Table 1.

Genetic characteristics of GRIK2 missense variants in individuals with NDDs

Variant	Number of probands	GRIK2 (GRCh38, chr6)	cDNA	CADD	PP2
p.Ala657Thr	6	101928516G>A	c.1969G>A	32	D; 1.0
p.Thr660Lys	3	101928526C>A	c.1979C>A	24.6	D; 1.0
p.Thr660Arg	2	102376401C>G	c.1979C>G	28	D; 1.0
p.Ile668Thr	1	102376425T>C	c.2003T>C	29.9	D; 1.0

The table shows the four GRIK2 variants identified by the resultant change in amino acid, the number of probands harboring that variant, the nucleotide change in GRIK2, and the site of the variants in cDNA encoding GluK2 protein. Note that the six individuals with p.Ala657Thr variants include a child described previously,¹⁷ who is referred to as proband A657T.1 in this study. CADD scores predicted that all four variants are among the most deleterious substitutions in the human genome.²² PP2 analysis predicted that the variants are most likely damaging (D).²³ CADD, combined annotation-dependent depletion; NDD, neurodevelopmental disorder; PP2, PolyPhen2.