link to: - https://boffosocko.com/2022/05/14/55804938/ - Aby Warburg's coinage of Verknüpfungszwang

Review coordinated by Life Science Editors Foundation

Reviewed by: Dr. Angela Andersen, Life Science Editors Foundation

Potential Conflicts of Interest: None

Punch line: Rare risk variants associated with schizophrenia converge on the cAMP/PKA pathway.

Why is this interesting? The cAMP/PKA pathway could be a mechanism & therapeutic target for neuropsychiatric disorders arising from different mutations.

Background: * About 1-4% of people will develop psychosis or schizophrenia. * Schizophrenia is a highly heritable disease. * Genetic loci associated with schizophrenia can be common variants, which typically have small effects on risk, or rare variants, which can have large effects. * Rare, protein-truncating variants substantially increase the risk for mental illnesses like schizophrenia. * Disease-associated genes have diverse functions (e.g.): 1. RNA binding (RBM12) 2. transcriptional regulation (SP4, RB1CC1, SETD1A) 3. splicing (SRRM2) 4. signaling (AKAP11) 5. ion transport (CACNA1G, GRIN2A, GRIA3) 6. neuronal migration and growth (TRIO) 7. nuclear transport (XPO7) 8. ubiquitin ligation (CUL1, HERC1) ** What are the pathological mechanisms?* * A genetic screen identified the risk gene RBM12 as a novel repressor of GPCR/cAMP signaling (Semesta et al., PLOS Genetics, 2020). * Dysregulation of GPCR activity in the brain contributes to the pathophysiology of several neurological and neuropsychiatric disorders. * cAMP is a critical second messenger that mediates all important aspects of neuronal function, including development, excitability, and plasticity.

Results: * Use knockout HEK293 cells to verify that RBM12 is novel repressor of the GPCR/cAMP pathway that extends to multiple GPCRs coupled to the stimulatory G protein (e.g. dopamine 1 receptor, beta-2 adrenergic receptor). * Show RBM12 also represses this pathway in iPSC-derived neurons. RBM12 knockdown yielded hyperactive upregulation of NR4A1 and FOS mRNAs, two known CREB-dependent immediate early genes induced by neuronal activity. * RBM12 loss leads to increased PKA activity and supraphysiological CREB-dependent transcriptional responses. * RBM12 loss increased expression of the endogenous β2-AR transcriptional target mRNAs, PCK1 and FOS. * RBM12 loss increased CREB transcriptional reporter expression in response to a panel of endogenous or synthetic β2-AR agonists.<br /> * Transcriptional responses are orchestrated from endosomal β2-ARs in wild-type cells but from both plasma membrane and endosomal β2-ARs in RBM12 knockout cells. * Their results suggest that cAMP production and transcriptional signaling are independently subject to RBM12 regulation. * The neuropsychiatric disease-linked mutations fail to rescue GPCR-dependent hyperactivation in cells depleted of RBM12. * Defined β2-AR-dependent transcriptional targets in “wild-type” and RBM12 knockdown neurons by differential expression analysis between each respective basal and isoproterenol conditions. 669 unique β2-AR-dependent transcriptional targets across the two cell lines. * Discerned β2-AR-dependent targets that were exclusive to wild-type or RBM12 knockdown only (qualitatively distinct targets) versus targets that are in wt and RBM12 kd but upregulated to different extents (quantitatively distinct targets). * 21 wild-type- and 115 RBM12 knockdown-specific target genes. Factors involved in synaptic plasticity and schizophrenia such as JUN, ARC (encoding the activity-regulated cytoskeleton-associated protein), BDNF, and NRXN3 (encoding the cell adhesion molecule neurexin-3-alpha) were induced by GPCR signaling only in RBM12 knockdown neurons, while GRIA2 (encoding the AMPA receptor) and CBLN2 (encoding cerebellin 2 precursor) were upregulated upon GPCR signaling only in wt neurons. * the remaining 533 genes were induced in both wt & RBM12-depeleted, with a trend toward RBM12-dependent hyperactivation. * loss of RBM12 leads to aberrant expression of ADCY, PDE, and PRKACA, suggesting this mechanism underlies the hyperactive GPCR/cAMP/PKA signaling phenotypes.

