PubMed Health⌕ Search

Biomedical subjects

M S Lyu

Publications and source records attributed to M S Lyu.

25 records · Page 2Linked to original sources
PubMed1995

Expression of Brca1 is associated with terminal differentiation of ectodermally and mesodermally derived tissues in mice.

We have isolated genomic and cDNA clones of Brca1, a mouse homolog of the recently cloned breast cancer-associated gene, BRCA1. Brca1 encodes an 1812-amino-acid protein with a conserved zinc finger domain and significant homology to the human protein. Brca1 maps to Chromosome 11 within a region of conserved synteny with human chromosome 17, consistent with the mapping of the human gene to 17q21. Brca1 transcripts are expressed in a variety of cultured cells but reveal a specific and dynamic expression pattern during embryonic development. For example, expression is observed first in the otic vesicle of embryonic day 9.5 (E9.5) embryos. This expression diminishes and is replaced by expression in the neuroectoderm at E10.5. By E11-12.5, higher levels are observed in differentiating keratinocytes and in whisker pad primordia. Transcripts also become evident in epithelial cells of the E14-17 kidney. Brca1 expression occurs in differentiating epithelial cells of several adult organs as well, suggesting a general role in the functional maturation of these tissues. Consistent with this, Brca1 transcripts are expressed in both alveolar and ductal epithelial cells of the mammary gland. During pregnancy, there is a large increase in Brca1 mRNA in mammary epithelial cells, an increase that parallels their functional differentiation. Because high rates of breast cancer are associated with loss of BRCA1 in humans, it is possible that this gene provides an important growth regulatory function in mammary epithelial cells. In addition, increased transcription of mammary Brca1 during pregnancy might contribute, in part, to the reduced cancer risk associated with exposure to pregnancy and lactation.

Amino Acid Sequence↗
PubMed1995

Establishment and characterization of a cell line (CUMC-3) derived from a human squamous carcinoma of the uterine cervix.

A new cell line, CUMC-3, has been derived from an invasive nonkeratinizing squamous cell carcinoma of the uterine cervix in a 32-year-old patient. It has been maintained in long-term culture for 59 months, and passaged over 310 times. Monolayer-cultured cells were polygonal in shape, showing a pavement-like arrangement and a tendency to pile up without contact inhibition. The epithelial nature of the cultured CUMC-3 cells was also confirmed by transmission electron microscopy which demonstrated the presence of desmosomes and tonofilaments. The cells were highly tumorigenic in nude mice and the transplanted tumors were poorly differentiated squamous carcinoma which closely resembled the original tumor. Cultured cells obtained from the CUMC-3-derived nude mouse tumor, CUMC-3N, also were studied for its characterization. Repeated chromosome analysis revealed a stable clone with the modal chromosome number of 78. The metaphase of this cell line had multiple structural aberrations of chromosomes 1, 3, 8, 10, 11, 20, and X and showed several markers of unknown origin. The results of isozyme analyses were distinct from the HeLa cell line. The identical genetic signature was demonstrated both in CUMC-3 and in CUMC-3N cells. Cultured CUMC-3 cells produced human chorionic gonadotropin beta-subunit and tumor antigen of squamous cell carcinoma (TA-4). Cytosol estrogen receptors were found in this cell line but progesterone receptors were not measured. HLA typing of CUMC-3 cells indicated the presence of DR4, DR8, DQw3, and DQw6. The result of oncogene analysis using Southern blotting technique revealed no amplification of oncogene c-myc. Analysis of the DNA samples extracted from the CUMC-3 cells showed the presence of human papillomavirus type 16 DNA. Using the single-strand conformation polymorphism technique, we have screened CUMC-3 cells for p53 mutation in exons 4 to 9. No mobility shift was observed in this cell line. This cell line may be useful in studying the in vitro and in vivo properties of human cervical carcinoma.

Adult↗
PubMed1994

Genetic mapping of the amphotropic murine leukemia virus receptor on mouse chromosome 8.

Southern blotting with a molecular clone of the amphotropic murine leukemia virus receptor identified restriction enzyme length polymorphisms among different taxonomic groups of mice. Analysis of the progeny of two interspecies genetic crosses was used to establish the genetic map location of the mouse gene encoding this receptor, Ram1, within the proximal region of chromosome 8.

Animals↗
PubMed1994

The mouse gene encoding the GM2 activator protein (Gm2a): cDNA sequence, expression, and chromosome mapping.

The GM2 activator protein forms a substrate-complex with GM2 ganglioside, which enables degradation of the ganglioside by beta-hexosaminidase A. Mutations in the human GM2 activator protein gene (GM2A) result in the GM2 gangliosidosis AB variant, a severe neurological disease. We have isolated and sequenced a mouse GM2 activator protein (Gm2a) cDNA with complete protein coding and 3' untranslated regions. Expression of the Gm2a transcript (approximately 2.3 kb) was apparent in all tissues examined and was most abundant in kidney and testis. The Gm2a gene was mapped to a region on mouse chromosome (Chr) 11 that is homologous with a segment of human chromosome 5 containing the orthologous human gene. In addition, a Gm2a-related sequence (Gm2a-rs1) was mapped to mouse Chr 5.

Animals↗
PubMed1994

Two distinct protein isoforms are encoded by ntk, a csk-related tyrosine protein kinase gene.

Recently, we and others have cloned cDNAs encoding a second member of the Csk family of inhibitory tyrosine protein kinases, which we have termed Ntk. Intriguingly, the mouse ntk cDNA sequences published by two independent groups differed by the presence or absence of a 136 nucleotide-insert near their 5' ends. In this report, we demonstrate that this 136 nucleotide-sequence likely corresponds to a complete exon in the ntk gene (termed exon 2), and that the two types of cDNAs/transcripts are produced by alternative splicing. Using ribonuclease protection assays, it was also established that brain and lymphoid organs, as well as most hemopoietic cells, predominantly expressed ntk transcripts lacking exon 2. In contrast, selected hemopoietic cell lines, such as the immature myeloid cell lines 32D cl3(G) and WEHI-3B, exclusively possessed exon 2-bearing RNAs. Interestingly, exon 2 introduced a novel in-frame upstream AUG in the ntk transcript, which is in the appropriate context for translation initiation. Evidence was obtained that this AUG is utilized in vivo, and that it extends the amino-terminal sequence of Ntk by 40 amino acids. Indeed, while exon 2-deficient ntk RNAs were translated into a 52 kilodalton (kDa) polypeptide (p52ntk), those bearing exon 2 produced a 56 kDa protein (p56ntk). Furthermore, p56ntk, but not p52ntk, was recognized by an antiserum directed against the novel amino-terminal sequence encoded by exon 2. Additional biochemical characterizations showed that p52ntk and p56ntk were localized to the cytoplasm, and that they partially accumulated in the detergent-insoluble cellular fraction. This last finding suggested that the Ntk proteins can associate with the cytoskeleton. Finally, through linkage analysis of two multilocus crosses, the ntk gene was mapped to Chromosome 10 in the mouse. Taken together, these data showed that ntk, a csk-related tyrosine protein kinase gene, encodes two protein isoforms expressed in distinct cell types. Moreover, they raised the possibility that Ntk may be involved in the regulation of Src-like enzymes in detergent-insoluble cellular compartments.

3T3 Cells↗