Showing papers on "X chromosome published in 1987"

Clonal analysis of human colorectal tumors

Abstract: The clonal composition of human colorectal tumors was studied by means of restriction fragment length polymorphisms (RFLPs). First, X-linked RFLPs were used to examine the pattern of X chromosome inactivation in colorectal tumors of females. All 50 tumors examined showed monoclonal patterns of X chromosome inactivation; these tumors included 20 carcinomas as well as 30 adenomas of either familial or spontaneous type. Second, RFLPs of autosomes were used as clonal markers to detect the somatic loss or gain of specific chromosomal sequences in colorectal tumors. Among other changes, it was found that somatic loss of chromosome 17p sequences occurred in over 75 percent of the carcinomas examined, but such loss was rare in adenomas. These data support a monoclonal origin for colorectal neoplasms, and suggest that a gene on the short arm of chromosome 17 may be associated with progression from the benign to the malignant state.

Clonal Analysis Using Recombinant DNA Probes from the X-Chromosome

Abstract: It has been demonstrated that restriction fragment length polymorphisms of X-chromosome genes can be used in conjunction with methylation patterns to determine the clonal composition of human tumors. In this report, we show that several X-chromosome probes can be used for such analyses. In particular, probes derived from the hypoxanthine phosphoribosyltransferase gene and the phosphoglycerate kinase gene could be used for clonal analysis in over 50% of American females. The X-inactivation patterns observed with these probes were found to accurately reflect clonality in more than 95% of 92 tumors tested.

Involvement of chromosome X in primary cytogenetic change in human neoplasia: nonrandom translocation in synovial sarcoma

Abstract: A translocation that involves chromosome X (band p112) and chromosome 18 (band q112) was observed in short-term in vitro cultures of cells from five synovial sarcomas and one malignant fibrous histiocytoma In four of these tumors, the translocation t(X;18)(p112;q112) was reciprocal The two other tumors had complex translocations: t(X;18;21)(p112;q112;p13) and t(X;15;18)(p112;q23;q112) A translocation between chromosomes X and 18 was not detected in other histological types of soft tissue sarcoma The X;18 rearrangement appears to characterize the synovial sarcoma and is the first description of a primary, nonrandom change in the sex chromosome of a human solid tumor

Age related reactivation of an X-linked gene

Abstract: We have investigated age-related reactivation of the X chromosome by devising a model in which reactivation of a single gene in one cell among many can be identified. We have used mice with an X-autosomal translocation giving consistent non-random inactivation of the normal X (as judged by biochemical and cytogenetic techniques), that also carry a defective form of a histochemically demonstrable X-linked enzyme. When the gene for the normal enzyme was located on the inactivated normal X a uniformly negative histochemical picture would be predicted in doubly heterozygous animals. A very small proportion of enzyme-positive cells was found in young animals. This proportion increased very significantly with age, but the patch size did not change, showing that the result was not due to preferential division of enzyme-positive cells, but was instead due to the conversion of previously enzyme-negative to enzyme-positive cells. These observations provide the first evidence with a true X-linked gene for an age-related decrease in the stability of the X-inactivation mechanism.

Proposed Mechanism of Inheritance and Expression of the Human Fragile-X Syndrome of Mental Retardation

Abstract: A mechanism is proposed for the inheritance and expression of the fragile-X-linked syndrome of mental retardation in humans. Two independent events are required for expression of the syndrome: the fragile-X mutation, and X chromosome inactivation in pre-oogonial cells. The fragile-X mutation at site Xq27 has little or no effect until the chromosome is inactivated in a female as part of the process of dosage compensation. At a stage where the inactivated X chromosome would normally be reactivated in preparation for oogenesis, the mutation results in a local block to the reactivation process. This block to reactivation leads to mental retardation in progeny by reducing the level of products from the unreactivated Xq27 region in male cells, and, for a heterozygous female, in somatic cells in which the normal X chromosome has been inactivated. Published data relevant to this proposed mechanism are discussed.

Familial Premature Ovarian Failure Due to an Interstitial Deletion of the Long Arm of the X Chromosome

Abstract: We describe a family in which four women had menstrual irregularities and a partial deletion of the long arm of the X chromosome (Xq). Three of the four women had premature ovarian failure (at the ages of 24 to 37 years). Chromosome-banding studies initially suggested that a terminal portion of Xq was deleted. However, DNA-hybridization studies showed that an interstitial portion of Xq was deleted and that the affected women had a 46,XX,del(X)(pter-q21.3::q27-qter) karyotype. These findings help clarify the role of Xq in ovarian function and indicate that the accurate description of such abnormalities requires a combination of cytogenetic and DNA-hybridization analysis.

