A conserved annexin A6-mediated membrane repair mechanism in muscle, heart, and nerve.

Membrane instability and disruption underlie myriad acute and chronic disorders. Anxa6 encodes the membrane-associated protein annexin A6 and was identified as a genetic modifier of muscle repair and muscular dystrophy. To evaluate annexin A6's role in membrane repair in vivo, we inserted sequences encoding green fluorescent protein (GFP) into the last coding exon of Anxa6. Heterozygous Anxa6gfp mice expressed a normal pattern of annexin A6 with reduced annexin A6GFP mRNA and protein. High-resolution imaging of wounded muscle fibers showed annexin A6GFP rapidly formed a repair cap at the site of injury. Injured cardiomyocytes and neurons also displayed repair caps after wounding, highlighting annexin A6-mediated repair caps as a feature in multiple cell types. Using surface plasmon resonance, we showed recombinant annexin A6 bound phosphatidylserine-containing lipids in a Ca2+- and dose-dependent fashion with appreciable binding at approximately 50 µM Ca2+. Exogenously added recombinant annexin A6 localized to repair caps and improved muscle membrane repair capacity in a dose-dependent fashion without disrupting endogenous annexin A6 localization, indicating annexin A6 promotes repair from both intracellular and extracellular compartments. Thus, annexin A6 orchestrates repair in multiple cell types, and recombinant annexin A6 may be useful in additional chronic disorders beyond skeletal muscle myopathies.

Stress Regulation of Sustained Attention and the Cholinergic Attention System.

BACKGROUND: Stress exacerbates symptoms of schizophrenia and attention-deficit/hyperactivity disorder, which are characterized by impairments in sustained attention. Yet how stress regulates attention remains largely unexplored. We investigated whether a 6-day variable stressor altered sustained attention and the cholinergic attention system in male and female rats. METHODS: Sustained attention was tested with the sustained attention task. Successful performance on the sustained attention task relies on the release of acetylcholine (ACh) into the cortex from cholinergic neurons in the nucleus basalis of Meynert (NBM). Thus, we evaluated whether variable stress (VS) altered the morphology of these neurons with a novel approach using a Cre-dependent virus in genetically modified ChAT::Cre rats, a species used for this manipulation only. Next, electrochemical recordings measured cortical ACh following VS. Finally, we used RNA sequencing to identify VS-induced transcriptional changes in the NBM. RESULTS: VS impaired attentional performance in the sustained attention task and increased the dendritic complexity of NBM cholinergic neurons in both sexes. NBM cholinergic neurons are mainly under inhibitory control, so this morphological change could increase inhibition on these neurons, reducing downstream ACh release to impair attention. Indeed, VS decreased ACh release in the prefrontal cortex of male rats. Quantification of global transcriptional changes revealed that although VS induced many sex-specific changes in gene expression, it increased several signaling molecules in both sexes. CONCLUSIONS: These studies suggest that VS impairs attention by inducing molecular and morphological changes in the NBM. Identifying mechanisms by which stress regulates attention may guide the development of novel treatments for psychiatric disorders with attention deficits.

Sex differences in stress regulation of arousal and cognition.

There are sex differences in the prevalence and presentation of many psychiatric disorders. For example, posttraumatic stress disorder (PTSD) and major depression are more common in women than men, and women with these disorders present with more hyperarousal symptoms than men. In contrast, attention deficit hyperactivity disorder (ADHD) and schizophrenia are more common in men than women, and men with these disorders have increased cognitive deficits compared to women. A shared feature of the aforementioned psychiatric disorders is the contribution of stressful events to their onset and/or severity. Here we propose that sex differences in stress responses bias females towards hyperarousal and males towards cognitive deficits. Evidence from clinical and preclinical studies is detailed. We also describe underlying neurobiological mechanisms. For example, sex differences in stress receptor signaling and trafficking in the locus coeruleus-arousal center are detailed. In learning circuits, evidence for sex differences in dendritic morphology is provided. Finally, we describe how evaluating sex-specific mechanisms for responding to stress in female and male rodents can lead to better treatments for stress-related psychiatric disorders.