Summary of Scientific Workshops
Presentations at the 1st World Conference IASO - Tampere, Finland, 4-8 July, 2000
Presented by: Dr. Jill Clayton-Smith
Many of those attending the general sessions of the IASO meeting will not have had an opportunity to attend the scientific sessions or will have found the medical and scientific jargon used in those sessions difficult to follow. This report summarizes the proceedings of the Scientific Workshops in a format which can hopefully be understood by a more general audience. The abstracts for the presentations were included in the conference program. The aim of this summary is not to cover every detail but to bring out the main points of the presentations and discussion. Comment would also be welcomed from those researchers present who would like to add or alter anything that is included here and I would encourage any of you who would like further information to seek it from the presenters of the abstracts.
Genetic Mechanisms in Angelman Syndrome
The first three sessions concern genetics. This is a complicated subject. Dr. Beaudet prepared a handout summarizing the genetic mechanisms of Angelman syndrome in more detail and some of you may have picked up this handout yesterday.
The majority of individuals have a deletion of Chromosome 15 which occurred on the mother's chromosome (70%). This doesn't mean that the mother herself had the deletion, it is meant that the deletion occurred for the first time in the chromosome which came from the mother. A very small number of individuals have a rearrangement of Chromosome 15 which predisposes them to a deletion (1%). A small group (2%) have uniparental disomy (UPD) and 3-5% have an imprinting defect . About 5 % of individuals have a UBE3A mutation and in about 10-15 % there is no demonstrable abnormality of Chromosome 15.
The group from Italy studied their Angelman patients (150 patients from 148 families), looking at these particular genetic mechanisms. They had results from around 111 patients as 39 of them were still undergoing investigation. Only 46.8% of their population had a deletion. The main question raised by this presentation was whether the incidence of de novo deletions was really lower in Italy than it was in other parts of the world. There are other possibilities, for instance, there could have been biased ascertainment of the group of Angelman patients without deletions.
In order to detect which genetic mechanism is involved in AS in individual families, it's necessary to have some sort of strategy for genetic investigation. Ellie Smith from Australia gave us this example of the diagnostic strategy used there and other groups are broadly in agreement with this strategy. Methylation analysis is the single most important investigation and is the first line test. If the typical AS methylation abnormality is found then the possibilities are that this is a deletion, uniparental disomy or an imprinting defect. The FISH test should then be carried out to identify deletions and further DNA tests will confirm whether there is UPD or an imprinting defect. Strictly speaking, FISH is not absolutely necessary in every case and if methylation is normal, then FISH is unlikely to be helpful. Ideally, however, every child should have a routine chromosome analysis to rule out chromosome rearrangements which might predispose to Angelman Syndrome.
The group from Australia also reported their experiences with a PCR based methylation test. PCR stands for Polymerase Chain Reaction and it's probably the most commonly used technique in the molecular genetic laboratory. It's a very quick procedure, so a PCR methylation test is quicker than the other technique in standard use which is called Southern blotting. The Australian experience shows that it is a very reliable way of looking at methylation and many laboratories have adopted this PCR methylation technique. In theory, there's a small risk of getting false positive results if you do this type of methylation test, but if this happens then you should detect that on the subsequent investigations and the consensus is that this is a good type of methylation test.
There were several presentations which mentioned UBE3A mutations and they are found in about 20% of the non-deletion, non-disomy and non-imprinting group (NDDI), so they are well worth looking for in this group, especially if you have families where more than one child is affected with Angelman Syndrome where the pickup rate in those families is around 80 %. The UBE3A gene is a relatively large gene and that the mutations are scattered all along the length and so it can be quite time consuming to look through the gene and find each specific change or mutation.
Continuing on the theme of genetics, the issue was raised as to whether some mothers may be more predisposed than others to have a child with Angelman Syndrome. In fact, three families were described during the course of the workshops where a mother had a minor abnormality in the arrangement of her chromosomes which possibly did put her at increased risk.
In the first family, the mother of an Angelman child had an extra little piece if chromosome 15 called a satellite. Chromosome 15 satellites are usually attached to the top of the chromosome 15 and are a normal variation in the general population. All Chromosome 15's, when you look at them, are a little different and just like we have different noses and ears, our Chromosomes 15's have different satellites which give them individuality. When this particular mother's chromosomes were examined, the piece of satellite DNA from Chromosome 15 had actually moved and become attached to one of the other chromosomes. And the question has been raised as to whether this had any relevance to the fact that this mother then had an Angelman Syndrome child. It wasn't something that other individuals within the audience had seen in other families, so we don't know whether this is definitely relevant or not.
