X chromosome constitution and the human female phenotype

Summary The correlations of abnormal X chromosome constitutions and the resulting phenotypes in the human female are reviewed. The following hypotheses put forward to explain these correlations are discussed in detail: (1) The damage is done before X inactivation; (2) An effect is exerted between reactivation of the X chromosome(s) and meiosis in oocytes; (3) A recessive gene(s) in hemizygous condition might be expressed in the cases in which the same X is active in all cells; (4) A change in the number of presumed active regions on the inactive X chromosomes might have an effect; (5) A position effect, in that the region Xq13-q27 has to be intact in both X chromosomes to allow normal development, may be responsible; (6) An effect during the period when cells with different inactivation patterns compete is a probability; (7) The original X inactivation may be neither regular nor random.The conclusion reached is that the phenotypic effects of a specific X chromosome aberration may be simultaneously exerted through different pathways (Tables 1 and 2). Hypotheses (2), (4), (5), and (6) are considered probable. Hypothesis (3) has been discarded, and there is very little evidence for hypotheses (1) and (7).     

The effect of chromosome constitution on growth in culture of human spontaneous abortions

Summary The effect of chromosome constitution on growth in culture was evaluated by comparing the length of time in culture until cytogenetic analysis among chromosomally normal and abnormal spontaneous abortions. We observed a significant effect of both tissue type and cell type, but not chromosome constitution, on the rate of growth of the cultures.     

Frequency and distribution of chromosome abnormalities in human spermatozoa

This study reviews the frequency and distribution of numerical and structural chromosomal abnormalities in spermatozoa from normal men obtained by the human-hamster system and by multicolor-FISH analysis on decondensed sperm nuclei. Results from large sperm karyotyping series analyzed by chromosome banding techniques and results from multicolor FISH in sperm nuclei (of at least 10(4) spermatozoa per donor and per probe) were reviewed in order to establish baseline values of the sperm chromosome abnormalities in normal men. In karyotyping studies, the mean disomy frequency in human sperm is 0.03% for each of the autosomes, and 0.11% for the sex chromosomes, lower than those reported in sperm nuclei by FISH studies using a similar methodology (0.09% and 0.26%, respectively). Both types of studies coincide in that chromosome 21 and sex chromosomes have a greater tendency to suffer segregation errors than the rest of the autosomes. The mean incidence of diploidy, only available from multicolor FISH in sperm nuclei, is 0.19%. Inter-donor differences observed for disomy and diploidy frequencies among FISH studies of decondensed sperm nuclei using a similar methodology could reflect real differences among normal men, but they could also reflect the subjective application of the scoring criteria among laboratories. The mean frequency of structural aberrations in sperm karyotypes is 6.6%, including all chromosome types of abnormalities. Chromosome 9 shows a high susceptibility to be broken and 50% of the breakpoints are located in 9q, between the centromere and the 9qh+ region. Structural chromosome aberrations for chromosomes 1 and 9 have also been analyzed in human sperm nuclei by multicolor FISH. Unfortunately, this assay does not allow to determine the specific type of structural aberrations observed in sperm nuclei. An association between advancing donor age and increased frequency of numerical and structural chromosome abnormalities has been reported in spermatozoa of normal men.     

Radiation- and chemical-induced structural chromosome aberrations in human spermatozoa

An apoptotic phenotype induced by oxygen radicals or Bax expression has been observed in Saccharomyces cerevisiae yeast cells by electron and fluorescence microscopy. In this work, we analyzed DNA content and cellular morphology of S. cerevisiae after H(2)O(2) or UV treatment by TdT-mediated dUTP nick end labeling (TUNEL)-test and flow cytofluorimetry. A TUNEL-positive phenotype was observed in both cases, on the same samples a dose-dependent increase in the sub-G(1) population was pointed out by flow cytometry. Sub-G(1) cells were isolated by flow sorting and analyzed by electron microscopy. This population showed condensed chromatin in the nucleus and cell shrinking. This paper reports the first evidence of apoptosis in yeast cells induced by DNA damage after UV irradiation.     

