Genetics and autism

National Autistic Society position statement

The NAS welcomes research into all areas which will throw light on the causes behind autism. The NAS is not a medical research charity but has followed research, particularly that of the International Molecular Genetic Study of Autism, with great interest. This study (Bailey and Monaco 1996; International Molecular Genetic Study 1998; Bailey 1998) began in 1995 to try to identify genes predisposing people to autism.  It had become clear that the increased rate of autism amongst close relatives had a genetic basis. If the genes responsible could be identified the possibility of new types of treatment and preventing the more severe manifestations of the disorder becomes stronger.

Since family and twin studies (Smalley et al 1988; Bailey et al 1995; Folstein and Rutter 1977; Steffenburg et al 1989) showed that there was an increased rate of autism amongst relatives of those with the disorder it has been evident that genetic factors play an important role in its causation. However, it is a complex and complicated picture and does not appear likely to be due to a single gene.

Researchers in the International Molecular Genetic Study (which comprises centres in Denmark, France, Germany, the Netherlands, the USA and the UK including London, Oxford and Newcastle universities), and the Collaborative Autism Project (at Tufts/New England Medical Center, Duke and Iowa universities), are currently examining a number of chromosome sites that could be implicated. It is not yet clear which genes are involved although the search is narrowing.  Furthermore it is likely that there may be more than one site involved. It seems that autism arises with the interaction of a small number of specific genes coming together in individuals. The Duke University (Maddox et al 1999) research is interesting as it locates defects in small parts of chromosomes 7 and 15. This seems close to work done by the International Molecular Genetic Study of Autism which also highlighted concerns in the chromosome 7 region among UK families.

Important research is also reviewed (Rodier 2000) which implicates a gene, HOXA1, which is active in the brain stem when the first neurons are forming in the embryo. This gene, which resides on chromosome 7, is only active during development and appears a better candidate to explain a congenital disorder like autism.  Whilst it looks as if variant alleles of HOXA1 are involved in the pathogenesis of autism HOXA1 is not alone and interacts with other, as yet unidentified, genes.  It also appears to be variably expressed so its presence does not necessarily mean that autism will arise in an affected individual.
 
The NAS certainly welcomes further corroboration that autism is a neurobiological disorder and looks forward to further results from the many studies being undertaken.

References:

Bailey, A. and Monaco, A.P. (1996) Revealing the roots of autism. MRC News, Autumn/Winter, pp32-35.

Bailey, A. et al (1995) Autism as a strongly genetic disorder: evidence from a British twin study. Psychological Medicine, 25, pp 63-77.

Bailey, T. (1998) Genes for autism: the search is on. Communication, Spring, pp 10-12.

Folstein, S. and Rutter, M. (1977) Infantile autism: a genetic study of 21 twin pairs. Journal of Child Psychology and Psychiatry, 18, pp 297-321.

International Molecular Genetic Study of Autism Consortium (1998) A full genome screen for autism with evidence for linkage to a region on chromosome 7q. Human Molecular Genetics, 7(3), pp 571-578.

Maddox, L.O. et al. (1999) Autistic disorder and chromosome 15q11-q13: construction and analysis of a BAC/PAC contig. Genomics, 62 (3), December, pp 325-331.

Piven, J. and Palmer, P. (1999) Psychiatric disorder and the broad autism phenotype: evidence from a family study of multiple-incidence autism families. American Journal of Psychiatry, 156 (4), April, pp 557-563.

Rodier, P.M. (2000) The early origins of autism. Scientific American, February, pp 38-45.

Smalley, S. et al. (1988) Autism and genetics: a decade of research. Archives of General Psychiatry, 45, pp 953-961.

Steffenburg, S. et al. (1989) A twin study of autism in Denmark, Iceland, Norway and Sweden. Journal of Child Psychology and Psychiatry, 30, pp 405-416.

Notes to editors:

• Autism (including Asperger syndrome) is a lifelong developmental disability. It is a spectrum condition occurring in varying degrees of severity and affects an estimated 535,000 people in the UK. It is characterised by difficulties in communication, social interaction and social understanding.
• The National Autistic Society is the UK's leading charity for people with autistic spectrum disorders and their families. Founded in 1962, it continues to spearhead national and international initiatives and provide a strong voice for all people with autism. The NAS provides a wide range of services to help people with autism and Asperger syndrome live their lives with as much independence as possible.
• The NAS relies on the support of its members and donors to continue its vital work for people with autism. To become a member, make a donation or to find out more about the work of the NAS, visit the NAS website www.autism.org.uk or call the NAS donation line 08702 33 40 40, (national rates apply).
• In March 2004 Vodafone UK has entered into a three-year 'cause partnership' with The National Autistic Society. The mobile phone company hopes to raise over £6 million for the charity during this period. Vodafone's support will enable the NAS to expand the reach of existing programmes, which raise awareness of autism and support people with autism and their carers.
• For more information about autism and for help in your area, call the NAS Autism Helpline supported by Barclays: 0845 070 4004 10am-4pm, Monday to Friday, (local rates apply).

Related resources

• Autism and genetics: a briefing paper