It’s not Autism, it’s Sotos Syndrome – and more about GABA therapies

 Peter the wild boy, with Pitt Hopkins Syndrome

I recently returned from a 25 year class reunion; of the 200 or so class members about 120 turned up. Of the 200 we know that at least 5 have a son with autism and at least one has a nephew with autism.  So I had my first ever “autism lunch” discussing all those tricky issues we are left to deal with.

What was immediately apparent was how different each child’s “autism” was and that none of them were the autism-lite variants that are now being so widely diagnosed in older children. or even adults .  Of the six, two are non-verbal, one is institutionalized, yet one talks a lot.  Three sets of parents are big ABA fans and one child did not respond to ABA.

You may be wondering about that high incidence of autism.  This was not a gathering of science boffins or mathematicians; this was at a business school.  One thing is obvious, you can correlate some autism incidence with educational level.  You can connect all sorts of measures of IQ to autism, from having a math prodigy in the family, to having professors at Ivy league type Universities, particularly in Mathematics.  It does appear to be true that the so-called clever genes are also associated with some types of autism.

I presume that if my science-only university organized such events the incidence of autism would be even higher.

On the way back home we met an acquaintance at the airport, who was telling us all about his son with Sotos Syndrome.  "It is not autism", we were informed, but then I am not quite sure what is.  When you look it up, many of the symptoms look just like autism.  In fact, it is a single gene dysfunction that leads to gigantism and various elements of autism.

This brings me to the painting above of Peter the Wild Boy; it is not me I should point out.  The above Peter was a German boy who came to live in England in the 18^th Century; he was non-verbal and is now thought to have had Pitt Hopkins Syndrome.  Like Sotos, this is another very rare single gene disorder.

We have already come across Rett Syndrome, which for some reason is treated as autism.

Fragile X is thought of as a syndrome where autism can be comorbid.

Timothy Syndrome is fortunately extremely rare, but I have already drawn on it in my own research into autism.

There are also autism related disorders involving multiple genes.

Prader–Willi syndrome  is a rare genetic disorder in which seven genes (or some subset thereof) on chromosome 15 (q 11–13) are deleted or unexpressed (chromosome 15q partial deletion) on the paternal chromosome.  If the maternally derived genetic material from the same region is affected instead, the sister Angelman Syndrome is the result.

The most frequent disorder caused by known multiple gene overexpression is Down Syndrome.  We saw in earlier post that DS is caused by the presence of all or part of a third copy of chromosome 21.  This results in over-expression of some 300 genes.

Why So Many Syndromes

Even before the days of genetic testing, these syndromes had been identified.  How could that be?  Each syndrome is marked by clear physical differences.

These physical differences where used to identify those affected.

Within autism too, sometimes there are physical differences.  Big heads, small heads, slim stature or heavy stature, advanced bone age or retarded bone age.

So many syndromes , but no therapies

Many of the rare syndromes have their own foundations funding research, mainly on the basis that if there is a known genetic dysfunction there should be matching therapy somewhere.

As of today, there are no approved therapies for any of these syndromes.

The Futility of Genetic Research?

A great deal of autism research funding goes into looking for target genes.  The idea goes that once you know which gene is the problem you can work out how to correct it.  There are numerous scientific journal dedicated to this approach.

Since no progress has been made in treating known genetic conditions leading to “autism”, is all this research effort well directed?  Some clever researchers think it is not.

All I can do is make my observations from the side lines.

What do Down Syndrome, Autism and Pitt Hopkins Syndrome all have in common?

In at least some of those affected, they have the identical excitatory-inhibitory imbalance of GABA, that can be corrected by Bumetanide.

If you did whole exome genetic testing on the responders with these three conditions you would not find a common genetic dysfunction; and yet they respond to the same therapy.

I am actually all for continued genetic research, but those involved have got to understand its limitations, as well as its potential.

More on GABA

This post returns to the theme of the dysfunctional GABA neurotransmitter because the research indicates it is present in numerous of the above-mentioned conditions. 

Table 1.  Summary of GABAA signaling alterations in neurodevelopmental disorders (click for the full Table)

·        Autism

·        Fragile X

·        Rett Syndrome

·        Down Syndrome

·        Neurofibromatosis type 1

·        Tourette syndrome

·        Schizophrenia

·        Tuberous sclerosis complex (TSC)

·        Prader-Willi syndrome

·        Angelman Syndrome

Based on feedback to me, we should add Pitt Hopkins Syndrome to the above list.

