Cytogenetics and cell genetics最新文献

Many studies have been published establishing the background frequencies of disomic and diploid sperm in normal men by fluorescence in situ hybridization (FISH) analysis, with highly significant variance among the reports. Besides interdonor heterogeneity and differences in the experimental protocols used, the question of inherent differences in chromosome malsegregation and meiotic arrest among different geographic and ethnic groups of donors has been raised. In this study, multicolor FISH analysis was carried out on semen samples from 10 nonsmoking, nondrinking Chinese men from the People's Republic of China. The results were compared to FISH data on 10 nonsmoking, nondrinking Canadians under the same experimental conditions, in the same laboratory. A total of 200,497 sperm was scored in the Chinese donors and compared to 202,320 sperm from Canadian donors. Approximately 10,000 sperm per chromosome probe per donor were analyzed. The mean hybridization efficiency was 99.99%. The frequencies of X-bearing and Y-bearing sperm were not significantly different from the expected 50% for each individual and for the combined data from all donors (49.73% vs. 49.46%, P = 0.3946). The mean disomy frequencies (range) were 0.07% (0.02%-0.12%) for chromosome 13, 0.18% (0.09%-0.19%) for chromosome 21, 0.05% (0. 01%-0.09%) for 24,XX, 0.02% (0.01%-0.06%) for 24,YY, and 0.29% (0. 13%-0.49%) for 24,XY. The mean diploidy frequency (range) was 0.38% (0.22%-0.73%) for 13-21 hybridizations and 0.32% (0.07%-0.70%) for XY hybridizations. Highly significant interdonor heterogeneity was found for diploidy (P = 0.0000) and for XY disomy (P = 0.0011), but no age effect was observed in any category of disomic or diploid sperm. The data reported here show no marked differences in disomy and diploidy frequencies between the mainland Chinese and Canadian groups, if donor heterogeneity is taken into account.

A member of the tumor necrosis factor (TNF) superfamily, human TNFSF14 (hTNFSF14)/HVEM-L (herpes virus entry mediator ligand) was isolated as a cellular ligand for HVEM/TR2 and human lymphotoxin beta receptor (LTbetaR). TNFSF14 induces apoptosis and suppresses tumor formation. We have isolated a cDNA clone for a mouse homologue of hTNFSF14 by signal sequence trap (SST) screening which we recently developed. The deduced amino acid sequence of the mouse TNFSF14 (mTNFSF14) cDNA comprised 239 amino acid residues and was 77% identical to the hTNFSF14 protein. In Northern blot analysis, 2.1 kb and 4.2kb mTNFSF14 transcripts were detected in spleen and lung, and in heart, respectively. Fluorescence in situ hybridization analysis localized the mTNFSF14 gene Tnfsf14 to chromosome 17 which is tightly linked with Tnf, Lta, and Ltb.

Heterochromatin protein 1 (HP1) is a nonhistone chromosomal protein, first identified in Drosophila, that plays a dose-dependent role in gene silencing. Three orthologs, HP1alpha, HP1beta, and HP1gamma, have been characterized in mammals. While HP1alpha and HP1beta have been unambiguously localized in heterochromatin by immunocytochemical methods, HP1gamma has been found either exclusively associated with euchromatin or present in both euchromatin and heterochromatin. Here, using an antibody directed against a peptide epitope at the carboxyl-terminal end of the molecule, we localize HP1gamma in both euchromatin and heterochromatin compartments of interphase nuclei, as well as in the pericentromeric chromatin and arms of mitotic chromosomes of 3T3 cells. This dual location was also observed in nuclei expressing HP1gamma as a fusion protein with green fluorescent protein. In contrast, when the distribution of HP1gamma was analyzed with antibodies directed against an amino-terminal epitope, the protein was detectable in euchromatin and not in heterochromatin, except for transient heterochromatin staining during the late S phase, when the heterochromatin undergoes replication. These data suggest that the controversial immunolocalization of HP1gamma in chromatin is due to the use of antibodies directed against topologically distinct epitopes, those present at the amino-terminal end of the molecule being selectively masked in nonreplicative heterochromatin.

In this study we have used FISH to examine the relationship between a group of homeobox genes, namely DLX1/DLX2, EVX2 and four HOXD genes (10, 11, 12, 13), that map to region q31 on chromosome 2, and the FRA2G and FRA2H fragile sites located at 2q31 and 2q32.1 respectively. Our results indicate that these homeobox genes lie between the two fragile regions.

Secretin is an endocrine hormone that stimulates the secretion of bicarbonate-rich pancreatic fluids. Recently, it has been discussed that secretin deficiency may be implicated in autistic syndrome, suggesting that the hormone could have a neuroendocrine function in addition to its role in digestion. In the present study, the human secretin gene (SCT) was isolated from a bacterial artificial chromosome genomic library. SCT contains four exons, with the protein coding regions spanning 713 bp of genomic DNA. Human SCT is similar structurally to the secretin genes of other species. Amino acid conservation, however, is most pronounced within the exon encoding the biologically active mature peptide. Northern blot analysis shows that human SCT transcripts are located in the spleen, intestinal tract, and brain. Radiation hybrid mapping places the SCT locus on chromosome 11p15.5.