Sxr Region Research Articles

FPGA-based GEM detector signal acquisition for SXR spectroscopy system

The presented work is related to the Gas Electron Multiplier (GEM) detector soft X-ray spectroscopy system for tokamak applications. The used GEM detector has one-dimensional, 128 channel readout structure. The channels are connected to the radiation-hard electronics with configurable analog stage and fast ADCs, supporting speeds of 125 MSPS for each channel. The digitalized data is sent directly to the FPGAs using fast serial links. The preprocessing algorithms are implemented in the FPGAs, with the data buffering made in the on-board 2Gb DDR3 memory chips. After the algorithmic stage, the data is sent to the Intel Xeon-based PC for further postprocessing using PCI-Express link Gen 2. For connection of multiple FPGAs, PCI-Express switch 8-to-1 was designed. The whole system can support up to 2048 analog channels. The scope of the work is an FPGA-based implementation of the recorder of the raw signal from GEM detector. Since the system will work in a very challenging environment (neutron radiation, intense electro-magnetic fields), the registered signals from the GEM detector can be corrupted. In the case of the very intense hot plasma radiation (e.g. laser generated plasma), the registered signals can overlap. Therefore, it is valuable to register the raw signals from the GEM detector with high number of events during soft X-ray radiation. The signal analysis will have the direct impact on the implementation of photon energy computation algorithms. As the result, the system will produce energy spectra and topological distribution of soft X-ray radiation. The advanced software was developed in order to perform complex system startup and monitoring of hardware units. Using the array of two one-dimensional GEM detectors it will be possible to perform tomographic reconstruction of plasma impurities radiation in the SXR region.

Y chromosome short arm-Sxr recombination in XSxr/Y males causes deletion of Rbm and XY female sex reversal.

We earlier described three lines of sex-reversed XY female mice deleted for sequences believed close to the testes-determining gene (Sry) on the Y chromosome short arm (Yp). The original sex-reversed females appeared among the offspring of XY males that carried the Yp duplication Sxr on their X chromosome. Earlier cytogenetic observations had suggested that the deletions resulted from asymmetrical meiotic recombination between the Y and the homologous Sxr region, but no direct evidence for this hypothesis was available. We have now analyzed the offspring of XSxr/Y males carrying an evolutionarily divergent Mus musculus domesticus Y chromosome, which permits detection and characterization of such recombination events. This analysis has enabled the derivation of a recombination map of Yp and Sxr, also demonstrating the orientation of Yp with respect to the Y centromere. The mapping data have established that Rbm, the murine homologue of a gene family cloned from the human Y chromosome, lies between Sry and the centromere. Analysis of two additional XY female lines shows that asymmetrical Yp-Sxr recombination leading to XY female sex reversal results in deletion of Rbm sequences. The deletions bring Sry closer to Y centromere, consistent with the hypothesis that position-effect inactivation of Sry is the basis for the sex reversal.

Recombination between the X and Y chromosomes and the Sxr region of the mouse.

The Sxr (sex-reversed) region that carries a copy of the mouse Y chromosomal testis-determining gene can be attached to the distal end of either the Y or the X chromosome. During male meiosis, Sxr recombined freely between the X and Y chromosomes, with an estimated recombination frequency not significantly different from 50% in either direction. During female meiosis, Sxr recombined freely between the X chromosome to which it was attached and an X-autosome translocation. A male mouse carrying the original Sxra region on its Y chromosome, and the shorter Sxrb variant on the X, also showed 50% recombination between the sex chromosomes. Evidence of unequal crossing-over between the two Sxr regions was obtained: using five markers deleted from Sxrb, 3 variant Sxr regions were detected in 159 progeny (1.9%). Four other variants (one from the original cross and three from later generations) were presumed to have been derived from illegitimate pairing and crossing-over between Sxrb and the homologous region on the short arm of the Y chromosome. The generation of new variants throws light on the arrangement of gene loci and other markers within the short arm of the mouse Y chromosome.

