Mediator Complex Component Gene

Abstract Signaling events triggered by hydrogen peroxide (H2O2) regulate plant growth and defense by orchestrating a genome-wide transcriptional reprogramming. However, the specific mechanisms that govern H2O2-dependent gene expression are still poorly understood. Here, we identify the Arabidopsis Mediator complex subunit MED8 as a regulator of H2O2 responses. The introduction of the med8 mutation in a constitutive oxidative stress genetic background (catalase-deficient, cat2) was associated with enhanced activation of the salicylic acid pathway and accelerated cell death. Interestingly, med8 seedlings were more tolerant to oxidative stress generated by the herbicide methyl viologen (MV) and exhibited transcriptional hyperactivation of defense signaling, in particular salicylic acid- and jasmonic acid-related pathways. The med8-triggered tolerance to MV was manipulated by the introduction of secondary mutations in salicylic acid and jasmonic acid pathways. In addition, analysis of the Mediator interactome revealed interactions with components involved in mRNA processing and microRNA biogenesis, hence expanding the role of Mediator beyond transcription. Notably, MED8 interacted with the transcriptional regulator NEGATIVE ON TATA-LESS, NOT2, to control the expression of H2O2-inducible genes and stress responses. Our work establishes MED8 as a component regulating oxidative stress responses and demonstrates that it acts as a negative regulator of H2O2-driven activation of defense gene expression.

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State dependent effects on the frequency response of prestin’s real and imaginary components of nonlinear capacitance

Scientific Reports ◽

10.1038/s41598-021-95121-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Joseph Santos-Sacchi ◽

Dhasakumar Navaratnam ◽

Winston J. T. Tan

Keyword(s):

Frequency Response ◽

Outer Hair Cell ◽

Absolute Magnitude ◽

Total Charge ◽

Charge Movement ◽

Membrane Tension ◽

Nonlinear Capacitance ◽

Complex Component ◽

Trade Offs ◽

Voltage Dependent

AbstractThe outer hair cell (OHC) membrane harbors a voltage-dependent protein, prestin (SLC26a5), in high density, whose charge movement is evidenced as a nonlinear capacitance (NLC). NLC is bell-shaped, with its peak occurring at a voltage, Vh, where sensor charge is equally distributed across the plasma membrane. Thus, Vh provides information on the conformational state of prestin. Vh is sensitive to membrane tension, shifting to positive voltage as tension increases and is the basis for considering prestin piezoelectric (PZE). NLC can be deconstructed into real and imaginary components that report on charge movements in phase or 90 degrees out of phase with AC voltage. Here we show in membrane macro-patches of the OHC that there is a partial trade-off in the magnitude of real and imaginary components as interrogation frequency increases, as predicted by a recent PZE model (Rabbitt in Proc Natl Acad Sci USA 17:21880–21888, 2020). However, we find similar behavior in a simple 2-state voltage-dependent kinetic model of prestin that lacks piezoelectric coupling. At a particular frequency, Fis, the complex component magnitudes intersect. Using this metric, Fis, which depends on the frequency response of each complex component, we find that initial Vh influences Fis; thus, by categorizing patches into groups of different Vh, (above and below − 30 mV) we find that Fis is lower for the negative Vh group. We also find that the effect of membrane tension on complex NLC is dependent, but differentially so, on initial Vh. Whereas the negative group exhibits shifts to higher frequencies for increasing tension, the opposite occurs for the positive group. Despite complex component trade-offs, the low-pass roll-off in absolute magnitude of NLC, which varies little with our perturbations and is indicative of diminishing total charge movement, poses a challenge for a role of voltage-driven prestin in cochlear amplification at very high frequencies.

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MED12-Related (Neuro)Developmental Disorders: A Question of Causality

Genes ◽

10.3390/genes12050663 ◽

2021 ◽

Vol 12 (5) ◽

pp. 663

Author(s):

Stijn van de Plassche ◽

Arjan PM de Brouwer

Keyword(s):

Developmental Disorders ◽

De Novo ◽

Expression Patterns ◽

Mediator Complex ◽

Gene Expression Patterns ◽

Facial Dysmorphism ◽

Regulation Of Transcription ◽

Feeding Difficulties ◽

Missense Variants ◽

Pathogenic Variants

MED12 is a member of the Mediator complex that is involved in the regulation of transcription. Missense variants in MED12 cause FG syndrome, Lujan-Fryns syndrome, and Ohdo syndrome, as well as non-syndromic intellectual disability (ID) in hemizygous males. Recently, female patients with de novo missense variants and de novo protein truncating variants in MED12 were described, resulting in a clinical spectrum centered around ID and Hardikar syndrome without ID. The missense variants are found throughout MED12, whether they are inherited in hemizygous males or de novo in females. They can result in syndromic or nonsyndromic ID. The de novo nonsense variants resulting in Hardikar syndrome that is characterized by facial clefting, pigmentary retinopathy, biliary anomalies, and intestinal malrotation, are found more N-terminally, whereas the more C-terminally positioned variants are de novo protein truncating variants that cause a severe, syndromic phenotype consisting of ID, facial dysmorphism, short stature, skeletal abnormalities, feeding difficulties, and variable other abnormalities. This broad range of distinct phenotypes calls for a method to distinguish between pathogenic and non-pathogenic variants in MED12. We propose an isogenic iNeuron model to establish the unique gene expression patterns that are associated with the specific MED12 variants. The discovery of these patterns would help in future diagnostics and determine the causality of the MED12 variants.

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Stromal MED12 exon 2 mutations in complex fibroadenomas of the breast

Journal of Clinical Pathology ◽

10.1136/jclinpath-2020-207062 ◽

2020 ◽

pp. jclinpath-2020-207062

Author(s):

Edaise M da Silva ◽

Francisco Beca ◽

Ana Paula Martins Sebastiao ◽

Melissa P Murray ◽

Catarina Silveira ◽

...

Keyword(s):

Reverse Transcriptase ◽

Laser Capture Microdissection ◽

Sanger Sequencing ◽

Mediator Complex ◽

Telomerase Reverse Transcriptase ◽

Exon 2 ◽

Stromal Component ◽

Hotspot Mutations ◽

Laser Capture

AimsHere we explore the presence of mediator complex subunit 12 (MED12) exon 2 and telomerase reverse transcriptase (TERT) promoter hotspot mutations in complex fibroadenomas (CFAs) of the breast.MethodsThe stromal components from 18 CFAs were subjected to Sanger sequencing of MED12 exon 2 and the TERT promoter hotspot loci. The epithelial and stromal components of two MED12 mutated CFAs were subjected to laser capture microdissection, and Sanger sequencing of MED12 exon 2, TERT promoter and PIK3CA exons 9 and 20, separately.ResultsMED12 exon 2 mutations were identified in the stroma of 17% of CFAs. The analyses of epithelial and stromal components, microdissected separately, revealed that MED12 mutations were restricted to the stroma. No TERT promoter or PIK3CA mutations in exons 9 and 20 were detected in analysed CFAs.ConclusionsLike conventional fibroadenomas, MED12 exon 2 mutations appear to be restricted to the stromal component of CFAs, supporting the notion that CFAs are stromal neoplasms.

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