CHRNA4 and early-onset autosomal dominant Alzheimer disease: There were five co-cited references published in Nature: In 2001, Brejc K studied the crystal structure of the molluscan acetylcholine-binding protein (AChBP), a structural and functional homologue of the amino-terminal ligand-binding domain of a nAChR a-subunit, which assisted in the development of anti-Alzheimer’s disease and nicotine addiction drugs [24].