(iii) STU 34 family with c.131G>C variant inNAGPA gene
We observed this variant in both affected and unaffected family members. This may be explained by incomplete penetrance that may fail to show any symptoms in unaffected or could be due to phenocopies in affected members who may not be real carriers of variant but tend to display stuttering under environmental effects19. Also variants observed in normal individuals may cause stuttering but left un-informative owing to early recovery28 but in our family no such recovery was reported.
Since its frequency was also low in ExAC database the role of this variant remains inconclusive. In addition to this the conservation score is also found to be low across the species. Only one study21 has reported this variant among stuttering population of European descent.