Protein constitution of the chromosome axis

Diverse studies indicate that certain nonhistone proteins may be responsible for maintaining the integrity of the eukaryotic chromosomes. In view of their dispersal during nuclear division and their acknowledged role in gene expression, none of the nuclear matrix proteins can be regarded as integral proteins of the chromosome. Topoisomerase II, structural maintenance of chromosome (SMC) proteins and high-mobility-group (HMG) proteins exhibit characteristic enzymatic and mechanochemical roles as well as transitory association with chromosomes. Hence they may be regarded as accessory chromosome proteins. In contrast, certain high molecular weight synaptonemal complex proteins (SCPs) exhibit chemical and physical properties that suggest a structural role as the chromosome axis. It is proposed in an experimentally testable model that, in the minimal structure of a eukaryotic chromosome, the terminals of the loops of DNA-histone solenoids are constitutively affixed to chromosome axis proteins that have elastic properties.     

Specific staining of the human No. 1 chromosome in spermatozoa

Summary A new differential staining technique specific for the secondary constriction region of the human No. 1 chromosome makes it possible to study the transmission of this chromosome during mitosis and meiosis and to determine the meiotic non-disjunction frequency for chromosome No. 1 in ejaculated spermatozoa.

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Zusammenfassung Eine neue differentiale F?rbetechnik, die für die Sekund?rkonstriktion auf dem menschlichen Chromosom Nr. 1 spezifisch ist, erm?glicht es, die übertragung dieses Chromosoms w?hrend der Mitose und Meiose zu verfolgen und die meiotische Nondisjunktion-H?ufigkeit des Chromosomes Nr. 1 in ejaculierten Spermatozoen zu bestimmen.

     

Experimental alterations in the chromosome constitution of Sciara

Summary Using two reciprocal translocations between chromosomes X and IV in S. coprophila it has been possible to derive two kinds of aneuploid females. Both of the aneuploid complements are detrimental — one is lethal, the other may give rise to viable, fertile adults. Males with aneuploid somatic complements have not been obtained; three different aneuploid complements were tested but gave negative results. Males with euploid soma and aneuploid germ line have been produced in three separate instances; they are viable and fertile.Dedicated to Professor H. Bauer on the occasion of his sixtieth birthday.The studies reported here were supported by grant GB-42 from the National Science Foundation.     

Types of structural chromosome aberrations and their incidences in human spermatozoa X-irradiated in vitro

We studied the effects of in vitro X-irradiation on human sperm chromosomes, using our interspecific in vitro fertilization system between human spermatozoa and zona-free hamster oocytes. 28 semen samples from 5 healthy men were exposed to 0.23, 0.45, 0.91 and 1.82 Gy of X-rays. Totals of 2098 and 2862 spermatozoa were karyotyped in the control and the irradiated groups, respectively. The incidence of spermatozoa with X-ray-induced structural chromosome aberrations (Y) increased linearly with increasing dosage (D), being best expressed by the equation, Y = 0.08 + 34.52 D. The incidence of breakage-type aberrations was more than 9 times higher than that of exchange-type aberrations. Both of them showed linear dose-dependent increases, which were expressed by the regression lines, Y = -0.014 + 0.478 D and Y = -0.010 + 0.057 D, respectively. The incidence of chromosome-type aberrations was about 6 times higher than that of chromatid-type aberrations. Their dose-dependent increases were expressed by the regression lines, Y = -0.015 + 0.462 D and Y = -0.006 + 0.079 D, respectively. These results are discussed in relation to the previous data obtained with gamma-rays. The repair mechanism of X-ray-induced sperm DNA lesions is also discussed.     

The acrosome reaction in human spermatozoa

During gamete interaction, sperm acrosome reaction (AR) induced by oocyte investment is a prerequisite event for the spermatozoa to pass through the zona pellucida (ZP), fuse with and penetrate the oocyte. Progesterone (P4), secreted by cumulus cells, is an important cofactor for the occurrence of this exocytosis event. The AR results from the fusion between outer acrosomal and plasma membranes, leading to inner acrosomal membrane exposure. Binding of agonists, P4 or ZP3 glycoprotein, to plasma membrane sperm receptors activates intraspermatic signals and enzymatic pathways involved in the AR. Among the proteins or glycoproteins described as potential sperm receptors for ZP, Gi/Go protein-coupled and tyrosine kinase receptors have been described. Sperm receptors for P4 are poorly characterized, except a putative GABA(A)-like receptor. ZP- and P4-promoted AR is mediated by an obligatory intracellular calcium increase, appearing first at the acrosome equatorial segment and spreading throughout the head. The plasma membrane channels involved in calcium entry are operated by a plasma membrane depolarization and protein phosphorylations mediated by protein kinase C and tyrosine kinase protein. Part of the calcium increase could also be due to intracellular store release through IP3- and nucleotide (cAMP)-gated channels. Besides adenylate cyclase and phospholipase C activations, intracellular calcium increase also stimulates PLA2 activity and actin depolymerization, leading to membrane fusion. Evaluation of AR by staining or fluorescent probes can be useful to predict fertilization success and to direct the therapeutic strategy in male infertility.     