DNA methylation stabilizes X chromosome inactivation in eutherians but not in marsupials: evidence for multistep maintenance of mammalian X dosage compensation

Abstract: In marsupials and eutherian mammals, X chromosome dosage compensation is achieved by inactivating one X chromosome in female cells; however, in marsupials, the inactive X chromosomes is always paternal, and some genes on the chromosome are partially expressed. To define the role of DNA methylation in maintenance of X chromosome inactivity, we examined loci for glucose-6-phosphate dehydrogenase and hypoxanthine phosphoribosyltransferase in a North American marsupial, the opossum Didelphis virginiana, by using genomic hybridization probes cloned from this species. We find that these marsupial genes are like their eutherian counterparts, with respect to sex differences in methylation of nuclease-insensitive (nonregulatory) chromatin. However, with respect to methylation of the nuclease-hypersensitive (regulatory) chromatin of the glucose-6-phosphate dehydrogenase locus, the opossum gene differs from those of eutherians, as the 5' cluster of CpG dinucleotides is hypomethylated in the paternal as well as the maternal gene. Despite hypomethylation of the 5' CpG cluster, the paternal allele, identified by an enzyme variant, is at best partially expressed; therefore, factors other than methylation are responsible for repression. In light of these results, it seems that the role of DNA methylation in eutherian X dosage compensation is to "lock in" the process initiated by such factors. Because of similarities between dosage compensation in marsupials and trophectoderm derivatives of eutherians, we propose that differences in timing of developmental events--rather than differences in the basic mechanisms of X inactivation--account for features of dosage compensation that differ among mammals.

Carrier Detection in X-Linked Agammaglobulinemia by Analysis of X-Chromosome Inactivation

Abstract: We used a recently developed strategy to analyze patterns of X-chromosome inactivation in human cell populations in order to study female members of families with X-linked agammaglobulinemia--i.e., to detect the carrier state and to test the hypothesis that the disorder results from a defect intrinsic in the development of B cells. According to this strategy, recombinant-DNA probes simultaneously detect restriction-fragment-length polymorphisms and patterns of methylation of X-chromosome genes. Random X-inactivation patterns were observed in isolated peripheral-blood granulocytes, T lymphocytes, and B lymphocytes of women who were not carriers. In contrast, one of the two X chromosomes was preferentially active in the peripheral B cells, but not the T cells or granulocytes, of three carriers of the disorder. This observation strongly supports the hypothesis that X-linked agammaglobulinemia results from an intrinsic defect in B-cell development. Moreover, the analysis described here can be used for direct identification of carriers in families with this disease.

(dC-dA)n.(dG-dT)n sequences have evolutionarily conserved chromosomal locations in Drosophila with implications for roles in chromosome structure and function.

Abstract: In situ hybridization of (dC-dA)n(dG-dT)n to the polytene chromosomes of Drosophila melanogaster reveals a clearly non-random distribution of chromosomal sites for this sequence Sites are distributed over most euchromatic regions but the density of sites along the X chromosome is significantly higher than the density over the autosomes All autosomes show approximately equal levels of hybridization except chromosome 4 which has no detectable stretches of (dC-dA)n(dG-dT)n Another striking feature is the lack of hybridization of the beta-heterochromatin of the chromocenter The specific sites are conserved between different strains of D melanogaster The same overall chromosomal pattern of hybridization is seen for the other Drosophila species studied, including D simulans, a sibling species with a much lower content of middle repetitive DNA, and D virilis, a distantly related species The evolutionary conservation of the distribution of (dC-dA)n(dG-dT)n suggests that these sequences are of functional importance The distribution patterns seen for D pseudoobscura and D miranda raise interesting speculations about function In these species a chromosome equivalent to an autosomal arm of D melanogaster has been translocated onto the X chromosome and acquired dosage compensation In each species the new arm of the X also has a higher density of (dC-dA)n(dG-dT)n similar to that seen on other X chromosomes In addition to correlations with dosage compensation, the depletion of (dC-dA)n(dG-dT)n in beta-heterochromatin and chromosome 4 may also be related to the fact that these regions do not normally undergo meiotic recombination

Carrier detection in X-linked severe combined immunodeficiency based on patterns of X chromosome inactivation.

