalies apparently are formed during or after the pairing process, as they were not seen in the largely unpaired early zygotene chromosomes. Their presence at all the other substages from mid-zygotene to late pachytene indicates that they are not eliminated before the synaptonemal complex decomposes at diplotene. Abnormal synaptonemal complexes were seen in all 19 crosses of N. crassa and N. intermedia that were examined, including matings between standard laboratory strains, inversions, Spore killers, and strains collected from nature. The frequency of affected nuclei and degree of abnormality within a nucleus varied in different matings. No abnormalities were present in the homothallic species Neurospora africana and Neurospora terricola. Structural chromosome aberrations, introgression, and heterozygosity have been eliminated as causes for pairing disorder. The abnormal synaptonemal complexes seemingly do not interfere with normal ascus development and ascospore formation. The affected nuclei are not aborted during meiotic prophase, nor are they eliminated by abortion of mature asci. The abnormal meiocytes do not lead to aneuploidy, as judged by the low frequency of white ascospores in crosses between wild type strains that have many abnormalities. Thus, the abnormal synatonemal complexes do not appear to prevent chiasma formation between homologues.Key words: Neurospora, meiosis, synaptonemal complex.

Elimination of multivalents during meiotic prophase in Scilla autumnalis. I. Diploid and triploid

Genome ◽  
1988 ◽  
Vol 30 (6) ◽  
pp. 930-939 ◽  
Author(s):  
J. White ◽  
G. Jenkins ◽  
J. S. Parker
Keyword(s):  
Meiotic Prophase ◽  
Three Dimensional ◽  
Low Frequency ◽  
Chiasma Formation ◽  
Root Tip ◽  
Synaptonemal Complexes ◽  
Dimensional Reconstruction ◽  
Scilla Autumnalis ◽  
Surface Spreading ◽  
Pairing Behaviour

The ultrastructure and pairing behaviour of the chromosomes of two diploid cytotypes and a triploid of Scilla autumnalis were investigated using the techniques of three-dimensional reconstruction from serial electron micrographs and whole-mount surface spreading of synaptonemal complexes. The diploids, designated AA and B7B7, have karyotypes that are virtually identical in appearance at mitotic metaphase but differ in length by 47% and in DNA content by 66%. All the chromosomes were identified during meiotic prophase in both diploids, enabling construction of accurate karyotypes, which were the same as those derived from root tip metaphases. Chromosome pairing was largely regular with very few structural chromosome rearrangements. These two observations permitted confident interpretations of multivalent configurations observed in polyploids containing multiples of the A and B7 genomes. In the triploid (AB7B7) during meiotic prophase lateral components are associated in groups of three, either as trivalents with several exchanges of pairing partners, or as bivalents and univalents in close alignment. The overall difference in length between A and B7 chromosomes is close to expected, but varies to some degree depending on the extent of pairing between the two chromosome types. Most of the synaptonemal complexes between A and B7 homoeologues are ineffective in terms of chiasma formation, as revealed by the low frequency of multivalents and heteromorphic bivalents at metaphase I. In other words, there is an elimination of multivalents during meiotic prophase in the triploid.Key words: Scilla autumnalis, synaptonemal complex, multivalents, elimination.

scholarly journals Meiotic cohesin REC8 marks the axial elements of rat synaptonemal complexes before cohesins SMC1β and SMC3

2003 ◽  
Vol 160 (5) ◽  
pp. 657-670 ◽  
Author(s):  
Maureen Eijpe ◽  
Hildo Offenberg ◽  
Rolf Jessberger ◽  
Ekaterina Revenkova ◽  
Christa Heyting
Keyword(s):  
Synaptonemal Complex ◽  
Sister Chromatid ◽  
Meiotic Prophase ◽  
S Phase ◽  
Synaptonemal Complexes ◽  
Sister Chromatids ◽  
Chromatid Cohesion ◽  
Axial Element ◽  
Striking Contrast ◽  
Metaphase I

In meiotic prophase, the sister chromatids of each chromosome develop a common axial element (AE) that is integrated into the synaptonemal complex (SC). We analyzed the incorporation of sister chromatid cohesion proteins (cohesins) and other AE components into AEs. Meiotic cohesin REC8 appeared shortly before premeiotic S phase in the nucleus and formed AE-like structures (REC8-AEs) from premeiotic S phase on. Subsequently, meiotic cohesin SMC1β, cohesin SMC3, and AE proteins SCP2 and SCP3 formed dots along REC8-AEs, which extended and fused until they lined REC8-AEs along their length. In metaphase I, SMC1β, SMC3, SCP2, and SCP3 disappeared from the chromosome arms and accumulated around the centromeres, where they stayed until anaphase II. In striking contrast, REC8 persisted along the chromosome arms until anaphase I and near the centromeres until anaphase II. We propose that REC8 provides a basis for AE formation and that the first steps in AE assembly do not require SMC1β, SMC3, SCP2, and SCP3. Furthermore, SMC1β, SMC3, SCP2, and SCP3 cannot provide arm cohesion during metaphase I. We propose that REC8 then provides cohesion. RAD51 and/or DMC1 coimmunoprecipitates with REC8, suggesting that REC8 may also provide a basis for assembly of recombination complexes.

