Hearing loss in a mouse model of 22q11.2 Deletion Syndrome

Highly demarcated structural alterations in the brain and impaired social incentive learning in Tbx1 heterozygous mice

Copy number variants (CNVs) are robustly associated with psychiatric disorders and changes in brain structures. However, because CNVs contain many genes, the precise gene-phenotype relationship remains unclear. Although various volumetric alterations in the brains of 22q11.2 CNV carriers have been identified in humans and mouse models, it is unknown how each gene encoded in the 22q11.2 region contributes to structural alterations, associated mental illnesses, and their dimensions. Our previous studies identified Tbx1, a T-box family transcription factor encoded in the 22q11.2 CNV, as a driver gene for social interaction and communication, spatial and working memory, and cognitive flexibility. However, it remains unclear how TBX1 impacts the volumes of various brain regions and their functionally linked behavioral dimensions. In this study, we used volumetric magnetic resonance imaging analysis to comprehensively evaluate brain region volumes and behavioral alterations relevant to affected structures in congenic Tbx1 heterozygous mice. Our data showed that the volumes of the anterior and posterior portions of the amygdaloid complex and its surrounding cortical regions were most robustly reduced in Tbx1 heterozygous mice. In an amygdala-dependent task, Tbx1 heterozygous mice were impaired in their ability to learn the incentive value of a social partner. The volumes of the primary and secondary auditory cortexes were increased, and acoustic, but not non-acoustic, sensorimotor gating was impaired in Tbx1 heterozygous mice. Our findings identify the brain's regional volume alterations and their relevant behavioral dimensions associated with Tbx1 heterozygosity.

Guardians of Immunity: Advances in Primary Immunodeficiency Disorders and Management

Primary immunodeficiency disorders (PIDs) are a heterogeneous group of genetic conditions profoundly impacting immune function. The investigation spans various PID categories, offering insights into their distinct pathogenic mechanisms and clinical manifestations. Within the adaptive immune system, B-cell, T-cell, and combined immunodeficiencies are dissected, emphasizing their critical roles in orchestrating effective immune responses. In the realm of the innate immune system, focus is directed toward phagocytes and complement deficiencies, underscoring the pivotal roles of these components in initial defense against infections. Furthermore, the review delves into disorders of immune dysregulation, encompassing hemophagocytic lymphohistiocytosis (HLH), autoimmune lymphoproliferative syndrome (ALPS), immune dysregulation, polyendocrinopathy, enteropathy, and X-linked(IPEX), and autoimmunity polyendocrinopathy candidiasis-ectodermal dystrophy(APECED), elucidating the intricate interplay between immune tolerance and autoimmunity prevention. Diagnostic strategies for PIDs are explored, highlighting advancements in genetic and molecular techniques that enable precise identification of underlying genetic mutations and alterations in immune function. We have also outlined treatment modalities for PIDs, which often entail a multidisciplinary approach involving immunoglobulin replacement, antimicrobial prophylaxis, and, in select cases, hematopoietic stem cell transplantation. Emerging therapies, including gene therapy, hold promise for targeted interventions. In essence, this review encapsulates the complexity of PIDs, emphasizing the critical importance of early diagnosis and tailored therapeutic interventions. As research advances, a clearer understanding of these disorders emerges, fostering optimism for enhanced patient care and management in the future.

Increased Central Auditory Gain and Decreased Parvalbumin-Positive Cortical Interneuron Density in the Df1/+ Mouse Model of Schizophrenia Correlate With Hearing Impairment

Background

Hearing impairment is a risk factor for schizophrenia. Patients with 22q11.2 deletion syndrome have a 25% to 30% risk of schizophrenia, and up to 60% also have varying degrees of hearing impairment, primarily from middle-ear inflammation. The Df1/+ mouse model of 22q11.2 deletion syndrome recapitulates many features of the human syndrome, including schizophrenia-relevant brain abnormalities and high interindividual variation in hearing ability. However, the relationship between brain abnormalities and hearing impairment in Df1/+ mice has not been examined.

Methods

We measured auditory brainstem responses, cortical auditory evoked potentials, and/or cortical parvalbumin-positive (PV+) interneuron density in over 70 adult mice (32 Df1/+, 39 wild-type). We also performed longitudinal auditory brainstem response measurements in an additional 20 animals (13 Df1/+, 7 wild-type) from 3 weeks of age.