Abstract: The X-linked form of severe combined immunodeficiency (XSCID) is underdiagnosed because no methods have been available for detecting carriers. Although boys with XSCID are deficient in T cells, female carriers are immunologically normal. Carriers' normal immune function would be expected if all their T cells were derived from precursors whose X chromosome bearing the XSCID mutation was inactivated early in embryogenesis. Using somatic cell hybridization to separate the active and inactive X chromosomes and restriction fragment length polymorphisms to distinguish them, we have determined the lymphocyte X inactivation pattern in XSCID carriers and their female relatives. In the T cells of three carriers, the X chromosome bearing the XSCID mutation was consistently inactive. Nonrandom X inactivation was also found in the T cells of one at-risk female, while two others had normal, random X inactivation. This method constitutes a generally applicable carrier test for XSCID.

Isolation and characterization of a steroid sulfatase cDNA clone: genomic deletions in patients with X-chromosome-linked ichthyosis

Abstract: We have isolated several cDNA clones from a lambda gt11 expression library by screening with antibodies prepared against the microsomal enzyme steroid sulfatase, which is deficient in classical X-chromosome-linked ichthyosis patients. One of these clones (p422) has been assigned by mapping with a somatic cell hybrid panel and by in situ hybridization to Xp22.3. Clone p422 therefore has a coincident localization with the previously identified locus for steroid sulfatase expression in the region of the X chromosome escaping from inactivation. Twelve steroid sulfatase-deficient patients, including eight cases of classical ichthyosis, were found to be deleted for genomic sequences detected by the clone.

Dosage Compensation in Drosophila: Evidence That daughterless and Sex-lethal Control X Chromosome Activity at the Blastoderm Stage of Embryogenesis.

Abstract: Dosage compensation is a mechanism that equalizes the expression of X chromosome linked genes in males, who have one X chromosome, with that in females, who have two. In Drosophila, this is achieved by the relative hyperactivation of X-linked genes in males, as was first shown by Muller using a phenotypic assay based on adult eye color. Several genes involved in regulating dosage compensation have been identified through the isolation of mutations that are sex-specific lethals. However, because of this lethality it is not straightforward to assay the relative roles of these genes using assays based on adult phenotypes. Here this problem is circumvented using an assay based on embryonic phenotypes. These experiments indicate that dosage compensation is established early in development and demonstrate that the daughterless and Sex-lethal gene products are involved in regulating X chromosome activity at the blastoderm stage of embryogenesis.

Localization and cloning of Xp21 deletion breakpoints involved in muscular dystrophy

Abstract: Twenty-nine deletion breakpoints were mapped in 220 kb of the DXS164 locus relative to potential exons of the Duchenne and Becker muscular dystrophy gene. Four deletion junction fragments were isolated to acquire outlying Xp21 loci on both the terminal and centromere side of the DXS164 locus. The junction loci were used for chromosome walking, searches for DNA polymorphisms, and mapping against deletion and translocation breakpoints. Forty-four unrelated deletions were analyzed using the junction loci as hybridization probes to map the endpoints between cloned Xp21 loci. DNA polymorphisms from the DXS164 and junction loci were used to follow the segregation of a mutation in a family that represents a recombinant. Both the physical and genetic data point to a very large size for this X-linked muscular dystrophy locus.

Three-dimensional organization of Drosophila melanogaster interphase nuclei. II. Chromosome spatial organization and gene regulation.

Abstract: In the preceding article we compared the general organization of polytene chromosomes in four different Drosophila melanogaster cell types. Here we describe experiments aimed at testing for a potential role of three-dimensional chromosome folding and positioning in modulating gene expression and examining specific chromosome interactions with different nuclear structures. By charting the configurations of salivary gland chromosomes as the cells undergo functional changes, it is shown that loci are not repositioned within the nucleus when the pattern of transcription changes. Heterologous loci show no evidence of specific physical interactions with one another in any of the cell types. However, a specific subset of chromosomal loci is attached to the nuclear envelope, and this subset is extremely similar in at least two tissues. In contrast, no specific interactions between any locus and the nucleolus are found, but the base of the X chromosome, containing the nucleolar organizer, is closely linked to this organelle. These results are used to evaluate models of gene regulation that involve the specific intranuclear positioning of gene sequences. Finally, data are presented on an unusual class of nuclear envelope structures, filled with large, electron-dense particles, that are usually associated with chromosomes.

