Biomedical subjects
Publications and source records attributed to S Heuertz.
A linkage study of six families with spondyloepiphyseal dysplasia tarda (SEDL) has been performed. A linkage to site DXS41 (theta = 0.08; z = 3.07) and DXS92 (theta = 0.05; z = 2.95) has been established. We propose that the SEDL locus lies on the distal part of the short arm of the X chromosome.
Four kindreds segregating for Alport's syndrome (ASLN) compatible with a X-linked inheritance were studied for linkage with polymorphic markers of the human X chromosome. No recombinant was observed between the ASLN locus and the DXS101 and DXS94 loci, the maximum lod scores were z = 3.93 and 3.50 respectively. Linkage data between the ASLN locus and the other genetic markers used in the present study are in keeping with the assignment of the mutation to the proximal Xq arm.
Linkage studies have been performed in 5 incontinentia pigmenti (IP) families totaling 29 potentially informative meioses. Ten probes of the Xp arm were used, six of them were precisely localized on the X chromosome, using hamster X human somatic cell hybrids containing a broken X chromosome derived from an incontinentia pigmenti patient carrying an X;9 translocation [46,XX,t(X;9)(p11.21;q34)]. The following order for probes is proposed: pter - (DXS7, DXS146, DXS255) - IP1 - (DXS14, DXS90) - DXS106 - qter. The negative lod scores obtained exclude the possibility that in the families studied, the gene for IP is located in Xp11 or in the major part of the Xp arm.
According to the theoretical mechanism of DNA demethylation by 5-azacytidine, the complete demethylation of one site will require two cell divisions. If reexpression is directly related to demethylation, a maximal reexpression is expected after two cell divisions. In a hamster X human hybrid cell line containing an inactive human X chromosome treated by 5-azacytidine, we show that HPRT reactivation frequency is increased more than 10-fold when cells are allowed to divide 14 times before the selection for the HPRT reactivants. We suggest that the delay corresponds to changes in chromatin conformation.
The replication pattern of a human inactive X chromosome reactivated for one to four genes by 5-azacytidine has been studied by the BrdU-33258-Hoechst-Giemsa technique in four subclones of a somatic hamster-human hybrid. In one of them the pattern was clearly modified. In the three others the changes were not significant. No correlation was found between expression and replication.
A family is reported in which the index case presented with an acute form of maple syrup urine disease (MSUD), whereas two of her sisters and her father were found to have an almost asymptomatic form of the disease. It is proposed that the members of this family are compound heterozygotes for the classical deficient mutant gene and for a "variant" allele.
DNAs from 25 independent hamster X bovine somatic cell hybrids were submitted to the Southern blot analysis with probes made of unique cellular fragments adjacent to single-copy proviruses from three different bovine tumors. It appeared that these cellular sequences, and thus the respective proviruses, belonged to three different chromosomes in the three different tumors examined.
Hamster-human hybrids which contained an inactive human X chromosome were treated by 5-azacytidine. Hypoxanthine guanine phosphoribosyltransferase derepressed hybrids were selected and derepression of three other loci, phosphoglycerate kinase, alpha-galactosidase, and glucose-6-phosphate dehydrogenase were studied. Among 32 hybrids selected for hypoxanthine guanine phosphoribosyltransferase, two were found to be reactivated at four X loci. The independence or nonindependence of the reactivation events will be discussed. No correlation was found between the time of replication and the expression or nonexpression of the X chromosome genes: X chromosomes reactivated at four loci remained late replicating; conversely early replication can exist without the expression of some X genes.
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Human/hamster hybrid cell cultures were examined for the presence of ARSA and other marker enzymes. Many of these hybrids were also analyzed for human chromosomes. Our results confirm the assignment of ARSA to chromosome 22.
Twelve hamster x cattle (Bos taurus) cell hybrids showed loss of cattle chromosomes, which allows their use for chromosome mapping of cattle. Genes coding for G6PD, alpha-GAL A, PGK, and (indirectly) HGPRT are synteneic and localized on the X chromosome.
The expression of HLA, human and mouse beta2-microglobulin (beta2m), P red blood cell antigen and a receptor for marmoset red blood cells (MaRBC) were studied on 18 man/mouse and man/Chinese hamster hybrids. A positive correlation was found between the expression of HLA, P, and the receptor for MaRBC, which we interpret as a possible synteny between these different loci. We studied 3 hybrid clones where HLA antigens are still expressed despite the absence of human beta2m and where redistribution experiments demonstrate that HLA is associated with mouse beta2m. Synteny between HLA and the receptor for MaRBC can be a useful tool to select HLA-positive hybrid clones.
The human heteroploid cell line D98/AH-2 shows a low level of glycosaminoglycans (GAG) synthesis as compared with normal human diploid fibroblasts. Cellular hybrids were obtained by fusion of the D98/AH-2 cell line with normal fibroblasts, and fibroblasts derived from patients with mucopolysaccharidosis type II. In these hybrids the rate of GAG synthesis is intermediate between those of the parental cell lines.
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