Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Example Input: Imatinib was the first BCR-ABL tyrosine kinase inhibitor to become clinically available. In this study, we retrospectively evaluated the long-term efficacy of low-dose imatinib (final maintenance dose <300mg per day) due to intolerance, in comparison to optimal-dose imatinib (300mg per day) in patients with Philadelphia chromosome-positive chronic myeloid leukemia in the chronic phase. The Kaplan-Meier estimates of the median time to complete cytogenetic response, major molecular response, and complete molecular response were longer for 31 patients receiving low-dose imatinib (360, 1360, and 1420days, respectively) than 74 patients receiving optimal-dose imatinib (170, 420, and 720days, respectively). However, the differences in response shrank over time and progression-free survival were comparable between the two groups. These findings suggest that long-term treatment with low-dose imatinib is an acceptable alternative for patients with intolerance to the optimal dose.
Example Output: What tyrosine kinase, involved in a Philadelphia- chromosome positive chronic myelogenous leukemia, is the target of Imatinib (Gleevec)?

Example Input: Restless legs syndrome (RLS), also known as Willis-Ekbom disease, is a sensory-motor neurological disorder with a circadian component. RLS is characterized by uncomfortable sensations in the extremities, generally at night or during sleep, which often leads to an uncontrollable urge to move them for relief. Recently, genomic studies identified single-nucleotide polymorphisms in BTBD9, along with three other genes, as being associated with a higher risk of RLS. Little is known about the function of BTBD9 or its potential role in the pathophysiology of RLS. We therefore examined a line of Btbd9 mutant mice we recently generated for phenotypes similar to symptoms found in RLS patients. We observed that the Btbd9 mutant mice had motor restlessness, sensory alterations likely limited to the rest phase, and decreased sleep and increased wake times during the rest phase. Additionally, the Btbd9 mutant mice had altered serum iron levels and monoamine neurotransmitter systems. Furthermore, the sensory alterations in the Btbd9 mutant mice were relieved using ropinirole, a dopaminergic agonist widely used for RLS treatment. These results, taken together, suggest that the Btbd9 mutant mice model several characteristics similar to RLS and would therefore be the first genotypic mouse model of RLS. Furthermore, our data provide further evidence that BTBD9 is involved in RLS, and future studies of the Btbd9 mutant mice will help shine light on its role in the pathophysiology of RLS. Finally, our data argue for the utility of Btbd9 mutant mice to discover and screen novel therapeutics for RLS.
Example Output: Willis-Ekbom disease is also known as?

Example Input: The 80-string koto (or hachijugen) was an invention of Japanese composer Michio Miyagi which appeared In 1923.
Example Output:
By whom was 80-string koto discovered?