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PubMed1988

Early increase in histone H1(0) mRNA during differentiation of F9 cells to parietal endoderm.

We have isolated and characterized cDNA clones coding for the H1 histone subtype H1(0) in mouse teratocarcinoma cells. The mRNA is 2100 nt long and contains a coding sequence which is highly related to that of the human H1(0) gene. Using this cDNA as a probe, we have shown that, in comparison to undifferentiated F9 cells, differentiated F9 teratocarcinoma cells contain large amounts of H1(0) mRNA. This increase takes place very early during differentiation and does not correlate with changes in the rate of cell division. This indicates that the accumulation of H1(0) mRNA is not the result of reduced proliferation. Most likely on the contrary, the increase in the amount of H1(0) and the resulting effects on the formation of high order chromatin structures are parts of the differentiation program induced in F9 cells.

Amino Acid Sequence↗
PubMed1992

Basement membrane lectin binding sites are decreased in the esophageal endoderm during the arrival of presumptive muscle mesenchyme in the developing asteroid Pisaster ochraceus.

Basement membranes (BMs) of vertebrates and invertebrates have been shown to contain glycoproteins and proteoglycans, which include oligosaccharides and glycosaminoglycans. Lectin binding sites were characterized in the BM of gastrulating embryos of the starfish, Pisaster ochraceus. In early and mid-gastrulae, the fluorescein isothiocyanate (FITC)-lectin conjugates of concanavalin A (Con A) and wheat germ agglutinin (WGA) reveal the presence of mannose/glucose and glucosamine/sialic acid residues in the BM of all regions of the embryos. However, in the late gastrula embryo, an apparent reduction of these components is observed over the esophageal BM. Ultrastructural studies using the lectin-gold conjugates Con A, Limax flavus agglutinin (LFA), specific for sialic acid, and Dolichos biflorus agglutinin (DBA), specific for galactosamine, demonstrate that most mannose/glucose and galactosamine-containing residues lie in the lamina densa, whereas most sialic acid residues are located over the lamina lucida. In addition, a statistical analysis of lectin binding in the late gastrula embryo reveals that the amount of labelling with both Con A and LFA is significantly reduced in the esophageal region, suggesting that mannose/glucose and sialic acid residues are reduced in this region. These results confirm the observations of the FITC-lectin studies described above. They also confirm earlier studies that demonstrated a difference in BM morphology of the esophageal region (Crawford, '88). Mesenchyme cells, some of which arise from the forming coeloms (Crawford, '90), and which may represent a distinct population, colonize exclusively on this esophageal BM, where they later differentiate into muscle. Quantitative differences in BM glycoconjugates may act to direct the presumptive muscle cells to the region of the esophagus.

Animals↗
PubMed1995

Cloning, characterization, and development expression of a rat lung alveolar type I cell gene in embryonic endodermal and neural derivatives.

We report here the identification and characterization of a novel gene, T1 alpha, expressed in high abundance in adult rat lung, fetal lung, and early fetal brain. T1 alpha was identified by a monoclonal antibody previously shown to be specific for an antigen expressed by alveolar epithelial type I cells. The cDNA for T1 alpha is 1.85 kb and identifies a single mRNA species of the same size on Northern blots of adult rat lung. The longest open reading frame of the cDNA is 498 bases which would encode a protein of approximately 18 kDa. The protein has a putative membrane spanning domain near the C-terminus but lacks consensus sequences for N-glycosylation. Northern blots and RT-PCR show high expression of T1 alpha in adult lung, with marginally detectable expression in adult brain, intestine, and kidney. RT-PCR analysis shows expression of T1 alpha in freshly isolated type I cells (50-60% purity) but not in highly purified type II cells or other lung cells. We believe therefore that T1 alpha is primarily if not uniquely expressed in alveolar type I cells in the adult rat. Polyclonal antisera against a 16-amino-acid peptide identified in the deduced sequence reacts with the apical membranes of adult type I cells in lung tissue sections but does not label other cell types. The above antiserum as well as the original monoclonal antibody recognize a single approximately 18-kDa protein derived from bacterial expression of a construct containing the T1 alpha open reading frame. By RT-PCR T1 alpha is detected in rat lung from Day 13.5 onward, but is detected by in situ hybridization earlier in lung, brain and neural derivatives, and foregut. Expression is down-regulated in all but lung tissues as development proceeds.

Amino Acid Sequence↗
PubMed1997

HNF-6 is expressed in endoderm derivatives and nervous system of the mouse embryo and participates to the cross-regulatory network of liver-enriched transcription factors.

Hepatocyte nuclear factor-6 (HNF-6) is a liver-enriched transcription factor that contains a single cut domain and a novel type of homeodomain. Here we have studied the developmental expression pattern of HNF-6 in the mouse. In situ hybridization experiments showed that HNF-6 mRNA is detected in the liver at embryonic day (E) 9, at the onset of liver differentiation. HNF-6 mRNA disappeared transiently from the liver between E12.5 and E15. In transfection experiments HNF-6 stimulated the expression of HNF-4 and of HNF-3 beta, two transcription factors known to be involved in liver development and differentiation. HNF-6 was detected in the pancreas from E10.5 onward, where it was restricted to the exocrine cells. HNF-6 was also detected in the developing nervous system. Both the brain and the spinal cord started to express HNF-6 at E9-9.5 in postmitotic neuroblasts. Later on, HNF-6 was restricted to brain nuclei, to the retina, to the ventral horn of the spinal cord, and to dorsal root ganglia. Our observations that HNF-6 contributes to the control of the expression of transcription factors and is expressed at early stages of liver, pancreas, and neuronal differentiation suggest that HNF-6 regulates several developmental programs.

Animals↗