Polarization rotation and the electrocaloric effect in barium titanate

We study the electrocaloric effect in the classic ferroelectric BaTiO₃ through a series of phase transitions driven by applied electric field and temperature. We find both negative and positive electrocaloric effects, with the negative electrocaloric effect, where temperature decreases with applied field, in monoclinic phases. Macroscopic polarization rotation is evident through the monoclinic and orthorhombic phases under applied field, and is responsible for the negative electrocaloric effect.

Distinct projection targets define subpopulations of mouse brainstem vagal neurons that express the autism-associated MET receptor tyrosine kinase

Detailed anatomical tracing and mapping of the viscerotopic organization of the vagal motor nuclei has provided insight into autonomic function in health and disease. To further define specific cellular identities, we paired information based on visceral connectivity with a cell-type specific marker of a subpopulation of neurons in the dorsal motor nucleus of the vagus (DMV) and nucleus ambiguus (nAmb) that express the autism-associated MET receptor tyrosine kinase. As gastrointestinal disturbances are common in children with autism spectrum disorder (ASD), we sought to define the relationship between MET-expressing (MET+) neurons in the DMV and nAmb, and the gastrointestinal tract. Using wholemount tissue staining and clearing, or retrograde tracing in a MET^EGFP transgenic mouse, we identify three novel subpopulations of EGFP+ vagal brainstem neurons: (a) EGFP+ neurons in the nAmb projecting to the esophagus or laryngeal muscles, (b) EGFP+ neurons in the medial DMV projecting to the stomach, and (b) EGFP+ neurons in the lateral DMV projecting to the cecum and/or proximal colon. Expression of the MET ligand, hepatocyte growth factor (HGF), by tissues innervated by vagal motor neurons during fetal development reveal potential sites of HGF-MET interaction. Furthermore, similar cellular expression patterns of MET in the brainstem of both the mouse and nonhuman primate suggests that MET expression at these sites is evolutionarily conserved. Together, the data suggest that MET+ neurons in the brainstem vagal motor nuclei are anatomically positioned to regulate distinct portions of the gastrointestinal tract, with implications for the pathophysiology of gastrointestinal comorbidities of ASD.

Specific Connectivity and Unique Molecular Identity of MET Receptor Tyrosine Kinase Expressing Serotonergic Neurons in the Caudal Dorsal Raphe Nuclei

Molecular characterization of neurons across brain regions has revealed new taxonomies for understanding functional diversity even among classically defined neuronal populations. Neuronal diversity has become evident within the brain serotonin (5-HT) system, which is far more complex than previously appreciated. However, until now it has been difficult to define subpopulations of 5-HT neurons based on molecular phenotypes. We demonstrate that the MET receptor tyrosine kinase (MET) is specifically expressed in a subset of 5-HT neurons within the caudal part of the dorsal raphe nuclei (DRC) that is encompassed by the classic B6 serotonin cell group. Mapping from embryonic day 16 through adulthood reveals that MET is expressed almost exclusively in the DRC as a condensed, paired nucleus, with an additional sparse set of MET+ neurons scattered within the median raphe. Retrograde tracing experiments reveal that MET-expressing 5-HT neurons provide substantial serotonergic input to the ventricular/subventricular region that contains forebrain stem cells, but do not innervate the dorsal hippocampus or entorhinal cortex. Conditional anterograde tracing experiments show that 5-HT neurons in the DRC/B6 target additional forebrain structures such as the medial and lateral septum and the ventral hippocampus. Molecular neuroanatomical analysis identifies 14 genes that are enriched in DRC neurons, including 4 neurotransmitter/neuropeptide receptors and 2 potassium channels. These analyses will lead to future studies determining the specific roles that 5-HT^MET+ neurons contribute to the broader set of functions regulated by the serotonergic system.

