The vertebrate body plan has conserved handed left-right (LR) asymmetry that is manifested in the heart, lungs, and gut. Leftward flow of extracellular fluid at the node (nodal flow) is critical for normal LR axis determination in the mouse. Nodal flow is generated by motile node cell monocilia and requires the axonemal dynein, left-right dynein (lrd). In the absence of lrd, LR determination becomes random. The cation channel polycystin-2 is also required to establish LR asymmetry. We show that lrd localizes to a centrally located subset of node monocilia, while polycystin-2 is found in all node monocilia. Asymmetric calcium signaling appears at the left margin of the node coincident with nodal flow. These observations suggest that LR asymmetry is established by an entirely ciliary mechanism: motile, lrd-containing monocilia generate nodal flow, and nonmotile polycystin-2 containing cilia sense nodal flow initiating an asymmetric calcium signal at the left border of the node.

Transplantation of pronuclei between one-cell-stage embryos was used to construct diploid mouse embryos with two female pronuclei ( biparental gynogenones ) or two male pronuclei ( biparental androgenones ). The ability of these embryos to develop to term was compared with control nuclear-transplant embryos in which the male or the female pronucleus was replaced with an isoparental pronucleus from another embryo. The results show that diploid biparental gynogenetic and androgenetic embryos do not complete normal embryogenesis, whereas control nuclear transplant embryos do. We conclude that the maternal and paternal contributions to the embryonic genome in mammals are not equivalent and that a diploid genome derived from only one of the two parental sexes is incapable of supporting complete embryogenesis.

The lats gene has been identified as a tumour suppressor in Drosophila melanogaster using mosaic screens. Mosaic flies carrying somatic cells that are mutant for lats develop large tumours in many organs. The human LATS1 homologue rescues embryonic lethality and inhibits tumour growth in lats mutant flies, demonstrating the functional conservation of this gene. Biochemical and genetic analyses have revealed that LATS1 functions as a negative regulator of CDC2 (ref. 3). These data suggest that mammalian LATS1 may have a role in tumorigenesis. To elucidate the function of mammalian LATS1, we have generated Lats1-/- mice. Lats1-/- animals exhibit a lack of mammary gland development, infertility and growth retardation. Accompanying these defects are hyperplastic changes in the pituitary and decreased serum hormone levels. The reproductive hormone defects of Lats1-/- mice are reminiscent of isolated LH-hypogonadotropic hypogonadism and corpus luteum insufficiency in humans. Furthermore, Lats1-/- mice develop soft-tissue sarcomas and ovarian stromal cell tumours and are highly sensitive to carcinogenic treatments. Our data demonstrate a role for Lats1 in mammalian tumorigenesis and specific endocrine dysfunction.

In nonneuronopathic type 1 Gaucher disease (GD1), mutations in the glucocerebrosidase gene (GBA1) gene result in glucocerebrosidase deficiency and the accumulation of its substrate, glucocerebroside (GL-1), in the lysosomes of mononuclear phagocytes. This prevailing macrophage-centric view, however, does not explain emerging aspects of the disease, including malignancy, autoimmune disease, Parkinson disease, and osteoporosis. We conditionally deleted the GBA1 gene in hematopoietic and mesenchymal cell lineages using an Mx1 promoter. Although this mouse fully recapitulated human GD1, cytokine measurements, microarray analysis, and cellular immunophenotyping together revealed widespread dysfunction not only of macrophages, but also of thymic T cells, dendritic cells, and osteoblasts. The severe osteoporosis was caused by a defect in osteoblastic bone formation arising from an inhibitory effect of the accumulated lipids LysoGL-1 and GL-1 on protein kinase C. This study provides direct evidence for the involvement in GD1 of multiple cell lineages, suggesting that cells other than macrophages may be worthwhile therapeutic targets.

Nuclear transplantation in the mouse embryo was achieved by using a method that combines microsurgical removal of the zygote pronuclei with the introduction of a donor nucleus by a virus-mediated cell fusion technique. Survival of embryos was greater than 90 per cent in tests of this procedure. The embryos developed to term at a frequency not significantly different from that of nonmanipulated control embryos. Because nuclei and cytoplasm from genetically distinct inbred mouse strains can be efficiently interchanged, this procedure may be useful in characterizing possible cytoplasmic contributions to the embryonic and adult phenotype.