Results

Electrophysiological markers of central auditory excitability were elevated in Df1/+ mice. PV+ interneurons, which are implicated in schizophrenia pathology, were reduced in density in the auditory cortex but not the secondary motor cortex. Both auditory brain abnormalities correlated with hearing impairment, which affected approximately 60% of adult Df1/+ mice and typically emerged before 6 weeks of age.

Conclusions

In the Df1/+ mouse model of 22q11.2 deletion syndrome, abnormalities in central auditory excitability and auditory cortical PV+ immunoreactivity correlate with hearing impairment. This is the first demonstration of cortical PV+ interneuron abnormalities correlating with hearing impairment in a mouse model of either schizophrenia or middle-ear inflammation.

Two novel mouse models mimicking minor deletions in 22q11.2 deletion syndrome revealed the contribution of each deleted region to psychiatric disorders

22q11.2 deletion syndrome (22q11.2DS) is a disorder caused by the segmental deletion of human chromosome 22. This chromosomal deletion is known as high genetic risk factors for various psychiatric disorders. The different deletion types are identified in 22q11.2DS patients, including the most common 3.0-Mb deletion, and the less-frequent 1.5-Mb and 1.4-Mb deletions. In previous animal studies of psychiatric disorders associated with 22q11.2DS mainly focused on the 1.5-Mb deletion and model mice mimicking the human 1.5-Mb deletion have been established with diverse genetic backgrounds, which resulted in the contradictory phenotypes. On the other hand, the contribution of the genes in 1.4-Mb region to psychiatric disorders is poorly understood. In this study, we generated two mouse lines that reproduced the 1.4-Mb and 1.5-Mb deletions of 22q11.2DS [Del(1.4 Mb)/+ and Del(1.5 Mb)/+] on the pure C57BL/6N genetic background. These mutant mice were analyzed comprehensively by behavioral tests, such as measurement of locomotor activity, sociability, prepulse inhibition and fear-conditioning memory. Del(1.4 Mb)/+ mice displayed decreased locomotor activity, but no abnormalities were observed in all other behavioral tests. Del(1.5 Mb)/+ mice showed reduction of prepulse inhibition and impairment of contextual- and cued-dependent fear memory, which is consistent with previous reports. Furthermore, apparently intact social recognition in Del(1.4 Mb)/+ and Del(1.5 Mb)/+ mice suggests that the impaired social recognition observed in Del(3.0 Mb)/+ mice mimicking the human 3.0-Mb deletion requires mutations both in 1.4-Mb and 1.5 Mb regions. Our previous study has shown that Del(3.0 Mb)/+ mice presented disturbance of behavioral circadian rhythm. Therefore, we further evaluated sleep/wakefulness cycles in Del(3.0 Mb)/+ mice by electroencephalogram (EEG) and electromyogram (EMG) recording. EEG/EMG analysis revealed the disturbed wakefulness and non-rapid eye moving sleep (NREMS) cycles in Del(3.0 Mb)/+ mice, suggesting that Del(3.0 Mb)/+ mice may be unable to maintain their wakefulness. Together, our mouse models deepen our understanding of genetic contributions to schizophrenic phenotypes related to 22q11.2DS.

Comprehensive analysis of a novel mouse model of the 22q11.2 deletion syndrome: a model with the most common 3.0-Mb deletion at the human 22q11.2 locus

The 22q11.2 deletion syndrome (22q11.2DS) is associated with an increased risk for psychiatric disorders. Although most of the 22q11.2DS patients have a 3.0-Mb deletion, existing mouse models only mimic a minor mutation of 22q11.2DS, a 1.5-Mb deletion. The role of the genes existing outside the 1.5-Mb deletion in psychiatric symptoms of 22q11.2DS is unclear. In this study, we generated a mouse model that reproduced the 3.0-Mb deletion of the 22q11.2DS (Del(3.0 Mb)/ +) using the CRISPR/Cas9 system. Ethological and physiological phenotypes of adult male mutants were comprehensively evaluated by visual-evoked potentials, circadian behavioral rhythm, and a series of behavioral tests, such as measurement of locomotor activity, prepulse inhibition, fear-conditioning memory, and visual discrimination learning. As a result, Del(3.0 Mb)/ + mice showed reduction of auditory prepulse inhibition and attenuated cue-dependent fear memory, which is consistent with the phenotypes of existing 22q11.2DS models. In addition, Del(3.0 Mb)/ + mice displayed an impaired early visual processing that is commonly seen in patients with schizophrenia. Meanwhile, unlike the existing models, Del(3.0 Mb)/ + mice exhibited hypoactivity over several behavioral tests, possibly reflecting the fatigability of 22q11.2DS patients. Lastly, Del(3.0 Mb)/ + mice displayed a faster adaptation to experimental jet lag as compared with wild-type mice. Our results support the validity of Del(3.0 Mb)/ + mice as a schizophrenia animal model and suggest that our mouse model is a useful resource to understand pathogenic mechanisms of schizophrenia and other psychiatric disorders associated with 22q11.2DS.

