The functional roles of the 12 structural genes (kcne2, gart, tmem50b, il10rb, ifnar2, urb1, grik1, usp16, ltn1, cyyr1, app, and jam2) were mostly analyzed in humans (Homo sapiens) and laboratory mice (Mus musculus), suggesting their close connection with the central nervous system, particularly in relation to the occurrence of behavioral disorders (17, 18), Alzheimer's disease (19–21), and Down syndrome (22). Here, LTN1 is linked to Down syndrome.