Discussion: * Dysregulation of GPCR signaling could contribute to the neuronal pathologies stemming from loss of RBM12. * RBM12 function is required for normal cAMP production downstream of many Gαs-coupled receptors with established roles in the nervous system consistent with dysregulation of cAMP/PKA pathway. Specifically, the entire repertoire of targets, many of which orchestrate processes essential for neuronal differentiation, gene reprogramming, and memory and learning, shows a trend towards hyperactivation in RBM12 depleted neurons. * Over 100 genes are induced in response to receptor stimulation only in the knockdown (e.g. ARC and BDNF, with crucial roles in synaptic function, plasticity, and learning. * RBM12 could act through other mechanisms, given that RBM12 knockdown neurons also affects the expression of genes involved in neuron differentiation, synapse organization, and neurogenesis. * A study on post-mortem brains of patients with bipolar affective disorder demonstrated elevated levels of the PKAcat subunit Cα in temporal and frontal cortices compared to matched normal brains. * A different report on patient-derived platelet cells found that the catalytic subunit of cAMP-dependent protein kinase was significantly upregulated in untreated depressed and manic patients with bipolar disorder compared with untreated euthymic patients with bipolar disorder and healthy subjects. * Mutations in the schizophrenia risk gene histone methyltransferase SET domain-containing protein 1 A (SETD1A) also led to transcriptional and signaling signatures supporting hyperactivation of the cAMP pathway through upregulation of adenylyl cyclases and downregulation of PDEs. This in turn resulted in increased dendritic branching and length and altered network activity in human iPSC-derived glutamatergic neurons.

Beautiful follow up to their PLOS Genetics paper, and compelling pathological mechanism in combination with the recent SETD1A Cell Reports paper.

Future work: * Does loss of RBM12 increase dendritic branching and length and alter network activity in human iPSC-derived glutamatergic neurons (e.g. does it phenocopy loss of SETD1A). * Does pharmacologically targeting the cAMP pathway rescue the phenotypes caused by loss of RBM12? * If RBM12 is ubiquitously expressed, why is the disease neuronal? What is the relevant GPCR/neuronal mechanism? * How does RBM12 affect the abundance of the transcripts encoding the GPCR/cAMP effectors? * Do mutations in any of these other rare risk genes converge on GPCR? (transcriptional regulation (SP4, RB1CC1), splicing (SRRM2). signaling (AKAP11). ion transport (CACNA1G, GRIN2A, GRIA3), neuronal migration and growth (TRIO), nuclear transport (XPO7). ubiquitin ligation (CUL1, HERC1))

That's nearly a 15% reduction! It's also comparable to reductions seen in CFS (though CFS was per weight rather than per surface area, they should be comparable metrics). However, this is in comparison to bipolar, who themselves probably lack normal blood volume, so it's possible schizophrenia is a more extreme version of CFS where the blood volume is radically reduced. Will need more studies.

This implies a causal role. The low parasympathetic tone precedes psychosis.

In contrast, sildenafil appears not to provide any acute benefit, (study). I'd only expected benefit due to sleep enhancement, so lack of acute benefit was unsurprising to me.

Given that risperidone was likely taken at night, and sildenafil was likely taken at the same time, it's my opinion that the benefits in this study were due to sleep improvement. This may be via the circadian clock, or a more direct effect on sleep, or both.

My remaining question is whether sildenafil improves sleep in healthy subjects. I'm especially interested in combining sildenafil with 100 to 300 mcg melatonin. Will they have synergistic effect? I expect so.

This is not surprising. It seems that L-theanine is clinically useful in the exact ways one would expect.

That's not a large enough sample to draw conclusions out subtypes. Interesting nonetheless.

Low incidence of side effects certainly sounds superior to atypical antipsychotics and tricyclic/tetracyclic antidepressants.

I stumbled upon this accidentally. I was going to add to my prediction that schizophrenia might be related to autism, but now that I've found this I need to publish my draft.

Edit: Here was the prediction I wrote. Copied unmodified, ensuring transparency.

March 28, 6:15pm Prediction: Some cases of schizophrenia are being misdiagnosed as autism. I recently took a Coursera.org course on schizophrenia. The negative symptoms look similar to some autism symptoms.

Before I look it up, there are a few other predictions I should make. Do I think schizophrenia and autism will be linked? If there’s cross-diagnosis, will this link be artificial or real? Last time I looked, people with aspergers had (more or less) normal sleep EEGs. In contrast, schizophrenia is associated with disrupted sleep spindles. I already know that schizophrenia and bipolar are genetically linked, but I don’t know what the bipolar sleep EEG looks like. That is to say, I don’t know if the lack of sleep abnormality in autism is evidence against a link to schizophrenia. All in all, I predict that there will be a real link (for example, genetic), but I have a low confidence in this prediction. The reason is that I expect there is little EEG sleep changes in bipolar, implying that there is a supra-mechanism causing all these effects; somewhat like metabolic syndrome, the same cause may manifest in different ways.

