Open AccessARHGEF9 disruption in a female patient is associated with X linked mental retardation and sensory hyperarousal
Author(s) -
Elysa J. Marco,
Fatima Abidi,
James Bristow,
Willow B. Dean,
Philip D. Cotter,
Rita J. Jeremy,
CE Schwartz,
Elliott H. Sherr
Publication year - 2009
Publication title -
bmj case reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.231
H-Index - 26
ISSN - 1757-790X
DOI - 10.1136/bcr.06.2009.1999
Subject(s) - gephyrin , guanine nucleotide exchange factor , medicine , genetics , neuroscience , biology , signal transduction , glycine receptor , glycine , amino acid
We identified a female patient with mental retardation and sensory hyperarousal. She has a de novo paracentric inversion of one X chromosome with completely skewed inactivation of the normal X chromosome. We aimed to identify whether a single gene or gene region caused her cognitive and behavioural impairment and that of others. Fluorescent in situ hybridisation (FISH) showed that the centromeric breakpoint disrupts a single gene: ARHGEF9 (CDC42 guanine nucleotide exchange factor (GEF) 9). We also found that the levels of the ARHGEF9 transcript from the patient are 10-fold less than those found in control samples. ARHGEF9 encodes a RhoGEF family protein: collybistin (hPEM), which is highly expressed in the brain. Collybistin can regulate actin cytoskeletal dynamics and may also modulate GABAergic and glycinergic neurotransmission through binding of a scaffolding protein, gephyrin, at the synapse. This potential dual role may explain both the mental retardation and hyperarousal observed in our patient.