The fragile X site in somatic cell hybrids: an approach for molecular cloning of fragile sites

Abstract: Fragile X syndrome is a common form of mental retardation associated with a fragile site on the human X chromosome. Although fragility at this site is usually evident as a nonstaining chromatid gap, it remains unclear whether or not actual chromosomal breakage occurs. By means of somatic cell hybrids containing either a normal human X or a fragile X chromosome and utilizing two genes that flank the fragile site as markers of chromosome integrity, segregation of these markers was shown to be more frequent if they encompass the fragile site under appropriate culture conditions. Hybrid cells that reveal marker segregation were found to contain rearranged X chromosomes involving the region at or near the fragile site, thus demonstrating true chromosomal breakage within this area. Two independent translocation chromosomes were identified involving a rodent chromosome joined to the human X at the location of the fragile site. DNA analysis of closely linked, flanking loci was consistent with the position of the breakpoint being at or very near the fragile X site. Fragility at the translocation junctions was observed in both hybrids, but at significantly lower frequencies than that seen in the intact X of the parental hybrid. This observation suggests that the human portion of the junctional DNA may contain part of a repeated fragility sequence. Since the translocation junctions join heterologous DNA, the molecular cloning of the fragile X sequence should now be possible.

Genes in subdivision 1B of the Drosophila melanogaster X-chromosome and their influence on neural development

Abstract: Genes within subdivision IB of the X-chromosome of Drosophila melanogaster are known to affect the development of both the central (CNS) and the peripheral (PNS) embryonic nervous system. In this paper we describe the phenotypes of embryos hemizygous for terminal and interstitial deletions of region 1B1–1B10, and of embryos carrying different mutations in certain genes of this region. A minimum of 6 genetic functions that are involved in neural development can be defined in this region. Three of these genes, mapping to the I'sc (a gene of the achaete-scute complex, ASC), elav and md loci, affect major and apparently different aspects of CNS development. Two additional genes of the ASC, ac and sea, also play a role in CNS development, although their participation can only be demonstrated under certain conditions. Finally, in the rightmost part of the region uncovered by the deletion Df(1)260.1, two not yet well separated functions are found to be required for embryonic CNS and compound eye development, res...

A partial deletion of the muscular dystrophy gene transmitted twice by an unaffected male.

Abstract: A gene of unknown function located in band Xp21 on the short arm of the human X chromosome gives rise to X-linked recessive muscular dystrophy, of either Duchenne or Becker type, when mutated. The gene encodes a large muscle-specific transcript of about 14 kilobases (kb) and its genomic size extends over more than 1,800 kb. The high mutation rate (about 10(-4) per generation) is likely to result from the large target size. Submicroscopic deletions, detectable with one or more of the dozen cloned DNA probes available for regions within the gene, constitute a significant proportion of the mutations. Because no such deletions have been found in normal individuals, it is assumed that intragenic deletions are the molecular basis of the mutations. The origin of deletions can be traced in families. With sufficient data collected, it will soon be possible to answer questions about the relative frequencies of mutations in male and female gametogenesis and about the timing of mutational events in mitotic or meiotic stages of germ cell development. We have studied a four generation family containing males who have Duchenne muscular dystrophy due to deletion of the sequence recognized by intragenic probe J-Bir. The deletion was present in two of five daughters of a woman who herself did not have the deletion. Haplotype analysis on 15 members of this family using nine informative restriction fragment length polymorphism (RFLP) markers indicated that the J-Bir deletion chromosome was transmitted from the unaffected father.

Normal and abnormal interchanges between the human X and Y chromosomes.

Abstract: A single obligatory recombination event takes place at male meiosis in the tips of the X- and Y-chromosome short arms (i.e. the pseudoautosomal region). The crossover point is at variable locations and thus allows recombination mapping of the pseudoautosomal loci along a gradient of sex linkage. Recombination at male meiosis in the terminal regions of the short arms of the X and Y chromosomes is 10- to 20-fold higher than between the same regions of the X chromosomes during female meiosis. The human pseudoautosomal region is rich in highly polymorphic loci associated with minisatellites. However, these minisatellites are unrelated to those resembling the bacterial Chi sequence and which possibly represent recombination hotspots. The high recombination activity of the pseudoautosomal region at male meiosis sometimes results in unequal crossover which can generate various sex-reversal syndromes.

Exchange of terminal portions of X- and Y-chromosomal short arms in human XX males.

