Background: Intellectual disability (ID) is a heterogonous disorder with complex etiology. The frequency of autosomal recessive inheritance defects was elevated in a consanguineous family. Methods: In this study, high-throughput DNA sequencing was performed in an Iranian consanguineous family with two affected individuals to find potential causative variants. Whole-exome sequencing was carried out on the proband and Sanger sequencing was implemented for validation of the likely causative variant in the family members. Results: A novel homozygous missense mutation (p. Arg122Trp) was detected in the PTRHD1 gene. Conclusion: PTRHD1 has been recently introduced as a candidate ID and Parkinsonism causing gene. Our findings are in agreement with the clinical spectrum of PTRHD1 mutations; however, our affected individuals suffer from ID manifestations.

Background and Objective: Sleep habits not only are affected by a person’, s health but also affect his/her growth and development. Students with Intellectual disability (ID) account for 3% of all students. Since sleep habits are among the basic foundations of learning during childhood, this study aimed to determine the parental view on the sleep habits of students with ID in Hamadan, Iran, during September 23 and December 21, 2019. Materials and Methods: In this descriptive-analytical cross-sectional study, 86 students with ID, aged 7-11 years, were selected using the convenience sampling method in Hamadan, Iran, during September 23 and December 21, 2019. Data were collected using a demographic inventory, as well as the Children's Sleep Habits Questionnaire (CSHQ). The pa-rental questionnaires were completed as self-reports by mothers or fathers of students with ID. Data were analyzed us-ing the independent t-test, analysis of variance (ANOVA), and one-way regression in SPSS software. Results: The mean ±,standard deviation (SD) of sleep habit score of students with ID was 73. 66 ±,6. 79. The cut-off score in the questionnaire was 41. 15% and 85% of the students had moderate and severe sleep disturbance. The highest mean score was for distress in morning awakenings (12. 67 ±,2. 83), indicating the presence of sleep disturbance among students with ID. Variables of age, sex, and weight of the students, educational attainment and job of parents, household income, private bedroom, and sleeping status could predict 61% of the students’,sleep habits. There was a significant relationship between the father’, s job and the sleep habits of the students (P < 0. 05). Conclusion: These findings shed light on sleep disturbances in students with ID. Results suggest that sleep habits in students with ID are associated with their father's job. Sleep health should be considered in planning health promotion strategies of these children.

In all organisms, transfer RNA (tRNA) molecules are required to undergo post-transcriptional modifications at different levels in order to convert into mature tRNAs. These modifications are critical for many aspects of tRNA function and structure, such as translational efficiency, flexibility, codon– anticodon interaction, stability, and fidelity. Up to now, over 100 modified nucleosides have been identified in tRNAs from all domains of life. Post-transcriptional modifications include different chemical processes such as methylation, deamination, or acetylation, with methylation reactions as the most common. tRNA methyltransferases are a family of enzymes involved in the post-transcriptional methylation of tRNA bases. Recent studies have reported different human diseases resulting from defects in tRNA methyltransferase activity, including cancer, diabetes and neurological disorders such as Intellectual disability (ID). In this article, we focused on biological function and characterization of tRNA methyltransferases associated with ID in order to explain how functional disruption of tRNA methyltransferases could lead to ID phenotype.

Intellectual disability (ID) is a common and highly heterogeneous neurodevelopmental disorder. The prevalence of ID is around 1%– 3% in the general population. ID is associated with a wide range of additional neurological disabilities and the results of various studies have disclosed the co-morbidity of ID and ataxia. The aim of this review is elucidation of the common molecular and cellular pathways in the etiology of ID and ataxia. Categorization of these genes with various cellular functions indicates several genetic collisions in the co-occurrence of ID and ataxia.