A fundamental question in development is how cells assemble to form a tubular network during organ formation. In glandular organs tubulogenesis is a multistep process requiring coordinated proliferation, polarization and reorganization of epithelial cells to from a lumen, and lumen expansion. Although it is clear that epithelial cells possess an intrinsic ability to organize into polarized structures, the mechanisms coordinating morphogenetic processes during tubulogenesis are poorly understood. Here, we demonstrate that parasympathetic nerves regulate ductal tubulogenesis in the developing salivary gland. We show that the neurotransmitter vasoactive intestinal peptide (VIP) secreted by the innervating ganglia promotes ductal growth, leads to the formation of a contiguous lumen, and facilitates lumen expansion through a cAMP/PKA-dependent pathway. Furthermore, we provide evidence that lumen expansion is independent of apoptosis and involves the cystic fibrosis transmembrane conductance regulator (CFTR), a cAMP-regulated Cl(−) channel. Thus, parasympathetic innervation coordinates multiple steps in tubulogenesis during organ formation.

One limitation to housing rodents in individually ventilated cages (IVCs) is the ineffectiveness of traditional health monitoring programs that test soiled bedding sentinels every quarter. Aerogen transmission does not occur with this method. Moreover, the transmission of numerous pathogens in bedding is uncertain, and sentinel susceptibility to various pathogens varies. A novel method using particle collection from samples of exhaust air was developed in this study which was also systematically compared with routine health monitoring using soiled bedding sentinels. We used our method to screen these samples for the presence of murine norovirus (MNV), a mouse pathogen highly prevalent in laboratory animal facilities. Exhaust air particles from prefilters of IVC racks with known MNV prevalence were tested by quantitative reverse transcription polymerase chain reaction (RT-qPCR). MNV was detected in exhaust air as early as one week with one MNV-positive cage per rack, while sentinels discharged MNV RNA without seroconverting. MNV was reliably and repeatedly detected in particles collected from samples of exhaust air in all seven of the three-month sampling rounds, with increasing MNV prevalence, while sentinels only seroconverted in one round. Under field conditions, routine soiled bedding sentinel health monitoring in our animal facility failed to identify 67% ( n = 85) of positive samples by RT-qPCR of exhaust air particles. Thus, this method proved to be highly sensitive and superior to soiled bedding sentinels in the reliable detection of MNV. These results represent a major breakthrough in hygiene monitoring of rodent IVC systems and contribute to the 3R principles by reducing the number of animals used and by improving experimental conditions.

A spontaneous mutation leading to the formation of congenital ovarian and testicular tumors was detected in the WKY/Ztm rat strain. The histological evaluation revealed derivatives from all three germ layers, thereby identifying these tumors as teratomas. Teratocarcinogenesis was accompanied by infertility and the underlying mutation was termed ter. Linkage analysis of 58 (WKY-ter×SPRD-Cu3) F2 rats associated the ter mutation with RNO18 (LOD = 3.25). Sequencing of candidate genes detected a point mutation in exon 4 of the dead-end homolog 1 gene (Dnd1), which introduces a premature stop codon assumed to cause a truncation of the Dnd1 protein. Genotyping of the recessive ter mutation revealed a complete penetrance of teratocarcinogenesis and infertility in homozygous ter rats of both genders. Morphologically non-tumorous testes of homozygous ter males were reduced in both size and weight. This testicular malformation was linked to a lack of spermatogenesis using immunohistochemical and histological staining. Our WKY-Dnd1ter/Ztm rat is a novel animal model to investigate gonadal teratocarcinogenesis and the molecular mechanisms involved in germ cell development of both genders.

BackgroundUbiquitous deletion of thioredoxin reductase 2 (Txnrd2) in mice is embryonically lethal and associated with abnormal heart development, while constitutive, heart-specific Txnrd2 inactivation leads to dilated cardiomyopathy and perinatal death. The significance of Txnrd2 in aging cardiomyocytes, however, has not yet been examined.Methods and ResultsThe tamoxifen-inducible heart-specific αMHC-MerCreMer transgene was used to inactivate loxP-flanked Txnrd2 alleles in adult mice. Hearts and isolated mitochondria from aged knockout mice were morphologically and functionally analyzed. Echocardiography revealed a significant increase in left ventricular end-systolic diameters in knockouts. Fractional shortening and ejection fraction were decreased compared with controls. Ultrastructural analysis of cardiomyocytes of aged mice showed mitochondrial degeneration and accumulation of autophagic bodies. A dysregulated autophagic activity was supported by higher levels of lysosome-associated membrane protein 1 (LAMP1), microtubule-associated protein 1A/1B-light chain 3-I (LC3-I), and p62 in knockout hearts. Isolated Txnrd2-deficient mitochondria used less oxygen and tended to produce more reactive oxygen species. Chronic hypoxia inducible factor 1, α subunit stabilization and altered transcriptional and metabolic signatures indicated that energy metabolism is deregulated.ConclusionsThese results imply a novel role of Txnrd2 in sustaining heart function during aging and suggest that Txnrd2 may be a modifier of heart failure.

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