Meiotic association between the XY chromosomes and unpaired autosomal elements as a cause of human male sterility

Intimate association between autosomal translocation trivalents and XY bivalents at pachytene was observed in a majority of cells of two men ascertained through primary sterility and found to be heterozygous for a 14;21 Robertsonian translocation. The association, studied by light and electron microscopy of spread first spermatocytes, was between the unpaired short arms of the normal chromosomes of the translocation trivalent and the differential axes of the XY chromosomes. In a minority of cells, this contact was not established, or not maintained, as alternative combinations between the elements available for non-homologous pairing were realized. Following a suggestion of Lifschytz and Lindsley (1972), sterility in these patients was attributed to spermatogenic arrest caused by physical contact of sex chromosomes with autosomal material and consequent interference with the normal metabolism of the sex chromosomes. Autosomal aberrations and polymorphisms, which lead to the presence of unpaired segments at meiosis, may thus play a critical role in a general mechanism of chromosomally-derived male sterility. It is proposed that such a mechanism may also be instrumental in the initiation of reproductive barriers in nature.     

Chromosome aberrations in F1 from irradiated male mice studied by their synaptonemal complexes

Possible implications of surface-spread synaptonemal complex (SC) karyotyping in analysing the causes of sterility of F1 from irradiated male mice are demonstrated in this work. After irradiation by 137Cs gamma-rays at a dose of 5 Gy the males were mated to unirradiated females and genetic analysis of fertility in the F1 progeny was carried out. Males with abnormal fertility were examined for the presence of chromosome aberrations in diakinesis-metaphase I and in pachytene by the method of surface-spread SC karyotyping. In most cases, SC karyotyping provides additional information and permits the detection and analysis of aberrations that are not revealed in diakinesis. Two reciprocal translocations, one X autosomal and one nonreciprocal translocation were discovered in five F1 males studied. It is concluded that the method is efficient in detecting translocations in pachytene in partially fertile F1 hybrids of irradiated and normal mice.     

Effect of estradiol treatment on male mice synaptonemal complexes: difference of sensitivity between neonates and adults

The effect of estrogen on pachytene spermatocytes was studied with the assistance of the synaptonemal complex analysis under electron microscopy. Male NMRI mice were injected with estradiol benzoate from birth onwards and allotted to different groups according to the dose administered: 1) three injections of either 12.5 g or 25 g or 50 g on d0, d5 and d10; 2) single injections of 50 g either on d0 or on d5 or on d10; 3) double injections of 50 g on d0 and d5; and 4) daily injection at the dose of 0.5 g/g BW from d0 to d27. Animals were sacrificed on day 28, 60 and 90. Adult male mice were treated daily with E2B (0.5 g/g BW) for one (from d30 to d60) or two months (from d30 up to d90) to test the age-related sensitivity to estrogen. A number of different SC anomalies were observed at each harvest time. Among all the anomalies, pairing failure (asynapsis) was predominant followed in decreasing order of importance by SC breakage (fragmentation of SCs), and heterotelomeric associations resulting either in quadrivalent-like figures or in trivalents. In E2B treated neonates the frequency of SC anomalies, which was less than 2% in controls, varied from 3.6 to 27% of pachytene cells regardless of the harvest time. In E2B treated adult mice, the SC anomalies were rare (<4%), but significantly different from controls in which the frequency of SC aberrations did not exceed 1% of pachytene cells. The prevalence of anomalies appeared to be independent of the TW decrease. Our observations suggest that estrogens act indirectly on SCs. Different mechanisms of action are discussed.Abbreviations BW body weight - E2B estradiol benzoate - d day - Gr(s) or gr(s) group(s) - LE(s) lateral element(s) - n number of examined mice - NAC number of abnormal cells - NPC number of cells at pachytene stage - SC(s) synaptonemal complex(es) - SD standard deviation - TW testicular weight     

Effect of estradiol treatment on male mice synaptonemal complexes: difference of sensitivity between neonates and adults.

