Meeting report of the European mouse complex genetics network SYSGENET

The second scientific meeting of the European systems genetics network for the study of complex genetic human disease using genetic reference populations (SYSGENET) took place at the Center for Cooperative Research in Biosciences in Bilbao, Spain, December 10–12, 2012. SYSGENET is funded by the European Cooperation in the Field of Scientific and Technological Research (COST) and represents a network of scientists in Europe that use mouse genetic reference populations (GRPs) to identify complex genetic factors influencing disease phenotypes (Schughart, Mamm Genome 21:331–336, 2010). About 50 researchers working in the field of systems genetics attended the meeting, which consisted of 27 oral presentations, a poster session, and a management committee meeting. Participants exchanged results, set up future collaborations, and shared phenotyping and data analysis methodologies. This meeting was particularly instrumental for conveying the current status of the US, Israeli, and Australian Collaborative Cross (CC) mouse GRP. The CC is an open source project initiated nearly a decade ago by members of the Complex Trait Consortium to aid the mapping of multigenetic traits (Threadgill, Mamm Genome 13:175–178, 2002). In addition, representatives of the International Mouse Phenotyping Consortium were invited to exchange ongoing activities between the knockout and complex genetics communities and to discuss and explore potential fields for future interactions.     

Acute creatine administration improves mitochondrial membrane potential and protects against pentylenetetrazol-induced seizures

A growing body of evidence indicates that creatine (Cr) exerts beneficial effects on a variety of pathologies where energy metabolism and oxidative stress play an etiological role. However, the benefits of Cr treatment for epileptics are still shrouded in controversy. In the present study, we found that acute Cr treatment (300 mg/kg, p.o.) prevented the increase in electroencephalographic wave amplitude typically elicited by PTZ (30, 45 or 60 mg/kg, i.p.). Cr treatment also increased the latency periods of first myoclonic jerks, lengthened the latency periods of the generalized tonic–clonic seizures and reduced the time spent in the generalized tonic–clonic seizures induced by PTZ (60 mg/kg). Administration of PTZ (all doses) decreased Na⁺, K⁺-ATPase activity as well as adenosine triphosphate (ATP) and adenosine diphosphate levels in the cerebral cortex, but Cr treatment prevented these effects. Cr administration also prevented increases in xanthine oxidase activity, adenosine monophosphate levels, adenosine levels, inosine levels and uric acid levels that normally occur after PTZ treatment (60 mg/kg, i.p.). We also showed that Cr treatment increased the total Cr (Cr + PCr) content, creatine kinase activity and the mitochondrial membrane potential (ΔΨ) in the cerebral cortex. In addition, Cr prevented PTZ-induced mitochondrial dysfunction characterized by decreasing ΔΨ, increasing thiobarbituric acid-reactive substance levels and increasing protein carbonylation. These experimental findings reinforce the idea that mitochondrial dysfunction plays a critical role in models of epileptic seizures and suggest that buffering brain energy levels through Cr treatment may be a promising therapeutic approach for the treatment of this neurological disease.     

Cytoplasmic localization of PML particles in laminopathies

There is growing evidence that laminopathies, diseases associated with mutations in the LMNA gene, are caused by a combination of mechanical and gene regulatory distortions. Strikingly, there is a large variability in disease symptoms between individual patients carrying an identical LMNA mutation. This is why classical genetic screens for mutations appear to have limited predictive value for disease development. Recently, the widespread occurrence of repetitive nuclear ruptures has been described in fibroblast cultures from various laminopathy patients. Since this phenomenon was strongly correlated with disease severity, the identification of biomarkers that report on these rupture events could have diagnostic relevance. One such candidate marker is the PML nuclear body, a structure that is normally confined to the nuclear interior, but leaks out of the nucleus upon nuclear rupture. Here, we show that a variety of laminopathies shows the presence of these cytoplasmic PML particles (PML CPs), and that the amount of these protein aggregates increases with severity of the disease. In addition, between clinically healthy individuals, carrying LMNA mutations, significant differences can be found. Therefore, we postulate that detection of PML CPs in patient fibroblasts could become a valuable marker for diagnosis of disease development.     