Differential patterning of genes involved in serotonin metabolism and transport in extra-embryonic tissues of the mouse

INTRODUCTION

Serotonin (5-HT) is an important neuromodulator, but recently has been shown to be involved in neurodevelopment. Although previous studies have demonstrated that the placenta is a major source of forebrain 5-HT during early forebrain development, the processes of how 5-HT production, metabolism, and transport from placenta to fetus are regulated are unknown. As an initial step in determining the mechanisms involved, we investigated the expression patterns of genes critical for 5-HT system function in mouse extraembryonic tissues.

METHODS

Mid-through late gestation expression of 5-HT system-related enzymes, Tph1, Ddc, Maoa, and 5-HT transporters, Sert/Slc6a4, Oct3/Slc22a3, Vmat2/Slc18a2, and 5-HT in placenta and yolk sac were examined, with cell type-specific resolution, using multiplex fluorescent in situ hybridization to co-localize transcripts and immunocytochemistry to co-localize the corresponding proteins and neurotransmitter.

RESULTS

Tph1 and Ddc are found in the syncytiotrophoblast I (SynT-I) and sinusoidal trophoblast giant cells (S-TGC), whereas Maoa is expressed in SynT-I, syncytiotrophoblast II (SynT-II) and S-TGC. Oct3 expression is observed in the SynT-II only, while Vmat2 is mainly expressed in S-TGC. Surprisingly, there were comparatively high expression of Tph1, Ddc, and Maoa in the yolk sac visceral endoderm.

DISCUSSION

In addition to trophoblast cells, visceral endoderm cells in the yolk sac may contribute to fetal 5-HT production. The findings raise the possibility of a more complex regulation of 5-HT access to the fetus through the differential roles of trophoblasts that surround maternal and fetal blood space and of yolk sac endoderm prior to normal degeneration.

Distinct intracellular signaling mediates C-MET regulation of dendritic growth and synaptogenesis

Hepatocyte growth factor (HGF) activation of the MET receptor tyrosine kinase influences multiple neurodevelopmental processes. Evidence from human imaging and mouse models shows that, in the forebrain, disruptions in MET signaling alter circuit formation and function. One likely means of modulation is by controlling neuron maturation. Here, we examined the signaling mechanisms through which MET exerts developmental effects in the neocortex. In situ hybridization revealed that hgf is located near MET-expressing neurons, including deep neocortical layers and periventricular zones. Western blot analyses of neocortical crude membranes demonstrated that HGF-induced MET autophosphorylation peaks during synaptogenesis, with a striking reduction in activation between P14 and P17 just before pruning. In vitro analysis of postnatal neocortical neurons assessed the roles of intracellular signaling following MET activation. There is rapid, HGF-induced phosphorylation of MET, ERK1/2, and Akt that is accompanied by two major morphological changes: increases in total dendritic growth and synapse density. Selective inhibition of each signaling pathway altered only one of the two distinct events. MAPK/ERK pathway inhibition significantly reduced the HGF-induced increase in dendritic length, but had no effect on synapse density. In contrast, inhibition of the PI3K/Akt pathway reduced HGF-induced increases in synapse density, with no effect on dendritic length. The data reveal a key role for MET activation during the period of neocortical neuron growth and synaptogenesis, with distinct biological outcomes mediated via discrete MET-linked intracellular signaling pathways in the same neurons. © 2016 Wiley Periodicals, Inc. Develop Neurobiol 76: 1160-1181, 2016.

Molecular Characterization of Six Small Heat Shock Proteins and Their Responses Under Cadmium Stress in Oxya chinensis (Orthoptera: Acridoidea)