Morphological and temporal sequence of meiotic prophase development at puberty in the male mouse

1984 ◽  
Vol 65 (1) ◽  
pp. 249-263
Author(s):  
P. Goetz ◽  
A.C. Chandley ◽  
R.M. Speed
Keyword(s):  
Synaptonemal Complex ◽  
Adult Male ◽  
Meiotic Prophase ◽  
Male Mouse ◽  
Late Pachytene ◽  
Diplotene Stage ◽  
Y Chromosomes ◽  
Correct Sequence ◽  
Xy Bivalent ◽  
Morphological Detail

The correct sequence of meiotic prophase development in the male mouse has been established by the use of pubertal males. The first wave of spermatogenesis at this time provides a unique opportunity to study progressive meiotic development in a direct way. Air-dried and micro-spread analyses have been carried out. Temporal and morphological progression at this time is entirely consistent with that occurring in the later waves of meiosis of the adult male. Morphological detail shows delayed pairing of the X and Y chromosomes relative to the autosomes. The longest XY synaptonemal complex is seen in early pachytene cells, occupying up to 72% of the length of the Y and 22% of the length of the X axis. By late pachytene, end-to-end pairing in the XY bivalent is established, the autosomal axes remaining fully paired. Desynapsis of the autosomes commences at early diplotene. A ‘diffuse’ diplotene stage in the male, comparable to the dictyate stage of the female, could not be found. Marked lengthening of the XY and autosomal axes did, however, occur through the diplotene stage.

An experimental analysis of bivalent interlocking in spermatocytes of the new Triturus vulgaris

1979 ◽  
Vol 37 (1) ◽  
pp. 125-141
Author(s):  
H.G. Callan ◽  
S.M. Pearce
Keyword(s):  
Heat Shock ◽  
Synaptonemal Complex ◽  
Nuclear Membrane ◽  
Experimental Analysis ◽  
Chiasma Frequency ◽  
Chiasma Formation ◽  
Meiotic Metaphase ◽  
Frequency Of Occurrence ◽  
Late Pachytene ◽  
Triturus Vulgaris

Interlocked bivalents at 1st meiotic metaphase are relatively uncommon in spermatocytes of the newt Triturus vulgaris, but their frequency of occurrence can be significantly increased by subjecting newts to a 24-h heat shock. Newt spermatocytes are sensitive to a heart shock at any stage between the end of premeiotic S and mid to late pachytene. The heat shock does not cause evidence desynapsis, nor does it significantly affect chiasma frequency; therefore the interlocked condition induced in spermatocytes which were subjected to a heat shock when they were in zygotene or pachytene is unlikely to be a consequence of synaptic trapping. By way of explanation it is suggested that a heat shock may cause telomers to detach from the nuclear membrane, or from the synaptonemal complex where the latter is attached to the membrane, thus allowing non-homologous chromonemata to become interwined before chiasmata have formed. If this explanation is valid, it is then further suggested that the recombination process which results in chiasma formation probably takes place in chromosomal regions lying outside the synaptonemal complex, rather than inside, between its 2 lateral elements.

Synaptonemal complex formation and metaphase I configuration patterns in a translocation heterozygote of rye (Secale cereale)

Genome ◽  
1989 ◽  
Vol 32 (1) ◽  
pp. 72-81 ◽  
Author(s):  
J. H. de Jong ◽  
J. van Eden ◽  
J. Sybenga
Keyword(s):  
Complex Formation ◽  
Synaptonemal Complex ◽  
Secale Cereale ◽  
Chiasma Formation ◽  
Terminal Segment ◽  
Pachytene Nucleus ◽  
Synaptonemal Complexes ◽  
Synaptonemal Complex Formation ◽  
Chromosome 1R ◽  
Metaphase I

