Spontaneous Mutations Play Role in Schizophrenia
> 6/10/2008 4:28:39 PM

While individuals with some family history of schizophrenia may face a higher risk of developing it themselves, the majority of cases betray no genetic roots, arising instead from rare, spontaneous and most likely pre-natal mutations of the gene codes that form the brain and the central nervous system. A new study shows schizophrenic individuals with no direct relatives with the disease to have an eightfold higher risk of presenting such “tiny anomalies.” Strangely, schizophrenic children whose families bear some additional history of the condition displayed almost none of the same mutations. This study further explores the findings of earlier work in the same area, and previous research also showed the occurrence of autism to work in nearly the same fashion. These findings more clearly define the relationship between schizophrenia and genetics, and researchers feel that they may explain why the condition “seems to defy natural selection” by maintaining a consistent presence in the general population despite its inherent deficiencies. If the condition were strictly genetic, it would almost certainly be phased out over generations.

South African researchers studied the genetic data of 359 individuals and their parents, nearly half of this patient pool having tested positive for non-familial schizophrenia. Their most significant finding was that spontaneous gene-based abnormalities in areas located along the many information pathways in the central nervous system were considerably more common among schizophrenic individuals whose conditions were not based on genetic inheritance. Interestingly, while the mutations recorded in this study were “spontaneous,” they were not completely random despite the fact that no other members of the affected subjects’ families suffered from the condition. Many of the mutations were inherited in the sense that evidence of their origins could be found in the affected individuals’ genetic codes - certain genes are either absent or duplicated, leading the brain to develop in unusual ways. These conditions most likely began at or immediately following conception.

Nearly identical patterns of genetic irregularity have been observed in autistic individuals. Again, while those with familial predispositions toward autism had twice the rate of abnormalities as members of a control group, the mutations were 10 times as common in autistic individuals without a family history of the disorder, and research indicates them to be causal elements rather than side-effects of the disorder itself. They did not come about because of parents who carried genes linked to schizophrenia and autism but because of the aforementioned mutations, the direct causes of which remain unclear. The causal irregularities are also more common among early-onset schizophrenic individuals whose symptoms begin during childhood, further hinting at the fact that they facilitate very fundamental changes in the developing brain.

This is not to downplay the influence of genetics in the schizophrenia equation. Most cases are “sporadic rather than familial,” but the condition still occurs far more often among children with schizophrenic family members. It clearly arises from one of two sources: genetic predisposition or spontaneous genetic mutation. But the mutations observed by the researchers occurred in only 10% of the population who were affected by non-familial schizophrenia, meaning that a large majority of these sporadic cases were not caused by the mutations considered in this study. Many of the ones that were occurred in chromosome 22, which has been linked by past research to a variety of developmental disorders. The relationship between schizophrenia and its “carrier gene” is just as complicated: the vast majority of individuals with the gene do not suffer from the condition even though they display many similar symptoms such as a difficulty following the movement of objects through the field of vision and a tendency to repeatedly make common syntax mistakes while communicating thoughts through language. Still, only 6.5% of the family members of schizophrenic individuals suffer from the condition themselves.

Schizophrenia remains a largely open subject despite our increased understanding of a significant share of individual cases. Further research is the only way for us to map the full spectrum of the illness and its influence, but based on how little we know we should be grateful for incremental progress. In short, schizophrenia (and autism) seem most often to be created by a series of genetic mutations unrelated to either genetic inheritance or environmental issues. They appear to be a sporadically occurring exception to nearly every neurological rule.

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