Small heat shock proteins (sHSPs) have been implicated in many physiological processes and play important roles in the response to various stresses. In this study, the full-length sequences of six sHSPs: OcHSP19.1, 19.8, 20.4, 20.7, 21.1, and 23.8 were obtained from the rice grasshopper Oxya chinensis transcriptome database. The deduced amino acid sequences of the six OcsHSPs contain a typical α-crystallin domain, which consists of approximately 100 amino acid residues and five β-strands. The phylogenetic analysis suggested that OcHSP23.8 was orthologous to the sHSPs of other species and that OcHSP19.1, 20.4, 20.7, and 21.1 were species specific, whereas OcHSP19.8 did not cluster closely to Orthoptera but was placed on the basal end of the cluster. Developmental stage-dependent and tissue-specific expression patterns were evaluated using quantitative real-time polymerase chain reaction. The six genes were expressed in all developmental stages and showed clear tissue specificity. The cadmium acute experiment indicates that Cd(2+) can induce the six genes. However, various response patterns were observed among these genes under Cd(2+) stress conditions. OcHSP19.1, 19.8, 20.4, and 20.7 were highly induced by 2.61 mM Cd(2+) at 24 h. OcHSP23.8 was significantly upregulated by 2.61 mM Cd(2+) at 6 h. For OcHSP21.1, the highest expression levels were found after treatment with 0.87 mM Cd(2+) for 24 h, 1.74 mM Cd(2+) for 36 h, and 2.61 mM Cd(2+) for 12 h. These differential characteristics will facilitate future investigations into the physiological functions of sHSPs.

Physical Interactions and Functional Relationships of Neuroligin 2 and Midbrain Serotonin Transporters

The neurotransmitter serotonin [5-hydroxytryptamine (5-HT)] modulates many key brain functions including those subserving sensation, emotion, reward, and cognition. Efficient clearance of 5-HT after release is achieved by the antidepressant-sensitive 5-HT transporter (SERT, SLC6A4). To identify novel SERT regulators, we pursued a proteomic analysis of mouse midbrain SERT complexes, evaluating findings in the context of prior studies that established a SERT-linked transcriptome. Remarkably, both efforts converged on a relationship of SERT with the synaptic adhesion protein neuroligin 2 (NLGN2), a post-synaptic partner for presynaptic neurexins, and a protein well-known to organize inhibitory GABAergic synapses. Western blots of midbrain reciprocal immunoprecipitations confirmed SERT/NLGN2 associations, and also extended to other NLGN2 associated proteins [e.g., α-neurexin (NRXN), gephyrin]. Midbrain SERT/NLGN2 interactions were found to be Ca(2+)-independent, supporting cis vs. trans-synaptic interactions, and were absent in hippocampal preparations, consistent with interactions arising in somatodendritic compartments. Dual color in situ hybridization confirmed co-expression of Tph2 and Nlgn2 mRNA in the dorsal raphe, with immunocytochemical studies confirming SERT:NLGN2 co-localization in raphe cell bodies but not axons. Consistent with correlative mRNA expression studies, loss of NLGN2 expression in Nlgn2 null mice produced significant reductions in midbrain and hippocampal SERT expression and function. Additionally, dorsal raphe 5-HT neurons from Nlgn2 null mice exhibit reduced excitability, a loss of GABAA receptor-mediated IPSCs, and increased 5-HT1A autoreceptor sensitivity. Finally, Nlgn2 null mice display significant changes in behaviors known to be responsive to SERT and/or 5-HT receptor manipulations. We discuss our findings in relation to the possible coordination of intrinsic and extrinsic regulation afforded by somatodendritic SERT:NLGN2 complexes.

[Management of pelvic injury associated with complete anterior sacroiliac joint dislocation]

OBJECTIVE

To investigate the management of pelvic injury associated with complete anterior sacroiliac joint dislocation.

METHODS

In the study, 6 cases of pelvic injury associated with complete anterior sacroiliac joint dislocation treated in Beijing Jishuitan Hospital from February 2008 to June 2014 were analyzed. We described the history and severity of injury, emergency treatment, and fracture radiology. In all the cases, the surgical treatment and postoperative functional exercise were performed. We followed up all the cases on an average of 1.6 years, assessed the postoperative recovery and summed up the treatment experience.