Four rye plants heterozygous for translocation 248, involving chromosomes 1R and 6R, were used for a comparative study of synaptonemal complex formation at midprophase I and chromosome configurations at metaphase I. Synaptonemal complexes were obtained with a cell-spreading technique and studied with electron microscopy. The total length of the synaptonemal complexes in the 28 analyzable pachytene nuclei varied considerably, both within and among plants. The variation of synaptonemal complex lengths of the bivalents in a nucleus was partly stage dependent; i.e., it was greater at early than at late pachytene. In all but one pachytene nucleus, pairing in the quadrivalent was regular, and the four pairing arms were usually easy to identify. Most noticeable was the variation of pairing saturation at the breakpoint of the quadrivalent. Pairing in the breakpoint region was delayed with respect to the pairing in the bivalents. Variation in the arm lengths of the quadrivalent was the result of incomplete and nonhomologous pairing at the breakpoint as well as differential contraction rates among chromosome segments. It was shown that the completion of delayed pairing throughout pachytene is mainly long-arm pairing. The actual breakpoint was therefore not in the middle of the unpaired segments, but more distal. The analysis of metaphase I nuclei revealed that chiasma frequency in this material was higher than in similar material used in former studies. When one of the translocation segments lacked a chiasma, this was in most cases the short translocated segment 1RS, the terminal segment of the satellite of chromosome 1R. Positive chiasma interference was demonstrated between the interstitial and exchanged segment in 1RS. This agreed with the observation of a negative correlation in extent of pairing between these two segments. Other interference phenomena, which have been described for this translocation in other material, remained undetected because of lack of variation in chiasma formation owing to high chiasma frequency.Key words: Secale cereale, meiosis, translocation, synaptonemal complex, metaphase I.

scholarly journals Analysis of the synaptonemal complex of the nine-banded armadillo, Dasypus novemcinctus

2000 ◽  
Vol 23 (3) ◽  
pp. 613-616 ◽  
Author(s):  
Márcia Denise da Paixão Scavone ◽  
Claudio Oliveira ◽  
Eduardo Bagagli ◽  
Fausto Foresti
Keyword(s):  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Dasypus Novemcinctus ◽  
Late Pachytene ◽  
Chromosome Synapsis ◽  
Structure Changes ◽  
Y Chromosomes ◽  
Bivalent Chromosome ◽  
In Cells

The synaptonemal complex (SC) of three specimens of the nine-banded armadillo (Dasypus novemcinctus) was analyzed. Thirty-two bivalents (2n = 64) were observed, 31 of them being autosomes and one an XY sexual bivalent. Chromosome synapsis processes and nucleolus structure changes were analyzed in zygotene and pachytene cells, allowing a detailed description of the beginning of meiotic prophase in this species. There was complete synapsis of X and Y chromosomes. Some abnormalities in SC were observed in cells during zygotene and at the beginning of pachytene, but not in cells in the middle and late pachytene, suggesting the occurrence of synaptic adjustments in their SC.

Chromosomal pairing in deer mice heterozygous for the presence of heterochromatic short arms

Genome ◽  
1988 ◽  
Vol 30 (1) ◽  
pp. 44-47 ◽  
Author(s):  
David W. Hale ◽  
Ira F. Greenbaum
Keyword(s):  
Low Frequency ◽  
Chromosomal Polymorphism ◽  
Chromosome 8 ◽  
Deer Mice ◽  
Chromosome 4 ◽  
Late Zygotene ◽  
Late Pachytene ◽  
Synaptonemal Complexes ◽  
Adjustment Mechanism ◽  
Chromosomal Pairing

The pattern of chromosomal pairing was analyzed in male deer mice (Peromyscus maniculatus and Peromyscus sitkensis) heterozygous for the presence of heterochromatic short arms. G- and C-banding of somatic metaphases indicated that the presence of heterochromatic short arms increased the length of chromosome 4 by 15% in P. sitkensis and that of chromosome 8 by 9% in P. maniculatus. Analysis of silver-stained late zygotene and early pachytene nuclei revealed a low frequency of unequal axial lengths in the synaptonemal complexes corresponding to the heteromorphic bivalents. All mid- and late pachytene nuclei, however, exhibited fully paired synaptonemal complexes with equalized axial lengths. These observations suggest the existence of an adjustment mechanism which functions to equalize the lengths of the two axes of the heteromorphic synaptonemal complex.Key words: synaptonemal complex, Peromyscus, heterochromatin, chromosomal polymorphism, synaptic adjustment.

