Yale, Autism and Morphology

  

In a recent post I introduced a new term – morphology.  Some scientific jargon serves to make things more confusing for the lay reader, but this really is a useful term to understand autism.

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.

Today we are talking about morphology as it relates to the growth of the human body in autism.

In earlier posts relating to hormones and growth factors (endocrinology) I made my own observations about Monty, aged 11 with ASD.  I commented how he fell from the 80% percentile in height, aged 2, to the 20^th percentile, where he is now.  I also noted how he went from very muscular to your average “floppy” toddler.

I did discuss this with a pediatric endocrinologist and asked what is the point of collecting this height and weight data for children, if nothing is done with it.  I did tell her all about the emerging use of the growth factor IGF-1 in treating autism and also the hypothesis that people with autism have low thyroid hormone T3 in the brain.

I concluded that endocrinologists do not know anything about autism, but I did learn all about bone age. 

Endocrinologists often use X rays of the hand to look for advanced or delayed bone age.  They look at the gaps in between the small bones to assess the degree of maturation.  The bigger the gap, the less mature the bones.  They have a big book of X-rays and they just flip through the pages until they find one like your X ray.  So if you are 11 years old, with bone structure of a 9 year old, then you would have delayed bone age.  In practical terms, this means you are likely to keep growing for longer than the average child.

Autism Research

As we have seen already, much data in autism is of dubious quality.  Studies are contradictory.  Much of this is due to mixing apples with kiwis and even pineapples. You cannot usefully compare data on severely autistic people with those ever so mildly affected, but still “autistic” by DSM. Even separating early onset and regressive autism is rare in studies.  There is no agreement as to what regressive really means and some scientists even think regression is just a development plateau – I guess they never see actual patients.

So I was pleased to come across some interesting research about autism morphology that seems credible.  Of all places, it was in a student publication from Yale.  On Facebook, Monty’s older brother keeps getting confused with his namesake, who is one of the reporters on the Yale student newspaper.    Not only does Yale have a daily student newspaper, but it also has its own Yale Scientific Magazine.

They must have a lot of free time over at Yale.

This was my first experience of student journalism at Yale.  I was impressed.

Autism may be predicted by overgrowth

Sizing Up Autism: The CorrelationBetween Autism and Abnormal Growth

  

One identified phenotype associated with autism is abnormally large Total Cerebral Volume (TCV) and, correspondingly, Head Circumference (HC) – collectively called macrocephaly. Researchers at Yale University’s Child Study Center have undertaken studies in the connectivity of growth and neural development to assess risk and predict developmental phenotype of young boys through growth measurement. A group of 184 boys aged birth to 24 months, composed of 55 typically developing controls, 64 with ASD, 34 with Pervasive Developmental Disorder Not Otherwise Specified (PDD-NOS), 13 with global developmental delays, and 18 with other developmental problems, was analyzed for head circumference, height, weight, and social, verbal and cognitive functioning. Boys with autism were significantly taller by 4.8 months, had a larger HC by 9.5 months, weighed more by 11.4 months, were in the top ten percent in size in infancy (correlated with lower adaptive functioning and social deficits), and showed accelerated HC growth in the first year of life.  


Here is actual study:-

Early Generalized Overgrowth in Boys With Autism

Main Outcome Measures: Age-related changes in HC (head circumference),

height, and weight between birth and age 24 months; measures of social, verbal, and cognitive functioning at age 2 years.

Results: Compared with typically developing controls, boys with autism were significantly longer by age 4.8 months, had a larger HC by age 9.5 months, and weighed more by age 11.4 months (P=.05 for all). None of the other clinical groups showed a similar overgrowth pattern. Boys with autism who were in the top 10% of overall physical size in infancy exhibited greater severity of social deficits (P=.009) and lower adaptive functioning (P=.03).

Conclusions: Boys with autism experienced accelerated HC growth in the first year of life. However, this phenomenon reflected a generalized process affecting other morphologic features, including height and weight. The

study highlights the importance of studying factors that influence not only neuronal development but also skeletal growth in autism.

  

The Yale researcher is Polish, as was the lady who wrote about oxidative stress in the brain lowering D2 and hence thyroid hormone T3 in the brain.

Conclusion

This does take us back to the earlier posts on human growth factors.  It does seem that at least in one sub-type of autism there is “excess” growth in the first two years that is visible in terms of morphology.  This growth spurt then halts.

We already have data showing that in autism the brain itself also “over-grows” up to the age of about three.  We can now generalize that in this sub-type everything is likely affected by this over-growth.

Why does the growth spurt halt? It is not for lack of the growth factor IGF-1, many people with autism actually have elevated levels of this growth factor.  It is simple and inexpensive to check; I did it.

The problem may relate to something called Akt, also known as protein kinase B (PKB).

IGF-1 is one of the most potent natural activators of the AKT signaling pathway, a stimulator of cell growth and proliferation.

Very recent research has highlighted abnormalities in the IGF-1 – Akt pathway and also in similar pathways related to the brain’s own growth factor, BDNF.  (Note that mTOR is also implicated in autism)

Dysregulation of the IGF-I/PI3K/AKT/mTOR signaling pathway in autism spectrum disorders

 Abnormalities in BDNF/TrkB/PI3Ksignaling pathways in autism

So while IGF-1 may be an effective therapy for some people with autism (it is already used experimentally), most likely the real problem is slightly different and a better intervention might relate to AKT/PKB.

We will follow up on these and other protein kinase shortly.

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.