The GABA dysfunction is not the same in all the above conditions, but at least in some people, Bumetanide is effective in cases of autism, Down Syndrome and Pitt Hopkins Syndrome.  I suspect that since it works in mice with Fragile-X , it will work in at least some humans.

GABA_A has already been covered in some depth in this blog, but I am always on the lookout for more on this subject, since interventions are highly effective.  It is complicated, but for those of you using Bumetanide, Low Dose Clonazepam, Oxytocin and some even Diamox, the paper below will be of interest.

Modulation of GABAergic transmission indevelopment and neurodevelopmental disorders: investigating physiology andpathology to gain therapeutic perspectives

Regular readers will know that in autism high levels of chloride Cl⁻ inside the neuron have been shown to make GABA excitatory rather than inhibitory.  This leads to neurons firing too frequently;  this results in effects ranging from anxiety to seizures and with reduced cognitive functioning.  Therapies revolve around reducing chloride levels, this can be done by restricting the flow in ,or by increasing the flow out.  The Na⁺/K⁺/Cl⁻ cotransporter NKCC1  imports Cl⁻ into the neuron.  By blocking this transporter using Bumetanide you can achieve lower Cl⁻ within the neuron, but with this drug you also affect NKCC2, an isoform present in the kidney, which is why Bumetanide is a diuretic.  Some experimental drugs are being tested that block NKCC1 without affecting NKCC2 and better cross the blood brain barrier. 

The interesting new approach is to restore Cl⁻ balance by increasing KCC2 expression at the plasma membrane.  This means increasing the number of transporters that carry  Cl⁻  out of the neurons.

Chloride extrusion enhancers as novel therapeutics for neurological diseases

In the Modulation of GABAergic transmission paper there is no mention of acetazolamide (Diamox) which I suggested in my posts could also reduce Cl⁻, but via the AE3 exchanger.  This would explain why Diamox can reduce seizures in some people.

The paper does mention oxytocin and it does occur to me that babies born via Cesarean/Caesarean section will completely miss this surge of the oxytocin hormone.  This oxytocin surge is suggested to be key to the GABA switch, which should occur soon after birth when GABA switches from excitatory to inhibitory.  In much autism this switch never takes place.

That would suggest that perhaps all babies born via Caesarean section should perhaps receive an artificial dose of oxytocin at birth.  This might then reduce the incidence of GABA dysfunctions in later life, which would include autism and some epilepsy.

Indeed, children born by Caesarean section (CS) are 20% more likely to develop autism.

Association Between Obstetric Mode of Delivery and Autism Spectrum Disorder - :  A Population-Based Sibling Design Study

Conclusions and Relevance  This study confirms previous findings that children born by CS are approximately 20% more likely to be diagnosed as having ASD. However, the association did not persist when using sibling controls, implying that this association is due to familial confounding by genetic and/or environmental factors.

So as not to repeat the vaccine/autism scare, the researchers do not say that Caesarean section leads to more autism, rather that the kinds of people who are born by Caesarean section already had an elevated risk of autism.  This is based on analysing sibling pairs, but I do not entirely buy into that argument.  They do not want to scare people from having a procedure that can be life-saving for mother and baby.

If you look at it rationally, you can see that the oxytocin surge at birth is there for an evolutionary reason.  It is very easy to recreate it with synthetic oxytocin.

Another interesting point is in the conflict of interest statement:-

Laura Cancedda is on the Provisional Application: US 61/919,195, 2013. Modulators of Intracellular Chloride Concentration For Treating An Intellectual Disability

Regular readers will note that in this blog we have known for some time that modifying GABA_A leads to improved cognitive function.  I even suggested to Ben-Ari that IQ should be measured in their autism trials for Bumetanide.  IQ is much less subjective than measures of autism.

Conclusion

My conclusion is that while genetic testing has its place, it is more productive to look at identifying and treating the downstream dysfunctions that are shared by many individual genetic dysfunctions.