A structural analysis of the Sxr region of the mouse Y chromosome

Three genetic functions have been mapped to the minute Sxr (sex-reversed) region of the mouse Y chromosome. These are Tdy, the primary testis determinant; Hya, the locus (either structural or regulatory) controlling the expression of the male-specific minor histocompatibility antigen H-Y; and Spy, a spermatogenic gene. Hya and Spy map to DNA deleted from the Sxr region in the deletion variant Sxr b (the Δ Sxr b DNA). With the object of cloning Hya and Spy, we initiated chromosome walking in the Δ Sxr b DNA. From three independent loci—Sx1, Zf2, and T5—we have isolated approximately 270 kb of Δ Sxr b DNA lying in three contigs of 145, 60, and 65 kb, respectively. Within 17 kb of the 3′ end of the Zfy-2 gene, low-copy repeat elements were found in a region that extends for ∼35 kb. Probes isolated from this region detect multiple Sxr loci, some of which map to the Δ Sxr b DNA present in the T5 contig DNA. Three of these multicopy probes detect Δ Sxr b loci not represented in our three contigs, which means that six distinct Δ Sxr b loci have now been identified. Here we present a preliminary model of the molecular structure of the DNA in this unique region.

A mouse Y chromosome pseudogene is related to human ubiquitin activating enzyme E1.

A 2041 bp DNA fragment isolated from the Sxr (sex reversed) region of the mouse Y Chromosome (Chr) was sequenced and characterized. The sequence, pY8/b, contains four exons that are highly similar to 525 contiguous bases from the cDNA of human ubiquitin activating enzyme E1. Two of the exons contain stop codons, indicating that pY8/b is not part of a functional gene. Sequences related to pY8/b were amplified from the Y Chr of the inbred mouse strain, C57BL/6J. These sequences may be portions of the recently discovered functional equivalent of pY8/b. Despite a high degree of similarity with the human E1 gene, the functional equivalent of pY8/b is not the mouse E1 gene, because unlike E1, the functional equivalent of pY8/b is expressed in a tissue-specific manner. These data are discussed with respect to theory on the evolution of the mammalian Y Chr, and in particular, to the prediction that functional genes on the Y Chr have a male-specific function.

Homology of a candidate spermatogenic gene from the mouse Y chromosome to the ubiquitin-activating enzyme El

The Sxr (sex-reversed) region, a fragment of the Y chromosome short arm, can cause chromosomally female XXSxr or XSxrO mice to develop as sterile males. The original Sxr region, termed Sxra, encodes: Tdy, the primary sex-determining gene; Hya, the controlling or structural locus for the minor transplantation antigen H-Y; gene(s) controlling the expression of the serologically detected male antigen (SDMA); Spy, a gene(s) required for the survival and proliferation of A spermatogonia during spermatogenesis; Zfy-1/Zfy-2, zinc-finger-containing genes of unknown function; and Sry, which is probably identical to Tdy. A deletion variant of Sxra, termed Sxrb, which lacks Hya, SDMA expression, Spy and some Zfy-2 sequences, makes positional cloning of these genes possible. We report here the isolation of a new testis-specific gene, Sby, mapping to the DNA deleted from the Sxrb region (the delta Sxrb interval). Sby has extensive homology to the X-linked human ubiquitin-activating enzyme E1. The critical role of this enzyme in nuclear DNA replication together with the testis-specific expression of Sby suggests Sby as a candidate for the spermatogenic gene Spy.

Variable spread of X inactivation affecting the expression of different epitopes of the Hya gene product in mouse B-cell clones

Cloned B-cell lines from a female T16H/XSxr mouse in which Tdy expression was suppressed due to X inactivation and from a male X/XSxr mouse, both of the (kxb)F1 haplotype, were examined for H-Y expression. This was determined both by their ability to act as targets for H-2k and H-2b-restricted H-Y-specific cytotoxic T cells and by their ability to stimulate the proliferation of H-2Kk, H-2Db (class I) and Ab (class II)-restricted T-cell clones. In B-cell clones from the T16H/XSxr mouse, expression of H-Y/Db exhibited partial X inactivation and only a proportion (congruent to 30%) of the cells were targets for or stimulated H-2Db-restricted H-Y-specific T cells. In contrast, H-Y epitopes restricted by H-2k (H-Y/Kk, H-Y/Dk) and Ab (H-Y/Ab) exhibited no X inactivation. Furthermore, no inactivation of H-Y/Db, H-Y/Ab, or H-Yk was observed in the male X/XSxr mouse. These results indicate that the T16H/XSxr female is a mosaic, as a result of the variable spread of X inactivation into the Sxr region. They further suggest that the H-Y antigen recognized in association with H-2k and H-2Db class I molecules and Ab class II molecules may be the product of more than one gene.

