Life-long epigenetic programming of cortical architecture by maternal 'Western' diet during pregnancy

The evolution of human diets led to preferences toward polyunsaturated fatty acid (PUFA) content with 'Western' diets enriched in ω-6 PUFAs. Mounting evidence points to ω-6 PUFA excess limiting metabolic and cognitive processes that define longevity in humans. When chosen during pregnancy, ω-6 PUFA-enriched 'Western' diets can reprogram maternal bodily metabolism with maternal nutrient supply precipitating the body-wide imprinting of molecular and cellular adaptations at the level of long-range intercellular signaling networks in the unborn fetus. Even though unfavorable neurological outcomes are amongst the most common complications of intrauterine ω-6 PUFA excess, cellular underpinnings of life-long modifications to brain architecture remain unknown. Here, we show that nutritional ω-6 PUFA-derived endocannabinoids desensitize CB₁ cannabinoid receptors, thus inducing epigenetic repression of transcriptional regulatory networks controlling neuronal differentiation. We found that cortical neurons lose their positional identity and axonal selectivity when mouse fetuses are exposed to excess ω-6 PUFAs in utero. Conversion of ω-6 PUFAs into endocannabinoids disrupted the temporal precision of signaling at neuronal CB₁ cannabinoid receptors, chiefly deregulating Stat3-dependent transcriptional cascades otherwise required to execute neuronal differentiation programs. Global proteomics identified the immunoglobulin family of cell adhesion molecules (IgCAMs) as direct substrates, with DNA methylation and chromatin accessibility profiling uncovering epigenetic reprogramming at >1400 sites in neurons after prolonged cannabinoid exposure. We found anxiety and depression-like behavioral traits to manifest in adult offspring, which is consistent with genetic models of reduced IgCAM expression, to suggest causality for cortical wiring defects. Overall, our data uncover a regulatory mechanism whose disruption by maternal food choices could limit an offspring's brain function for life.

Stathmin is enriched in the developing corticospinal tract

Understanding the intra- and extracellular proteins involved in the development of the corticospinal tract (CST) may offer insights into how the pathway could be regenerated following traumatic spinal cord injury. Currently, however, little is known about the proteome of the developing corticospinal system. The present study, therefore, has used quantitative proteomics and bioinformatics to detail the protein profile of the rat CST during its formation in the spinal cord. This analysis identified increased expression of 65 proteins during the early ingrowth of corticospinal axons into the spinal cord, and 36 proteins at the period of heightened CST growth. A majority of these proteins were involved in cellular assembly and organization, with annotations being most highly associated with cytoskeletal organization, microtubule dynamics, neurite outgrowth, and the formation, polymerization and quantity of microtubules. In addition, 22 proteins were more highly expressed within the developing CST in comparison to other developing white matter tracts of the spinal cord of age-matched animals. Of these differentially expressed proteins, only one, stathmin 1 (a protein known to be involved in microtubule dynamics), was both highly enriched in the developing CST and relatively sparse in other developing descending and ascending spinal tracts. Immunohistochemical analyses of the developing rat spinal cord and fetal human brain stem confirmed the enriched pattern of stathmin expression along the developing CST, and in vitro growth assays of rat corticospinal neurons showed a reduced length of neurite processes in response to pharmacological perturbation of stathmin activity. Combined, these findings suggest that stathmin activity may modulate axonal growth during development of the corticospinal projection, and reinforces the notion that microtubule dynamics could play an important role in the generation and regeneration of the CST.

An enzymatic route to selenazolines

Ringing the changes: Selenazolines have applications in medicinal chemistry, but their synthesis is challenging. We report a new convenient and less toxic route to these heterocycles that starts from commercially available selenocysteine. The new route depends on a heterocyclase enzyme that creates oxazolines and thiazolines from serines/threonines and cysteines.

The quantitative proteomic response of Synechocystis sp. PCC6803 to phosphate acclimation

BACKGROUND

Inorganic phosphate (Pi) is a critical nutrient for all life and is periodically limiting in marine and freshwater provinces, yet little is understood how organisms acclimate to fluctuations in Pi within their environment. To investigate whole cell adaptation, we grew Synechocystis sp. PCC6803, a model freshwater cyanobacterium, in 3%, and 0.3% inorganic phosphate (Pi) media. The cells were allowed to acclimate over 60 days, and cells were harvested for quantitative high throughput mass spectrometry-based proteomics using the iTRAQ™ labelling technology.

RESULTS

In total, 120 proteins were identified, and 52 proteins were considered differentially abundant compared to the control. Alkaline phosphatase (APase) activities correlated significantly (p < 0.05) with observed relative PhoA abundances. PstS1 and PstS2 were both observed, yet PstS1 was not differentially more abundant than the control. Phycobilisome protein abundances appeared to be coordinated, and are significantly less abundant in 0.3% Pi than 3% Pi cultures. Also, the central metabolic cell function appears to have shifted towards the production of (NADPH) reducing energy and nucleotide sugars.

CONCLUSIONS

This acclimation response bears strong similarity to the previously reported response to nitrogen deprivation within Synechocystis sp. PCC 6803. However, it also demonstrates some characteristics of desiccation stress, such as the regulation of fatty acids and increased abundance of rehydrin in the 3% Pi culture.

Comparative quantitative proteomics of prochlorococcus ecotypes to a decrease in environmental phosphate concentrations

BACKGROUND

The well-lit surface waters of oligotrophic gyres significantly contribute to global primary production. Marine cyanobacteria of the genus Prochlorococcus are a major fraction of photosynthetic organisms within these areas. Labile phosphate is considered a limiting nutrient in some oligotrophic regions such as the Caribbean Sea, and as such it is crucial to understand the physiological response of primary producers such as Prochlorococcus to fluctuations in the availability of this critical nutrient.

RESULTS

Prochlorococcus strains representing both high light (HL) (MIT9312) and low light (LL) (NATL2A and SS120) ecotypes were grown identically in phosphate depleted media (10 μM Pi). The three strains displayed marked differences in cellular protein expression, as determined by high throughput large scale quantitative proteomic analysis. The only strain to demonstrate a significantly different growth rate under reduced phosphate conditions was MIT9312. Additionally, there was a significant increase in phosphate-related proteins such as PhoE (> 15 fold increase) and a depression of the Rubisco protein RbcL abundance in this strain, whereas there appeared to be no significant change within the LL strain SS120.

CONCLUSIONS

This differential response between ecotypes highlights the relative importance of phosphate availability to each strain and from these results we draw the conclusion that the expression of phosphate acquisition mechanisms are activated at strain specific phosphate concentrations.