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M A Glozak

Publications and source records attributed to M A Glozak.

6 recordsLinked to original sources
PubMed1998

BMP4- and RA-induced apoptosis is mediated through the activation of retinoic acid receptor alpha and gamma in P19 embryonal carcinoma cells.

Some growth factors, for example, members of the transforming growth factor-beta family, can induce apoptosis in a variety of cells. Retinoic acid (RA) also causes apoptosis in several malignant cell types. We have previously demonstrated that, although BMP2 or BMP4 cannot induce apoptosis alone, BMP2 or BMP4 and RA synergize to induce apoptosis in 95% of P19 embryonal carcinoma cells within 4 days of treatment. Such treatment also prevents neuronal differentiation of these cells. Retinoids exert their many effects through any of six distinct nuclear receptors. These retinoid-activated transcription factors directly regulate genes involved in cellular response such as apoptosis. Complete understanding of how BMP and RA specifically induce cell death requires identification of the retinoid receptors controlling apoptosis. By using receptor-selective retinoid agonists and antagonists, we have obtained evidence suggesting that activation of RAR alpha or gamma is sufficient to induce apoptosis in BMP4-treated cells.

Animals↗
PubMed1997

Induction of altered gene expression in early embryos.

This review focuses on known genes whose expression may be perturbed by teratogens during early embryogenesis (preorganogenesis). Teratogens may disrupt embryogenesis by modifying positional information. Genes controlling positional information include those specifying the primary body axes: anterior-posterior, dorsal-ventral, or left-right. These genes often encode transcription factors, whose regulation or activation can stimulate aberrant tissue differentiation and morphogenesis. Alternatively, teratogens may directly affect cell differentiation, proliferation, or apoptosis. Hydrophilic signalling molecules such as growth factors and hydrophobic molecules such as retinoids regulate these processes. The signalling pathways activated often induce the coordinate regulation of tissue specific gene expression. In addition to modifying individual signalling pathways, teratogens can synergize with or antagonize the effects of other teratogens through inappropriate interactions between signal transduction pathways. Since teratogens may often directly or indirectly perturb the expression of known or as yet undescribed developmentally critical genes, this review also provides a short description of techniques to identify genes whose expression is altered by teratogens.

Animals↗
PubMed1996

Specific induction of apoptosis in P19 embryonal carcinoma cells by retinoic acid and BMP2 or BMP4.

Retinoic acid (RA) affects the response of many cells to growth factors, including the bone morphogenetic proteins (BMPs). The BMPs are members of the TGF-beta, family of growth factors, originally identified by their bone-inducing activities. Their widespread expression suggests many roles other than that in osteogenesis. Because RA modulates the cell's response to growth factors, this may be a means by which the retinoids exert some of their known teratogenic effects. One such cellular response may be apoptosis. While apoptosis is required for normal development, the location and timing of its induction must be carefully controlled. Recently, several TGF-beta family members have been implicated in the induction of apoptosis in certain cell types. We show here, using P19 embryonal carcinoma cells, that the combination of RA and BMP2 or BMP4 synergistically induces apoptosis in 40% of the population within 24 hr. In contrast, RA alone induces apoptosis in only 10-15% of the population and each of the BMPs alone minimally induces apoptosis. Apoptosis depends on the dose of both the RA and the BMP as well as on new protein synthesis. Further, the induction of apoptosis prevents the formation of fully differentiated neurons and glial cells and instead leads to primarily smooth muscle cell differentiation. These results suggest that some of the malformations caused by retinoids may be due to the induction of inappropriate apoptosis in cells exposed to BMPs.

Apoptosis↗
PubMed1995

Identification and localization of a developmental stage-specific promoter activity from the murine lambda 5 gene.

The lambda 5 protein is expressed in pre-B cells in association with VpreB and mu-heavy chains, and is critical for differentiation to the B cell stage. Pre-B cell-specific expression of the lambda 5 and VpreB genes is regulated at the level of transcription initiation. In this report, we have identified several DNase l-hypersensitive sites 2.5- to 6.0-kb downstream of the lambda 5 gene, which are present in the pre-B cell line 70Z/3, but not in the myeloma cell line j558L. These sites, however, were shown to have no transcriptional enhancer activity as measured by transient transfection. Enhancer activity was identified within a 361-bp fragment (-296 to +65, where +1 is the major 5' transcription initiation site) upstream of the mouse lambda 5 gene. This activity is orientation and position independent, and is also tissue and differentiation stage specific (active in pre-B but not B and T cells). Deletion constructs indicate that three adjacent areas (-210 to -169, -153 to -64, and -64 to -22) are all necessary for enhancer activity. Pre-B cell-specific promoter activity was shown to reside within the -219 to +109 fragment. Basal promoter activity resides within the -64 to +109 fragment, but is not tissue specific or stage specific. A negative element within the -101 to -64 region is active in all lymphoid cell lines tested and therefore cannot by itself be responsible for the tissue and stage specificity. The data indicate that the elements responsible for the enhancer activity (-210 to -22) are part of the lambda 5 gene promoter and likely confer the tissue and stage specificity via positive elements within the -210 to -22 region.

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PubMedDate not supplied

The human lambda immunoglobulin enhancer is controlled by both positive elements and developmentally regulated negative elements.

We have recently reported the localization of the first transcriptional enhancer in the human lambda (lambda) immunoglobulin light chain locus. Enhancer activity was contained on a 1.2 kb SstI fragment, with partial activity retained on a core 111 bp PstI-SstI fragment. This enhancer is located 11.7 kb downstream of C lambda 7, the most 3' lambda constant region gene. Using a chloramphenicol acetyl transferase (CAT) assay system, we have now determined the boundaries of the complete enhancer and find it is two- to four-fold as active as the core fragment in both pre-B and B cell lines. Interestingly, a larger fragment, containing the complete enhancer as well as 5' and 3' flanking sequences has four- to eight-fold reduced activity when tested in pre-B cell lines, but full activity in B cell lines. This suggests the presence of developmentally regulated negative elements flanking the human lambda enhancer which prevent or reduce its activity at a developmentally incorrect time. By using in vivo footprinting we have begun to examine the protein interactions within this enhancer in a more physiologically relevant manner and have identified motifs which are shared with the murine lambda enhancers, as well as motifs unique to the human lambda enhancer.

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