Biomedical subjects

David Schlessinger

Publications and source records attributed to David Schlessinger.

24 records · Page 2Linked to original sources

PubMed2003

Plac8 and Plac9, novel placental-enriched genes identified through microarray analysis.

Microarray expression profiling of a collection of 15,000 mouse genes with placental and embryonic RNAs revealed candidates for placental-enriched genes, three of which we have confirmed and further characterized. One, Plac1, strongly expressed in all trophoblast-derived cells in the placenta, has been described earlier (Genomics 68 (2000) 305). Here we report that of the other two, Plac8 expression is restricted to the spongiotrophoblast layer during development, whereas Plac9 is weakly expressed though highly enriched in placenta. For both, cDNAs with complete open reading frames were recovered and exon-intron structures inferred from comparisons of mouse cDNA and genomic sequence. The predicted proteins (112 and 108 amino acids) both contain putative signal peptides, with a coiled-coil segment of mPLAC9 as the only other detected motif. Genomic sequence comparisons reveal that in addition to an apparent pseudogene on chromosome 1, Plac8 is expressed at mouse cytoband 5e3. It is tightly conserved in human in a syntenically equivalent ortholog at 4q21.23. Plac9 is present in a single copy on chromosome 14, with a syntenically equivalent human ortholog at 10q22.3. Putative promoter regions up to 10 kb 5' of the transcription units for Plac1, Plac8, and Plac9 contain sites for widely-expressed transcription factors which, by analogy to other instances, may be sufficient to explain placental enrichment.

Amino Acid Sequence↗

PubMed2002

Genes and translocations involved in POF.

Changes at a single autosomal locus and many X-linked loci have been implicated in women with gonadal dysgenesis [premature ovarian failure (POF) with deficits in ovarian follicles]. For the chromosome 3 locus, a forkhead transcription factor gene (FOXL2) has been identified, in which lesions result in decreased follicles by haploinsufficiency. In contrast, sporadic X; autosomal translocations are distributed at many points on the X, but concentrate in a critical region on Xq. The association of the breakpoints with genes involved in ovarian function is thus far weak (in four analyzed cases) and has not been related to pathology in other POF patients. While many more translocations can be analyzed in detail as the human genome sequence is refined, it remains possible that translocations like X monosomy (Turner syndrome) lead to POF not by interrupting specific genes important in ovarian development, but by causing aberrations in pairing or X-inactivation during folliculogenesis. It is noted that the critical region has unusual features, neighboring the X-inactivation center and including an 18 Mb region of very low recombination. These suggest that chromosome dynamics in the region may be sensitive to structural changes, and when modified by translocations might provoke apoptosis at meiotic checkpoints. Choices among models for the etiology of POF should be feasible based on studies of ovarian follicle development and attrition in mouse models. Studies would prominently include gene expression profiling of developmental-specific pathways in nascent ovaries with controlled levels of Foxl2 and interacting proteins, or with defined changes in the X chromosome.

Chromosomes, Human, X↗

PubMed2002

EDA targets revealed by skin gene expression profiles of wild-type, Tabby and Tabby EDA-A1 transgenic mice.

Mutations in the EDA gene cause anhidrotic ectodermal dysplasia (EDA), with lesions in skin appendage formation. To begin to analyze EDA pathways, we have used expression profiling on 15,000-gene mouse cDNA microarrays, comparing adult mouse skin from wild-type, EDA-defective (Tabby) mice, and Tabby mice supplemented with the EDA-A1 isoform, which is sufficient to rescue multiple Tabby phenotypes. Given the sensitivity of the current microarray system, 8500 genes (60%) were estimated to be expressed, including transcription factors and growth-regulatory genes that had not previously been identified in skin; but only 24 (0.16%), one-third of them novel, showed significant differences between wild type and Tabby. An additional eight genes not included in the 15,000 gene set were shown to have expression differences by real-time RT-PCR. Sixteen of 32 affected genes were restored significantly toward wild-type levels in EDA-A1 transgenic Tabby mice. Significant up-regulation in Tabby skin was observed for several dermal matrix genes, including Col1a1, Col1a2, Col3a1 and SPARC: In contrast, down-regulation occurred for the NEMO/NF-kappa B pathway, already implicated in skin appendage formation, and even more markedly for a second pathway, JNK/c-jun/c-fos and their target genes, that has not previously been clearly associated with skin development. These data are consistent with the regulation of the NF-kappa B pathway by EDA, and support its involvement in the regulation of the JNK pathway as well.

