To provide MDC (metalloproteinase like-disintegrin like-cysteine rich protein) 2α, 2β and 3 genes suspected to induce Alzheimer's dementia, cerebrovascular dementia, sequela of cerebral infarction, congential neurological disorder, etc., when the variation of the gene occurs.

A cDNA coding for a new MDC-like protein (e.g. MDC 2α protein encoded by the DNA of the formula) is separated from human brain mRNA by PCR using a synthetic DNA primer designed based on the DNA of an MDC-family protein and the partial structure of the separated protein is determined. A cDNA encoding the whole length is acquired from a human brain cDNA library by using the DNA fragment as a probe and the structure is analyzed obtain the new protein belonging to the MDC family, e.g. a DNA coding for the MDC 2α protein of the formula.