Task: Question Answering
Input (English): Context: A 29-year-old man with a history of elevated creatine kinase and necrotizing myopathy was reviewed. Prominent red cell acanthocytosis in association with reduced Kell antigen expression was present, findings consistent with the McLeod syndrome. Investigation of the patient's XK gene revealed a novel TGG- to-TAG transition at position 1023 in exon 3. This point mutation creates an in-frame stop codon (W314X), and predicts a truncated XK protein of 313 amino acids, compared with 444 amino acids in the normal XK protein. The mutation was not identified in the patient's mother or sister indicating that this mutation was spontaneous. 
 Question: Mutation of which gene is associated with McLeod syndrome?
Output (English): xk