GNB5 mutation causes a novel neuropsychiatric disorder featuring attention deficit hyperactivity disorder, severely impaired language development and normal cognition.
BACKGROUND
Neuropsychiatric disorders are common forms of disability in humans. Despite recent progress in deciphering the genetics of these disorders, their phenotypic complexity continues to be a major challenge. Mendelian neuropsychiatric disorders are rare but their study has the potential to unravel novel mechanisms that are relevant to their complex counterparts.


RESULTS
In an extended consanguineous family, we identified a novel neuropsychiatric phenotype characterized by severe speech impairment, variable expressivity of attention deficit hyperactivity disorder (ADHD), and motor delay. We identified the disease locus through linkage analysis on 15q21.2, and exome sequencing revealed a novel missense variant in GNB5. GNB5 encodes an atypical β subunit of the heterotrimeric GTP-binding proteins (Gβ5). Gβ5 is enriched in the central nervous system where it forms constitutive complexes with members of the regulator of G protein signaling family of proteins to modulate neurotransmitter signaling that affects a number of neurobehavioral outcomes. Here, we show that the S81L mutant form of Gβ5 has significantly impaired activity in terminating responses that are elicited by dopamine.


CONCLUSIONS
We demonstrate that these deficits originate from the impaired expression of the mutant Gβ5 protein, resulting in the decreased ability to stabilize regulator of G protein signaling complexes. Our data suggest that this novel neuropsychiatric phenotype is the human equivalent of Gnb5 deficiency in mice, which manifest motor deficits and hyperactivity, and highlight a critical role of Gβ5 in normal behavior as well as language and motor development in humans.
Department of Genetics, King Faisal Specialist Hospital and Research Center, MBC-03, PO Box 3354, Riyadh, 11211, Saudi Arabia.
Hanan E
HE
Shamseldin
Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, #3C2, Jupiter, FL, 33458, USA.
Ikuo
I
Masuho
Department of Pediatrics, King Saud Medical City, Riyadh, Saudi Arabia.
Ahmed
A
Alenizi
Department of Neurosciences, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.
Suad
S
Alyamani
Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, #3C2, Jupiter, FL, 33458, USA.
Dipak N
DN
Patil
Department of Genetics, King Faisal Specialist Hospital and Research Center, MBC-03, PO Box 3354, Riyadh, 11211, Saudi Arabia.
Niema
N
Ibrahim
Department of Neuroscience, The Scripps Research Institute, 130 Scripps Way, #3C2, Jupiter, FL, 33458, USA. Kirill@scripps.edu.
Kirill A
KA
Martemyanov
Department of Genetics, King Faisal Specialist Hospital and Research Center, MBC-03, PO Box 3354, Riyadh, 11211, Saudi Arabia. falkuraya@kfshrc.edu.sa.|Department of Anatomy and Cell Biology, College of Medicine, Alfaisal University, Riyadh, Saudi Arabia. falkuraya@kfshrc.edu.sa.
Fowzan S
FS
Alkuraya
Attention deficit hyperactivity disorder (ADHD); G protein coupled receptors (GPCR); Hippocampus; Linkage; Mendelian; Neuropsychiatric disorders; Striatum
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