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L J Shapiro

Publications and source records attributed to L J Shapiro.

At least 19 recordsLinked to original sources
PubMed1992

Characterization of a low copy repetitive element S232 involved in the generation of frequent deletions of the distal short arm of the human X chromosome.

There are several copies of related sequences on the distal short arm of the human X chromosome and the proximal long arm of the Y chromosome which were originally detected by cross hybridization with a genomic DNA clone, CRI-S232. Recombination between two S232-like sequences flanking the steroid sulfatase locus has been shown to cause frequent deletions in the X chromosome short arm, resulting in steroid sulfatase deficiency. We now report the characterization of several S232-like sequences. Restriction mapping and sequence analysis show that each S232 unit contains 5 kb of unique sequence in addition to two elements, RU1 and RU2, composed of a variable number of tandem repeats. RU1 consists of 30 bp repeating units and its length shows minimal variation between individuals. The RU2 elements in the hypervariable S232 loci on the X chromosome consist of repeating sequences which are highly asymmetric, with about 90% purines and no C's on one strand. The X-derived RU2 elements range from 0.6 kb to over 23 kb among different individuals, accounting entirely for the observed polymorphism at the S232 loci. Although the repeating units of the RU2 elements in the nonpolymorphic S232 loci on the Y chromosome share high sequence homology with those on the X chromosome, they exhibit much higher intrarepeat sequence variation. S232 homologous sequences are found in great apes, old world and new world monkeys. In chimpanzees and gorillas the S232-like sequences are polymorphic in length.

Animals↗
PubMed1992

Prenatal diagnosis and investigation of a fetus with chondrodysplasia punctata, ichthyosis, and Kallmann syndrome due to an Xp deletion.

We report the prenatal diagnosis of a male fetus with X-linked recessive chondrodysplasia punctata (CDPX), steroid sulphatase (STS) deficiency, X-linked Kallmann syndrome (KAL), and a chromosome deletion at Xp22.31. Biochemical analysis of bone from this case indicates that CDPX is not a defect of vitamin K metabolism. Immunocytochemical study of the brain suggests that KAL is a defect in neuronal migration.

Adult↗
PubMed1992

Physical mapping of loci in the distal half of the short arm of the human X chromosome: implications for the spreading of X-chromosome inactivation.

The relative order of 11 loci in the distal half of the short arm of the human X chromosome was examined using a panel of somatic cell hybrids containing structurally rearranged X chromosomes. The results show that the gene for phosphoribosylpyrophosphate synthetase 2 (PRPS2) is located between ZFX (zinc finger protein, X-linked) and STS (steroid sulfatase). The results also confirm the localization of ZFX distal to POLA (alpha-DNA polymerase). Previous studies have shown that STS and ZFX escape X-inactivation whereas POLA undergoes inactivation. Evaluation of PRPS2 expression in somatic cell hybrids containing inactive human X chromosomes showed that PRPS2 undergoes X-inactivation. These results provide further evidence for interspersion of loci that do and do not undergo X-inactivation on the human X chromosome.

Arylsulfatases↗
PubMed1992

Sequence analysis of a partial deletion of the human steroid sulfatase gene reveals 3 bp of homology at deletion breakpoints.

The majority of patients with steroid sulfatase deficiency have a deletion of the entire STS gene located on the distal short arm of the human X chromosome; however, two patients with partial gene deletions have been identified. We now report the sequences at the breakpoints of a deletion of the 3' end of the STS gene. The deletion starts within intron 7 of the gene and extends over 150 kb downstream toward the centromere. Analysis of sequences flanking the deletion breakpoints revealed 3 bp of homology. The 3' flanking sequence provides a new probe for isolation of YAC clones and for studying patients with deletions in this region of the X chromosome.

Arylsulfatases↗
PubMed1992

Expression of the X-inactivation-associated gene XIST during spermatogenesis.

Mammalian X-chromosome inactivation is thought to be controlled by the X inactivation centre (XIC, X-controlling element -Xce-in mice). A human gene, XIST and its mouse counterpart, Xist, which map to the XIC/Xce, are expressed exclusively from inactive X chromosomes, suggesting their involvement in the process of X-inactivation. We now report the presence of Xist/XIST transcripts in newborn and adult mouse testes, and in human testicular tissue with normal spermatogenesis, but not in the testes of patients who lack germ cells. Our results indicate that while the X chromosome in males is active in somatic cells, it undergoes inactivation during spermatogenesis.

Animals↗
PubMed1992

Structure and expression of the human pseudoautosomal gene XE7.

The human pseudoautosomal region comprises a 2.6 megabase segment of the distal short arms of the X and Y chromosomes. Complete DNA sequence homology between the two sex chromosomes is found in this region, and is believed to be important in mediating X-Y pairing in male meiosis. The only known functional genes in this region are MIC2 and CSF2R; in addition a pseudoautosomal location has been proposed for a genetic locus controlling stature. Here we report the structure of a recently identified pseudoautosomal gene, XE7, and its expression in human tissues. Analysis of genomic and cDNA clones shows that alternative RNA splicing results in the production of two predicted protein isoforms, one containing 385 amino acids and the other with 695 residues. The smaller polypeptide is a truncated version of the larger, and results from the inclusion of a cassette exon that introduces an in-frame stop codon into the mRNA. The XE7 gene appears to be ubiquitously expressed, and the production of both protein isoforms is predicted in each of several tissues examined.

