Autism-Relevant Social Abnormalities and Cognitive Deficits in Engrailed-2 Knockout Mice

Abstract

ENGRAILED 2 (En2) , a homeobox transcription factor, functions as a patterning gene in the early development and connectivity of rodent hindbrain and cerebellum, and regulates neurogenesis and development of monoaminergic pathways. To further understand the neurobiological functions of En2 , we conducted neuroanatomical expression profiling of En2 wildtype mice. RTQPCR assays demonstrated that En2 is expressed in adult brain structures including the somatosensory cortex, hippocampus, striatum, thalamus, hypothalamus and brainstem. Human genetic studies indicate that EN2 is associated with autism. To determine the consequences of En2 mutations on mouse behaviors, including outcomes potentially relevant to autism, we conducted comprehensive phenotyping of social, communication, repetitive, and cognitive behaviors. En2 null mutants exhibited robust deficits in reciprocal social interactions as juveniles and adults, and absence of sociability in adults, replicated in two independent cohorts. Fear conditioning and water maze learning were impaired in En2 null mutants. High immobility in the forced swim test, reduced prepulse inhibition, mild motor coordination impairments and reduced grip strength were detected in En2 null mutants. No genotype differences were found on measures of ultrasonic vocalizations in social contexts, and no stereotyped or repetitive behaviors were observed. Developmental milestones, general health, olfactory abilities, exploratory locomotor activity, anxiety-like behaviors and pain responses did not differ across genotypes, indicating that the behavioral abnormalities detected in En2 null mutants were not attributable to physical or procedural confounds. Our findings provide new insight into the role of En2 in complex behaviors and suggest that disturbances in En2 signaling may contribute to neuropsychiatric disorders marked by social and cognitive deficits, including autism spectrum disorders.

Serotonin abnormalities in Engrailed-2 knockout mice: New insight relevant for a model of Autism Spectrum Disorder

“…In particular they describe reduced social behavior as playing and sniffing, but not social communication in En2−/− mice compared to controls (Brielmaier et al, 2012;Cheh et al, 2006). This decrement in social and playing behavior is observed during the period in which normal mice behavior is evident in peer interaction (Terranova et al, 1993).…”

Towards Identification of Individual Etiologies by Resolving Genomic and Biological Conundrums in Patients with Autism Spectrum Disorders

“…Neuroanatomical expression profiling of En2 wild type mice demonstrated that EN2 is expressed in adult brain structures including the somatosensory cortex, hippocampus, striatum, thalamus, hypothalamus, and brainstem [Brielmaier et al, 2012]. En2 null mice, in contrast, exhibited deficits in reciprocal social interactions as juveniles and adults, and absence of sociability in adults, replicated in 2 independent cohorts.…”

Behavioral and Neuroanatomical Phenotypes in Mouse Models of Autism

“…Social behavior assays have been conducted with many of the mouse models in which imaging studies were conducted. Employing our 3-chambered social approach task, a simple yes-or-no assay for sociability [13], absence of sociability was reported in mice with mutations in genes including Shank3 [15,16], Cntnap2 [17], Pten [18], Tsc1 [19], En2 [20], Gabrb3 [21], Ube3a triplication [22], and oxytocin receptor knockouts [23]. Normal 3-chambered social approach appeared in mice with mutations in genes including oxytocin [24], Shank1 [25], Nlgn2 [26], Ephrin-A [27] and 16p11.2 deletion [28] Variable findings on social approach across laboratories and in mouse lines generated on different genetic backgrounds have been reported for mutations including Fmr1 [29,30], Nlgn3 [31][32][33][34], and Nlgn4 [35,36].…”

“…Abnormal reciprocal interactions in various social pairings were reported in several mutant lines, including Shank3 [16,47,48], En2 [20,49], Gabrb3 [50], Pten [51], Tsc1 [19], and BTBR [10,52,53].…”

“…Although anxiety is a common feature of FXS, Fmr1 KO mice display low anxiety-like behaviors [69]. Low scores on learning and memory tasks such as water maze spatial navigation, fear-conditioned freezing, novel object recognition, and touchscreen visual discrimination were seen in mice with mutations in genes including Nf1, En2, 16p11.2 deletion, and Plaur with decreased gamma-aminobutryic acid-ergic cortical interneurons [20,28,[70][71][72]. Further investigations of phenotypes in mice that have face validity and neuroanatomical construct validity to both diagnostic and associated symptoms of autism may prove particularly revealing.…”