Woronin bodies,their impact on stress resistance and virulence of the pathogenic mould Aspergillus fumigatus and their anchoring at the septal pore of filamentous Ascomycota

Hyphae of filamentous Ascomycota consist of compartments that are connected via septal pores. To avoid a dramatic loss of cellular content after wounding, fungi developed mechanisms to occlude their septal pores. In most Pezizomycotina, so‐called Woronin bodies are anchored in proximity to the pore. This is a prominent example for precise spatial positioning of organelles, but so far the underlying molecular organization has remained largely unknown. Using the pathogenic mould Aspergillus fumigatus, we provide evidence that Woronin bodies are important for stress resistance and virulence. Furthermore the molecular machinery anchoring them at the septum is described. Namely, we have identified Lah as the tethering protein and provide evidence that the Woronin body protein HexA binds to the septal pore in a Lah‐dependent manner. Moreover, we demonstrate that a striking poly‐histidine motif targets HexA to the septal cell wall. Thus, the axis HexA‐Lah is an excellent candidate for the tether linking Woronin bodies to the septum. This model applies to A. fumigatus, but most likely also to the vast majority of the Pezizomycotina. Our findings shed light on the evolution of Woronin body anchoring and provide a basis for the development of novel strategies to combat fungal pathogens like A. fumigatus.     

Identification and characterization of non-saccharomyces spoilage yeasts isolated from Brazilian wines

The industry of fine wines and also locally consumed table wines is emerging in Brazil with an increasing volume and economic impact. Enologists in this region currently lack information about the prevalence and characteristics of spoilage yeasts, which may contaminate and potentially undervalue Brazilian wines. Herein, we analyzed 50 local red wines including 27 fine wines (V. vinifera) and 23 table wines (V. labrusca). Presumptive spoilage yeasts were isolated on differential medium, and classified by RFLP-PCR and sequencing of the ITS1-5.8S-ITS2 and D1/D2 26S rDNA loci. The prevalence of spoilage yeasts in fine wines (11 %) was comparable to that reported in European and US wines, and significantly lower than that observed for local table wines (70 %). The majority of isolates belonged to Brettanomyces bruxelliensis, followed by Pichia guillermondii, and more rarely Candida wickerhamii and Trigonopsis cantarelli. The Brettanomyces isolates varied greatly in off-flavor production, displayed ethanol tolerance (>10 % by volume), tolerated sulfite (≥0.68 mg/l mSO₂), and 39 % of them grew on ethanol as sole carbon source. We discuss the causes and consequences of spoilage yeasts in relation to the Brazilian wine industry.     

TNF-related weak inducer of apoptosis (TWEAK) promotes kidney fibrosis and Ras-dependent proliferation of cultured renal fibroblast

Tumor necrosis factor-like weak inducer of apoptosis (TWEAK) regulates apoptosis, proliferation and inflammation in renal epithelial cells and plays a role in acute kidney injury. However, there is little information on the chronic effects of TWEAK. We hypothesized that TWEAK may influence renal fibrosis and regulate kidney fibroblast biology, in part, through Ras pathway.We studied a chronic model of experimental unilateral ureteral obstruction in wild type and TWEAK deficient mice, and a murine model of systemic TWEAK overexpression. TWEAK actions were also explored in cultured renal and embryonic fibroblasts.TWEAK and TWEAK receptor expression was increased in the obstructed kidneys. The absence of TWEAK decreased early kidney tubular damage, inflammatory infiltrates and myofibroblast number. TWEAK deficient mice had decreased renal fibrosis 21 days after obstruction, as assessed by extracellular matrix staining. In mice without prior underlying kidney disease, systemic overexpression of TWEAK induced kidney inflammation and fibrosis. In cultured fibroblasts, TWEAK induced proliferation through activation of the Ras/ERK pathway. TWEAK also activated nuclear factor κB (NFκB)-dependent inflammatory chemokine production in murine renal fibroblasts.In conclusion, lack of TWEAK reduces renal fibrosis in a model of persistent kidney insult and overexpression of TWEAK led to renal fibrosis. TWEAK actions on renal fibroblasts may contribute to the in vivo observations, as TWEAK promotes inflammatory activity and proliferation in fibroblast cultures.     

