Familial MND and Genetic Testing

If more that one person in your family is, or has been, affected by motor neurone disease (MND), you may like to read the following information about the genetics of MND, genetic testing and further research into MND. 

Genetics and MND

Approximately 10% of people who have been diagnosed with Motor Neurone Disease have what is known as familial MND which is where there is more than one affected person in a family. The remaining 90% of people with MND are the only affected person in their family and are said to have ‘sporadic’ MND.

Familial MND is caused by a mutation in a gene. At the time of publication, the genes identified by research to cause inherited MND are: SOD1, TDP-43, FUS, C9ORF72 and NEK1.

People who have a genetic mutation have a 50/50 chance of passing the mutated gene onto their children. The chance of a person who inherits an MND-related genetic mutation developing MND during their lifetime is high but as yet uncertain and not all people with the mutated gene will develop MND.

The age at which symptoms of MND appear in people with an MND-related genetic mutation varies greatly. It can be as early as the 20s and as late as the 80s. As well, the age of onset can vary considerably within a family, even though the mutation carried by family members is the same. The average age of onset of familial MND is around 45 years.

Mutations in the genes that cause MND are also found in some people who have sporadic MND. The number of people with sporadic MND who also have an MND-related gene mutation is not known.

An MND diagnosis will inevitably give rise to some very difficult feelings and emotions, and this can be even more complex for those that have familial MND. You may have concern for your family, children and your children’s children. There is genetic testing available if needed for your siblings or children, over the age of 18 years. Anyone considering this should seek specialised advice, so you and your family are fully and correctly informed. It is recommended you talk to your GP, Neurologist or MND Queensland who can assist you through this journey and help you connect with a Genetic Counsellor where required

MND-related genetic mutations

• In 1993 the first genetic mutation related to MND was discovered in the superoxide dismutase 1 gene (SOD1). About 20% of familial MND is caused by mutations in the SOD1 gene. 
• In 2008 mutations in the TAR DNA binding protein (TDP-43) gene code were found to cause TDP–43 to become toxic, causing MND in a small percentage of MND families. Researchers are yet to find out how and why TDP-43 behaves abnormally to cause MND.
• In 2009 a gene mutation that causes a rare inherited form of MND, FUS (Fused in Sarcoma, a protein) was discovered. Researchers have found that genetic mutations of FUS are a cause of MND for a small number of familial forms of MND and account for between 3% - 5% of MND families. 
• In 2011 the discovery of mutations in the C9ORF72 gene was announced and hassince been found in about 40% of all families with familial MND.

Although there are still some MND families in which the faulty gene has not yet been identified, the SOD1 gene and other MND-related gene mutations discovered in recent years now account for about 65% of all people with familial MND. 

Current research

Researchers continue in their quest to find the mutations in other genes that cause familial MND in the 35% of familial MND families in which the genetic cause has yet to be identified.

Researchers are carrying out further studies to:

• understand how the known genetic faults cause MND
• work out how many of those with a faulty gene will actually go on to develop MND later in life 
• identify mutations in other genes which may cause familial MND 
• discover ways of preventing and treating familial and sporadic MND

Relevance of the discovery of gene mutations that cause MND

It is now possible to test for the presence of mutations in the SOD1, TDP43, FUS and C9ORF72 genes in a person diagnosed with familial MND. Other family members can also be tested to determine if they have the same mutation that caused MND in their relative. For example, adult children or brothers and sisters of an affected person can be tested.

Unborn children can be tested to determine if they have inherited the mutation known in the family.

Pre-implantation genetic diagnosis (PGD), an advanced screening technique, can be used in conjunction with IVF to determine whether an embryo has inherited the familial MND gene.

Some people who have an MND gene mutation may never develop symptoms. For those with an MND gene mutation who go on to develop symptoms, it is not possible to predict the age when symptoms will first appear.

Research will increase our understanding of the mechanism by which these mutations cause MND, and may lead to treatments which can prevent or delay the onset of MND in someone with an MND-related genetic mutation. It is possible that research into MND caused by genetic mutations will also contribute to our understanding of the causes of other types of MND. 

Some issues associated with testing for MND gene mutations

Some reasons people have given for wanting to know if they have an MND-related genetic mutation: 

• I am the sort of person who wants to know as much as possible about myself and my future and find it hard to live with uncertainty. 
• To enable me to plan my life. 
• To help with decisions about marriage and having a family. 
• To provide information of importance to my children. 
• If I do not have the gene, the information may help when I apply for jobs, life insurance, superannuation or when taking on long-term financial commitments. 
• If I have a genetic mutation and it becomes possible to prevent MND, I can make use of the preventative measures. 

Some reasons people have given for not wanting to know if they have an MND-related genetic mutation: 

• I can accept living with uncertainty and will be able to plan my life without knowledge of my genetic status. 
• I would not change my plans regarding marriage and having a family, whatever the test result. 
• I do not think I would cope with knowing that I have the gene and will have an increased risk of developing MND. 
• If I have a genetic mutation, the information may limit my life opportunities for example, in relation to career choices, life insurance, superannuation and financial matters. 
• Relationships with my family, friends and workmates may change if I am shown to have the gene. 
• I am always free to change my mind and can take the test in the future if, for example, a treatment becomes available that can prevent MND.

MND associations – what role do they play

• Provide guidance and advice for people with MND, families and health professionals 
• Produce and disseminate information 
• Fundraise and advocate for MND research 
• Advocate for the development of clinical programs which have a written protocol and provide full counselling and support for those taking the test 
• Promote the sharing of knowledge and experience as research proceeds and clinical testing programs expand 
• Support clinical programs which provide diagnostic testing 

Frequently asked questions