In the second family, one chromosome 15 was actually attached on to one of the other chromosomes. This is called a Robertsonian translocation. In this situation , although a person who has a Robertsonian translocation can be quite normal there's an increased risk in of having a child who has the wrong number of Chromosome 15's . Uniparental disomy (UPD) may also result giving rise to AS or Prader-Willi syndrome depending upon which parent contributed both chromosome 15s.
A third family was presented in which instead of having just two Chromosome 15's a child also had an extra little piece of 15, called a marker 15, and it was thought that having this marker present, had actually predisposed that child to acquiring a deletion of chromosome 15.
The message from these observations is that it is important for every individual to have a routine chromosome tests as well as having the methylation test so that we can see if these types of chromosome rearrangements occur frequently and determine whether they are important in causing AS.
Imprinting Centre Studies
There were two papers which looked at imprinting center studies and these were from Dr. Buiting from Germany and Dr. Shemer from Israel. In the normal situation an individual inherits one chromosome from mother and one chromosome from father. In AS individuals with imprinting defects, they still inherit one from the mother and one from father, but the one from mother behaves as though it came from the father, it hasn't got a special maternal "imprint" to tell it that it came from the mother. The process of imprinting is dependent upon the activity of a specific genetic sequence on Chromosome 15 called the imprinting centre. The imprinting centre has two parts, one part is important in setting the maternal imprint and one in setting the paternal imprint, but the presentations concluded that both of these parts must actually interact in order for the normal maternal imprinting process to take place.
In the general discussion following the genetics sessions the need for us to use correct terminology was stressed. Often, if we come from different countries, we do use different terminology but there are some things which we need to be more consistent about. Dr. Horsthemka pointed out that it's very important to differentiate between imprinting defect (which means any problem causing the imprinting to be unusual) and imprinting mutation (which is when we've actually identified something in that important part of the imprinting center). This distinction is important because the genetic counseling aspects could be quite different in the two situations. Other things that came out in the session is that studying just a single family can be very important in helping to work out what causes Angelman Syndrome. Dr. Buiting's work on the imprinting center study had been based on one family and we didn't need to study hundreds of individuals to get that important information.
One of the presentations by Dr. Ramsden, from Manchester, talked about how investigations for Angelman Syndrome could be made available to clinical geneticists, so providing a service for families who attended a genetic counseling clinic who are asking for investigations. Dr. Smith from Australia also talked about provision of genetic services for families.. At present, there are two types of genetic testing being done; One is research testing in research labs to make new discoveries and the other one is service testing to provide testing and counseling for families of Angelman children and individuals. In research laboratories, there is likely to be access to more funding and better equipment and more sensitive methods of detection than in some of the service laboratories. The other emphasis within the genetic sessions was the importance of communication between the parents, the clinicians and the molecular geneticist.
Clinical Studies
Some of the clinical studies in Angelman Syndrome were summarised. The word "phenotype" is mentioned frequently. It means the signs and the symptoms the individual shows, whereas the word "genotype" means the underlying genetic abnormality. Put simply, phenotype-genotype correlation means what are the differences in the signs and the symptoms between the different groups of Angelman Syndrome patients where you have different underlying genetic abnormalities? And from the presentations in the General Session and the Workshops, the general consensus of opinion is that patients with a deletion will often ( but not always) have more typical signs than patients with UBE3A mutations, or with imprinting center problems or uniparental disomy (UPD). However there are no hard and fast rules about this. Parents of children with deletions might feel that their children will definitely have more problems but we have to bear in mind the fact that all children are individuals and that even within the group of deletion patients, there will be some children who really have fewer problems than patients within the other groups. So phenotype/genotype correlation merely generalizes across large groups of patients.
Dr. Kyllerman, from Sweden, discussed screening of a large group of Swedish patients according to the consensus diagnostic criteria for AS that had been published previously. In the consensus criteria published by Williams et al. in 1995 there are lists of features that need to be "consistently" present or which are "usually" presently or which "may" be present in Angelman Syndrome. If you fulfill a certain number of these criteria, then you are deemed to have a clinical diagnosis of Angelman Syndrome. Dr. Kyllerman looked at his group to see how many of his patients fit the clinical criteria and then looked at the underlying genetic testing and in fact showed that if you stick religiously to the clinical criteria, only testing those who fulfill the criteria, you will miss some cases with Angelman Syndrome. The main limitations with the consensus criteria were that there wasn't enough emphasis placed on the "behavioral uniqueness" of AS children and so the criteria should include more of the behavioral features . The criteria mention some features such as something called an occipital groove, which is a groove across the back of head and in actual fact, in Dr. Kyllerman's large series, this wasn't found in really very many patients and isn't a very good diagnostic feature.
