CONCLUSION
Decades of research has finally tied stuttering to certain genes and changes in brain. Mutation screening of the three implicated genes (GNPTAB , GNPTG and NAGPA) among 64 PWS, resulted in a likely pathogenic allele frequency of 1.6%. Recurrence of mutations in the three genes among our south Indian stuttering cohort corroborates the causative of these genes to stuttering. Thus mutational screening ended up with a minimal resolution of 3.1% (2/64) that could be ascribed to these genes but remains inconclusive. Hence involvement of more stuttering genes are predicted and can certainly be addressed using next generation sequencing technology. Since stuttering is a complex disorder two highly multiplex families were chosen from existing database6 to identify new genes involved in related pathways using exome sequencing in the second paper submitted in the series.