Paneth cell carcinoma of the ampulla of Vater.

We describe a Paneth cell carcinoma arising within the ampulla of Vater in a 64-year-old man. The phenotype of virtually all neoplastic cells was consistent with that of Paneth cells, based on routine morphology and their strong positive immunostaining for lysozyme. Additional widespread positive immunostaining for carcinoembryonic antigen and CA 19.9 supports a totipotential cell as the origin of such neoplastic cells. This case, therefore, represents a true Paneth cell carcinoma, as opposed to inclusion of occasional neoplastic Paneth cells into a poorly differentiated adenocarcinoma. This pattern of differentiation is rare, and predictions regarding its ultimate biological behavior and malignant potential must be guarded.

The unsolved enigmas of leukemia inhibitory factor.

Leukemia inhibitory factor (LIF) is a polyfunctional glycoprotein cytokine whose inducible production can occur in many, perhaps all, tissues. LIF acts on responding cells by binding to a heterodimeric membrane receptor composed of a low-affinity LIF-specific receptor and the gp130 receptor chain also used as the receptor for interleukin-6, oncostatin M, cardiotrophin-1, and ciliary neurotrophic factor. LIF is essential for blastocyst implantation and the normal development of hippocampal and olfactory receptor neurons. LIF is used extensively in experimental biology because of its key ability to induce embryonic stem cells to retain their totipotentiality. LIF has a wide array of actions, including acting as a stimulus for platelet formation, proliferation of some hematopoietic cells, bone formation, adipocyte lipid transport, adrenocorticotropic hormone production, neuronal survival and formation, muscle satellite cell proliferation, and acute phase production by hepatocytes. Unwanted actions of LIF can be minimized by circulating soluble LIF receptors and by intracellular suppression by suppressors of cytokine-signaling family members. However, the outstanding problems remain of how the induction of LIF is mediated in response to demands from such a heterogeneity of target tissues and why it makes design sense to use LIF in the regulation of such a diverse and unrelated series of biological processes.

Gene expression profiling of embryo-derived stem cells reveals candidate genes associated with pluripotency and lineage specificity.

Large-scale gene expression profiling was performed on embryo-derived stem cell lines to identify molecular signatures of pluripotency and lineage specificity. Analysis of pluripotent embryonic stem (ES) cells, extraembryonic-restricted trophoblast stem (TS) cells, and terminally-differentiated mouse embryo fibroblast (MEF) cells identified expression profiles unique to each cell type, as well as genes common only to ES and TS cells. Whereas most of the MEF-specific genes had been characterized previously, the majority (67%) of the ES-specific genes were novel and did not include known differentiated cell markers. Comparison with microarray data from embryonic material demonstrated that ES-specific genes were underrepresented in all stages sampled, whereas TS-specific genes included known placental markers. Investigation of four novel TS-specific genes showed trophoblast-restricted expression in cell lines and in vivo, whereas one uncharacterized ES-specific gene, Esg-1, was found to be exclusively associated with pluripotency. We suggest that pluripotency requires a set of genes not expressed in other cell types, whereas lineage-restricted stem cells, like TS cells, express genes predictive of their differentiated lineage.

Loss of holocytochrome c-type synthetase causes the male lethality of X-linked dominant microphthalmia with linear skin defects (MLS) syndrome.

Girls with MLS syndrome have microphthalmia with linear skin defects of face and neck, sclerocornea, corpus callosum agenesis and other brain anomalies. This X-linked dominant, male-lethal condition is associated with heterozygous deletions of a critical region in Xp22.31, from the 5' untranslated region of MID1 at the telomeric boundary to the ARHGAP6 gene at the centromeric boundary. HCCS, encoding human holocytochrome c-type synthetase, is the only gene located entirely inside the critical region. Because single gene analysis is not feasible in MLS patients (all have deletions), we generated a deletion of the equivalent region in the mouse to study the molecular basis of this syndrome. This deletion inactivates mouse Hccs, whose homologs in lower organisms (cytochrome c or c1 heme lyases) are essential for function of cytochrome c or c1 in the mitochondrial respiratory chain. Ubiquitous deletions generated in vivo lead to lethality of hemizygous, homozygous and heterozygous embryos early in development. This lethality is rescued by expression of the human HCCS gene from a transgenic BAC, resulting in viable homozygous, heterozygous and hemizygous deleted mice with no apparent phenotype. In the presence of the HCCS transgene, the deletion is easily transmitted to subsequent generations. We did obtain a single heterozygous deleted female that does not express human HCCS, which is analogous to the low prevalence of the heterozygous MLS deletion in humans. Through the study of these genetically engineered mice we demonstrate that loss of HCCS causes the male lethality of MLS syndrome.

Histological and histochemical analysis of embryoid bodies.

We examined the histological structure of embryoid bodies arising from aggregation of mouse embryonic stem (ES D3) cells after 7, 12, 18 and 26 days of in vitro culture. Morphology of originally solid embryoid bodies was affected by the process of cavitation that resulted in formation of cystic embryoid bodies and by spontaneous differentiation of the ES D3 cells. We applied in situ immunophenotyping to characterise cell populations that spontaneously differentiated inside the embryoid bodies in the various stages. The most distinct cell populations that were found inside embryoid bodies were alpha-fetoprotein-positive endodermal cells and myogenic cells that expressed desmin, myogenin or smooth muscle actin. ES D3-derived endothelial cells generated during vasculogenesis inside the embryoid bodies differed from mature endothelial cells because they did not stain for von Willebrand factor. These cells also differed from endothelial cell that were generated during angiogenesis since they did not stain for the intermediate filament nestin. Our results demonstrate the usefulness of this in vitro model for studying early embryogenesis.