RESULTS

All the 6 patients with fractures recovered without infection and nerve symptoms after surgery. Their X-rays showed good reduction of sacroiliac joints. All the cases were followed up on an average of 1.6 years. Six months after surgery, the Majeed scores were perfect in 2 cases, good in 2, fair in 1, and poor in 1. The patients with poor scores suffered persistent pain, and decreased physical activity, and when walking long distances, they needed a walking stick. The 2 patients with low scores could not resume the original work.

CONCLUSION

Pelvic injury associated with complete anterior sacroiliac joint dislocation is a special type of the pelvic injury since the managements during the emergency phase are difficult.The surgery should be done as early as possible, and the anterior approach is available for the reduction and fixation.

Performance and Cost Comparisons for Continuous Rearing of Arma chinensis (Hemiptera: Pentatomidae: Asopinae) on a Zoophytogenous Artificial Diet and a Secondary Prey

The impact of a zoophytogenous, insect-free artificial diet and a secondary prey, pupae of Chinese oak silk moth Antheraea pernyi (Guérin-Méneville) (Lepidoptera: Saturniidae), on the developmental rate, life history parameters, and fertility was examined for F6, F9, and F12 consecutive generations for domesticated Arma chinensis (Fallou) (Heteroptera: Pentatomidae). This study showed that when fed an insect-free artificial diet during both the nymphal and adult stages, developmental times were prolonged, and fecundity, egg viability, net reproductive rates (R0), and intrinsic rates of increase (rm) declined. As a result, the cost to rear A. chinensis on the artificial diet approached 1.7 times the cost of rearing A. chinensis on pupae of A. pernyi. Future diet improvements should attempt to reduce developmental time, increase fecundity, and egg viability and use less costly nutrient sources.

EUS-guided FNA cytology of pancreatic neuroendocrine tumour (PanNET): a retrospective study of 132 cases over an 18-year period in a single institution

OBJECTIVE

To determine the diagnostic accuracy and pitfalls of endoscopic ultrasound (EUS)-guided fine needle aspiration (FNA) cytology of pancreatic neuroendocrine tumour (PanNET).

METHODS

A search of our laboratory information system was performed from July 1992 to June 2010 to identify all FNA cytology and corresponding surgical specimens in which the diagnosis of PanNET was rendered or considered.

RESULTS

One hundred and thirty-two cases diagnosed by EUS-guided FNA were collected. Histological correlation was available for 77 (58%) of FNAs; 55 patients may have been treated elsewhere or had no surgery because of advanced disease or co-morbidity. Among 56 cases diagnosed as PanNET on FNA, 54 (96%) were confirmed histologically; the remaining two were poorly differentiated adenocarcinoma with focal neuroendocrine features in one case and no tumour was found in the other. Follow-up histology of nine patients diagnosed as suspicious for PanNET on FNA showed four PanNETs, two pancreatic ductal adenocarcinomas (PDA), one solid pseudopapillary tumour (SPT) and two cases of chronic pancreatitis. Nine cases rendered by FNA as atypical (n = 3), no atypical cells identified (n = 4) or unsatisfactory (n = 2) were PanNETs on histology. Lastly, three cases of oncocytic variant of PanNET were misdiagnosed on FNA as either adenocarcinoma (n = 2) or as suspicious for carcinoma (n = 1).

CONCLUSIONS

Overall, 54 of the 70 histologically confirmed PanNET cases (77%) were correctly diagnosed by preoperative FNA as PanNET. FNA cases designated as no atypical cells identified and unsatisfactory (7/132, 5%) were attributable to sampling error. Diagnostic pitfalls in our study mainly included PDA, SPT and chronic pancreatitis.

