Generation and validation of novel conditional flox and inducible Cre alleles targeting fibroblast growth factor 18 (Fgf18)

Background: Fibroblast growth factor 18 (FGF18) functions in the development of several tissues, including the lung, limb bud, palate, skeleton, central nervous system, and hair follicle. Mice containing a germline knockout of Fgf18 (Fgf18−/−) die shortly after birth. Postnatally, FGF18 is being evaluated for pathogenic roles in fibrosis and several types of cancer. The specific cell types that express FGF18 have been difficult to identify, and the function of FGF18 in postnatal development and tissue homeostasis has been hampered by the perinatal lethality of Fgf18 null mice. Results: We engineered a floxed allele of Fgf18 (Fgf18flox) that allows conditional gene inactivation and a CreERT2 knockin allele (Fgf18CreERT2) that allows the precise identification of cells that express Fgf18 and their lineage. We validated the Fgf18flox allele by targeting it in mesenchymal tissue and primary mesoderm during embryonic development, resulting in similar phenotypes to those observed in Fgf18 null mice. We also use the Fgf18CreERT2 allele, in combination with a conditional fluorescent reporter to confirm known and identify new sites of Fgf18 expression. Conclusion: These alleles will be useful to investigate FGF18 function during organogenesis and tissue homeostasis, and to target specific cell lineages at embry- onic and postnatal time points

Requirements for NuMA in maintenance and establishment of mammalian spindle poles

Microtubules of the mitotic spindle in mammalian somatic cells are focused at spindle poles, a process thought to include direct capture by astral microtubules of kinetochores and/or noncentrosomally nucleated microtubule bundles. By construction and analysis of a conditional loss of mitotic function allele of the nuclear mitotic apparatus (NuMA) protein in mice and cultured primary cells, we demonstrate that NuMA is an essential mitotic component with distinct contributions to the establishment and maintenance of focused spindle poles. When mitotic NuMA function is disrupted, centrosomes provide initial focusing activity, but continued centrosome attachment to spindle fibers under tension is defective, and the maintenance of focused kinetochore fibers at spindle poles throughout mitosis is prevented. Without centrosomes and NuMA, initial establishment of spindle microtubule focusing completely fails. Thus, NuMA is a defining feature of the mammalian spindle pole and functions as an essential tether linking bulk microtubules of the spindle to centrosomes

Astrocyte inactivation of the pRb pathway predisposes mice to malignant astrocytoma development that is accelerated by PTEN mutation

We have inactivated pRb, p107, and p130 in astrocytes by transgenic expression of T (a truncated SV40 T antigen) under the GFAP promoter. Founder mice died perinatally with extensive expansion of neural precursor and anaplastic astrocyte populations. In astrocytes, aberrant proliferation and extensive apoptosis were induced. Using a conditional allele of T, early lethality was circumvented, and adult mice developed high-grade astrocytoma, in which regions of decreased apoptosis expressed activated Akt. Indeed, astrocytoma development was accelerated in a , but not , background. These studies establish a highly penetrant preclinical model for astrocytoma based on events observed in the human disease and further provide insight into the role of PTEN mutation in astrocytoma progression

Amplifying Environmental Politics: Ocean Noise

Scientific evidence suggests that rising levels of anthropogenic underwater sound (“ocean noise”) produced by industrial activities are causing a range of injuries to marine animals—in particular, whales. These developments have forced states and development proponents into acknowledging ocean noise as a threat to marine economic activity. This paper delivers a Gramsci-inspired critique of the modernizations of ocean noise regulation being wrought by science, state and politics. Gramsci was acutely interested in the dynamic and social nature of scientific research, and his writings affirm science\u27s powers and ambitions. At the same time, he was keen to observe how science participates in the process he called hegemony. Using examples drawn from Canada\u27s West Coast, I suggest that capital is engaging ocean noise not only as a regulatory problem issuing from legal duties and legitimacy concerns, but opportunities linked to the commercialization of ocean science

Attenuated sensing of SHH by <i>Ptch1</i> underlies evolution of bovine limbs

The large spectrum of limb morphologies reflects the wide evolutionary diversification of the basic pentadactyl pattern in tetrapods. In even-toed ungulates (artiodactyls, including cattle), limbs are adapted for running as a consequence of progressive reduction of their distal skeleton to symmetrical and elongated middle digits with hoofed phalanges. Here we analyse bovine embryos to establish that polarized gene expression is progressively lost during limb development in comparison to the mouse. Notably, the transcriptional upregulation of the Ptch1 gene, which encodes a Sonic hedgehog (SHH) receptor, is disrupted specifically in the bovine limb bud mesenchyme. This is due to evolutionary alteration of a Ptch1 cis-regulatory module, which no longer responds to graded SHH signalling during bovine handplate development. Our study provides a molecular explanation for the loss of digit asymmetry in bovine limb buds and suggests that modifications affecting the Ptch1 cis-regulatory landscape have contributed to evolutionary diversification of artiodactyl limbs