A newly identified fatty alcohol oxidase gene is mainly responsible for the oxidation of long-chain ω-hydroxy fatty acids in Yarrowia lipolytica.

Nine potential (fatty) alcohol dehydrogenase genes and one alcohol oxidase gene were identified in Yarrowia lipolytica by comparative sequence analysis. All relevant genes were deleted in Y. lipolytica H222ΔP which is lacking ß-oxidation. Resulting transformants were tested for their ability to accumulate ω-hydroxy fatty acids and dicarboxylic acids in the culture medium. The deletion of eight alcohol dehydrogenase genes (FADH, ADH1-7), which may be involved in ω-oxidation, led only to a slightly increased accumulation of ω-hydroxy fatty acids, whereas the deletion of the fatty alcohol oxidase gene (FAO1), which has not been described yet in Y. lipolytica, exhibited a considerably higher effect. The combined deletion of the eight (fatty) alcohol dehydrogenase genes and the alcohol oxidase gene further reduced the formation of dicarboxylic acids. These results indicate that both (fatty) alcohol dehydrogenases and an alcohol oxidase are involved in ω-oxidation of long-chain fatty acids whereby latter plays the major role. This insight marks the first step toward the biotechnological production of long-chain ω-hydroxy fatty acids with the help of the nonconventional yeast Y. lipolytica. The overexpression of FAO1 can be further used to improve existing strains for the production of dicarboxylic acids.

Transcranial focused ultrasound modulates the emergence of learned helplessness via midline theta modification.

BACKGROUND: Helplessness and hopelessness are states closely related to depressive disorders. They ensue following the anticipated absence of valid behavioral options to alleviate an aversive state. One neural structure involved in the detection of such options, is the cingulate cortex (CC), which conveys the evaluation of behavior against the value of its outcome. Accordingly, CC-related EEG measures are thought to correlate to feedback evaluation but also to anxious and conflict-related states, signaling the need for further adaptation to current requirements. Against this background, this study investigated the role of CC functioning in the emergence and prevention of helpless/hopeless states by applying low-intensity transcranial focused ultrasound (litFUS) neuromodulation prior to a learned helplessness task. METHOD: In a randomized controlled double blind experimental setup with 55 participants, litFUS was used to inhibit the right lateral prefrontal cortex (lPFC), a region closely connected to CC modulation. Participants were instructed to play 8 games of chess against a computer that was unbeatable to them, while an EEG was recorded. Theta oscillation in midline electrodes, playing performance and self-rate measures on cognitive, affective and physiological parameters were assessed. RESULTS: The results show a considerable influence of litFUS neuromodulation of the lPFC on midline theta activity (Fz and Pz electrode position) which in turn correlated to several psychological variables including self-report data on emotion, cognition, and arousal as well as behavioral measures (playing performance). LIMITATIONS: Due to the small sample size and sample characteristics, results cannot be generalized to the field of clinical application. A replication of results in larger samples and in context of other sonication parameters is needed to increase the robustness of results and to maximize the efficacy of litFUS application. CONCLUSIONS: We conclude that the development of learned helplessness/hopelessness could be positively influenced in its course by litFUS neuromodulation of the right lPFC. In line with previous results, especially the posterior midline electrode Pz seems to be an interesting target for further research in this field as theta activity at this electrode is correlated to control perception and motivated behavior. To our knowledge, this is the first study to use neuromodulation to monitor and manipulate the development of helplessness in the laboratory.

Inhibition of midfrontal theta with transcranial ultrasound explains greater approach versus withdrawal behavior in humans.

