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AuthorMohammed, Idris
AuthorSelvaraj, Senthil
AuthorAhmed, Wesam S.
AuthorAl-Barazenji, Tara
AuthorHammad, Ayat S.
AuthorDauleh, Hajar
AuthorSaraiva, Luis R.
AuthorAl-Shafai, Mashael
AuthorHussain, Khalid
Available date2024-03-13T05:14:57Z
Publication Date2023
Publication NameInternational Journal of Molecular Sciences
ResourceScopus
ISSN16616596
URIhttp://dx.doi.org/10.3390/ijms242216361
URIhttp://hdl.handle.net/10576/52973
AbstractThe leptin–melanocortin pathway is pivotal in appetite and energy homeostasis. Pathogenic variants in genes involved in this pathway lead to severe early-onset monogenic obesity (MO). The MC4R gene plays a central role in leptin–melanocortin signaling, and heterozygous variants in this gene are the most common cause of MO. A targeted gene panel consisting of 52 obesity-related genes was used to screen for variants associated with obesity. Variants were analyzed and filtered to identify potential disease-causing activity and validated using Sanger sequencing. We identified two novel heterozygous variants, c.253A>G p.Ser85Gly and c.802T>C p.Tyr268His, in the MC4R gene in two unrelated patients with morbid obesity and evaluated the functional impact of these variants. The impact of the variants on the MC4R gene was assessed using in silico prediction tools and molecular dynamics simulation. To further study the pathogenicity of the identified variants, GT1-7 cells were transfected with plasmid DNA encoding either wild-type or mutant MC4R variants. The effects of allelic variations in the MC4R gene on cAMP synthesis, MC4R protein level, and activation of PKA, ERB, and CREB signaling pathways in both stimulated and unstimulated ɑ-MSH paradigms were determined for their functional implications. In silico analysis suggested that the variants destabilized the MC4R structure and affected the overall dynamics of the MC4R protein, possibly leading to intracellular receptor retention. In vitro analysis of the functional impact of these variants showed a significant reduction in cell surface receptor expression and impaired extracellular ligand binding activity, leading to reduced cAMP production. Our analysis shows that the variants do not affect total protein expression; however, they are predicted to affect the post-translational localization of the MC4R protein to the cell surface and impair downstream signaling cascades such as PKA, ERK, and CREB signaling pathways. This finding might help our patients to benefit from the novel therapeutic advances for monogenic forms of obesity.
SponsorThis research was supported by the Qatar National Research Fund [QNRF-NPRP 10-6100017-AXX] awarded to Professor Khalid Hussain and Qatar National Research Fund (Qatar Research Development and Innovation Council) and the Early Career Researcher Award (ECRA) [ECRA02-008-3-007] awarded to Dr. Mashael Al-Shafai, and a Sidra Medicine (a member of Qa-tar Foundation) grant SDR400141, awarded to Luis R. Saraiva.
Languageen
PublisherMultidisciplinary Digital Publishing Institute (MDPI)
Subjectchildhood obesity
MC4R
monogenic obesity
Qatar
severe obesity
TitleFunctional Characterization of Novel MC4R Variants Identified in Two Unrelated Patients with Morbid Obesity in Qatar
TypeArticle
Issue Number22
Volume Number24
dc.accessType Open Access


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