Effect of dietary cadmium on the activity of glutathione S-transferase and carboxylesterase in different developmental stages of the Oxya chinensis (Orthoptera: Acridoidea)

Glutathione S-transferases (GSTs) and carboxylesterases (CarEs) play important roles in the detoxification of endogenous and exogenous compounds. In this study, the biochemical effects of dietary cadmium (Cd) on the activities of GST and CarE in different developmental stages of the rice grasshopper Oxya chinensis Thunberg were studied. The results showed that the effects of the Cd concentration and developmental stage on GST activity were statistically significant. GST activity in O. chinensis increased at the highest Cd concentration in most nymphs, suggesting that GST is typically inducible by Cd. However, GST activity was inhibited in adults under Cd stress owing to life-stage-specific physiological characteristics. The results showed that the substrates, developmental stage, and Cd concentration had statistically significant effects on CarE activity. In most studies of CarE activity, the interaction between any two studied factors was statistically significant, although the interaction effects of the substrates, developmental stages, and Cd concentrations were not significant, which implied that the insect physiological condition and the external environmental may affect CarE activity. The results suggest that the insect's life stage and enzyme substrates should be considered when enzyme activity under Cd stress is studied.

Prenatal expression of MET receptor tyrosine kinase in the fetal mouse dorsal raphe nuclei and the visceral motor/sensory brainstem

Signaling via MET receptor tyrosine kinase (MET) has been implicated in a number of neurodevelopmental events, including cell migration, dendritic and axonal development and synaptogenesis. Related to its role in the development of forebrain circuitry, we recently identified a functional promoter variant of the MET gene that is associated with autism spectrum disorder (ASD). The association of the MET promoter variant rs1858830 C allele is significantly enriched in families with a child who has ASD and co-occurring gastrointestinal conditions. The expression of MET in the forebrain had been mapped in detail in the developing mouse and rhesus macaque. However, in mammals, its expression in the developing brainstem has not been studied extensively throughout developmental stages. Brainstem and autonomic circuitry are implicated in ASD pathophysiology and in gastrointestinal dysfunction. To advance our understanding of the neurodevelopmental influences of MET signaling in brainstem circuitry development, we employed in situ hybridization and immunohistochemistry to map the expression of Met and its ligand, Hgf, through prenatal development of the mouse midbrain and hindbrain. Our results reveal a highly selective expression pattern of Met in the brainstem, including a subpopulation of neurons in cranial motor nuclei (nVII, nA and nXII), B6 subgroup of the dorsal raphe, Barrington's nucleus, and a small subset of neurons in the nucleus of solitary tract. In contrast to Met, neither full-length nor known splice variants of Hgf were localized in the prenatal brainstem. RT-PCR revealed Hgf expression in target tissues of Met-expressing brainstem neurons, suggesting that MET in these neurons may be activated by HGF from peripheral sources. Together, these data suggest that MET signaling may influence the development of neurons that are involved in central regulation of gastrointestinal function, tongue movement, swallowing, speech, stress and mood.

Cyclophilin A and nuclear factor of activated T cells are essential in cyclosporine-mediated suppression of polyomavirus BK replication

Immunosuppressants have impacts on the development of polyomavirus-associated nephropathy. We previously demonstrated that cyclosporin A (CsA) suppressed polyomavirus BK (BKV) replication. The role of cyclophilin A (CypA) and nuclear factor of activated T cells (NFAT) in CsA-imposed suppression of BKV replication was determined in this study. Results demonstrated that knockdown of CypA but not CypB significantly reduced BKV large T antigen (TAg) expression and BKV titer. Overexpression of CypA reversed CypA siRNA-induced inhibition in BKV TAg expression. In addition, CypA overexpression attenuated the suppressive effect of CsA on TAg expression, suggesting CypA implicated in CsA-mediated anti-BKV effect. Knockdown of NFATc3 abrogated TAg expression, while overexpression of NFATc3 promoted TAg expression and augmented BKV promoter activity. NFATc3 binding to the BKV promoter was verified by chromatin immunoprecipitation assay and electrophoretic mobility shift assay. Renal histology also displayed an increase in NFATc3 expression in tubulointerstitium of BKV-associated nephropathy. Furthermore, overexpression of NFATc3 rescued CsA-mediated inhibition of BKV load and TAg expression. A CsA analog, NIM811, which cannot block NFAT functionality, failed to suppress TAg expression. In conclusion, CypA and NFAT are indispensable in BKV replication. CsA inhibits BKV replication through CypA and NFAT, which may be potential targets of anti-BKV treatment.

