Table 3.

Overview of mutations in GNPTAB, GNPTG, and NAGPA found in stuttering versus those found in mucolipidosis

GNPTAB, GNPTG, and NAGPA mutations
Stuttering	Mucolipidosis
Typically heterozygous	Homozygous
Typically missense	Many null alleles
Modest reduction of enzymatic function	Very low to zero enzymatic function
Different sites than mutations in mucolipidosis	Different sites than mutations in stuttering