Actin and microtubules in neurite initiation: are MAPs the missing link?

During neurite initiation microtubules align to form a tight bundle and actin filaments reorganize to produce a growth cone. The mechanisms that underlie these highly coordinated cytoskeletal rearrangements are not yet fully understood. Recently, various levels of coordination between the actin- and microtubule-based cytoskeletons have been observed during cellular migration and morphogenesis, processes that share some similarities to neurite initiation. Direct, physical association between both cytoskeletons has been suggested, because microtubules often preferentially grow along actin bundles and transiently target actin-rich adhesion complexes. We propose that such physical association might be involved in force-based interactions and spatial organization of the two networks during neurite initiation as well. In addition, many signaling cascades that affect actin filaments are also involved in the regulation of microtubule dynamics, and vice versa. Although several candidates for mediating these effects have been identified in non-neuronal cells, the general mechanism is still poorly understood. In neurons certain plakins and neuron-specific microtubule associated proteins (MAPs), like MAP1B and MAP2, which can bind to both microtubules and F-actin, are promising candidates to play key roles in the specific cytoskeletal rearrangements controlling the transition from an undifferentiated state to neurite-bearing morphology. Here we review the effects of MAPs on microtubules and actin, as well as the coordination of both cytoskeletons during neurite initiation.     

Teleost Fish Genomes Contain a Diverse Array of L1 RetrotransposonLineages That Exhibit a Low Copy Number and High Rate of Turnover

Retrotransposable elements exhibit a wide range of variation in population dynamics, abundance, and lineage diversity among host genomes across taxa. This range of diversity is illustrated by a single well-defined constituent monophyletic clade of L1 non-LTR retrotransposons that is shared between mammalian and teleost fish genomes. Despite the clear phylogenetic relationships that exist between mammalian and teleost L1 sequences, these elements exhibit markedly different dynamics within their respective taxa. While mammalian genomes typically contain a single, abundant lineage of L1 elements that traces millions of years of evolution, the zebraflsh genome was recently shown to exhibit a high diversity of ancient lineages coexisting at a very low copy number and apparently exhibiting a high rate of turnover. In the present study, a combination of degenerate PCR, lineage-specific PCR, and genomic Southern blot analysis is utilized to demonstrate high L1 lineage diversity, low copy number, and a high proportion of polymorphic inserts in the genomes of the killifish species, Fundulus heteroclitus. Additional species surveyed by degenerate PCR include Cyprinodon variegatus, Rivulus marmoratus, and Menidia beryllina. These results further support the generality of the differences that exist in host–element dynamics between teleost fish and mammalian genomes with regard to L1 retrotransposons.Reviewing Editor: Dr. Axel Meyer     

The Enigma of <Emphasis Type="Italic">Solanum maglia</Emphasis> in the Origin of the Chilean Cultivated Potato, <Emphasis Type="Italic">Solanum tuberosum</Emphasis> Chilotanum Group<Superscript>1</Superscript>

The Enigma of Solanum maglia in the Origin of the Chilean Cultivated Potato, Solanum tuberosum Chilotanum Group. Landrace potato cultivars occur in two broad geographic regions: the high Andes from western Venezuela south to northern Argentina (Solanum tuberosum Andigenum Group, “Andigenum”), and lowland south-central Chile (S. tuberosum Chilotanum Group, “Chilotanum”), with a coastal desert and 560 km between southernmost populations of Andigenum and Chilotanum. Unlike Andigenum landraces, Chilotanum landraces are adapted to long days and carry a 241 base pair plastid DNA deletion. However, Andigenum and Chilotanum landraces are morphologically similar. We investigated a hypothesis that Chilotanum landraces arose from Solanum maglia, a rare tuber-bearing species found in Chile and Argentina. This hypothesis was formulated first based on morphological analyses of starch grains of extant and preserved (12,500 years before present) S. maglia, and on putative sympatry of extant S. maglia and Chilotanum landraces. Our new starch grain analyses fail to support this hypothesis; we could find no evidence of current sympatric distributions, and S. maglia lacks the 241-bp plastid deletion. However, microsatellite data group all accessions of S. maglia exclusively with Chilotanum, which is supported by our previous observation at the single locus of the waxy gene. These results could be interpreted in various ways, but all explanations have problems. One explanation is that S. maglia is a progenitor of Chilotanum. However, the plastid deletion in Chilotanum but not S. maglia cannot be easily explained. Another explanation is that Chilotanum was formed by hybridization between S. maglia and pre-Chilotanum, but this conflicts with prior cladistic analyses. These new data shed light on aspects of this question and highlight various evolutionary scenarios, but the origin of Chilotanum and the involvement of S. maglia in its origin remain an enigma.     

