Splice-specific deficiency of the PTSD-associated gene PAC1 leads to a paradoxical age-dependent stress behavior

Abstract

25The pituitary adenylate cyclase-activating polypeptide receptor (PAC1, also known as 26 ADCYAP1R1) is associated with post-traumatic stress disorder and modulation of 27 stress response in general. Alternative splicing of PAC1 results in multiple gene 28 products, which differ in their mode of signalling and tissue distribution. However, 29 the roles of distinct splice variants in the regulation of stress behavior is poorly 30 understood. Alternative splicing of a short exon, which is known as the "hop 31 cassette", occurs during brain development and in response to stressful challenges. To 32 examine the function of this variant, we generated a splice-specific zebrafish mutant 33 lacking the hop cassette, which we designated 'hopless'. We show that hopless mutant 34 larvae display increased anxiety-like behavior, including reduced dark exploration and 35 impaired habituation to dark exposure. Conversely, adult hopless mutants displayed 36 superior ability to rebound from an acute stressor, as they exhibited reduced anxiety-37 like responses to an ensuing novelty stress. We propose that the developmental loss of 38 a specific PAC1 splice variant mimics prolonged mild stress exposure, which in the 39 long term, predisposes the organism's stress response towards a resilient phenotype. 40Our study presents a unique genetic model demonstrating how early-life state of 41 anxiety paradoxically correlates with reduced stress susceptibility in adulthood. 42 43 44 45 46 47 48 49 50 51 52 53 PAC1 (a.k.a. Adcyap1r1) is a G-protein coupled receptor (GPCR) that serves as the 54 high-affinity receptor for pituitary adenylate cyclase-activating polypeptide (PACAP). 55 PAC1 has pleiotropic functions and was demonstrated to be involved in the regulation 56 of several homeostatic processes including metabolic rate and food consumption 1,2 , 57 circadian rhythm 3 and, in particular, stress response 4,5 . Intracerebroventricular injection 58 of PACAP increased phosphorylated cyclic AMP response element binding protein 59(pCREB) and CRH immunoreactivity in the rat paraventricular nucleus 6 . PACAP 60 knockout mice display blunted hypothalamic CRH levels in response to restraint 61 challenge 7 . PACAP/PAC1 signaling was also associated with hypothalamo-pituitary-62 adrenal activity and stress-related behaviors in humans and rodents 5,8,9 . Furthermore, 63 this pathway was correlated with stress-related risky behaviors in human and 64 rodents 10,11 . Overall, these findings support positive stress regulation by PAC1; yet, 65 some data suggest that it may also act to suppress stress phenotypes 4,12 . 66It has been suggested that genetic vulnerability to post-traumatic stress disorder 67 (PTSD) may depend on PAC1 expression and single-nucleotide polymorphism (SNP) 68 in the PAC1 gene. Ressler et al. demonstrated that a specific PAC1 genotype is strongly 69 correlated with susceptibility to PTSD in women, probably due to perturbed expression 70 of PAC1 resulting in impaired stress responses 13 . The same PAC1 SNP was associat...

Glucocorticoid-sensitive period of corticotroph development – implications in early life stress

“…Upon treatment with dexamethasone, we observed a drastic impairment in the ability of larvae to recover from the stressful challenge (Figure 4A; p<0.01 comparing control and dexamethasone following stress, n=8 unstressed, n=32 stressed, 2-way ANOVA followed by Sidak's post-hoc multiple comparisons test). To further substantiate our claim, we used an additional zebrafish larval behavioural assay: the light-dark preference test, which is a standard measure of stress-responsive behaviour (9,16,17). In this assay, a freely swimming larva is introduced in an arena divided into a lit half and a dark half and its preference for each of the two halves is monitored.…”

Uncovering the impacts of alternative splicing on the proteome with current omics techniques

“…Differentiated cells and tissues also show specific splicing patterns, as it has been described for the brain, heart, skeletal muscle, testis, and liver, as well as for erythrocytes and immune cells, among others (Baralle & Giudice, 2017; Bhate et al, 2015; Licatalosi & Darnell, 2010; Lynch, 2004; Nakka et al, 2018; Pimentel et al, 2016; Tapial et al, 2017). Finally, alternative splicing is also related to physiologic response to changing conditions, such as DNA damage response, thermal regulation, or even adaptation to stress conditions (Biran et al, 2020; Haltenhof et al, 2020; Shkreta & Chabot, 2015).…”