Alternative Splicing↗
PubMed1992

Role of the pseudoautosomal region in sex-chromosome pairing during male meiosis: meiotic studies in a man with a deletion of distal Xp.

Meiotic studies were undertaken in a 24-year-old male patient with short stature, chondrodysplasia punctata, ichthyosis, steroid sulfatase deficiency, and mild mental retardation with an inherited cytologically visible deletion of distal Xp. Molecular investigations showed that the pseudoautosomal region as well as the steroid sulfatase gene were deleted, but telomeric sequences were present at the pter on the deleted X chromosome. A complete failure of sex-chromosome pairing was observed in the primary spermatocytes of the patient. Telomeric approaches between the sex chromosomes were made at zygotene in some cells, but no XY synaptonemal complex was formed. The sex chromosomes were present as univalents at metaphase I, and germ-cell development was arrested between metaphase I and metaphase II in the vast majority of cells, consistent with the azoospermia observed in the patient. The failure of XY pairing in this individual indicates that the pseudoautosomal sequences play an important role in initiating XY pairing and formation of synaptonemal complex at meiosis.

Adult↗
PubMed1992

The human enamel protein gene amelogenin is expressed from both the X and the Y chromosomes.

Amelogenins, a family of extracellular matrix proteins of the dental enamel, are transiently but abundantly expressed by ameloblasts during tooth development. Amelogenins seem to regulate the formation of crystallites during the secretory stage of enamel development, while they are specifically degraded during tooth-bud maturation. In this paper we report the characterization of the AMGX and AMGY genes on the short arms of the human X and Y chromosomes which encode the amelogenins. Our studies on the expression of the amelogenin genes in male developing tooth buds showed that both the AMGX and AMGY genes are transcriptionally active and encode potentially functional proteins. We have isolated genomic and cDNA clones from both the AMGX and AMGY loci and have studied the sequence organization of these two genes. Reverse transcriptase (RT)PCR amplification of the 5' portion of the amelogenin transcripts revealed several alternatively spliced products. The splicing pattern observed in the Y-derived mRNA varies from that of the X-derived mRNA. The promoter regions from both genes and the predicted amelogenin protein sequences are presented. This information will be useful for studying the molecular basis of X-linked amelogenesis imperfecta, for understanding the evolution and regulation of gene expression on the mammalian sex chromosomes, and for investigating the role of amelogenin genes during tooth development.

Amelogenin↗
PubMed1991

X/Y translocations resulting from recombination between homologous sequences on Xp and Yq.

Several regions of sequence homology between the human X and Y chromosomes have been identified. These segments are thought to represent areas of these chromosomes that have engaged in meiotic recombination in relatively recent evolutionary times. Normally, the X and Y chromosomes pair during meiosis and exchange DNA only within the pseudoautosomal region at the distal short arms of both chromosomes. However, it has been suggested that aberrant recombination involving other segments of high homology could be responsible for the production of X/Y translocations. We have studied four X/Y translocation patients using molecular probes detecting homologous sequences on X and Y chromosomes. In one translocation the breakpoints have been isolated and sequenced. The mapping data are consistent with the hypothesis that X/Y translocations arise by homologous recombination. The sequencing data from one translocation demonstrate this directly.

Base Sequence↗
PubMed1991

Expression of epidermal growth factor in the rat kidney. An immunocytochemical and in situ hybridization study.

The renal localization and the site of synthesis of epidermal growth factor (EGF) were investigated in the rat kidney by immunohistochemistry and in situ hybridization techniques. EGF was localized in the cells of the thick ascending limb of Henle (TAL) and distal convoluted tubule (DCT). At the ultrastructural level, EGF immunoreactivity was distributed on the apical membrane and trans-Golgi complex of the TAL and DCT cells. These segments of the rat nephron also hybridized to prepro-EGF cRNA probes in a specific manner, indicating that TAL and DCT are the sites of EGF synthesis in the rat kidney.

Animals↗
PubMed1991

A multipoint linkage map of the distal short arm of the human X chromosome.

The distal portion of the short arm of the human X chromosome (Xp) exhibits many unique and interesting features. Distal Xp contains the pseudoautosomal region, a number of disease loci, and several cell-surface markers. Several genes in this area have also been observed to escape X-chromosomal inactivation. The characterization of new polymorphic loci in this region has permitted the construction of a refined multipoint linkage map extending 15 cM from the Xp telomere. This interval is known to contain the loci for the diseases X-linked ichthyosis, chondrodysplasia punctata, and Kallmann syndrome, as well as the cell-surface markers Xg and 12E7. This region also contains the junction between the pseudoautosomal region and strictly X-linked sequences. The locus MIC2 has been demonstrated by linkage analysis to be indistinguishable from the pseudoautosomal junction. The steroid sulfatase locus has been mapped to an interval adjacent to the DXS278 locus and 6 cM from the pseudoautosomal junction. The polymorphic locus (STS) DXS278 was shown to be informative in all families studied, and linkage analysis reveals that the locus represents a low-copy repeat with at least one copy distal to the STS gene. The generation of a multipoint linkage map of distal Xp will be useful in the genetic dissection of many of the unique features of this region.