By focusing on individual genes there is a big risk of just giving up, so if you have Pitt Hopkins Syndrome, like Peter the Wild Boy, it is a single gene cause of “autism” and there is no known therapy.  Well it seems that it shares downstream consequences with many other types of autism, so it is treatable after all.

I also think more people need to consider that cognitive dysfunction (Intellectual Disability/MR) may indeed be treatable, and not just via GABA; so good luck to Laura Cancedda.

Arbaclofen Given a Second Chance by the Simons Foundation

 Light at the end of the tunnel, for some

I did recently write about autism drugs that target the GABA_B receptor.

Western doctors have Baclofen and a few did have experimental use of the more potent version called Arbaclofen, or R-Baclofen.  We saw that Russian doctors have a wider choice.

The rights to use Arbaclofen have been acquired by the Simons Foundation, and they intend to restart autism trials in humans.

Mouse studies support second chance for fragile X drug

  

Arbaclofen was found to be effective in some people with Fragile-X and autism, but it failed its clinical trial and the developer, Seaside Therapeutics, went out of business.

The Simons Foundation, for those who do not know, is probably the best thing to ever happen to people with autism.  The founder of the foundation is an American multi-billionaire, former fund manager and mathematician.  He has a daughter with autism and decided to do something about it.

Having already funded a great deal of research, including by some of the scientists on my Dean’s List, it looks like he is going one step further and taking ownership over the trial drugs themselves.  Being a mathematician he is not averse to funding the most complex areas of research which include genetics and ion channels.  Being a fund manager he understands risk.  Being rich also helps, but you also need to be philanthropic.

Given the poor performance to date of developing practical therapies from the vast wealth of existing autism research, this is a very encouraging development.

There is now a large industry being made out of autism research, but the only coordinated part of it seems to be the Simons Foundation.  Interestingly the Simons Foundation focuses its effort on the very best scientists and not the existing autism researchers.  Apparently they want Nobel Laureates and future Nobel Laureates.  That sounds good to me.

Some people are concerned that by focusing on specific areas like genetics, the Simons Foundation may miss other possibly fruitful avenues.  But it is usually the case that an intelligent person's well thought out strategy is better than no strategy, and, at the end of the day, Simons’ billions are his to spend as he pleases.

Hopefully Simons will do for autism, what Bill and Melinda Gates are doing for polio and malaria.

Targeted pharmacological treatment of autism spectrum disorders: fragile X and Rett syndrome

Today’s post is to refer the scientists among you to a very thorough paper looking at possible drug therapies for two specific variants of autism, Fragile X and Rett Syndrome.

Targeted pharmacological treatment of autism spectrum disorders: fragile X and Rett syndromes

  

These are single gene autisms and, as such, it is very much easier to study them than classic autism(s) or regressive autism(s).

We have already seen that much can be learnt from Fragile X and Retts.  What helps treat these disorders may give useful pointers to treat other types of autism and some therapies may be directly transferable, in some cases.

Note the use of baclofen, memantine, lovastatin, rapamycin, a PAK inhibitor, two potassium channel drugs, oxytocin, and even lithium.

Ganaxalone is a positive allosteric modulator of the GABA_A receptor, probably affects the neurosteroid site.  It does not have the drawbacks of benzodiazepines.  I wonder whether it exhibits interesting effects at tiny doses? 

Tuning GABAa receptors

Treatment of Autism with low dose Phenytoin

Acamprosate appears to be neuro-protective, but the mechanism of action is unknown and controversial.  It is a drug a drug used for treating alcohol and benzodiazepine dependence.  A surprising number of off-label autism drugs are used for to treat substance abuse.

The paper is well worth a read for those who are heavily into the subject.

GERD/Reflux, Autism, Head Banging and mGlu5

This brief post addresses one further issue as to why people with autism can often suffer from various nasty gastrointestinal (GI) problems. 

First a recap.

Mast Cell Activation

We have already seen that some people’s GI problems are caused by mast cell activation/degranulation.  These cells are activated by allergens (certain foods in this case) and then they release histamine and other pro-inflammatory agents like IL-6.  Degranulation of mast cells can itself cause pain, but the main problem is the resulting damage/inflammation caused by the IL-6 and histamine.

