Olfactory bulb anomalies in KBG syndrome mouse model and patients.

ANKRD11 (ankyrin repeat domain 11) is a chromatin regulator and the only gene associated with KBG syndrome, a rare neurodevelopmental disorder. We have previously shown that Ankrd11 regulates murine embryonic cortical neurogenesis. Here, we show a novel olfactory bulb phenotype in a KBG syndrome mouse model and two diagnosed patients. Conditional knockout of Ankrd11 in murine embryonic neural stem cells leads to aberrant postnatal olfactory bulb development and reduced size due to reduction of the olfactory bulb granule cell layer. We further show that the rostral migratory stream has incomplete migration of neuroblasts, reduced cell proliferation as well as aberrant differentiation of neurons. This leads to reduced neuroblasts and neurons in the olfactory bulb granule cell layer. In vitro, Ankrd11-deficient neural stem cells from the postnatal subventricular zone display reduced migration, proliferation, and neurogenesis. Finally, we describe two clinically and molecularly confirmed KBG syndrome patients with anosmia and olfactory bulb and groove hypo-dysgenesis/agenesis. Our report provides evidence that Ankrd11 is a novel regulator of olfactory bulb development and neuroblast migration. Moreover, our study highlights a novel clinical sign of KBG syndrome linked to ANKRD11 perturbations in mice and humans.