Recent reviews highlighted low-intensity transcranial focused ultrasound (TUS) as a promising new tool for non-invasive neuromodulation in basic and applied sciences. Our preregistered double-blind within-subjects study (N = 152) utilized TUS targeting the right prefrontal cortex, which, in earlier work, was found to positively enhance self-reported global mood, decrease negative states of self-reported emotional conflict (anxiety/worrying), and modulate related midfrontal functional magnetic resonance imaging activity in affect regulation brain networks. To further explore TUS effects on objective physiological and behavioral variables, we used a virtual T-maze task that has been established in prior studies to measure motivational conflicts regarding whether participants execute approach versus withdrawal behavior (with free-choice responses via continuous joystick movements) while allowing to record related electroencephalographic data such as midfrontal theta activity (MFT). MFT, a reliable marker of conflict representation on a neuronal level, was of particular interest to us since it has repeatedly been shown to explain related behavior, with relatively low MFT typically preceding approach-like risky behavior and relatively high MFT typically preceding withdrawal-like risk aversion. Our central hypothesis is that TUS decreases MFT in T-maze conflict situations and thereby increases approach and reduces withdrawal. Results indicate that TUS led to significant MFT decreases, which significantly explained increases in approach behavior and decreases in withdrawal behavior. This study expands TUS evidence on a physiological and behavioral level with a large sample size of human subjects, suggesting the promise of further research based on this distinct TUS-MFT-behavior link to influence conflict monitoring and its behavioral consequences. Ultimately, this can serve as a foundation for future clinical work to establish TUS interventions for emotional and motivational mental health.

Investigating the role of the right inferior frontal gyrus in control perception: A double-blind cross-over study using ultrasonic neuromodulation.

Being able to control inner and environmental states is a basic need of living creatures. The perception of such control is based on the perceived ratio of outcome probabilities given the presence and the absence of agentic behavior. If an organism believes that options exist to change the probability of a given outcome, control perception (CP) may emerge. Nonetheless, regarding this model, not much is known about how the brain processes CP from this information. This study uses low-intensity transcranial focused ultrasound neuromodulation in a randomized-controlled double blind cross-over design to investigate the impact of the right inferior frontal gyrus of the lateral prefrontal cortex (lPFC) on this process. 39 healthy participants visited the laboratory twice (once in a sham, once in a neuromodulation condition) and rated their control perception regarding a classical control illusion task. EEG alpha and theta power density were analyzed in a hierarchical single trial-based mixed modeling approach. Results indicate that the litFUS neuromodulation changed the processing of stimulus probability without changing CP. Furthermore, neuromodulation of the right lPFC was found to modulate mid-frontal theta by altering its relationship with self-reported effort and worrying. While these data indicate lateral prefrontal sensitivity to stimulus probability, no evidence emerged for the dependency of CP on this processing.

Measurement invariance testing of longitudinal neuropsychiatric test scores distinguishes pathological from normative cognitive decline and highlights its potential in early detection research.

OBJECTIVE: Alzheimer's disease (AD) is a growing challenge worldwide, which is why the search for early-onset predictors must be focused as soon as possible. Longitudinal studies that investigate courses of neuropsychological and other variables screen for such predictors correlated to mild cognitive impairment (MCI). However, one often neglected issue in analyses of such studies is measurement invariance (MI), which is often assumed but not tested for. This study uses the absence of MI (non-MI) and latent factor scores instead of composite variables to assess properties of cognitive domains, compensation mechanisms, and their predictability to establish a method for a more comprehensive understanding of pathological cognitive decline. METHODS: An exploratory factor analysis (EFA) and a set of increasingly restricted confirmatory factor analyses (CFAs) were conducted to find latent factors, compared them with the composite approach, and to test for longitudinal (partial-)MI in a neuropsychiatric test battery, consisting of 14 test variables. A total of 330 elderly (mean age: 73.78 ± 1.52 years at baseline) were analyzed two times (3 years apart). RESULTS: EFA revealed a four-factor model representing declarative memory, attention, working memory, and visual-spatial processing. Based on CFA, an accurate model was estimated across both measurement timepoints. Partial non-MI was found for parameters such as loadings, test- and latent factor intercepts as well as latent factor variances. The latent factor approach was preferable to the composite approach. CONCLUSION: The overall assessment of non-MI latent factors may pose a possible target for this field of research. Hence, the non-MI of variances indicated variables that are especially suited for the prediction of pathological cognitive decline, while non-MI of intercepts indicated general aging-related decline. As a result, the sole assessment of MI may help distinguish pathological from normative aging processes and additionally may reveal compensatory neuropsychological mechanisms.