The effective therapy is a mast cell stabilizer.  These include Verapamil (better known as a calcium channel blocker), Cromolyn Sodium, Ketotifen, Azelastine and to a lesser extent most anti-histamines like Claritin, Zyrtec etc.  Quercetin, the flavonoid, also has an effect.

Pancreatic Dysfunction

We also saw that L-type calcium channel (Cav1.2) dysfunction in the pancreas may disrupt the production of certain digestive enzymes.  The lack of these enzymes will disrupt the digestive process and likely affects other processes elsewhere in the body.  Verapamil blocks the Cav1.2 channel.

Ulcerative Colitis

We saw that inflammation and colitis, as diagnosed by an endoscopy, is another comorbidity of autism; this may be in part caused by the mast cell degranulation, but it does fit with the broader hypothesis of the over-activated immune system.  We saw how the potassium ion channel Kv1.3 was the mechanism behind some useful immuno-suppressive therapies, including those TSO parasites.  For those who are skeptical, here is another recent study, I just found:-

Expression of T-cell KV1.3 potassium channel correlates with pro-inflammatory cytokines and diseaseactivity in ulcerative colitis.

  

Kv1.3 should then be a target to treat ulcerative colitis and, I believe, autism itself. Some Kv1.3 blockers exist today; one is Verapamil, another is Curcumin, for those who prefer supplements to drugs.

Curcumin Serves as a Human Kv1.3 Blocker to Inhibit Effector Memory T Lymphocyte Activities

Before I forget to write this down somewhere, it appears that Kv1.3 can also be modulated by PKA and PKC, which decrease its activity. 

Dual Regulation of the n Type K+ Channel in Jurkat T  lymphocytes by Protein Kinases A and C*

We have already come across protein kinase B (PKB) and there will be a post soon of PKA, PKB and PKC.  This all links back to oxidative stress, neuroinflammation and even those dendritic spines.

  

Reflux

Today’s post is about reflux, sometimes known as gastroesophageal reflux disease (GERD) or gastro-oesophageal reflux disease (GORD).  Reflux is when the acid from the stomach rises through the esophagus/oesophagus to the mouth.

Many adults suffer from reflux from time to time and there are many OTC and prescription drug treatments. It can cause pain and discomfort, and would be particularly troubling if you could neither verbalize, nor understand your symptoms.

Why this post?

You may wonder why I have jumped from broccoli (the previous post) to reflux.  There is a reason.

I was recently listening to a conversation between doctors about a head-banging child and then came “it’s not autism; he’s got reflux, that is why he was banging his head.”

That sounded very odd to me.

It turns out many people with autism suffer from reflux, so you could say it is a comorbidity.  But why might that be?

mGlu5 receptors and disease

In an earlier, rather complicated, post I introduced the glutamate receptor, mGlu5.  This receptor is at the centre of research into Fragile X at MIT.  Fragile X is the most common single gene cause of autism.  It has been shown that mGlu5 dysfunction appears in many types of autism and indeed schizophrenia (adult-onset autism).

   

I then chanced upon a recent paper on mGLu5 and came across this section:-

Through contributions to synaptic plasticity, mGlu5 receptors have been implicated in neuronal processes such as learning and memory as well as disorders including Fragile X Syndrome (FXS), tuberous sclerosis, autism, epilepsy, schizophrenia, anxiety, neuropathic pain, addiction, Alzheimer’s disease, Parkinson’s disease, L-DOPA-induced dyskinesias, and gastroesophageal reflux disease

That was quite a surprise, but yet another good lesson of why the comorbidities should all be carefully researched.

 

The full paper, for anyone with time on their hands is:- 

Location-dependent signaling of the Group 1 metabotropic glutamate receptor, mGlu5.

Conclusion

If you have autism, you may have an mGlu5 dysfunction.  This will become treatable once the needed PAMs (Positive Allosteric Modulators) and NAMs (Negative Allosteric Modulators) have been brought to market.  A great deal of research is ongoing.

In the meantime, mGlu5 dysfunction is quite possible elsewhere in the body.  mGlu5 dysfunction is associated with some very rare disorders, but the common ones are diabetes and reflux.

The head-banging boy very possibly had both autism and reflux; he did develop diabetes.

For more on autism and diabetes, a short, thought provoking, but technical, paper:-

Insulin signaling and autism

Interestingly, we saw earlier that Verapamil seems to offer protection against type 1 and 2 diabetes. This time it is its calcium channel blocking role that is the mechanism.

