Sanger sequencing was performed on available samples from all affected family members to determine whether the potential variant in the known genes of autosomal recessive intellectual disability co-segregated with the disease phenotype. Initially we performed a touchdown PCR. The amplified products were then purified using Sephadex Clean up and were consequently sequenced using BigDye Terminator v3.1 Cycle Sequencing Kit (Applied Biosystems, Thermo Fisher Scientific, USA). The resulting sequencing reactions were then purified Sephadex Clean up method. Capillary sequencing was performed in a Genetic Analyzer 3130 (Applied Biosystems, Thermo Fisher Scientific, USA) and the data were \u00a0analyzed using Sequencing Analysis software Sequencer 5.0.