Abstracts

Rationale: Miller-Dieker (MDS) and DiGeorge syndromes (DGS) are caused by deletions in regions 17p13 and 22q11.2 respectively. These syndromes are characterized by impaired brain development and cognitive deficits, non-neurological manifestations, while in many patients epilepsy may ensue. CRK and CRKL genes, that code for signaling adapters, are often included in the chromosomal deletions in MDS and DGS. Their putative role in the pathogenesis of neurologic deficits in MDS and DGS is unknown. Because complete knockouts of these genes in mice lead to early mortality, we studied conditional knockouts with targeted deletions of Crk and Crkol (mouse gene for CRKL) in the telencephalon, to investigate whether mutants manifest neurodevelopmental impairment and proneness to seizures, as noted in MDS and DGS. Methods: Crkflox/+ and Crkolflox/+ male and female mice were crossed to Foxg1Cre to drive deletion of Crk and/or Crkol in the telencephalon. Between PN3-18, littermate control mice and Crk+/-; Crkol+/- mice were weighted and tested for surface righting time (SRT), open field activity (OFA) and negative geotaxis (NG), blinded to genotype. Between PN16-19 Barnes Maze test of visuospatial learning and memory was done. Two-hour video-monitoring records (PN4-5) were analyzed for spasms, whereas different cohorts were monitored with epidural video-EEG for spontaneous seizures. Results: Foxg1Cre-driven Crk+/-; Crkol+/- mutants had slower weight gain rates (0.20g/d, n=5 vs 0.28 g/d, n=20, P=0.01) and higher failure rates in OFA (60% vs 42.8%, P=0.006), NG (21.3% vs 9.7%, P=0.004) and Barnes Maze test (P=0.02) compared to controls.  There were no significant differences in the frequency of behavioral spasms between PN4-5 although numbers of mutants were low. An increase in the threshold to flurothyl induced clonic seizures (P=0.03, median test) was seen in PN36-39 mutants (n=4) compared to controls (n=20). Poor background organization (2/2 mutants), focal frontal epileptic spikes (2/2 mutants) and right frontal-onset spontaneous seizures (1/2 mutants) were detected in the long-term video-EEG recordings from adult Crk+/-; Crkol+/- mutants. EEG in controls (n=4) showed no abnormalities. Conclusions: This first set of data suggests that Foxg1Cre-driven Crk+/-; Crkl+/- loss in mouse telencephalon may lead to impaired neurodevelopmental milestones, visuospatial learning and memory defects. Although Crk+/-; Crkl+/- mutants did not have increased susceptibility to flurothyl seizures, spontaneous focal epileptic discharges and seizure were observed. Further studies will be useful to confirm whether the risk for epilepsy is higher in this strain. Funding: Funded by NINDS R01NS91170 and U54NS100064, Department of Defense W81XWH-13-1-0180 grants (ASG), NIH MH070596 and HD090260 (JMH), and NIH K12 GM102779 (CAB).