Patients suffering with seizures and mental retardation often also have hypomagnesaemia [low blood magnesium]. By studying families experiencing these symptoms researchers identified mutations in a gene called CNNM2 to be at the root. Normal CNNM2 encodes a protein involved in the transport and absorption of magnesium in cells. Knocking down the gene in a zebrafish model system led to abnormalities in brain development (affecting a region called the midbrain-hindbrain boundary), and neurological functioning, and disturbed the balance of magnesium in cells. Pictured are other outcomes seen in the zebrafish larvae, which include kidney cysts, an enlarged pericardial cavity, and notochord defects. These results are in line with symptoms shown in humans suffering from hypomagnesaemia and bearing mutated CNNM2. The team also found that the mutation has a recessive mode of inheritance – meaning that to see the deleterious effects an individual must inherit a mutant gene from each parent.
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