Verapamil drug may reverse diabetes related death of pancreatic beta cells

No big surprise that Verapamil is an ingredient of the autism Polypill.

Verapamil drug may reverse diabetes-related death of pancreatic beta cells

Dendritic Spines in Autism – Why, and potentially how, to modify them

This blog is getting rather more detailed than I had anticipated.  

Today’s post is about something very complex, but not fully understood by anyone, so I will be somewhat superficial in my coverage.  Just click on the links to learn more detail.

There are two words that may be new to you – Morphology and Dendritic Spines.

Morph in Twin Decks

Morphology, in biology, the study of the size, shape, and structure of animals, plants, and microorganisms and of the relationships of the parts comprising them.

For today it is really could be thought of as the variability in size and shape of something.

A dendritic spine is a small protrusion from a neuron's dendrite that typically receives input from a single synapse. Dendritic spines serve as a storage site for synaptic strength and help transmit electrical signals to the neuron's cell body. Most spines have a bulbous head (the spine head), and a thin neck that connects the head of the spine to the shaft of the dendrite. The dendrites of a single neuron can contain hundreds to thousands of spines. In addition to spines providing an anatomical substrate for memory storage and synaptic transmission, they may also serve to increase the number of possible contacts between neurons.

Now we combine our two new words and have a better summary of what this post is about:

Morphology of dendritic spines and mental disease

It turns out that shape of dendritic spines may play a key role in mental disease, including autism.

The shape is not fixed and live imaging studies have revealed that spines are remarkably dynamic, changing size and shape over timescales of seconds to minutes and of hours to days.

The shape is important as it impacts on function, malformations lead to dysfunctions that can affect a myriad of brain functions.

Here are some variations in the shape of dendritic spines.

In case you are thinking this is all rather abstract, let’s jump forward to a patent for a possible new treatment for autism.

Afraxis Patent

Methods for treating autism 

  

SUMMARY OF THE INVENTION

Described herein are p21 -activated kinase (PA ) inhibitors that alleviate, ameliorate, delay onset of, inhibit progression of, or reduce the severity of at least one of the symptoms associated with autism.

Claims  

WHAT IS CLAIMED IS:

1. A method for treating autism comprising administering to an individual in need thereof a therapeutically effective amount of a p21 -activated kinase (PAK) inhibitor.

2. The method of claim 1, wherein the PAK inhibitor modulates dendritic spine morphology or synaptic function.

3. The method of claim 2, wherein the PAK inhibitor modulates dendritic spine density.

4. The method of claim 2 or 3, wherein the PAK inhibitor modulates dendritic spine length.

5. The method of any of claims 1-4, wherein the PAK inhibitor modulates dendritic spine neck diameter.

6. The method of any one of claims 1-5, wherein the PAK inhibitor modulates dendritic spine head volume.

7. The method of any one of claims 1-6, wherein the PAK inhibitor modulates dendritic spine head diameter.

8. The method of claim 1 or 2, wherein the PAK inhibitor modulates the ratio of the number of mature dendritic spines to the number of immature dendritic spines.

9. The method of claim 1 or 2, wherein the PAK inhibitor modulates the ratio of the dendritic spine head diameter to dendritic spine length.

10. The method of claim 1 or 2, wherein the PAK inhibitor modulates synaptic function.

Etc …

Of course, plenty of patents turn out to be worthless nonsense, but I think the people at Afraxis do know what they are doing; time will tell.

Morphology or Number of Dendritic Spines?

The PAK1 researchers and others believe the morphology (shape) of the dendritic spines is the problem, others believe the problem is that there are just too many of them.

Research has shown that a particular gene (NrCAM) can increase/decrease the number of dendritic spines.

Studies at University of North Carolina showed that knocking out the NrCAM gene caused mice to exhibit the same sorts of social behaviors associated with autism in humans.

Researchers from Columbia University found an overabundance of the protein MTOR in mice bred to develop a rare form of autism. By using a drug to limit MTOR in mice, the Columbia researchers were able to decrease the number of dendritic spines and thus prune the overabundance of synaptic connections during adolescence. As a result, the social behaviors associated with autism were decreased. However, the drug (Rapamycin) used to limit MTOR can cause serious side effects.