Characters of DNA constitution in the rye B chromosome

We have used chromosome microdissection and microcloning to construct a DNA library of the entire B chromosome （B） of rye. New rye B-specific sequences have been screened from this pool, blasted with other sequences and analyzed to elucidate the characters of DNA constitution and the possible pathway of the origin of the rye B chromosome. We report the discovery of a new sequence that is specific to the rye B centromere.     

Exposure to acrylonitrile induced DNA strand breakage and sex chromosome aneuploidy in human spermatozoa

To explore acrylonitrile (ACN)-induced DNA strand breakage and sex chromosome aneuploidy in human spermatozoa, semen parameters were examined among 30 acrylonitrile-exposed workers according to WHO laboratory manual for the examination of human sperm. DNA strand breakage of sperm cells was investigated among 30 ACN-exposed workers using single cell gel electrophoresis (SCGE). The frequency of sex chromosome aneuploidy in sperm cells was analyzed among nine ACN-exposed workers using fluorescence in situ hybridization (FISH). The geometrical mean of sperm density was 75 x 10(6)ml(-1) in exposure group, significantly lower than 140 x 10(6)ml(-1) in the control. The geometrical mean of sperm number per ejaculum was 205 x 10(6) in exposure group, significantly lower than 280 x 10(6) in the control. The rates of comet sperm nuclei were 28.7% in exposure group, significantly higher than 15.0% in the control. Mean tail length was 9.8 microm in exposure group, longer than 4.3 microm in the control. The frequency of sex chromosome disomy was 0.69% in exposure group, significantly higher than 0.35% in the control. XY-bearing sperm was the most common sex chromosome disomy, with an average rate of 0.37% in exposure group, and 0.20% in the control. XX- and YY-bearing sperm accounted for an additional 0.09 and 0.23% in exposure group, and 0.05 and 0.10% in the control. The results indicate that ACN affect semen quality among ACN-exposed workers. ACN or its metabolites could induce reproductive defects as an in vivo multipotent genotoxic agent by inducing DNA strand breakage and sex chromosome non-disjunction in spermatogenesis.     

Estimation of aneuploidy levels in human spermatozoa using chromosome specific probes and in situ hybridisation

Summary The paper describes an attempt to estimate the frequency of aneuploid human spermatozoa with disomic Y chromosome and disomic chromosome 1 complements, using chromosome specific probes and in situ hybridisation. This approach was used as an alternative to the differential staining techniques that have been applied to spermatozoa in previous studies aimed at estimating levels of aneuploidy for chromosome 1 and the Y chromosome. A frequency of 1.8 per 1000 YY-bearing spermatozoa and 3.5 per 1000 disomy 1 spermatozoa was found, both figures being in excess of those found by sperm genome karyotyping. The technical limitations of the method are discussed.     

Detection of chromosome 17- and X-bearing human spermatozoa using fluorescence in situ hybridization.

Fluorescence in situ hybridization (FISH) with DNA probes specific to chromosomes 17 and the X has been applied to human ejaculated sperm. After sperm nuclei were decondensed with EDTA and DTT, biotinylated alpha satellite DNA probes TR17 and TRX were separately used on preparations from thirteen healthy donors. After hybridization 96% of sperm were labelled with the TR17 probe and 48% of sperm were labelled with the TRX probe. Frequencies of 0.33% disomic 17 and 0.29% disomic X sperm were found. The frequencies of diploid sperm were assessed as 0.37% using the TR17 probe and 0.20% using the TRX probe which labelled only one half of the sperm; after correcting the result from the X-probe to 0.40% the two frequencies are very similar.