TBX1 is required for normal stria vascularis and semicircular canal development

Little is known about the role of TBX1 in post-otocyst stages of inner ear development. Here, we report on mice with a missense mutation of Tbx1 that are viable with fully developed but abnormally formed inner ears. Mutant mice are deaf due to an undeveloped stria vascularis and show vestibular dysfunction associated with abnormal semicircular canal formation. We show that TBX1 is expressed in endolymph-producing strial marginal cells and vestibular dark cells of the inner ear and is an upstream regulator of Esrrb, which previously was shown to control the developmental fate of these cells. We also show that TBX1 is expressed in sensory cells of the crista ampullaris, which may relate to the semicircular canal abnormalities observed in mutant mice. Inner ears of mutant embryos have a non-resorbed fusion plate in the posterior semicircular canal and a single ampulla connecting anterior and lateral canals. We hypothesize that the TBX1 missense mutation prevents binding with specific co-regulatory proteins. These findings reveal previously unknown functions of TBX1 during later stages of inner ear development.

A mouse model of 22q11.2 deletions: Molecular and behavioral signatures of Parkinson's disease and schizophrenia

Individuals with chromosome 22q11.2 deletions are at increased risk of developing psychiatric conditions, most notably, schizophrenia (SZ). Recently, clinical studies have also implicated these recurrent 22q11.2 deletions with the risk of early-onset Parkinson's disease (PD). Thus far, the multiple mouse models generated for 22q11.2 deletions have been studied primarily in the context of congenital cardiac, neurodevelopmental, and psychotic disorders. One of these is the Df1/+ model, in which SZ-associated and developmental abnormalities have been reported. We present the first evidence that the mouse model for the 22q11.2 deletion exhibits motor coordination deficits and molecular signatures (that is, elevated α-synuclein expression) relevant to PD. Reducing the α-synuclein gene dosage in Df1/+ mice ameliorated the motor deficits. Thus, this model of the 22q11.2 deletion shows signatures of both SZ and PD at the molecular and behavioral levels. In addition, both SZ-associated and PD-relevant deficits in the model were ameliorated by treatment with a rapamycin analog, CCI-779. We now posit the utility of 22q11.2 deletion mouse models in investigating the mechanisms of SZ- and PD-associated manifestations that could shed light on possible common pathways of these neuropsychiatric disorders.

Understanding the aetiology and resolution of chronic otitis media from animal and human studies

Inflammation of the middle ear, known clinically as chronic otitis media, presents in different forms, such as chronic otitis media with effusion (COME; glue ear) and chronic suppurative otitis media (CSOM). These are highly prevalent diseases, especially in childhood, and lead to significant morbidity worldwide. However, much remains unclear about this disease, including its aetiology, initiation and perpetuation, and the relative roles of mucosal and leukocyte biology, pathogens, and Eustachian tube function. Chronic otitis media is commonly modelled in mice but most existing models only partially mimic human disease and many are syndromic. Nevertheless, these models have provided insights into potential disease mechanisms, and have implicated altered immune signalling, mucociliary function and Eustachian tube function as potential predisposing mechanisms. Clinical studies of chronic otitis media have yet to implicate a particular molecular pathway or mechanism, and current human genetic studies are underpowered. We also do not fully understand how existing interventions, such as tympanic membrane repair, work, nor how chronic otitis media spontaneously resolves. This Clinical Puzzle article describes our current knowledge of chronic otitis media and the existing research models for this condition. It also identifies unanswered questions about its pathogenesis and treatment, with the goal of advancing our understanding of this disease to aid the development of novel therapeutic interventions.

Summary: Chronic middle ear inflammation is a common disease. Animal models, and in particular mouse models, have been used to elucidate some potential mechanisms, including dysfunction in immune signalling, mucociliary function or Eustachian tube function.