Functionalized nanosystems for targeted mitochondrial delivery

Mitochondrial dysfunction including oxidative stress and DNA mutations underlies the pathology of various diseases including Alzheimer's disease and diabetes, necessitating the development of mitochondria targeted therapeutic agents. Nanotechnology offers unique tools and materials to target therapeutic agents to mitochondria. As discussed in this paper, a variety of functionalized nanosystems including polymeric and metallic nanoparticles as well as liposomes are more effective than plain drug and non-functionalized nanosystems in delivering therapeutic agents to mitochondria. Although the field is in its infancy, studies to date suggest the superior therapeutic activity of functionalized nanosystems for treating mitochondrial defects.     

Obesity-related metabolic dysfunction in dogs: a comparison with human metabolic syndrome

ABSTRACT: BACKGROUND: Recently, metabolic syndrome (MS) has gained attention in human metabolic medicine given its associations with development of type 2 diabetes mellitus and cardiovascular disease. Canine obesity is associated with the development of insulin resistance, dyslipidaemia, and mild hypertension, but the authors are not aware of any existing studies examining the existence or prevalence of MS in obese dogs.Thirty-five obese dogs were assessed before and after weight loss (median percentage loss 29%, range 10-44%). The diagnostic criteria of the International Diabetes Federation were modified in order to define canine obesity-related metabolic dysfunction (ORMD), which included a measure of adiposity (using a 9-point body condition score [BCS]), systolic blood pressure, fasting plasma cholesterol, plasma triglyceride, and fasting plasma glucose. By way of comparison, total body fat mass was measured by dual-energy X-ray absorptiometry, whilst total adiponectin, fasting insulin, and high-sensitivity C-reactive protein (hsCRP) were measured using validated assays. RESULTS: Systolic blood pressure (P = 0.008), cholesterol (P = 0.003), triglyceride (P = 0.018), and fasting insulin (P < 0.001) all decreased after weight loss, whilst plasma total adiponectin increased (P = 0.001). However, hsCRP did not change with weight loss. Prior to weight loss, 7 dogs were defined as having ORMD, and there was no difference in total fat mass between these dogs and those who did not meet the criteria for ORMD. However, plasma adiponectin concentration was less (P = 0.031), and plasma insulin concentration was greater (P = 0.030) in ORMD dogs. CONCLUSIONS: In this study, approximately 20% of obese dogs suffer from ORMD, and this is characterized by hypoadiponectinaemia and hyperinsulinaemia. These studies can form the basis of further investigations to determine path genetic mechanisms and the health significance for dogs, in terms of disease associations and outcomes of weight loss.     

BioBanking: an environmental scientist’s view of the role of biodiversity banking offsets in conservation

Offsets, first formalised in the United States of America in the 1970s for wetland mitigation, are now widely used globally with the aim to mitigate loss of biodiversity due to development. Embracing biodiversity offsets is one method of governments to meet their commitments under the Millennium Development Goals and the Convention on Biological Diversity. Resource extraction companies see them as a method of gaining access to land, while the community may perceive them as a way of enhancing environmental outcomes. In New South Wales, Australia, BioBanking legislation was introduced in late 2006 with the aim of ‘no net loss’ of biodiversity associated with development, particularly expanding urban and coastal development. The strengths of the legislation are that it aims to enhance threatened species conservation, and raise the profile of conservation of threatened species and habitats. Weaknesses include (1) the narrowness of the definition of biodiversity; (2) the concepts are based on a flawed logic and immature, imprecise and complex science which results in difficulties in determining biodiversity values; (3) likely problems with management and compliance; and (4) an overall lack of resources for implementation and long-term monitoring. It is concluded that the legislation is a concerted effort to deal with biodiversity loss, however, stakeholders have concerns with the process, and it is unworkable with the complexity of such ecosystems (compared for example to carbon credit trading), and underdeveloped disciplines such as restoration biology and ecology. Despite these criticisms, there is a need for all stakeholders to work to improve the outcomes.