This is exactly what I expected. In fact, I would have been extremely surprised if this weren't the case. I just google "schizophrenia bipolar genes" expecting this result.

I had the thought a few minutes ago, and google it right away. This means that I wasn't able to write it down as a prediction. Nonetheless, I think this points in favor of my prediction abilities. My confidence was inordinately high (i.e. on the order of 90%) even before collecting any evidence. Compare that to other high confidence beliefs (e.g. CFS is caused partly by blood volume), for which I have confidence on the order of 95%, but I have good evidence for that belief. Thus, this instance provides data that my confidence meter is reliable. I'll continue to make an effort to write down predictions ahead of time (to eliminate publication bias).

There are several reasons I suspected this would be the case. Firstly, personal subjective experience; that's what gave me the first inkling. Secondly, the connection of mania with long periods of sleeplessness. If the sleep deprivation causes the mania, then bipolar may be a sleep disorder. This is backed up by the sleep deprivation therapy for depression. Additionally, the connection of depression to sleep disturbance implies that sleep may also be causal in low mood. Furthermore, given that schizophrenia is associated with disrupted sleep spindles, it follows that the two sleep disorders, namely schizophrenia and bipolar, may be closely related genetically (via sleep regulating genes). Moreover, I knew that schizophrenia and bipolar were two of the most heritable psychological conditions; given that both are highly genetic and both involve sleep, it follows that they would likely be closely linked. Finally, I know mania can be associated with delusions, so there are several symptom crossovers. All in all, it is highly surprising that I have not seen this discussed before. Neither documentaries on schizophrenia nor documentaries on manic depression/bipolar have mentioned a link. Nor have studies I've read (admittedly few on this particular topic) mentioned anything of the sort. I shall have to look through the literature to see if this idea has been around for long.

Fascinating that there are acute benefits (presumably in addition to chronic benefits). Given that negative symptoms in particular are resolved, it may simply be stimulating effects.

Not only am I unsurprised by this, but I'd be surprised if it were otherwise. The logic is that schizophrenia is a sleep disorder, and exercise enhances sleep. Additionally, lack of movement is one of the negative symptoms of schizophrenia. Therefore, this poverty of movement may play a role in the pathogenesis of schizophrenia symptoms.

I need to start a google search document with predictions prior to actually searching. It will slow down my research speed, but it is necessary in order to provide unbiased data on my intuitive understanding of diseases. It seems like the majority of my strong intuitions are true. Edit: I'll just record the search phrase in my hypothes.is notes. This one was "exercise schizophrenia"

That is an interesting set of improvements. These are negative symptoms that are resolved, which is largely what I'd expect. I'd bet there is some effect on positive symptoms too, but with low certainty. Moreover, these results are excellent in that negative symptoms are the hardest to treat.

41:20 Influenza caused an uptick in schizophrenia. Given context, it sounds like she's talking about the mothers catching the flu during pregnancy.

Schizophrenia is unique to humans. There are also regions that human and other species have, but have undergone more rapid evolution in humans called Human Accelerated regions (HAR).

Maybe these HARs and Schizophrenia are linked.

Also HARs are regions whose purpose is to regulate the expression of other genes, not so much directly code for a protein.

Humans are the only ones that develop schizophrenia

McDonald, K., Ding, T., French, P., Jones, P. B., Baio, G., Kirkbride, J. B., & Wohland, P. (2020, April 27). Forecasting population need for mental health care: a Bayesian methodology applied to the epidemiology of psychotic disorders in England. Retrieved from psyarxiv.com/bvcgu

Psychiatry, T. L. (2020). Mental health and COVID-19: Change the conversation. The Lancet Psychiatry, 0(0). https://doi.org/10.1016/S2215-0366(20)30194-2

The paraventricular axis is interesting and could relate to chronic pain. It also has some linkage to schizophrenia and possibly low latent inhibition, IIRC. yes.It is the area I thought. How very curious. The pain drug developed in the 70's was Thalidomide, a disaster in Britain as the Ramones sang about and the American doctor who stopped it recieved a Presidential medal and was then tasked with reforming our system of clinical trials that we use today. https://www.ncbi.nlm.nih.gov/pubmed/31009420