Breaking the species barrier: derivation of germline-competent embryonic stem cells from Mus spretus x C57BL/6 hybrids

Embryonic stem (ES) cells, which can differentiate into almost all types of cells, have been derived from the house mouse Mus musculus, rat, rabbit, humans, and other species. Transmission of the genotype to the offspring of chimeras has been achieved only with M. musculus ES cells. limiting targeted mutagenesis using ES cells to this species. Mus spretus, which exhibits many genetic polymorphisms with M. musculus, displays dominant resistance to cancer and inflammation, making derived inbred strains very useful in positional cloning and interspecies mapping. We show here for the first time the derivation of ES cells from hybrid blastocysts, obtained by the mating of two different species, namely Mus muscalus and Mus spretus, and their use for the generation of chimeric mice that transmit the Mus spretus genotype and phenotype to the offspring. These hybrid ES cells allow the genetic manipulation of Mus spretus, as an alternative to Mus musculus

The pituitary adenylate cyclase–activating polypeptide is a physiological inhibitor of platelet activation

The pituitary adenylate cyclase–activating polypeptide (PACAP) is a neuropeptide of the vasoactive intestinal peptide/secretin/glucagon superfamily. Studies in two related patients with a partial trisomy 18p revealed three copies of the PACAP gene and elevated PACAP concentrations in plasma. The patients suffer from severe mental retardation and have a bleeding tendency with mild thrombocytopenia, and their fibroblasts show increased PACAP mRNA levels. The PACAP receptor (vasoactive intestinal peptide/pituitary adenylate cyclase–activating peptide receptor 1 [VPAC1]) in platelets and fibroblasts is coupled to adenylyl cyclase activation. Accordingly, we found increased basal cAMP levels in patients’ platelets and fibroblasts, providing a basis for the reduced platelet aggregation in these patients. Megakaryocyte-specific transgenic overexpression of PACAP in mice correspondingly increased PACAP release from platelets, reduced platelet activation, and prolonged the tail bleeding time. In contrast, the PACAP antagonist PACAP(6-38) or a monoclonal PACAP antibody enhanced the collagen-induced aggregation of normal human platelets, and in PACAP knockout mice, an increased platelet sensitivity toward collagen was found. Thus, we found that PACAP modulates platelet function and demonstrated what we believe to be the first hemostatic defect associated with PACAP overexpression; our study suggests the therapeutic potential to manage arterial thrombosis or bleeding by administration of PACAP mimetics or inhibitors, respectively