Anatomic Malformations of the Middle and Inner Ear in 22q11.2 Deletion Syndrome: Case Series and Literature Review

BACKGROUND AND PURPOSE

The 22q11.2 deletion syndrome is characterized by a heterogenic phenotype, including hearing loss. The underlying cause of hearing loss, especially sensorineural hearing loss, is not yet clear. Therefore, our objective was to describe anatomic malformations in the middle and inner ear in patients with 22q11.2 deletion syndrome.

MATERIALS AND METHODS

A retrospective case series was conducted in 2 tertiary referral centers. All patients with 22q11.2 deletion syndrome who had undergone CT or MR imaging of the temporal bones were included. Radiologic images were evaluated on predetermined parameters, including abnormalities of the ossicular chain, cochlea, semicircular canals, and vestibule.

RESULTS

There were 26 patients (52 ears) with a CT or MR imaging scan available. A dense stapes superstructure was found in 18 ears (36%), an incomplete partition type II was suspected in 12 cochleas (23%), the lateral semicircular canal was malformed with a small bony island in 17 ears (33%), and the lateral semicircular canal and vestibule were fused to a single cavity in 15 ears (29%).

CONCLUSIONS

Middle and inner ear abnormalities were frequently encountered in our cohort, including malformations of the lateral semicircular canal.

The impact of biological sex on the response to noise and otoprotective therapies against acoustic injury in mice

BACKGROUND

Noise-induced hearing loss (NIHL) is the most prevalent form of acquired hearing loss and affects about 40 million US adults. Among the suggested therapeutics tested in rodents, suberoylanilide hydroxamic acid (SAHA) has been shown to be otoprotective from NIHL; however, these results were limited to male mice.

METHODS

Here we tested the effect of SAHA on the hearing of 10-week-old B6CBAF1/J mice of both sexes, which were exposed to 2 h of octave-band noise (101 dB SPL centered at 11.3 kHz). Hearing was assessed by measuring auditory brainstem responses (ABR) at 8, 16, 24, and 32 kHz, 1 week before, as well as at 24 h and 15-21 days following exposure (baseline, compound threshold shift (CTS) and permanent threshold shift (PTS), respectively), followed by histologic analyses.

RESULTS

We found significant differences in the CTS and PTS of the control (vehicle injected) mice to noise, where females had a significantly smaller CTS at 16 and 24 kHz (p < 0.0001) and PTS at 16, 24, and 32 kHz (16 and 24 kHz p < 0.001, 32 kHz p < 0.01). This sexual dimorphic effect could not be explained by a differential loss of sensory cells or synapses but was reflected in the amplitude and amplitude progression of wave I of the ABR, which correlates with outer hair cell (OHC) function. Finally, the frequency of the protective effect of SAHA differed significantly between males (PTS, 24 kHz, p = 0.002) and females (PTS, 16 kHz, p = 0.003), and the magnitude of the protection was smaller in females than in males. Importantly, the magnitude of the protection by SAHA was smaller than the effect of sex as a biological factor in the vehicle-injected mice.

CONCLUSIONS

These results indicate that female mice are significantly protected from NIHL in comparison to males and that therapeutics for NIHL may have a different effect in males and females. The data highlight the importance of analyzing NIHL experiments from males and females, separately. Finally, these data also raise the possibility of effectors in the estrogen signaling pathway as novel therapeutics for NIHL.

Mapping the distribution of stem/progenitor cells across the mouse middle ear during homeostasis and inflammation

The middle ear epithelium is derived from neural crest and endoderm, which line distinct regions of the middle ear cavity. Here, we investigate the distribution of putative stem cell markers in the middle ear, combined with an analysis of the location of label-retaining cells (LRCs) to create a map of the middle ear mucosa. We show that proliferating cells and LRCs were associated with specific regions of the ear epithelium, concentrated in the hypotympanum at the base of the auditory bulla and around the ear drum. Sox2 was widely expressed in the endodermally derived ciliated pseudostratified epithelium of the hypotympanum. This part of the middle ear showed high levels of Wnt activity, as indicated by the expression of Axin2, a readout of Wnt signalling. Keratin 5 showed a more restricted expression within the basal cells of this region, with very little overlap between the Sox2- and keratin 5-positive epithelium, indicating that these genes mark distinct populations. Little expression of Sox2 or keratin 5 was observed in the neural crest-derived middle ear epithelium that lined the promontory, except in cases of otitis media when this epithelium underwent hyperplasia. This study lays the foundation for furthering our understanding of homeostasis and repair in the middle ear.