Illegitimate pairing of the X and Y chromosomes in Sxr mice

X/Y male mice carrying the sex reversal factor, Sxr, on their Y chromosomes typically produce 4 classes of progeny (recombinant X/X Sxr male male and X/Y non-Sxr male male, and non-recombinant X/X female female and X/Y Sxr male male) in equal frequencies, these deriving from obligatory crossing over between the chromatids of the X and Y during meiosis. Here we show that X/Y males that, exceptionally, carry Sxr on their X chromosome, rather than their Y, produce fewer recombinants than expected. Cytological studies confirmed that X-Y univalence is frequent (58%) at diakinesis as in X/Y Sxr males, but among those cells with X-Y bivalents only 38% showed normal X-Y pseudo-autosomal pairing. The majority of such cells (62%) instead showed an illegitimate pairing between the short arms of the Y and the Sxr region located at the distal end of the X, and this can be understood in terms of the known homology between the testis-determining region of the Y short arm and that of the Sxr region. This pairing was sufficiently tenacious to suggest that crossing over took place between the 2 regions, and misalignment and unequal exchange were suggested by indications of bivalent asymmetry. Metaphase II cells deriving from meiosis I divisions in which the normal X-Y exchange had not occurred were also found. The cytological data are therefore consistent with the breeding results and suggest that normal pseudo-autosomal pairing and crossing over is not a prerequisite for functional germ cell formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Spermatogenesis in XO,Sxr mice: Role of the Y chromosome

The goal of this investigation was to evaluate the role of the Y chromosome in spermatogenesis by a quantitative and qualitative analysis of spermatogenesis as it occurs in the absence of a significant portion of the Y chromosome, i.e., in XO,Sxr male mice. Although these mice have the testis-determining portion of the Y chromosome on their single X chromosome, they lack most of the Y chromosome. Since it was found that all sperm-specific structures were assembled in a normal spatial and temporal pattern in spermatids of XO,Sxr mice, the genes controlling these structures cannot be located on the Y chromosome outside of the Sxr region, and are more likely to be on autosomes or on the X chromosome. In spite of the assembly of the correct sperm-specific structures, spermatogenesis was not quantitatively normal in XO,Sxr mice and significantly reduced numbers of spermatids were found in the seminiferous tubules of these mice. Furthermore, two size classes of spermatids were found in the testes of XO,Sxr mice, normal and twice-normal size. These findings are suggestive of abnormalities of meiosis in XO,Sxr spermatocytes, which lack one of the two sex chromosomes, and may not implicate function of specific genes on the Y chromosome. Morphological abnormalities of spermatids, which were not unique to XO,Sxr mice, were observed and these may be due to either a defective testicular environment because of reduced numbers of germ cells or to the lack of critical Y chromosome-encoded products. Since pachytene spermatocytes of XO,Sxr mice exhibited a sex vesicle, it can be concluded that the assembly of this structure does not depend on the presence of either a complete Y chromosome or the pairing partner for the X chromosome.

Sex determination and the Y chromosome: The application of molecular genetic technique to behavioral genetics

In mammals, the Y chromosome mediates both gonadogenesis and spermatogenesis. It is also known to influence such traits as histocompatibility, sperm head morphology, pubertal (but not adult) testosterone level, sexual behavior, and aggressive behavior. An immediate goal in my laboratory is the isolation and characterization of the Y chromosomal gene responsible for initiating differentiation of the primitive bipotential gonads to become testes: the Y chromosomal gonadogenesis gene. Function of this gene initiates a cascade of events involving large numbers of other genes scattered throughout the genome, but it is not responsible for initiating development of all of the male phenotype; where : is XXSxr karyotype males, bearing the Sxr region of the Y chromosome which includes this gene, are sterile. It is not known if this gene influences those behaviors known to be influenced by the Y chromosome. If animals with an XXSxr karyotype, transgenic for specific Y chromosomal genes, could be produced, questions such as this could be answered. The developmental biology of the testis, molecular genetics of the Sxr region of the Y chromosome, and isolation of the testis determination gene from DNA of XXSxr males are discussed. Also discussed are the production of transgenic mice and the prospects for using such animals as coisogenic strains, differing by precisely known DNA sequences, in behavior genetic analysis. Such animals could be used both to test for behavioral phenotype and to dissect out biochemical and neurological mechanisms responsible for the behavior.