Animals↗

PubMed2002

Overgrowth of a mouse model of the Simpson-Golabi-Behmel syndrome is independent of IGF signaling.

The type 1 Simpson-Golabi-Behmel overgrowth syndrome (SGBS1) is caused by loss-of-function mutations of the X-linked GPC3 gene encoding glypican-3, a cell-surface heparan sulfate proteoglycan that apparently plays a negative role in growth control by an unknown mechanism. Mice carrying a Gpc3 gene knockout exhibited several phenotypic features that resemble clinical hallmarks of SGBS1, including somatic overgrowth, renal dysplasia, accessory spleens, polydactyly, and placentomegaly. In Gpc3/DeltaH19 double mutants (lacking GPC3 and also carrying a deletion around the H19 gene region that causes bialellic expression of the closely linked Igf2 gene by imprint relaxation), the Gpc3-null phenotype was exacerbated, while additional SGBS1 features (omphalocele and skeletal defects) were manifested. However, results from a detailed comparative analysis of growth patterns in double mutants lacking GPC3 and also IGF2, IGF1, or the type 1 IGF receptor (IGF1R) provided conclusive genetic evidence inconsistent with the hypothesis that GPC3 acts as a growth suppressor by sequestering or downregulating an IGF ligand. Nevertheless, our data are compatible with a model positing that there is downstream convergence of the independent signaling pathways in which either IGFs or (indirectly) GPC3 participate.

Abnormalities, Multiple↗

PubMed2002

The EDA gene is a target of, but does not regulate Wnt signaling.

Lesions in the anhidrotic ectodermal dysplasia (EDA) gene cause the recessive human genetic disorder X-linked anhidrotic ectodermal dysplasia, which is characterized by the poor development of ectoderm-derived structures. Ectodysplasin-A, the protein encoded by the EDA gene, is a member of the tumor necrosis factor ligand superfamily that forms a collagen triple helix, suggesting functions in signal transduction and cell adhesion. In an effort to elucidate the function of EDA in pathways regulating ectodermal development, we have analyzed promoter elements of the gene. We show here that a binding site for the lymphocyte enhancer factor 1 (Lef-1) transcription factor is active. In electrophoretic mobility shift assays, Lef-1 specifically bound to its site in the EDA promoter. Over-expression of both Lef-1 and beta-catenin significantly increased EDA transcription in co-transfection studies. In addition, indirect stabilization of endogenous beta-catenin stimulated EDA transcription 4- to 13-fold. This is the first direct evidence of a relationship between EDA and the Wnt pathway. We have also investigated whether EDA might function in a feedback loop to modulate Wnt signaling. Over-expression of EDA neither stimulated basal transcription of Wnt-dependent genes, nor inhibited Wnt-dependent activation of transcription. Taken together, our results demonstrate that Wnt signaling does control EDA gene expression, but ectodysplasin-A does not feedback on the Wnt pathway.

Animals↗

PubMed2002

PLAC1, a trophoblast-specific gene, is expressed throughout pregnancy in the human placenta and modulated by keratinocyte growth factor.

Plac1, a placenta-specific gene, is expressed exclusively by cells of trophoblastic lineage in the mouse, and maps to a region of the X chromosome known to be important in placental growth. These studies were undertaken to define the cellular location of the mRNA for the human orthologue, PLAC1, within the human placenta, and to examine its expression throughout gestation. By Northern analysis, PLAC1 mRNA was detected in term human placenta, migrating as a single 1.7 kb transcript, but in no other fetal or adult tissues tested. Expression was observed throughout gestation, whereas mouse Plac1 is significantly reduced after 12.5 dpc. Using an (35)S-labeled riboprobe, PLAC1 expression was trophoblast-specific at all stages of gestation (8-41 weeks); no expression was seen in cells within the stromal compartment or decidua. Using BeWo choriocarcinoma cells as a trophoblast model, keratinocyte growth factor (KGF) stimulated steady-state PLAC1 mRNA expression approximately twofold by Northern analysis and quantitative real-time PCR. Stimulation was observed only after 24 hr of exposure, suggesting that the stimulatory effect of KGF is secondary to the promotion of trophoblast growth or differentiation. No change in mRNA levels resulted from exposure to insulin-like growth factor II (IGF-II). Trophoblast-specific expression throughout gestation and responsiveness to KGF are consistent with a fundamental role for PLAC1 at the maternal-fetal interface.

Cell Line↗