Activin and GDF11 collaborate in feedback control of neuroepithelial stem cell proliferation and fate

Studies of the olfactory epithelium model system have demonstrated that production of neurons is regulated by negative feedback. Previously, we showed that a locally produced signal, the TGFβ superfamily ligand GDF11, regulates the genesis of olfactory receptor neurons by inhibiting proliferation of the immediate neuronal precursors (INPs) that give rise to them. GDF11 is antagonized by follistatin (FST), which is also produced locally. Here, we show that Fst(-/-) mice exhibit dramatically decreased neurogenesis, a phenotype that can only be partially explained by increased GDF11 activity. Instead, a second FST-binding factor, activin βB (ACTβB), inhibits neurogenesis by a distinct mechanism: whereas GDF11 inhibits expansion of INPs, ACTβB inhibits expansion of stem and early progenitor cells. We present data supporting the concept that these latter cells, previously considered two distinct types, constitute a dynamic stem/progenitor population in which individual cells alternate expression of Sox2 and/or Ascl1. In addition, we demonstrate that interplay between ACTβB and GDF11 determines whether stem/progenitor cells adopt a glial versus neuronal fate. Altogether, the data indicate that the transition between stem cells and committed progenitors is neither sharp nor irreversible and that GDF11, ACTβB and FST are crucial components of a circuit that controls both total cell number and the ratio of neuronal versus glial cells in this system. Thus, our findings demonstrate a close connection between the signals involved in the control of tissue size and those that regulate the proportions of different cell types.

Glial precursors clear sensory neuron corpses during development via Jedi-1, an engulfment receptor

During the development of peripheral ganglia, 50% of the neurons that are generated undergo apoptosis. How the massive numbers of corpses are removed is unknown. We found that satellite glial cell precursors are the primary phagocytic cells for apoptotic corpse removal in developing mouse dorsal root ganglia (DRG). Confocal and electron microscopic analysis revealed that glial precursors, rather than macrophages, were responsible for clearing most of the dead DRG neurons. Moreover, we identified Jedi-1, an engulfment receptor, and MEGF10, a purported engulfment receptor, as homologs of the invertebrate engulfment receptors Draper and CED-1 expressed in the glial precursor cells. Expression of Jedi-1 or MEGF10 in fibroblasts facilitated binding to dead neurons, and knocking down either protein in glial cells or overexpressing truncated forms lacking the intracellular domain inhibited engulfment of apoptotic neurons. Together, these results suggest a cellular and molecular mechanism by which neuronal corpses are culled during DRG development.

A new Kondo antiferromagnet Ce(Ni(0.25)In(1.75))

We find that Ce(Ni(0.25)In(1.75)) crystallizes in the hexagonal AlB(2)-type structure with lattice parameters a = 0.4850(5) nm and c = 0.3908(5) nm. Magnetic susceptibility, electrical resistivity and low-temperature specific heat data reveal that the bulk phase transition at 3.7 ± 0.2 K in Ce(Ni(0.25)In(1.75)) is to an antiferromagnetic state. The magnetic contribution to the resistivity ρ(mag) of Ce(Ni(0.25)In(1.75)) increases as ln(T) when temperature is lowered from room temperature and reaches a plateau at 9 K, followed by a rapid decrease around 4 K. These results associated with a reduction of the Ce magnetic moment and of the magnetic entropy at T(N) suggest that Ce(Ni(0.25)In(1.75)) could be a Kondo antiferromagnet. The Kondo temperature is estimated to be of order 6 K.