Duplication, Deletion, and Polymorphism in the Sex-Determining Region of the Mouse Y Chromosome

The ZFY gene in the sex-determining region of the human Y chromosome encodes a "zinc-finger" protein that may be the testis-determining factor, TDF. Although the Y chromosomes of most placental mammals carry a single homolog of ZFY, the mouse Y chromosome has two homologs, both in the sex-determining (Sxr) region. Zfy-1 alone may suffice to determine maleness; Zfy-2 is dispensable, as it was deleted in an Sxr variant that retains sex-determining function but has lost other genes. Both loci mapped near the centromere of the mouse Y chromosome. The Y chromosomes of the subspecies Mus musculus musculus and M. m. domesticus were distinguishable by a Zfy-1 restriction fragment polymorphism, which can be used to study their differing interactions with autosomal sex-determining genes.

Molecular aspects of sex determination in mice: an alternative model for the origin of the Sxr region.

Using a combination of in situ mapping and DNA analysis with recombinant DNA probes specific for the Sxr region of the mouse Y chromosome, we show that both the gene(s) controlling primary sex determination and the expression of the male-specific antigen H-Y (Tdy and Hya respectively) are located on the minute short arm of the mouse Y chromosome. We demonstrate that the H-Y- variant of Sxr (Sxr') arose by a partial deletion within the Sxr region and propose an alternative model for the generation of the original Sxr region.

Molecular and cytogenetic evidence for the location of Tdy and Hya on the mouse Y chromosome short arm.

Using a combination of in situ mapping and DNA analysis with recombinant DNA probes specific for the Sxr region of the mouse Y chromosome, we show that both the gene(s) controlling sex determination and the expression of the male-specific antigen H-Y (Tdy and Hya, respectively) are located on the minute short arm of the mouse Y chromosome. We demonstrate that the H-Y- variant of Sxr (Sxr') arose by a partial deletion within the Sxr region. Also, we show that intrachromosomal recombination between the Y short arm and Sxr' can sometimes occur during male meiosis, restoring the deleted DNA sequences and resulting in an H-Y+ mouse (male 719 in this paper). Based on these results, we propose a model for the generation of the original Sxr region and the Sxr' and Sxr719 variants.

Location of the genes controlling H-Y antigen expression and testis determination on the mouse Y chromosome.

Sex-reversed XX male mice that carry the variant form of the testis-determining Sxr region, Sxr', do not express male-specific H-Y antigen. In a stock of mice segregating for Sxr', we detected an exceptional XX male that proved positive for H-Y antigen. DNA fingerprinting revealed that the banding pattern characteristic of Sxr' had been replaced by the pattern associated with the native testis-determining region of the normal Y chromosome of that stock, presumably by pairing and crossing-over between the two testis-determining regions of the father's Y Sxr' chromosome. Pairing between the two ends of such a chromosome in a loop-like configuration has been observed by electron microscopy. However, an anomalous crossing-over event of this kind would only give rise to the observed result if the native homologue of the Sxr region were situated on the very minute short arm of the Y chromosome. We therefore conclude that the two linked genes Tdy and Hya, controlling testis determination and H-Y antigen expression, respectively, are located on the short arm of the mouse Y chromosome.

The use of specific DNA probes to analyse the Sxr mutation in the mouse

The mouse Y chromosome plays a fundamental role in the control of primary sex determination and fertility. Both genetic and molecular biological evidence has shown that much of the necessary information is contained in a minute piece of the Y (the Sxr region) which has arisen by a duplication of the pericentric region of the normal Y and the transposition of one copy to the distal pseudoautosomal region. The present article describes the isolation of random Y-chromosome probes and their use to investigate this Sxr region at the molecular level. Total mouse Y-chromosome libraries were constructed from flow-sorted material and a Sxr regional library after specific microdissection and cloning. Transcription has been detected in the testis using both Sxr-specific and non Sxr-located genomic probes taken from these libraries. In addition, we have been able to confirm the presence of an active steroid sulphatase gene on the mouse Y. This gene is located in the distal portion of the pseudoautosomal region and is tightly linked to Sxr. Finally, using an Sxr-specific probe we can define multiple Y-chromosome haplotypes in the mouse showing that the region is evolving very rapidly.