HSP70-2 is required for desynapsis of synaptonemal complexes during meiotic prophase in juvenile and adult mouse spermatocytes

Development ◽  
1997 ◽  
Vol 124 (22) ◽  
pp. 4595-4603 ◽  
Author(s):  
D.J. Dix ◽  
J.W. Allen ◽  
B.W. Collins ◽  
P. Poorman-Allen ◽  
C. Mori ◽  
...  
Keyword(s):  
Meiotic Prophase ◽  
Spermatogenic Cells ◽  
Targeted Disruption ◽  
Late Pachytene ◽  
Homologous Chromosomes ◽  
Synaptonemal Complexes ◽  
Tissue Sections ◽  
Adult Mice ◽  
Pachytene Spermatocytes ◽  
Prophase Of Meiosis

Spermatogenic cells synthesize a unique 70-kDa heat shock protein (HSP70-2) during prophase of meiosis I, and targeted disruption of the Hsp70-2 gene has shown that this protein is required for spermatogenic cell differentiation in adult mice. HSP70-2 is associated with synaptonemal complexes formed between paired homologous chromosomes during meiotic prophase. The present study focuses on the nearly synchronous first wave of spermatogenesis in 12- to 28-day old juvenile mice to determine more precisely when HSP70-2 is required and what meiotic processes are affected by its absence. Spermatogenesis in homozygous mutant mice (Hsp70-2[−/−]) proceeded normally until day 15 when increasing numbers of pachytene spermatocytes became apoptotic and differentiation of cells beyond the pachytene stage began to falter. Synaptonemal complexes assembled in Hsp70-2(−/−) mice and spermatocytes developed through the final pachytene substage. However, synaptonemal complexes failed to desynapse and normal diplotene spermatocytes were not observed. Metaphase spermatocytes were not seen in tissue sections from testes of Hsp70-2(−/−) mice, and expression of mRNAs and antigens characteristic of late pachytene spermatocytes (e.g., cyclin A1) and development of spermatids did not occur. Thus, HSP70-2 is required for synaptonemal complex desynapsis, and its absence severely impairs the transition of spermatogenic cells through the late meiotic stages and results in apoptosis beginning with the first wave of germ cell development in juvenile mice.

Identical megabase transgenes on mouse chromosomes 3 and 4 do not promote ectopic pairing or synapsis at meiosis

Genome ◽  
1997 ◽  
Vol 40 (5) ◽  
pp. 770-773 ◽  
Author(s):  
P. B. Moens ◽  
J. A. M. Heddle ◽  
B. Spyropoulos ◽  
H. H. Q. Heng
Keyword(s):  
In Situ Hybridization ◽  
Fluorescence In Situ Hybridization ◽  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Nuclear Volume ◽  
Dna Interactions ◽  
Synaptonemal Complexes ◽  
Meiotic Chromosomes ◽  
Ectopic Pairing

To investigate ectopic interactions at the chromatin level, we examined the meiotic organization of 1–2 mb phage λ transgenes on mouse chromosomes 3 and 4 by fluorescence in situ hybridization in combination with immunocytology of meiotic chromosomes. At early meiotic prophase, the transgenes are sufficiently dispersed in the nuclear volume to permit potential DNA–DNA interactions, but no synaptonemal complexes form between the sites of transgenes residing on different chromosomes. At later stages, when the chromatin is more condensed, the transgenes on different chromosomes are not preferentially associated as they are when they are on the same chromosome. At diplotene and metaphase I, no formations were observed that could be interpreted as reciprocal crossovers or chiasmata between the transgenes located on chromosomes 3 and 4. It appears that in normal fertile mice, a 1- to 2-mb homology is insufficient to initiate synapsis between nonhomologs, and it is concluded that homology is assessed within the broader context of the chromosome to initiate synapsis at meiotic prophase.Key words: transgenes, ectopic pairing, meiosis, synaptonemal complex, immunocytology, FISH.

Elimination of multivalents during meiotic prophase in Scilla autumnalis. II. Tetraploid

Genome ◽  
1988 ◽  
Vol 30 (6) ◽  
pp. 940-946 ◽  
Author(s):  
G. Jenkins ◽  
J. White ◽  
J. S. Parker
Keyword(s):  
Synaptonemal Complex ◽  
Meiotic Prophase ◽  
Chiasma Formation ◽  
Serial Sections ◽  
Genomic Constitution ◽  
Homologous Chromosomes ◽  
Multivalent Formation ◽  
Whole Mount ◽  
Scilla Autumnalis ◽  
Pairing Behaviour

The pairing behaviour of chromosomes during meiotic prophase in two Scilla autumnalis tetraploids was investigated by observing synaptonemal complexes from serial sections and whole-mount surface spreads. In one of the tetraploids with the genomic constitution AAB7B7 pairing at first metaphase of meiosis is restricted to homologous chromosomes and only bivalents appear. In the second tetraploid, AB7B7B7, some multivalents are found at first metaphase, but most of the configurations are bivalent. The bivalents, however, result from chiasma formation between homoeologous as well as homologous chromosomes. Both tetraploids show extensive multivalent formation at zygotene. The transformation of these multivalents to bivalents is described and interpreted in the two tetraploid forms.Key words: Scilla autumnalis, synaptonemal complex, multivalents, elimination, polyploids.

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