tokens: Exome sequencing of four unrelated affected individuals showed that all carried the de novo missense variant c.649C > T ( p. Arg217Cys ) or c.650G > A ( p. Arg217His ) in SLC25A24 , a solute carrier 25 family member coding for calcium - binding mitochondrial carrier protein ( SCaMC-1 , also known as SLC25A24 ) .