Ellie Smith, from Australia, has a wealth of data gathered over the years from running a dedicated Angelman Syndrome Clinic. She had analyzed some of this data for us and one example, was the observation of walking in Angelman Syndrome. Her data showed that most children were walking by the age from 4 to5 yrs, but some may walk much later. In general, the earlier the onset of walking, the better you are at it. But it's impossible to say that a child will never walk because there were some individuals who walked very later on in life. I think one point which was interesting is that Dr. Smith's Angelman Clinic is completely unfunded and the work was done in her "spare" time and overall, there is more difficultly in getting funding for clinical research than there is for the sort of more academic and scientific based research.
Finally, Dr. Charlie Williams gave a good review of conditions which are Angelman-like but not Angelman Syndrome. They included several chromosome abnormalities apart from chromosome 15 such as a condition which is caused by a tiny deletion of Chromosome 22. Several other genetic conditions caused by single gene faults may also give rise to Angelman-like symptoms.
Adaptive Behaviour
There was a presentation by the Spanish group on Adaptive Behavior. This simply means "how well an Angelman child is developing or functioning". Thirty (30) patients were studied and parents scored their children on a scale, something called an ICAP scale which covered questions about motor skills, social and communication skills , their personal life skills and their life skills in their community. The social and communication skills were the lowest which one would expect in AS where there is a specific deficit in communication skills.. One point raised in the discussion was that maybe some of the scales that were used to test Angelman children are inappropriate for this group because they do have such difficulty with verbal performance and it would be interesting to know if there are any good scales for testing in children who are specifically non-verbal.
If individuals had seizures or the very typical behavioral features associated with Angelman Syndrome, it was associated with lower scores on the ICAP scale. But if they had a sleep disorder, then it didn't make any difference to how you functioned. So it seemed to be that even if you had poor sleeping, it didn't alter how well you did during the day.
Melatonin
Discussion of melatonin therapy is of interest to many families and Dr. Saitoh, from Japan, spoke about a small study which was carried out there. Four out of the six patients were successfully treated by melatonin with improvement in sleep. General conclusions are that melatonin works for some people, so it's worth a try but it doesn't work for everyone. It's clear there is no set dose of melatonin to give and it varies very much from one individual to another. One individual may respond very well to a very small dose and other individuals need a much higher dose. Dr Swaab mentioned that even if two Angelman children take the same dose of melatonin, the level of melatonin in their blood stream may be quite different. So it is important to try and monitor the level of melatonin and that this can actually be done quite simply if you look at saliva levels of melatonin and you don't need to take blood. In the questions and discussions afterwards there were several parents who mentioned that they had good results from melatonin even though this study and the previous one by Joe Wagstaff, showed that there was sometimes difficulty in maintaining an effect even if that been an initial response. There was overall a positive response from parents in the audience.
Seizures
Dr. Laan from the Netherlands talked about the EEG in AS and the characteristic EEG findings can be found in AS individuals with all types of genetic abnormalities. The most characteristic pattern to look for is something called a triphasic wave. In some patients with Angelman Syndrome, these EEG changes aren't always seen on the very first time you do an EEG, but may be seen on subsequent occasions, so it could be worth repeating an EEG if you don't see them the first time and your still convinced about the diagnosis of AS. Dr Laan looked specifically at a group of individuals with UBE3A mutations and found that seizures were present in this group, but they were milder. A lot of discussion in the general session focused on the fact that it was the fact that the deletion patients who tended to have the seizures, but they are present in other groups. Most individuals with seizures, in the Australian study of Ellie Smith's, had an onset by 5 yrs of age and after that it was unusual to start developing a severe seizure disorder. Again, there were a few exceptions to that rule.
Behaviour
There were two presentations which covering the topic of behaviour. One study covered autism and we often hear the word autistic in relation to Angelman Syndrome individuals. An investigator from the UK studied a small group of Angelman Syndrome children and videoed the children. Independent observers, scored whether they had autistic features or not. The conclusion was that Angelman Syndrome children are not truly autistic, although in the discussion it was pointed out that there may be a sub-group of children who show more autistic-type features. None have autism as described in the true sense.
A very interesting, and original study on smiling and laughing in AS was reported There has been a lot in the literature about the happy and sociable nature of Angelman children and some of the very first articles mention that these individuals would smile and laugh for no reason whatsoever. Some people wondered whether the laughing could be seizure activity. In this present study, three children were investigated and they were observed in different situations Firstly they were observed when they were just on their own, then when they were interacting with another adult. One patient was also observed interacting with his mother. It was shown that the frequency of laughter is affected by environment so that if Angelman individuals come in contact with other people, they do get more smiley and laugh more. This is something many of us have observed. When they are on their own (in a less stimulating environment for them), then the frequency of smiling and laughter is really reduced. This shows that they need some sort of environmental stimulus to stimulate the laughter and they don't laugh for no reason whatsoever.
Several people mentioned that their children laughed if they were anxious and not always because they were happy. There also appear to be different types of smiling and laughing. Angelman children might smile in a slightly different way on one occasion then they do in another situation. The suggestion here is that the different types of smiling might be used as a communication method.
