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It has been reported that endogenous retroviruses can contaminate human cell lines that have been passaged as xenotransplants in immunocompromised mice. We previously developed and described 2 human pancreatic β cell lines (EndoC-βH1 and EndoC-βH2) that were generated in this way. Here, we have shown that B10 xenotropic virus 1 (Bxv1), a xenotropic endogenous murine leukemia virus (MuLV), is present in these 2 recently described cell lines. We determined that Bxv1 was also present in SCID mice that were used for in vivo propagation of EndoC-βH1/2 cells, suggesting that contamination occurred during xenotransplantation. EndoC-βH1/2 cells released Bxv1 particles that propagated to human 293T and Mus dunni cells. Mobilization assays demonstrated that Bxv1 transcomplements defective MuLV-based retrovectors. In contrast, common rodent β cell lines, rat INS-1E and RIN-5F cells and mouse MIN6 and pTC3 cells, displayed either no or extremely weak xenotropic helper activity toward MuLV-based retrovectors, although xenotropic retrovirus sequences and transcripts were detected in both mouse cell lines. Bxv1 propagation from EndoC- βH1/2 to 293T cells occurred only under optimized conditions and was overall poorly efficient. Thus, although our data imply that MuLV-based retrovectors should be cautiously used in EndoC-βH1/2 cells, our results indicate that an involuntary propagation of Bxv1 from these cells can be easily avoided with good laboratory practices., Introduction Diabetes is caused by deficiency or malfunction of pancreatic p cells. Our understanding of the mechanisms underlying β cell maintenance and failure in humans has been hampered by the [...]

Recently, the expression of the peptide hormone ghrelin was detected in [alpha]-cells of the islets of Langerhans as well as in [epsilon]-cells, a newly discovered endocrine cell type, but it remains unclear how the latter is related in lineage to the four classical islet cell types, [alpha]-, [beta]-, [delta]-, and PP-cells. Here, we provide further evidence that ghrelin is predominantly produced in the [alpha]-cells of mouse islets but also in single hormone ghrelin-secreting [epsilon]-cells. We additionally demonstrate that pancreatic e-cells derive from Neurogenin3-expressing precursor cells and their genesis depends on Neurogenin3 activity. Furthermore, our data indicate that the number of ghrelin-producing cells is differentially regulated during pancreas morphogenesis by the homeodomain-containing transcription factors Arx, Pax4, and Pax6. Arx mutants lack [ghrelin.sup.+] [glucagon.sup.+] [alpha]-cells whereas Pax4 mutants develop an excess of these cells. Importantly, the [ghrelin.sup.+] [glucagon.sup.-] [epsilon]-cell population is not affected following Arx or Pax4 disruption. In contrast, the loss of Pax6 provokes an unexpected increase of the [ghrelin.sup.+] [glucagon.sup.-] [epsilon]-cell number which is not due to increased proliferation. Thus, we demonstrate that the development of ghrelin-producing cells is differentially dependent on Neurogenin3 in different domains of the gastrointestinal tract and that, in the endocrine pancreas, [epsilon]-cell genesis does not require Arx or Pax4 activities but is antagonized by Pax6. Keywords: Ghrelin; Pancreas; Neurogenin3; Arx; Pax4; Pax6; Development; Endocrine; Glucagon

Brain 4 (Brn4/Pou3f4) and Pax6 are POU-homeodomain and paired-homeodomain transcription factors, respectively, that are expressed in the brain and the glucagon-expressing cells in the pancreas. Brn4 expression begins at embryonic day 10 in the pancreas, just before pax6 and both appear in the glucagon immunoreactive cells. At a later time point, E19, no Brn4 co-localization is observed with insulin of somatostatin but a rare pancreatic polypeptide (PP)-producing cell can be found, while Pax6 is found in all endocrine cells. These data suggest that brn4 is the only [alpha]-cell specific transcription factor yet identified; therefore, we sought to analyze [alpha]-cell development and function in mice with a targeted disruption of the brn4 gene. In homozygous brn[4.sup.-/-] mice, pancreatic bud formation, glucagon cell numbers and physiological measurements all appear normal. Examination of other transcription factors found in the glucagon cells showed normal Pax6 and Nkx2.2 immunoreactivity, suggesting that Brn4 does not regulate these transcription factors. Pax6 mutant mice (pax[6.sup.Sey/Sey]), with a natural inactivating mutation in pax6, have few endocrine cells but normal numbers of Brn4 and Nkx2.2 cells. The pancreatic phenotype of the pax6 mutants can be rescued with a YAC clone containing the human Pax6 gene. Keywords: Pax6; Brn4; Transcription factors; Pancreas; Glucagon; Endocrine; Development; Embryology

Mice carrying loss-of-function mutations in certain Notch pathway genes display increased and accelerated pancreatic endocrine development, leading to depletion of precursor cells followed by pancreatic hypoplasia. Here, we have investigated the effect of expressing a constitutively active form of the Notch1 receptor ([Notch1.sup.ICD]) in the developing pancreas using the pdxl promoter. At el0.5 to e12.5, we observe a disorganized pancreatic epithelium with reduced numbers of endocrine cells, confirming a repressive activity of Notch1 upon the early differentiation program. Subsequent branching morphogenesis is impaired and the pancreatic epithelium forms cyst-like structures with ductal phenotype containing a few endocrine cells but completely devoid of acinar cells. The endocrine cells that do form show abnormal expression of cell type-specific markers. Our observations show that sustained Notch1 signaling not only significantly represses endocrine development, but also fully prevents pancreatic exocrine development, suggesting that a possible role of Notch1 is to maintain the undifferentiated state of common pancreatic precursor cells. Keywords: Notch; Pancreas; Gut; Exocrine; Endocrine; Duct; PDX1; Nkx6.1; Development; Embryology

The expression of cocaine- and amphetamine-regulated transcript (CART) mRNA in the arcuate nucleus of genetically obese rodents is determined by leptin signalling, as disruption of either circulating leptin levels or the leptin receptor leads to reduced expression of CART. It appears that circulating leptin is usually a repressor of neuropeptide Y (NPY) production in the arcuate nucleus. Leptin-mediate suppression of food intake could be regulated by a balanced reduction and induction of NPY and CART respectively.