A new study suggests that some mutations associated with autism may go undetected. These mutations, which arise spontaneously, can be mistaken for inherited mutations. The study found that these spontaneous mutations can be present in a small fraction of cells in a parent’s blood, making them difficult to detect. However, they can still be passed along to children if they are present in sperm or egg cells. This means that the presence of mutations in parents’ cells should be taken into consideration when studying de novo mutations shared among siblings.
The study analyzed genes in 1,007 pairs of siblings from 251 families to identify shared mutations and chromosomes. They found that in over half of the cases, the mutation was present in the parent’s blood. This finding suggests that the presence of a mutation in the parent’s blood can lead to incorrect conclusions about inheritance. In fact, approximately 4% of thought-to-be inherited mutations are actually de novo mosaic mutations.
The researchers also analyzed the risk of passing down a de novo mosaic mutation to multiple children. They found that siblings are more likely to share the mutation if it is present in a large proportion of the parent’s blood cells. Additionally, the likelihood of a de novo mutation from a mosaic parent decreases with age. The study also found that mothers are more likely to transmit mosaic mutations, while fathers are more likely to have classic de novo mutations in sperm.
To help assess the risk of recurrence for a given mutation, the researchers developed a calculator. Using this calculator, they found that the risk of another child in a family carrying a de novo mutation leading to epilepsy was 83 times higher than for a classic de novo mutation.
Overall, this study highlights the importance of considering the presence of mosaic inherited mutations in parents when studying autism mutations. It also suggests that some mutations that appear spontaneous in a child may actually be mosaic in the parent. These findings have implications for understanding the genetic basis of autism and assessing recurrence risk in families.
For more reports from the 2018 American Society of Human Genetics annual meeting, please click here.
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