Orofacial Problems
A study by a dentist from Sweden on orofacial problems in AS was reported. It's quite common for Angelman individuals to present to dentists and the main presenting features are with drooling or with feeding difficulties or swallowing difficulties. Dental examination is difficult, and may even be hazardous to the dentist! The study mentioned the presence in Angelman Syndrome individuals, of something called a "Frontal Open Bite". This describes a situation where the molars of the top and the bottom teeth actually abut against one another so that you can't close your jaws together. Reasons for this developing could be tongue protrusion, biting habits or mouthing habits, and possibly the use of a dummy (pacifier). It seems that if you keep your mouth open for a long period the molars at the back can actually grow longer and this stops the jaws closing together properly. The dentist did some interesting work on trying to prevent and improve this problem of Frontal Open Bite by using some special appliances (inserted into the mouth) and also by use of physiotherapy and behavioral modifications (encouraging the lips to be kept shut and mouth to be kept shut). These types of therapy are recommended rather than surgery.
Neuromuscular/Neurology
Two presentations looked at neuromuscular disorders and neurological abnormalities in AS. Bernard Dan, from Belgium, has studied in detail the muscle groups that Angelman Syndrome individuals use when they move from lying to standing and compared that to normal children, who where aged matched. A normal child who gets up from laying to standing, will vary the way in which they get up from one occasion to another. An AS child always tends to use the same method. This will be the way in which he or she can do it most safely without endangering themselves. They may have difficulty doing it in other ways because they do have some intrinsic differences in their muscle tone and they can't use some of the other ways of getting up that other children would normally use i.e. they are limited in their repertoire of movements.
The second presentation encompassing neuromuscular problems, was a presentation by Matthias Riedel on something called Manual Manipulation. This is a type of therapy. Which is fairly intensive and involved two weeks of therapy using specific types of manipulation. At the same time you have occupational therapy and physiotherapy and the whole programme is aimed at improving proprioception and movement. Proprioception really means an awareness of where your body parts are in space. If you undergo this sort of therapy, it's thought that the child gains a better awareness of where the different parts of their body are and therefore can actually plan and execute movements in a much better way. Dr Riedel only looked at a small group of children but parental feedback after this 2 week intensive therapy, was good and many parents had indicated they would like to try another 2 weeks at some stage. Further information about this therapy is available at (http://www.AMM-Rheintalklink.de).
Neuroscience - Gaba
Neuroscientists have been working on the role of a substance called GABA. GABA is a substance found within the brain which damps down brain activity and stops over- excitability within the brain. GABA has to act by binding to a receptor in the brain. A GABA receptor sits on the membrane of the cell in the brain and this receptor is made of different subunits. These are of different types and have different numbers such as Alpha5 and Beta3. The team from Finland has carried out detailed studies on these GABA receptors and their components and has shown that the different components of the receptors have different roles but that they have to interact with each other in order to carry out these roles. There have been some studies to show that in deletion patients, the activity of these GABA receptors sitting in the brain was actually decreased. Special scanning techniques were used to indicate this. This would tie in with the hypothesis proposed by Professor Olsen that if you only have one copy of a GABA a receptor gene (as in a deletion patient) then it interferes with the GABA receptor activity within the brain in some way.
Epidemiology
And finally we had a paper from Cheryl Bodycombe, in the UK, on Epidemiology. Many people ask about the frequency Angelman Syndrome in the general population. There have been several articles in the literature regarding this but it's been quite difficult to obtain accurate estimates of the incidence and prevalence of Angelman Syndrome. The incidence figures that have been mentioned range from the figure of 1in 8,500 in Sweden to one as low as 1 in 94,000 in Cheryl Bodycombe's UK study. Although there is no doubt that not every AS individual in the UK had been ascertained in this latter study, there is no reason to suspect that the incidence of AS is markedly different in different countries. It's been calculated that Angelman Syndrome accounts for 2 percent of severe mental retardation in Sweden which is a well defined population that is easier to study, so other countries would be expected to have similar incidence figures. The number of individuals referred for testing for Angelman Syndrome has increased dramatically over the years. For instance, in the Manchester Laboratory in the UK, if you look at the graph of patients referred for testing the numbers go up exponentially. This increase in numbers of individuals of being diagnosed and referred for testing is most likely reflecting the fact that people are more aware of Angelman Syndrome and are considering the diagnosis more readily, rather than that being a true rise in incidence over these years. We still need a good epidemiological study to try and obtain an accurate estimate of what the incidence and prevalence of Angelman Syndrome are. This information may well help with sorts of planning for future health service provision and for care for these individuals and it may be one way in which the International Organizations would be able to help.
Jill Clayton-Smith - Tampere, July 2000
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