Human DNA contains several variations, which can affect the structure and normal functioning of a protein. These variations could be single nucleotide polymorphisms (SNPs) or insertion-deletions (InDels). SNPs, as opposed to InDels, are more commonly present in DNA and may cause genetic disorders. In the current study, several bioinformatic tools were used to prioritize the pathogenic variants in the SLITRK1 gene. Out of all of the variants, 16 were commonly predicted to be pathogenic by these tools. All the variants had very low frequency, i.e., <0.0001 in the global population. The secondary structure of all filtered variants was predicted, but no structural change was observed at the site of variation in any variant. Protein stability analysis of these variants was then performed, which determined a decrease in protein stability of 10 of the variants. Amino acid conservation analysis revealed that all the amino acids were highly conserved, indicating their structural and functional importance. Protein 3D structure of wildtype SLITRK1 and all of its variants was predicted using I-TASSER, and the effect of variation on 3D structure of the protein was observed using the Missense3D tool, which presented the probable structural loss in three variants, i.e., Asn529Lys, Leu496Pro and Leu94Phe. The wildtype SLITRK1 protein and these three variants were independently docked with their close interactor protein PTPRD, and remarkable differences were observed in the docking sites of normal and variants, which will ultimately affect the functional activity of the SLITRK1 protein. Previous studies have shown that mutations in SLITRK1 are involved in Tourette syndrome. The present study may assist a molecular geneticist in interpreting the variant pathogenicity in research as well as diagnostic setup.

Intellectual disability (ID) is a neuro-developmental condition that affects a person’s cognitive ability and results in a learning defect. It affects 1–3% of the general population; however, the ratio may be expected to be more in a consanguineous population. Herein in the present study, we identified a nuclear family from Dera Ismail Khan City in Pakistan. Whole exome sequencing was performed to map the pathogenic variant. Protein structural modeling and interaction studies were carried out to validate the variant with disease association. Molecular modeling of normal and mutated proteins was performed through I-TASSER and Chimera tools, while docking and interaction analysis was carried out using Cluspro. Clinical analysis of the patient determined mild intellectual disability and gait problem. Candidate gene analysis in this family found a homozygous missense mutation NM_002508:c.C2512T (p.Arg838Cys) in the 12th exon of NID1 gene. Molecular modeling of wild-type and mutant NID1 proteins determined a significant effect on the protein’s secondary and tertiary structure. Hence, based on the exome sequence analysis, NID1 is proposed to be a strong novel candidate ID gene in this family. The genetic mapping of the present family led us to determine a novel candidate gene to be associated with intellectual disability. Linkage of additional ID families with genes would confirm its validity and strengthen our notion. Furthermore, expression studies and pathway analysis will help in exploring the biological mechanism of learning and memory.

Background: Intellectual disability (ID) is characterized by impairments in cognitive functioning and adaptive behavior. Globally, it affects 1-3% of the general population, with an increased prevalence in consanguineous families. It is a clinically heterogeneous disorder that can manifest as a variable phenotype. Intellectual developmental disorder and retinitis pigmentosa (IDDRP) is a rare syndrome in which patients present with both ID and retinitis pigmentosa. Aims and Objectives: This study examined a consanguineous family to identify disease-associated pathogenic mutations and elucidate their potential functional impact in patients with IDDRP. Methodology: Clinical assessment of the patients revealed characteristics consistent with both intellectual disability (ID) and retinitis pigmentosa. Individuals affected by IDDRP were subjected to whole exome sequencing (WES), and the identified candidate pathogenic variants were validated by Sanger sequencing. Computational analyses were conducted to evaluate the impact of these mutations on the protein structure and function. Results: WES identified a protein-truncating variant, c.2605A>T (p.Lys869Ter), in the Sphase cyclin A-associated protein in the endoplasmic reticulum (SCAPER) gene. SCAPER has previously been reported to cause IDDRP. In silico analyses revealed structural and interactional alterations in the SCAPER protein. This variant is novel in the Pakistani population and has not been previously reported. This variant exhibits an autosomal recessive mode of inheritance and segregates among the investigated affected and unaffected family members. Conclusion: The present study expands the spectrum of disease-causing variants in SCAPER and will contribute to a better understanding of the genetic etiology of IDDRP.