RESUMEN
Sound sensitivity is one of the most common sensory complaints for people with autism spectrum disorders (ASDs). How and why sounds are perceived as overwhelming by affected people is unknown. To process sound information properly, the brain requires high activity and fast processing, as seen in areas like the medial nucleus of the trapezoid body (MNTB) of the auditory brainstem. Recent work has shown dysfunction in mitochondria, which are the primary source of energy in cells, in a genetic model of ASD, Fragile X syndrome (FXS). Whether mitochondrial functions are also altered in sound-processing neurons, has not been characterized yet. To address this question, we imaged the MNTB in a mouse model of FXS. We stained MNTB brain slices from wild-type and FXS mice with two mitochondrial markers, TOMM20 and PMPCB, located on the Outer Mitochondrial Membrane and in the matrix, respectively. These markers allow exploration of mitochondrial subcompartments. Our integrated imaging pipeline reveals significant sex-specific differences between genotypes. Colocalization analyses between TOMM20 and PMPCB reveal that the integrity of mitochondrial subcompartments is most disrupted in female FXS mice compared to female wildtype mice. We highlight a quantitative fluorescence microscopy pipeline to monitor mitochondrial functions in the MNTB from control or FXS mice and provide four complementary readouts. Our approach paves the way to understanding how cellular mechanisms important to sound encoding are altered in ASDs.
RESUMEN
Mitochondria are multifunctional organelles of key importance for cell homeostasis. The outer mitochondrial membrane (OMM) envelops the organelle, and the inner mitochondrial membrane (IMM) is folded into invaginations called cristae. As cristae composition and functions depend on the cell type and stress conditions, they recently started to be considered as a dynamic compartment. A number of proteins are known to play a role in cristae architecture, such as OPA1, MIC60, LETM1, the prohibitin (PHB) complex and the F1FO ATP synthase. Furthermore, phospholipids are involved in the maintenance of cristae ultrastructure and dynamics. The use of new technologies, including super-resolution microscopy to visualize cristae dynamics with superior spatiotemporal resolution, as well as high-content techniques and datasets have not only allowed the identification of new cristae proteins but also helped to explore cristae plasticity. However, a number of open questions remain in the field, such as whether cristae-resident proteins are capable of changing localization within mitochondria, or whether mitochondrial proteins can exit mitochondria through export. In this Review, we present the current view on cristae morphology, stability and composition, and address important outstanding issues that might pave the way to future discoveries.
Asunto(s)
Mitocondrias , Membranas Mitocondriales , Microscopía , Proteínas Mitocondriales , FosfolípidosRESUMEN
OBJECTIVES: This study sought to determine whether the pharmacokinetic (PK) and pharmacodynamic (PD) responses to high or standard clopidogrel loading doses (LDs) differ according to CYP2C19*2 allele. BACKGROUND: CYP2C19 loss-of-function alleles are associated with reduced responsiveness to standard clopidogrel doses. METHODS: Young post-myocardial infarction patients heterozygous (wild type [wt]/*2, n = 43) or homozygous (*2/*2, n = 8) for the CYP2C19*2 genetic variant were matched with patients not carrying the variant (wt/wt, n = 58). All patients were randomized to a 300- or 900-mg clopidogrel LD. The relative reduction in residual platelet aggregation (RR-RPA, %) and the area under the plasma concentration time curve of active metabolite from baseline to 6 h after loading (AUC(0-6)) were compared according to both LD and CYP2C19*2 carriage. RESULTS: The 300-mg LD led to a gene-dose effect for RR-RPA (-65.7% ± 35.9% in wt/wt vs. -48.0% ± 38.4% in wt/*2 vs. -14.6% ± 32.4% in *2/*2; overall p value = 0.003, p = 0.03 for wt/wt versus wt/*2, p = 0.04 for wt/*2 versus *2/*2) with minor effect in *2/*2 carriers. After the 900-mg LD, the effect of the CYP2C19*2 variant on platelet inhibition was fully compensated in wt/*2 carriers but not in *2/*2 carriers (-83.6% ± 25.8% in wt/wt vs.-77.2% ± 26.9% in wt/*2 vs. -29.5% ± 26.8% in *2/*2; overall p value = 0.0003, p = 0.20 for wt/wt versus wt/*2, p < 0.001 for wt/*2 versus *2/*2). A similar pattern was observed for the active metabolite AUC(0-6) according to carriage of CYP2C19*2 for both LDs. There was a significant correlation between PK and PD responses irrespective of the LD. CONCLUSIONS: Carriers of CYP2C19*2 display significantly lower responses to clopidogrel with a gene-dose effect. Clopidogrel resistance can be overcome by increasing the dose in heterozygous carriers but not in homozygous carriers. (Clopidogrel and Response Variability Investigation Study 2 [CLOVIS-2]; NCT00822666).