The effect of estrogen on pachytene spermatocytes was studied with the assistance of the synaptonemal complex analysis under electron microscopy. Male NMRI mice were injected with estradiol benzoate from birth onwards and allotted to different groups according to the dose administered: 1) three injections of either 12.5 micrograms or 25 micrograms or 50 micrograms on d0, d5 and d10; 2) single injections of 50 micrograms either on d0 or on d5 or on d10; 3) double injections of 50 micrograms on d0 and d5; and 4) daily injection at the dose of 0.5 micrograms/g BW from d0 to d27. Animals were sacrificed on day 28, 60 and 90. Adult male mice were treated daily with E2B (0.5 micrograms/g BW) for one (from d30 to d60) or two months (from d30 up to d90) to test the age-related sensitivity to estrogen. A number of different SC anomalies were observed at each harvest time. Among all the anomalies, pairing failure (asynapsis) was predominant followed in decreasing order of importance by SC breakage (fragmentation of SCs), and heterotelomeric associations resulting either in quadrivalent-like figures or in trivalents. In E2B treated neonates the frequency of SC anomalies, which was less than 2% in controls, varied from 3.6 to 27% of pachytene cells regardless of the harvest time. In E2B treated adult mice, the SC anomalies were rare (< 4%), but significantly different from controls in which the frequency of SC aberrations did not exceed 1% of pachytene cells. The prevalence of anomalies appeared to be independent of the TW decrease. Our observations suggest that estrogens act indirectly on SCs. Different mechanisms of action are discussed.     

Three-dimensional architecture of chromosome fibres in the crane fly: co-oriented autosomal bivalents and amphitelic sex univalents during prometaphase

A technique for the fixation of cells during live observation (Nicklas et al. 1979) was used to investigate chromosomes which were moving at the time of fixation. Chromosome fibres were reconstructed by tracking their microtubules in longitudinal serial sections. A considerable proportion of non-kinetochoric microtubules (free microtubules, fMTs) is skewed with respect to the fibre axis. These skew fMTs contribute to the degree of disorder. It was found that the difference in the relative proportion of skew fMTs between active fibres (oriented in the direction of movement) and passive fibres (oriented backwards) is significantly correlated with the chromosome velocity (correlation coefficient r=0.796, P=0.01). It can be concluded that the pulling force generated in the chromosome fibre is a function of skew fMTs.     

Genetics and evolution of hybrid male sterility in house mice

Comparative genetic mapping provides insights into the evolution of the reproductive barriers that separate closely related species. This approach has been used to document the accumulation of reproductive incompatibilities over time, but has only been applied to a few taxa. House mice offer a powerful system to reconstruct the evolution of reproductive isolation between multiple subspecies pairs. However, studies of the primary reproductive barrier in house mice-hybrid male sterility-have been restricted to a single subspecies pair: Mus musculus musculus and Mus musculus domesticus. To provide a more complete characterization of reproductive isolation in house mice, we conducted an F(2) intercross between wild-derived inbred strains from Mus musculus castaneus and M. m. domesticus. We identified autosomal and X-linked QTL associated with a range of hybrid male sterility phenotypes, including testis weight, sperm density, and sperm morphology. The pseudoautosomal region (PAR) was strongly associated with hybrid sterility phenotypes when heterozygous. We compared QTL found in this cross with QTL identified in a previous F(2) intercross between M. m. musculus and M. m. domesticus and found three shared autosomal QTL. Most QTL were not shared, demonstrating that the genetic basis of hybrid male sterility largely differs between these closely related subspecies pairs. These results lay the groundwork for identifying genes responsible for the early stages of speciation in house mice.     

Nonhomologous synapsis of the sex chromosomes in the heteromorphic bivalents of two X-7 translocations in male mice: R5 and R6

Electron microscopy of pachytene nuclei of mice heterozygous for either of two reciprocal X-7 translocations (R5 or R6) revealed a high frequency of heteromorphic bivalents involving the translocated chromosomes. In both translocations the break was in the proximal third of the 7 and the distal third of the X, but the R5 breaks were closer to the 7 centromere and X telomere than the R6 breaks. In both translocations the 7 frequently synapsed nonhomologously with the X7. In R5 the part of the X to which the 7 synapsed may include a region that synapses with the Y in normal mice. However, in R6 the 7 synapsed with a portion of the X that never synapses with the Y (Synapsis was clearl in the differentiated region). In both translocations the Y synapsed maximally with the X portion of the 7X in those nuclei in which there was nonhomologous synapsis of the 7 with the X7. The Y occasionally synapsed nonhomologously with the 7 portion of the 7X. The behavior of the bivalents suggests that the autosomal portions of the 7X and X7 may alter the behavior of the sex-chromosome portions. Both the nonhomologous synapsis of the Y with the 7X and the timing of events during pachytene have led us to question the homology between the X and Y in this species.     