Foxg1 promotes olfactory neurogenesis by antagonizing Gdf11

Foxg1, a winged-helix transcription factor, promotes the development of anterior neural structures; in mice lacking Foxg1, development of the cerebral hemispheres and olfactory epithelium (OE) is severely reduced. It has been suggested that Foxg1 acts by positively regulating the expression of growth factors, such as Fgf8, which support neurogenesis. However, Foxg1 also binds Smad transcriptional complexes, allowing it to negatively regulate the effects of TGFbeta family ligands. Here, we provide evidence that this latter effect explains much of the ability of Foxg1 to drive neurogenesis in the OE. We show that Foxg1 is expressed in developing OE at the same time as the gene encoding growth differentiation factor 11 (Gdf11), a TGFbeta family member that mediates negative-feedback control of OE neurogenesis. Mutations in Gdf11 rescue, to a considerable degree, the major defects in Foxg1(-/-) OE, including the early, severe loss of neural precursors and olfactory receptor neurons, and the subsequent collapse of both neurogenesis and nasal cavity formation. Rescue is gene-dosage dependent, with loss of even one allele of Gdf11 restoring substantial neurogenesis. Notably, we find no evidence for a disruption of Fgf8 expression in Foxg1(-/-) OE. However, we do observe both a failure of expression of follistatin (Fst), which encodes a secreted Gdf11 antagonist normally expressed in and around OE, and an increase in the expression of Gdf11 itself within the remaining OE in these mutants. Fst expression is rescued in Foxg1(-/-);Gdf11(-/-) and Foxg1(-/-);Gdf11(+/-) mice. These data suggest that the influence of Foxg1 on Gdf11-mediated negative feedback of neurogenesis may be both direct and indirect. In addition, defects in development of the cerebral hemispheres in Foxg1(-/-) mice are not rescued by mutations in Gdf11, nor is Gdf11 expressed at high levels within these structures. Thus, the pro-neurogenic effects of Foxg1 are likely to be mediated through different signaling pathways in different parts of the nervous system.

Gene targeting of ErbB3 using a Cre-mediated unidirectional DNA inversion strategy

Recombinase-mediated unidirectional DNA inversion and transcriptional arrest is a promising strategy for high throughput conditional mutagenesis in the mouse. Banks of mouse embryonic stem cells with defined, transcriptionally silent insertions that can be activated by Cre recombinase would take advantage of existing transgenic Cre lines to rapidly produce hundreds of lineage specific and temporally controlled knockout mice for each gene, thereby introducing significant parallelism to functional gene annotation. However, the extent to which this strategy results in effective gene knockout has not been established. To test the feasibility of this strategy we targeted ErbB3, a member of the ErbB family of tyrosine kinase receptors, using this strategy. Insertion of a reversed "flipflox" vector consisting of a gene inactivation cassette (GI) and an internal ribosome entry site (IRES)-GFP reporter into intron 1 of ErbB3 was transcriptionally silent and did not affect ErbB3 expression. Crosses with ubiquitous and lineage specific Cre recombinase expressing lines permanently inverted the inserted GI cassette and blocked ErbB3 expression. Unidirectional DNA inversion by in vivo recombination is an effective strategy for targeted or ubiquitous gene knockout.

GDF11 controls the timing of progenitor cell competence in developing retina

The orderly generation of cell types in the developing retina is thought to be regulated by changes in the competence of multipotent progenitors. Here, we show that a secreted factor, growth and differentiation factor 11 (GDF11), controls the numbers of retinal ganglion cells (RGCs), as well as amacrine and photoreceptor cells, that form during development. GDF11 does not affect proliferation of progenitors-a major mode of GDF11 action in other tissues-but instead controls duration of expression of Math5, a gene that confers competence for RGC genesis, in progenitor cells. Thus, GDF11 governs the temporal windows during which multipotent progenitors retain competence to produce distinct neural progeny.