Aconitase overexpression changes the product ratio of citric acid production by Yarrowia lipolytica.

The yeast Yarrowia lipolytica secretes high amounts of various organic acids, like citric acid (CA) and isocitric acid (ICA) under an excess of carbon source and several conditions of growth limitation. Depending on the carbon source used, Y. lipolytica strains produce a mixture of CA and ICA in a characteristic ratio. To examine whether this CA/ICA product ratio can be influenced by gene-dose-dependent overexpression of aconitase (ACO)-encoding gene ACO1, a recombinant Y. lipolytica strain was constructed containing multiple copies of ACO1. The high-level expression of ACO in the ACO1 multicopy integrative transformant resulted in a shift of the CA/ICA product pattern into the direction of ICA. On sunflower oil, a striking increase of the ICA proportion from 35-49% to 66-71% was observed compared to wild-type strains without influencing the total amount of acids (CA and ICA) produced. On glycerol, glucose or sucrose, the ICA proportion increased only moderately from 10-12% to 13-17%. This moderate shift into the direction of ICA was also observed in an icl1-defective strain.

Citric acid production from sucrose using a recombinant strain of the yeast Yarrowia lipolytica.

The yeast Yarrowia lipolytica is able to secrete high amounts of several organic acids under conditions of growth limitation and carbon source excess. Here we report the production of citric acid (CA) in a fed-batch cultivation process on sucrose using the recombinant Y. lipolytica strain H222-S4(p67ICL1) T5, harbouring the invertase encoding ScSUC2 gene of Saccharomyces cerevisiae under the inducible XPR2 promoter control and multiple ICL1 copies (10-15). The pH-dependent expression of invertase was low at pH 5.0 and was identified as limiting factor of the CA-production bioprocess. The invertase expression was sufficiently enhanced at pH 6.0-6.8 and resulted in production of 127-140 g l(-1) CA with a yield Y (CA) of 0.75-0.82 g g(-1), whereas at pH 5.0, 87 g l (-1) with a yield Y (CA) of 0.51 g g(-1) were produced. The CA-productivity Q (CA) increased from 0.40 g l (-1) h(-1) at pH 5.0 up to 0.73 g l (-1) h(-1) at pH 6.8. Accumulation of glucose and fructose at high invertase expression level at pH 6.8 indicated a limitation of CA production by sugar uptake. The strain H222-S4(p67ICL1) T5 also exhibited a gene-dose-dependent high isocitrate lyase expression resulting in strong reduction (<5%) of isocitric acid, a by-product during CA production.

Overexpression of the ICL1 gene changes the product ratio of citric acid production by Yarrowia lipolytica.

The yeast Yarrowia lipolytica secretes high amounts of various organic acids, like citric (CA) and isocitric (ICA) acids, triggered by growth limitation caused by different factors and an excess of carbon source. Depending on the carbon source used, Y. lipolytica strains produce a mixture of CA and ICA in a characteristic ratio. To examine whether the CA/ICA product ratio can be influenced by gene-dose-dependent overexpression or by disruption of the isocitrate lyase (ICL)-encoding gene ICL1, recombinant Y. lipolytica strains were constructed, which harbour multiple ICL1 copies or a defective icl1 allele. The high-level expression of ICL in ICL1 multicopy integrative transformants resulted in a strong shift of the CA/ICA ratio into direction of CA. On glycerol, glucose and sucrose, the ICA proportion decreased from 10-12% to 3-6%, on sunflower oil or hexadecane even from 37-45% to 4-7% without influencing the total amount of acids (CA and ICA) produced. In contrast, the loss of ICL activity in icl1-defective strains resulted in a moderate 2-5% increase in the ICA proportion compared to ICL wild-type strains on glucose or glycerol.