Nucleofection of whole murine retinas

The mouse retina constitutes an important research model for studies aiming to unravel the cellular and molecular mechanisms underlying ocular diseases. The accessibility of this tissue and its feasibility to directly obtain neurons from it has increased the number of studies culturing mouse retina, mainly retinal cell suspensions. However, to address many questions concerning retinal diseases and protein function, the organotypic structure must be maintained, so it becomes important to devise methods to transfect and culture whole retinas without disturbing their cellular structure. Moreover, the postmitotic stage of retinal neurons makes them reluctant to commonly used transfection techniques. For this purpose some published methods employ in vivo virus-based transfection techniques or biolistics, methods that present some constraints. Here we report for the first time a method to transfect P15-P20 whole murine retinas via nucleofection, where nucleic acids are directly delivered to the cell nuclei, allowing in vitro transfection of postmitotic cells. A detailed protocol for successful retina extraction, organotypic culture, nucleofection, histological procedures and imaging is described. In our hands the A-33 nucleofector program shows the highest transfection efficiency. Whole flat-mount retinas and cryosections from transfected retinas were imaged by epifluorescence and confocal microscopy, showing that not only cells located in the outermost retinal layers, but also those in inner retinal layers are transfected. In conclusion, we present a novel method to successfully transfect postnatal whole murine retina via nucleofection, showing that retina can be successfully nucleofected after some optimization steps.     

Hepatic production of transthyretin L12P leads to intracellular lysosomal aggregates in a new somatic transgenic mouse model

Transthyretin (TTR) is a plasma and cerebrospinal fluid (CSF)-circulating homotetrameric protein. More than 100 point mutations have been identified in the TTR gene and several are related with amyloid diseases. Here we focused our attention in the TTR L12P variant associated with severe peripheral neuropathy and leptomeningeal amyloidosis. By using different cell lines derived from tissues specialized on TTR synthesis, such as the hepatocyte and the choroid plexus expressing WT, V30M, or L12P TTR variants we analyzed secretion, intracellular aggregation and degradation patterns. Also, we used liver-specific AAV gene transfer to assess expression of the L12P variant in vivo. We found the following: (i) decreased secretion with intracellular aggregation of TTR L12P in hepatoma cells relative to WT and V30M variant; this differential property of TTR L12P variant was also observed in mice injected with L12P AAV vector; (ii) differential N-glycosylation pattern of L12P variant in hepatoma cell lysates, conditioned media and mouse sera, which might represent an escape mechanism from ERAD degradation; (iii) intracellular L12P TTR aggregates mainly localized to lysosomes in cultured cells and liver; and (iv) none of the above findings were present in choroid plexus derived cells, suggesting particular secretion/quality control mechanisms that might contribute to leptomeningeal amyloidosis associated with the L12P variant. These observations open new avenues for the treatment of TTR associated leptomeningeal amyloidosis.     

Circaseptan Rhythms of Semen Characteristics of a Brazilian Breed (“Mangalarga”) Stallion

We describe the semen characteristics of a 21-year old “mangalarga” stallion living under natural temperature and photoperiod conditions in São José do Rio Pardo, São Paulo, Brazil (latitude 21°36' S; longitude 46°53' W). The horse fed on natural pasture and a nutritionally balanced feed twice a day (11:00 and 17:00 h). Water and a mineral supplement were available “ad libitum”. Semen was collected for over 36 months (Oct 89-Dec 92) almost daily between 08:00 and 10:00 h by an artificial vagina and evaluated for volume of ejaculate, spermatozoa motility and concentration by standard procedures. Analysis of data from a total of 128-days was performed according to the Fast Fourier Transform Technique (FFT). Statistically significant periods of 7-day were demonstrated for volume, motility, and spermatozoa concentration. Circaseptan rhythms and, particularly, the circannual rhythm (already described in a previous publication) are probably related to ecological diversity and reproductive strategies.