Molecular signals regulating proliferation of stem and progenitor cells in mouse olfactory epithelium

To understand how signaling molecules regulate the generation of neurons from proliferating stem cells and neuronal progenitors in the developing and regenerating nervous system, we have studied neurogenesis in a model neurogenic epithelium, the olfactory epithelium (OE) of the mouse. Our studies have employed a candidate approach to test signaling molecules of potential importance in regulating neurogenesis and have utilized methods that include tissue culture, in situ hybridization and mouse genetics. Using these approaches, we have identified three distinct stages of stem and transit amplifying progenitor cells in the differentiation pathway of olfactory receptor neurons (ORNs) and have identified mechanisms by which the development of each of these progenitor cell types is regulated by signals produced both within the OE itself and by its underlying stroma. Our results indicate that regulation of olfactory neurogenesis is critically dependent on multiple signaling molecules from two different polypeptide growth factor superfamilies, the fibroblast growth factors and the transforming growth factor beta (TGF-beta) group. In addition, they indicate that these signaling molecules interact in at least two important ways: first, opposing signals converge on cells at specific developmental stages in the ORN pathway to regulate proliferation and differentiation; and second, these signaling molecules--particularly the TGF-betas and their antagonists--play key roles in feedback loops that regulate the size of progenitor cell pools and thereby neuron number, during development and regeneration.

Apoptosis in primary cardiac tumours

Apoptosis, or programmed cell death, is now recognised as an important cellular event during both normal development and specific disease progression. Apoptosis has been suggested to play a critical role in several cardiovascular diseases, but has not yet been identified as a major influence in primary cardiac tumours. A retrospective review of the achieved material at Chang Gung Memorial Hospital revealed seven patients with cardiac myxoma and one with a tumour originating from the crista terminalis, from January 2002 to December 2002. The medical chart, surgical pathology reports and microscopic slides were available in all cases. All patients, including eight cardiac myxomas and one tumour from crista terminalis, were assessed for apoptosis by terminal deoxynucleotidyl transferase nick-end labelling assay. In this study, apoptosis is well documented in all seven myxoma and has even been reported in tumour from the crista terminalis. Interestingly, apoptosis appears related to the nature of the cell properties rather than the incidence of embolism. In conclusion, apoptosis is important in the progression of the primary cardiac tumours, but the mechanism of cardiac tumour regression still remains uncertain.

Autoregulation of neurogenesis by GDF11

In the olfactory epithelium (OE), generation of new neurons by neuronal progenitors is inhibited by a signal from neurons themselves. Here we provide evidence that this feedback inhibitory signal is growth and differentiation factor 11 (GDF11). Both GDF11 and its receptors are expressed by OE neurons and progenitors, and GDF11 inhibits OE neurogenesis in vitro by inducing p27(Kip1) and reversible cell cycle arrest in progenitors. Mice lacking functional GDF11 have more progenitors and neurons in the OE, whereas mice lacking follistatin, a GDF11 antagonist, show dramatically decreased neurogenesis. This negative autoregulatory action of GDF11 is strikingly like that of its homolog, GDF8/myostatin, in skeletal muscle, suggesting that similar strategies establish and maintain proper cell number during neural and muscular development.

Progenitor cells of the olfactory receptor neuron lineage

The olfactory epithelium of the mouse has many properties that make it an ideal system for studying the molecular regulation of neurogenesis. We have used a combination of in vitro and in vivo approaches to identify three distinct stages of neuronal progenitors in the olfactory receptor neuron lineage. The neuronal stem cell, which is ultimately responsible for continual neuron renewal in this system, gives rise to a transit amplifying progenitor identified by its expression of a transcription factor, MASH1. The MASH1-expressing progenitor gives rise to a second transit amplifying progenitor, the Immediate Neuronal Precursor, which is distinct from the stem cell and MASH1-expressing progenitor, and gives rise quantitatively to olfactory receptor neurons. Regulation of progenitor cell proliferation and differentiation occurs at each of these three cell stages, and growth factors of the fibroblast growth factor (FGF) and bone morphogenetic protein (BMP) families appear to play particularly important roles in these processes. Analyses of the actions of FGFs and BMPs reveal that negative signaling plays at least as important a role as positive signaling in the regulation of olfactory neurogenesis.