Children with Autism Have Extra Synapses in Brain

Dr. Tang measured synapse density in a small section of tissue in each brain by counting the number of tiny spines that branch from these cortical neurons; each spine connects with another neuron via a synapse.

By late childhood, she found, spine density had dropped by about half in the control brains, but by only 16 percent in the brains from autism patients.

“It’s the first time that anyone has looked for, and seen, a lack of pruning during development of children with autism,” Dr. Sulzer said, “although lower numbers of synapses in some brain areas have been detected in brains from older patients and in mice with autistic-like behaviors.”

Using mouse models of autism, the researchers traced the pruning defect to a protein called mTOR. When mTOR is overactive, they found, brain cells lose much of their “self-eating” ability. And without this ability, the brains of the mice were pruned poorly and contained excess synapses. “While people usually think of learning as requiring formation of new synapses, “Dr. Sulzer says, “the removal of inappropriate synapses may be just as important.”

“What’s remarkable about the findings,” said Dr. Sulzer, “is that hundreds of genes have been linked to autism, but almost all of our human subjects had overactive mTOR and decreased autophagy, and all appear to have a lack of normal synaptic pruning. This says that many, perhaps the majority, of genes may converge onto this mTOR/autophagy pathway, the same way that many tributaries all lead into the Mississippi River. Overactive mTOR and reduced autophagy, by blocking normal synaptic pruning that may underlie learning appropriate behavior, may be a unifying feature of autism.”

Maness, a member of the UNC Neuroscience Center and the Carolina Institute for Developmental Disabilities, also said that there are likely many other proteins downstream of NrCAM that depend on the protein to maintain the proper amount of dendritic spines. Decreasing NrCAM could allow for an increase in the levels of some of these proteins, thus kick starting the creation of dendritic spines.

Knocking out the gene NrCAM increases the number of dendritic spines  

   

Gene linked to increased dendritic spines -- asignpost of autism

  

The view from Japan

RIKEN is a large research institute in Japan, with an annual budget of US$760 million.  Their Brain Science Institute (BSI) has a mission to produce innovative research and technology leading to scientific discoveries of the brain.  So RIKEN  BSI is like MIT just for the brain.

Science does tend to stratify by geography.  Just as we saw that NGF (Nerve Growth Factor) is the preserve of the Italians, when it comes to PAK it is the Japanese.

As you can see below the Japanese are firmly behind PAK1. 

 Pak1 regulates dendritic branching and spine formation.

Abstract

The serine/threonine kinase p21-activated kinase 1 (Pak1) modulates actin and microtubule dynamics. The neuronal functions of Pak1, despite its abundant expression in the brain, have not yet been fully delineated. Previously, we reported that Pak1 mediates initiation of dendrite formation. In the present study, the role of Pak1 in dendritogenesis, spine formation and maintenance was examined in detail. Overexpression of constitutively active-Pak1 in immature cortical neurons increased not only the number of the primary branching on apical dendrites but also the number of basal dendrites. In contrast, introduction of dominant negative-Pak caused a reduction in both of these morphological features. The length and the number of secondary apical branch points of dendrites were not significantly different in cultured neurons expressing these mutant forms, suggesting that Pak1 plays a role in dendritogenesis. Pak1 also plays a role in the formation and maintenance of spines, as evidenced by the altered spine morphology, resulting from overexpression of mutant forms of Pak1 in immature and mature hippocampal neurons. Thus, our results provide further evidence of the key role of Pak1 in the regulation of dendritogenesis, dendritic arborization, the spine formation, and maintenance.

SHANK3 and Dendritic Spines

Mutations of the SHANK3 gene are known to cause autism. 

Researchers in France found that SHANK3 mutations lead to modification of dendritic spine morphology and they identified the mechanism.

SHANK3 mutations identified in autism lead to modification of dendritic spinemorphology via an actin-dependent mechanism

You may recall in my earlier posts on growth factors that it was this type of autism that responded to treatment with IGF1.