Cadmium toxicity: a possible cause of male infertility in Nigeria

Serum and seminal plasma cadmium (Cd) concentrations were estimated by atomic absorption spectrophotometry in 60 infertile adult male Nigerians (40 oligozoospermics and 20 azoospermics). The results were compared with Cd level in 40 normozoospermic subjects (matched age, with proven evidence of fertility). The relationship between Cd levels and spermatograms or the hypothalamic-pituitary-gonadal (HPG) -axis was investigated by correlating serum and seminal plasma Cd levels with semen characteristics and hormone levels. The seminal plasma Cd level was significantly higher than those of serum in all studied groups (p<0.001). The serum and seminal plasma Cd levels were increased (p<0.001) in azoospermics in comparison to oligozoospermic and control subjects. A significant negative correlation was observed between serum Cd level and all examined biophysical semen characteristics except sperm volume. A positive correlation was also observed between seminal plasma Cd and FSH. Results of the study for the first time implicate cadmium as a cause of infertility in male Nigerians as well as extend and support previous findings concerning cadmium toxicity and male infertility. The strong deleterious effect of cadmium on spermatogenesis may be due to the systemic and cellular toxicity. A possible relationship between this element and the HPG axis is also suggested.     

Sex bodies and synaptonemal complexes of Balb/C mice: antioxidant intervention of oxyradical insult

Spermatogenesis is inhibited in Balb/C mice as a result of oxyradical insult. However, mammalian spermatocytes and synaptonemal complexes retain their structure and function after oxyradical insult due to protection afforded by the antioxidant vitamin E. Control groups were compared with experimental groups which were fed various vitamin E-deficient diets and subjected to varying times in an humidified 100% oxygen (hyperoxia) chamber. Measurements were made of sex body volume (SBV), nuclear envelope aberrations (NEA), and synaptonemal complex structure in spermatocytes during pachytene of meiosis prophase I. Changes in the volume of the sex body were positively correlated with increased oxyradical insult. The structure of the synaptonemal complex was not altered in any of the experimental groups which is a significant observation. It is suggested that vitamin E affords antioxidant protection and inhibits the alteration of membranes and sex chromosomes in mice during meiosis.     

The genetics of hybrid male sterility between the allopatric species pair Drosophila persimilis and D. pseudoobscura bogotana: dominant sterility alleles in collinear autosomal regions

F(1) hybrid male sterility is thought to result from interactions between loci on the X chromosome and dominant-acting loci on the autosomes. While X-linked loci that contribute to hybrid male sterility have been precisely localized in many animal taxa, their dominant autosomal interactors have been more difficult to localize precisely and/or have been shown to be of relatively smaller effect. Here, we identified and mapped at least four dominant autosomal factors contributing to hybrid male sterility in the allopatric species pair Drosophila persimilis and D. pseudoobscura bogotana. Using these results, we tested predictions of reduced recombination models of speciation. Consistent with these models, three of the four QTL associated with hybrid male sterility occur in collinear (uninverted) regions of these genomes. Furthermore, these QTL do not contribute significantly to hybrid male sterility in crosses between the sympatric species D. persimilis and D. pseudoobscura pseudoobscura. The autosomal loci identified in this study provide the basis for introgression mapping and, ultimately, for molecular cloning of interacting genes that contribute to F(1) hybrid sterility.     

Evaluation of the Stag3 gene and the synaptonemal complex in a rat model (as/as) for male infertility

Affected males (as/as) from the mutant TT rat strain are sterile due to spermatogenesis impairment with meiotic arrest at the pachytene stage. The as locus is on rat chromosome 12, in a region that shows conserved synteny to cM 74-94 on mouse chromosome 5. Stag3, a new member of the stromalin protein family, is expressed specifically in testis and associates to the synaptonemal complex. Mouse Stag3 gene has been assigned to cM 78 on chromosome 5. In this study, we have characterized the rat Stag3 gene and examined it as a candidate for male infertility in as/as rats. The rat Stag3 cDNA is 4181 nucleotides long, contains a highly polymorphic hexanucleotide repeat in the coding region, and encodes a 1256 amino acid protein with 93 and 77% sequence identity to mouse and human Stag3 proteins, respectively. No mutations or differences in size or abundance of Stag3 mRNA were detected between as/as and control rats, suggesting that Stag3 is not responsible for the aspermic phenotype. In addition, immunohistochemistry with antibodies against SCP1 and SPC3 proteins suggest that the synaptonemal complex structures are not primarily affected in these rats.     

