Background: The number of reported genes causing non-syndromic autosomal recessive intellectual disability (NS-ARID) is increasing. For example, mutations in the ST3GAL3 gene have been reported to be associated with NS-ARID. In the present study, we aimed to determine the genetic cause of the NS-ARID in a five-generation consanguineous Iranian family. Methods: We subjected four patients with an initial diagnosis of NS-ID in an Iranian family. To identify the possible genetic cause(s), whole-exome sequencing was performed on the proband and Sanger sequencing was applied to investigate cosegregation analysis. Using in silico predictive tools, the possible impacts of the variant on the structure and function of ST3Gal-III were predicted. Results: The common clinical features were detected in all affected members who were suffering from a severe ID. Using whole-exome sequencing, a novel variant, c.704C>T or p.(Thr235Met), in exon 9 of the ST3GAL3 gene (NM_001270461.2, OMIM# 606494) was identified and verified by Sanger sequencing. This variant is located next to the VS motif of ST3Gal-III, which is a vital part of the catalytical domains. Conclusions: In the present study, we identified a novel missense variant, c.704C>T or p.(Thr235Met), in the ST3GAL3. To our knowledge, is the third variant in this gene to be associated with NS-ARID. Our findings highlight the need for further investigations into the mechanisms by which variants in ST3GAL3 contribute to neurological dysfunction.
ATP8A2 is a P4-ATPase that flips phosphatidylserine across membranes to generate and maintain transmembrane phospholipid asymmetry. Loss-of-function variants cause severe neurodegenerative and developmental disorders. We have identified three ATP8A2 variants in unrelated Iranian families that cause intellectual disability, dystonia, below-average head circumference, mild optic atrophy, and developmental delay. Additionally, all the affected individuals displayed tooth abnormalities associated with defects in teeth development. Two variants (p.As-p825His and p.Met438Val) reside in critical functional domains of ATP8A2. These variants express at very low levels and lack ATPase activity. Inhibitor studies indicate that these variants are misfolded and degraded by the cellular proteasome. We conclude that Asp825, which coordinates with the Mg 2+ ion within the ATP binding site, and Met438 are essential for the proper folding of ATP8A2 into a functional flippase. We also provide evidence on the association of tooth abnormalities with defects in ATP8A2, thereby expanding the clinical spectrum of the associated disease.
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Background
Marfan syndrome (MFS) is a multi‐systemic autosomal dominant disease of the connective tissue characterized by the early development of thoracic aneurysms/dissections, along with various manifestations of the ocular and skeletal systems. Due to the genetic and clinical heterogeneity, the clinical diagnosis of this disorder is challenging. Loss‐of‐function mutations in
FBN1
(encodes fibrillin‐1) lead to MFS type 1. Also, similar mutations in transforming growth factor β receptor 2 (
TGFBR2)
gene cause MFS type 2. Both proteins involve in TGF‐β signaling.
Methods
In this study, genetic screening using a panel involving 14 genes, especially
FBN1
and
TGFBR2
, were performed on seven representatives affected members of seven unrelated Iranian families suspected with MFS. To confirm the variants, Sanger sequencing was applied to other affected/unaffected members of the families.
Results
A total of 13 patients showed MFS manifestations. Using genetic screening, two novel and three previously reported variants in
FBN1
were identified. We also detected two variants (a novel and a previously reported variant) in the
TGFBR2
gene.
Conclusion
In this study, we introduce three novel variants identified through gene screening in seven Iranian MFS families. This report is expected to considerably improve genetic counseling for Iranian MFS families. Early precise molecular diagnosis can be helpful for better management and improving the life expectancy of these patients.
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