SHANK3 and IGF1 restore synaptic deficits in neurons from 22q13 deletion syndrome patients

If you take a broader look at today’s subject you will see that various growth factors are indeed closely involved.  Here is some comment from Wayman Lab at Washington State University:- 

"Not surprisingly, abnormalities in dendritic arborization and spinogenesis, which diminish neuronal connectivity, are a common feature of the cognitively compromised aging brain as well as numerous forms of mental retardation including Fragile X, Fetal alcohol, Downs and Retts syndromes.

It is clear that changes in synaptic activity and neurotropic factors (e.g., BDNF) are effective initiators of the remodeling process and result in long-term alterations in dendrite and spine structure. What is not known are the molecular mechanisms that underlie how they stimulate dendritic spine formation."

Take your pick

So it looks like three different methods may exist to potentially modify dendritic spine numbers and morphology:-

1.   PAK1

Much work is ongoing regarding PAK1.  It is my current favorite.

For those interested here is a recent study using FRAX486 on Fragile X mice.

Rescue of Fragile X Syndrome phenotypes in Fmr1 KO mice by the small molecule PAK inhibitor FRAX486

Abnormal dendritic spines are a common feature in FXS, idiopathic autism, and intellectual disability. Thus, this neuroanatomical abnormality may contribute to disease symptoms and severity. Here we take a hypothesis-driven, mechanism-based approach to the search for an effective therapy for FXS. We hypothesize that a treatment that rescues the dendritic spine defect may also ameliorate behavioral symptoms. Thus, we targeted a protein that regulates spines through modulation of actin cytoskeleton dynamics: p21-activated kinase (PAK). In a healthy brain, PAK and FMRP - the protein product of fmr1 - antagonize one another to regulate spine number and shape. Inhibition of PAK with a strategy utilizing mouse genetics reverses spine abnormalities as well as cognitive and behavioral symptoms in fmr1 KO mice, as we demonstrated in our previous publication. This discovery highlights PAK as a potential target for drug discovery research. In this thesis work, we build on this finding to test whether the small molecule FRAX486 - selected for its ability to inhibit PAK - can rescue behavioral, morphological, and physiological phenotypes in fmr1 KO mice. Our results demonstrate that seizures and behavioral abnormalities such as hyperactivity, repetitive movements, and habituation to a novel environment can all be rescued by FRAX486. Moreover, FRAX486 reverses spine phenotypes in adult mice, thereby supporting the hypothesis that a drug treatment which reverses the spine abnormalities can also treat neurological and behavioral symptoms.

2. mTOR

In spite of its noted toxicity, Rapamycin, is about to be tested in a clinical trial on a rare type of autism called TSC:-

Rapalogues for Autism Phenotype in TSC: A Feasibility Study (RAPT)

Funnily enough the trial is taking place at the Kennedy Krieger Institute.

When commenting on the use of Bumetanide for autism, I recall the President of the Institute was quoted as saying:-

"So many things cure cancer in mice and rats, and so many things cure all kinds of things and then when we give them to humans they have adverse effects and don't fix the problems we thought they could fix," says Gary Goldstein, president and CEO of the Kennedy Krieger Institute, a Baltimore-based clinic and research center. "I wouldn't give it to my child, I can tell you that."

I found it a little odd that he gave the green light to trialing Rapamycin in children, given the long list of very nasty side effects.

  

3.  NrCAM 

Manesslab at UNC is clearly the centre for research into finding therapeutic agents surrounding NrCAM.  It looks like this is still some way from trials in humans.

“Too many spines and too many excitatory connections that are not pruned between early childhood and adolescence could be one of the chief problems underlying autism. Our goal is to understand the molecular mechanisms involved in pruning and find promising targets for therapeutic agents.”

Conclusion

It should not be surprising that multiple pathways may have the same therapeutic benefit on dendritic spines.  We only need one to be safe and effective.

The link back to human growth factors is interesting since we know these are disturbed in autism and other mental conditions, but the dysfunction varies by sub-type.  In fact, Nerve Growth Factor (NGF) would likely be an effective therapy for dementia and perhaps even Retts syndrome.

In the next post we will learn some more interesting things about growth factor anomalies in autism.  It turns out that something called Akt, also known as protein kinase B (PKB), may be behind them all. A related protein called protein kinase C (PKC), is known to affect the morphology of dendritic spines. There is also protein kinase A (PKA).  Both PKA and PKB have been shown to have reduced activity in regressive autism, this will also be covered later.