Abstract: In most human 'XX males', DNA sequences normally found on Yp, the short arm of the Y chromosome, are present on Xp, the short arm of the X chromosome. To establish whether this transfer involves a terminal portion of Yp, and whether a terminal portion of Xp is lost in the process, we followed the inheritance of pseudoautosomal restriction fragment length polymorphisms in two XX-male families. One XX male apparently inherited the entire pseudoautosomal region of his father's Y chromosome and no part of the pseudoautosomal region of his father's X chromosome. The second XX male also inherited the entire pseudoautosomal region of his father's Y, but in addition inherited a proximal portion of the pseudoautosomal region of his father's X. These findings argue that XX males result from the transfer of a terminal portion of Yp onto Xp in exchange for a terminal portion of Xp (ref. 7). This implies that the testis-determining factor gene (TDF) maps distally in the strictly sex-linked portion of Yp, near the pseudoautosomal domain. The XX males described here appear to result from single (and, at least in the second case, unequal) crossovers proximal to the pseudoautosomal region on Yp and proximal to or within the pseudoautosomal region on Xp.

Congenital adrenal hypoplasia, myopathy, and glycerol kinase deficiency: molecular genetic evidence for deletions.

Abstract: Glycerol kinase deficiency (GKD) is an X-linked recessive trait that occurs in association with congenital adrenal hypoplasia (AH) and developmental delay with or without congenital dystrophic myopathy Several such patients have recently been reported to have cytological deletions of chromosome region Xp21 and/or of DNA markers that map near the locus for Duchenne muscular dystrophy (DMD) in band Xp21 We have examined the initial family reported in the literature and, using prometaphase chromosome studies and Southern blot analysis with 13 different DNA probes derived from band Xp21, have found no deletions within this region of the X chromosome When DNA samples from six other unrelated affected males were analyzed, four of them were found to have different-size deletions within Xp21 Thus, the form of GKD associated with AH and dystrophic myopathy exhibits significant genetic heterogeneity at the DNA level No deletions were detected in two patients with isolated GK deficiency Comparison of our molecular studies of unrelated patients with deletions of DNA segments allows us to define the region of Xp21 (between probes J-Bir and L14) that most likely contains the genes for GKD and AH This location is distal to the DMD locus The patients with progressive muscular dystrophy tended to have larger deletions that include markers known to derive from the DMD locus, while GKD/AH/dystrophic-myopathy patients without current evidence of deletion seemed to have a milder, nonprogressive form of congenital myopathy

Human genes encoding prothrombin and ceruloplasmin map to 11p11-q12 and 3q21-24, respectively.

Abstract: The gene for human prothrombin, or factor II (F2) has been assigned to 11p11-q12 by the combined use of a panel of somatic cell hybrid DNAs and in situ hybridization, using both cDNA and genomic probes. In addition, the cDNA probe for F2 recognizes a homologous sequence which has been tentatively mapped to the X chromosome. Similar approaches have been used to confirm the assignment of the ceruloplasmin gene, but to regionally localize it more proximally than previously reported (3q21-q24). These results provide further evidence that genes encoding the coagulation factors and related proteins are dispersed throughout the human genome.

47,XXX females, sex chromosomes, and tooth crown structure

Abstract: Enamel thickness of the maxillary permanent central incisors and canines in seven Finnish 47,XXX females, their first-degree male and female relatives, and control males and females from the general population were determined from radiographs. The results showed that enamel in teeth of 47,XXX females was clearly thicker than that of normal controls. On the other hand, the thickness of "dentin" (distance between mesial and distal dentinoenamel junctions) in 47,XXX females' teeth was about the same as that in normal control females, but clearly reduced as compared with that in control males. It is therefore obvious that in the triple-X chromosome complement the extra X chromosome is active in amelogenesis, whereas it has practically no influence on the growth of dentin. The calculations based on present and previous results in 45,X females and 47,XYY males indicate that the X chromosome increases metric enamel growth somewhat more effectively than the Y chromosome. Possibly, halfway states exist between active and repressed enamel genes on the X chromosome. The Y chromosome seems to promote dental growth in a holistic fashion.

Menkes syndrome in a girl with X‐autosome translocation

Abstract: We report on a girl with Menkes syndrome (M.S.) and X-2 reciprocal translocation. We conclude that the probable locus for M.S. gene is at band Xq13. This case and other previous case reports of X-linked disorders in females suggest that chromosome analysis is indicated in all females who present with manifestations of a known X-linked lethal condition in order to detect a possible associated balanced X-autosome translocation.