Identification of aberrant chromosomes based on the morphometry of the synaptonemal complexes in a sterile male mouse

The synaptonemal complexes (SCs) of surface-spread spermatocytes of male mouse from the F1 progeny of a male exposed to a mutagen have been examined by electron microscopy. Nonreciprocal translocation was recognised in analysing configuration of SC. Electron microscope analysis revealed translocation in 100% pachytene spermatocytes and light microscope analysis of air-dried metaphase spermatocytes demonstrated this in 58% cells. Different types of association of X-chromosome with aberrant chromosomes were discovered in pachytene spermatocytes. Computer analysis of relative length of SCs permits to detect a nonreciprocal translocation from chromosome 4 to chromosome 16. The length of the translocated fragment was determined to be from 66 to 75% of the length of chromosome 4. It has been impossible to discover a telomere fragment of chromosome 16, because the break point of chromosome 16 is too close to the distal end.     

水稻两种细胞质雄性不育“三系”及其F1杂交种线粒体DNA的RFLP分析

对水稻BT型和WA型细胞质的雄性不育系,相应保持系和恢复系以及杂种的mtDNA用12个线粒体探针进行了RFLP分析,结果如下(1)BT型和WA型不育系的mtDNA在组织结构上存在差异;(2)不育系的mtDNA与其保持系间存在显著差异,推测mtDNA与水稻的cms有关;(3)atp9探针检测到WA型不育系与F1之间的多态性,Frag36探针检测到BT型不育系与F1之间的多态性,Frag9探针检测到WA型和BT型不育系与其F1之间的多态性,证明核恢复基因影响mtDNA的结构;(4)对mtDNA的结构变异与细胞质雄性不育的关系进行了分析与探讨.     

水稻两种细胞质雄性不育“三系”及其F1杂交种线粒体DNA的RFLP分析

对水稻BT型和WA型细胞质的雄性不育系,相应保持系和恢复系以及杂种的mtD-NA用12个线粒探针进行了RFLP分析,结果如下：（1）BT型和WA型不育系的mtDNA在组织结构上存在差异;（2）不育系的mtDNA与其保持系间存在显著差异,推测mtDNA与水稻的cms有关;（3）atp9探针检测到WA型不育系与F1之间的多态性,Frag36探针检测到BT型不育系与F1之间的多态性,Frag9探针检测到WA型和BT型不育系与其F1之间的多态性,证明核恢复基因影响mtDNA的结构;（4）对mtDNA的结构变异与细胞质雄性不育的关系进行了分析与探讨。     

Disruption of Ssp411 causes impaired sperm head formation and male sterility in mice

Background

We previously cloned the Ssp411 gene. We found that the Ssp411 protein is predominantly expressed in elongated spermatids in the rat testis in a stage-dependent manner. Although our findings strongly suggested that Ssp411 might play an important role in mammalian spermatogenesis, this hypothesis has not been studied.

Occurrence of synaptonemal complexes and recombination nodules in a meiotic race of Meloidogyne hapla and their absence in a mitotic race

The early prophase of the first maturation division of oocytes is compared in two races of Meloidogyne hapla Chitwood. Light microscopic analysis suggested that chromatin of both Race A (meiotic parthenogenetic; n=17) and Race B (mitotic parthenogenetic; 3n=45) behaves similarly during early stages of maturation of oocytes (Triantaphyllou, 1966). Electron microscopic analysis shows that synaptonemal complexes and recombination nodules are observed at pachytene in Race A, but are absent in corresponding oocytes of Race B. Cylindrical granular complexes present in the cytoplasm at prepachytene stages are intimately associated with the nucleus at pachytene in Race A, but are absent in Race B.Paper number 5599 of the Journal Series of the North Carolina Agricultural Experiment Station, Raleigh, North Carolina 27650     

Mapping of sex hormone receptors and their modulators along the nephron of male and female mice

Renal functions are regulated by steroid sex hormones, but the exhaustive identification of their receptors along the nephron is still lacking. Here, we have localized all known nuclear or membrane-bound sex hormone receptors and some of their activators along the nephron of male and female mice. Almost all receptors are present in male and female kidney, some of them having very restricted localization. Only one gene tested among 11 (ARA54) exhibits a gender difference in the level of its expression. This first “renal map” of sex steroid receptor expression may serve as a pre-requisite for investigating the role of these hormones on kidney functions.