Alleles↗
PubMed1991

Uniparental heterodisomy for chromosome 14 in a phenotypically abnormal familial balanced 13/14 Robertsonian translocation carrier.

A 9-year-old mentally retarded girl with multiple congenital anomalies was found to carry a balanced 13/14 Robertsonian translocation [45,XX,t(13q14q)] which was also present in her father. Her mother carried a balanced reciprocal translocation between chromosomes 1 and 14 [46,XX,t(1;14) (q32;q32)]. Both of her parents were phenotypically normal. Molecular studies were carried out to determine the parental origin of chromosomes 1, 13, and 14 in the patient. Using probes for D14S13 and D14S22, we could show that the patient inherited both chromosomes 14 from her father and none from her mother. Similar studies using probes for chromosomes 1 (D1S76) and 13 (D13S37) loci showed the presence of both maternal and paternal alleles in the patient. Our findings indicate that paternal uniparental heterodisomy for chromosome 14 most likely accounts for the phenotypic abnormalities observed in our patient. It is suggested that uniparental disomy may be the basis for abnormal development in at least some phenotypically abnormal familial balanced-translocation carriers.

Blotting, Southern↗
PubMed1990

Evolution of the pseudoautosomal boundary in Old World monkeys and great apes.

Mammalian sex chromosomes are divided into sex-specific and pseudoautosomal regions. Sequences in the pseudoautosomal region recombine between the sex chromosomes; the sex-specific sequences normally do not. The interface between sex-specific and pseudoautosomal sequences is the pseudoautosomal boundary. The boundary is the centromeric limit to recombination in the pseudoautosomal region. In man, an Alu repeat element is found inserted at the boundary on the Y chromosome. In the evolutionary comparison conducted here, the Alu repeat element is found at the Y boundary in great apes, but it is not found there in two Old World monkeys. During the evolution of the Old World monkey and great ape lineages, homology between the sex chromosomes was maintained by recombination in the sequences telomeric to the Alu insertion site. The Alu repeat element did not create the present-day boundary; instead, it inserted at the preexisting boundary after the Old World monkey and great ape lineages diverged.

Animals↗
PubMed1990

Frequent deletions of the human X chromosome distal short arm result from recombination between low copy repetitive elements.

Substantial DNA deletions appear to be the molecular basis of several human genetic disorders but rarely account for the majority of observed mutations at any given locus. Exceptions in which deletions do account for the majority of observed abnormalities include the alpha-thalassemias, Duchenne muscular dystrophy, and steroid sulfatase deficiency. Variable deletion breakpoints have been recognized at the alpha-globin and dystrophin loci, but no information is available regarding STS deletions. We have found that these STS alterations usually involve breakpoints within highly similar sequence elements situated approximately 1.9 megabases apart on the X chromosome. It is surprising that these very large deletions produce such mild clinical abnormalities. These results may provide insight into the molecular mechanism of a number of human genetic defects.

Cell Line↗
PubMed1990

A long range restriction map of the distal human X chromosome short arm around the steroid sulfatase locus.

The distal short arm of the human X chromosome is of interest because it contains genes which escape X chromosome inactivation and because it is subject to frequent deletions in human patients. The steroid sulfatase gene has been particularly well studied as an example of a gene which escapes X inactivation and which is included in a number of these deletion events. For these reasons a physical map of the region around the STS gene would be of interest. We have constructed a rare cutting enzyme map of this area and have determined the position of several nearby markers with respect to STS. We have also oriented the 5' and 3' ends of the STS gene on this map and have determined the centromeric and telomeric portions of the region. Finally, we have shown that this map can be used to locate deletion breakpoints in STS deficient patients.

Arylsulfatases↗
PubMed1990

Cloning of cDNAs for human phosphoribosylpyrophosphate synthetases 1 and 2 and X chromosome localization of PRPS1 and PRPS2 genes.

Cloned cDNAs representing the entire, homologous (80%) translated sequences of human phosphoribosylpyrophosphate synthetase (PRS) 1 and PRS 2 cDNAs were utilized as probes to localize the corresponding human PRPS1 and PRPS2 genes, previously reported to be X chromosome linked. PRPS1 and PRPS2 loci mapped to the intervals Xq22-q24 and Xp22.2-p22.3, respectively, using a combination of in situ chromosomal hybridization and human x rodent somatic cell panel genomic DNA hybridization analyses. A PRPS1-related gene or pseudogene (PRPS1L2) was also identified using in situ chromosomal hybridization at 9q33-q34. Human HPRT and PRPS1 loci are not closely linked. Despite marked cDNA and deduced amino acid sequence homology, human PRS 1 and PRS 2 isoforms are encoded by genes widely separated on the X chromosome.

Animals↗