Given the task definition, example input & output, solve the new input case.
Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.
Example: In 1582 the united provinces invited francis, duke of anjou to lead them; but after a failed attempt to take antwerp in 1583, the duke left the netherlands again. after the assassination of william of orange (10 july 1584), both henry iii of france and elizabeth i of england declined the offer of sovereignty. however, the latter agreed to turn the united provinces into a protectorate of england (treaty of nonsuch, 1585), and sent the earl of leicester as governor-general. this was unsuccessful and in 1588 the provinces became a confederacy. the union of utrecht is regarded as the foundation of the republic of the seven united provinces, which was not recognized by the spanish empire until the peace of westphalia in 1648.
Output: In what year did francis, duke of anjou leave the netherlands?
The generated question is perfect. Because the question is based on second sentence of the input passage and its answer is 1583.

New input case for you: Christianson syndrome (CS) is caused by mutations in SLC9A6 and is characterized by severe intellectual disability, absent speech, microcephaly, ataxia, seizures, and behavioral abnormalities. The clinical phenotypes of CS and Angelman syndrome (AS) are similar. Differentiation between CS and AS is important in terms of genetic counseling. We report on two children with CS and confirmed mutations in SLC9A6 focusing on neuroimaging findings and review the available literature. Cerebellar atrophy (CA) occurs in approximately 60% of the patients with CS and develops after the age of 12 months. Hyperintense signal of the cerebellar cortex (CbC) is less common, and may be diffuse, patchy, or involve only the inferior part of the cerebellum and is best seen on coronal fluid attenuation inversion recovery images. CA and CbC-hyperintensity are not neuroimaging features of AS. In a child with the phenotype of AS, CA and/or CbC-hyperintensity are rather specific for CS and should prioritize sequencing of SLC9A6.
Output:
Mutation of which gene is implicated in the Christianson syndrome?