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Abstract [Objective] Tartaric acid not only affects the taste of grape berries but also determines the color, texture, microbial stability, and aging potential of the wine. It is of great value to explore the transcription factors and mechanisms that regulate tartaric acid biosynthesis, regulate the accumulation of tartaric acid in grapes through biotechnology or to cultivate wine grape varieties with high tartaric acid accumulation. [Methods] In this study, using ‘Traminer’ and ‘Marselan’ wine grapes as experimental materials, we cloned the tartaric acid related transcription factor VvbHLH79 by PCR. We performed bioinformatic and subcellular localization analyses of VvbHLH79. Furthermore, we measured the tartaric acid content and VvbHLH79 expression levels in grape berries at different developmental stages using HPLC and qRTPCR techniques. We also constructed a plant expression vector and the expression and tartaric acid content of VvbHLH79 were detected after transient transformation of young grape berries using Agrobacteriummediated fruiting pedicle infection, in order to clarify the role of the VvbHLH79 gene in regulating the content of tartaric acid in grape berries. [Results] (1) A grapevine VvbHLH79 gene was obtained by RNA-seq, with a CDS of 831 bp, amino acids of 277, molecular weight of 66.22 kD, and isoelectric point of 5.15. It belonged to the class of unstable hydrophilic proteins without signal peptides and transmembrane structures. Positions 147-232 of amino acid sequence contained the bHLH-SF conserved domain, which belonged to the bHLH transcription factor family. The protein was localized in the cell nucleus. (2) The grapevine VvbHLH79-encoded protein had the highest sequence similarity with the bHLH89-encoded protein in riverbank grape (accession number: XP_034699340.1), with a sequence identity of 99.64%. (3) There was a gradual decrease of VvbHLH79 expression during the development of ‘Traminer’ grape fruits, decreasing 67.25% from veraison to harvest. The accumulation of tartaric acids occurred mainly before color change of the grapes, with a rapid decrease after color change. (4) Transient expression of VvbHLH79 in low tartaric acid grapes resulted in a increase in tartaric acids, whereas silencing of VvbHLH79 in high tartaric acid grapes resulted in a decrease in tartaric acids, confirming that the VvbHLH79 gene positively regulated tartaric acid content. [Conclusion] The VvbHLH79 transcription factor may play a role in the tartaric acid biosynthesis in grape berries.

Posttranscriptional RNA modifications by adenosine-to-inosine (A-to-I) editing are abundant in the brain, yet elucidating functional sites remains challenging. To bridge this gap, we investigate spatiotemporal and genetically regulated A-to-I editing sites across prenatal and postnatal stages of human brain development. More than 10,000 spatiotemporally regulated A-to-I sites were identified that occur predominately in 3' UTRs and introns, as well as 37 sites that recode amino acids in protein coding regions with precise changes in editing levels across development. Hyper-edited transcripts are also enriched in the aging brain and stabilize RNA secondary structures. These features are conserved in murine and non-human primate models of neurodevelopment. Finally, thousands of cis-editing quantitative trait loci (edQTLs) were identified with unique regulatory effects during prenatal and postnatal development. Collectively, this work offers a resolved atlas linking spatiotemporal variation in editing levels to genetic regulatory effects throughout distinct stages of brain maturation.

The impact of apolipoprotein E ε4 (APOE4), the strongest genetic risk factor for Alzheimer's disease (AD), on human brain cellular function remains unclear. Here, we investigated the effects of APOE4 on brain cell types derived from population and isogenic human induced pluripotent stem cells, post-mortem brain, and APOE targeted replacement mice. Population and isogenic models demonstrate that APOE4 local haplotype, rather than a single risk allele, contributes to risk. Global transcriptomic analyses reveal human-specific, APOE4-driven lipid metabolic dysregulation in astrocytes and microglia. APOE4 enhances de novo cholesterol synthesis despite elevated intracellular cholesterol due to lysosomal cholesterol sequestration in astrocytes. Further, matrisome dysregulation is associated with upregulated chemotaxis, glial activation, and lipid biosynthesis in astrocytes co-cultured with neurons, which recapitulates altered astrocyte matrisome signaling in human brain. Thus, APOE4 initiates glia-specific cell and non-cell autonomous dysregulation that may contribute to increased AD risk.

RNA editing is a feature of RNA maturation resulting in the formation of transcripts whose sequence differs from the genome template. Brain RNA editing may be altered in Alzheimers disease (AD). Here, we analyzed data from 1,865 brain samples covering 9 brain regions from 1,074 unrelated subjects on a transcriptome-wide scale to identify inter-regional differences in RNA editing. We expand the list of known brain editing events by identifying 58,761 previously unreported events. We note that only a small proportion of these editing events are found at the protein level in our proteome-wide validation effort. We also identified the occurrence of editing events associated with AD dementia, neuropathological measures and longitudinal cognitive decline in: SYT11, MCUR1, SOD2, ORAI2, HSDL2, PFKP, and GPRC5B. Thus, we present an extended reference set of brain RNA editing events, identify a subset that are found to be expressed at the protein level, and extend the narrative of transcriptomic perturbation in AD to RNA editing.

The hemizygous R47H variant of triggering receptor expressed on myeloid cells 2 (TREM2), a microglia-specific gene in the brain, increases risk for late-onset Alzheimer’s disease (AD). Using transcriptomic analysis of single nuclei from brain tissues of patients with AD carrying the R47H mutation or the common variant (CV)–TREM2, we found that R47H-associated microglial subpopulations had enhanced inflammatory signatures reminiscent of previously identified disease-associated microglia (DAM) and hyperactivation of AKT, one of the signaling pathways downstream of TREM2. We established a tauopathy mouse model with heterozygous knock-in of the human TREM2 with the R47H mutation or CV and found that R47H induced and exacerbated TAU-mediated spatial memory deficits in female mice. Single-cell transcriptomic analysis of microglia from these mice also revealed transcriptomic changes induced by R47H that had substantial overlaps with R47H microglia in human AD brains, including robust increases in proinflammatory cytokines, activation of AKT signaling, and elevation of a subset of DAM signatures. Pharmacological AKT inhibition with MK-2206 largely reversed the enhanced inflammatory signatures in primary R47H microglia treated with TAU fibrils. In R47H heterozygous tauopathy mice, MK-2206 treatment abolished a tauopathy-dependent microglial subcluster and rescued tauopathy-induced synapse loss. By uncovering disease-enhancing mechanisms of the R47H mutation conserved in human and mouse, our study supports inhibitors of AKT signaling as a microglial modulating strategy to treat AD.