Prevalence of hearing loss and clinical otologic manifestations in patients with 22q11.2 deletion syndrome: A literature review

BACKGROUND

Hearing loss and otitis media are frequently reported in patients with 22q11.2 deletion syndrome.

OBJECTIVE OF REVIEW

Our objective was to review the current literature on the prevalence of hearing loss and otologic manifestations in patients with 22q11.2 deletion syndrome.

TYPE OF REVIEW

Systematic review.

SEARCH STRATEGY

We conducted a systematic search in PubMed and Embase combining the term "22q11.2 deletion syndrome" and synonyms with "hearing loss" and "otologic manifestations" and synonyms.

EVALUATION METHOD

We screened title/abstract and full text of all retrieved articles on pre-defined in- and exclusion criteria. The remaining articles were assessed on risk of bias. Outcome measures included the prevalence of hearing loss and otologic manifestations such as otitis media.

RESULTS

Our search yielded 558 unique studies of which a total of 25 articles were included for critical appraisal and data extraction. Twenty-one studies reported on hearing loss, and 21 studies on otologic manifestations. The prevalence of hearing loss varied from 6.0% to 60.3%, where in most studies conductive hearing loss was most prevalent. Rates of recurrent or chronic otitis media varied from 2.2% to 89.8%.

CONCLUSION

Although a very broad range in prevalences is reported in different studies, hearing loss and recurrent or chronic otitis media are frequently present in patients with 22q11.2 deletion syndrome. Regular check-ups and audiometric testing are advised in these patients.

Panel 3: Genetics and Precision Medicine of Otitis Media

Objective The objective is to perform a comprehensive review of the literature up to 2015 on the genetics and precision medicine relevant to otitis media. Data Sources PubMed database of the National Library of Medicine. Review Methods Two subpanels were formed comprising experts in the genetics and precision medicine of otitis media. Each of the panels reviewed the literature in their respective fields and wrote draft reviews. The reviews were shared with all panel members, and a merged draft was created. The entire panel met at the 18th International Symposium on Recent Advances in Otitis Media in June 2015 and discussed the review and refined the content. A final draft was made, circulated, and approved by the panel members. Conclusion Many genes relevant to otitis media have been identified in the last 4 years in advancing our knowledge regarding the predisposition of the middle ear mucosa to commensals and pathogens. Advances include mutant animal models and clinical studies. Many signaling pathways are involved in the predisposition of otitis media. Implications for Practice New knowledge on the genetic background relevant to otitis media forms a basis of novel potential interventions, including potential new ways to treat otitis media.

Persistent gating deficit and increased sensitivity to NMDA receptor antagonism after puberty in a new mouse model of the human 22q11.2 microdeletion syndrome: a study in male mice

BACKGROUND

The hemizygous 22q11.2 microdeletion is a common copy number variant in humans. The deletion confers high risk for neurodevelopmental disorders, including autism and schizophrenia. Up to 41% of deletion carriers experience psychotic symptoms.

METHODS

We present a new mouse model (Df(h22q11)/+) of the deletion syndrome (22q11.2DS) and report on, to our knowledge, the most comprehensive study undertaken to date in 22q11.2DS models. The study was conducted in male mice.

RESULTS

We found elevated postpubertal N-methyl-D-aspartate (NMDA) receptor antagonist-induced hyperlocomotion, age-independent prepulse inhibition (PPI) deficits and increased acoustic startle response (ASR). The PPI deficit and increased ASR were resistant to antipsychotic treatment. The PPI deficit was not a consequence of impaired hearing measured by auditory brain stem responses. The Df(h22q11)/+ mice also displayed increased amplitude of loudness-dependent auditory evoked potentials. Prefrontal cortex and dorsal striatal elevations of the dopamine metabolite DOPAC and increased dorsal striatal expression of the AMPA receptor subunit GluR1 was found. The Df(h22q11)/+ mice did not deviate from wild-type mice in a wide range of other behavioural and biochemical assays.

LIMITATIONS

The 22q11.2 microdeletion has incomplete penetrance in humans, and the severity of disease depends on the complete genetic makeup in concert with environmental factors. In order to obtain more marked phenotypes reflecting the severe conditions related to 22q11.2DS it is suggested to expose the Df(h22q11)/+ mice to environmental stressors that may unmask latent psychopathology.

CONCLUSION

The Df(h22q11)/+ model will be a valuable tool for increasing our understanding of the etiology of schizophrenia and other psychiatric disorders associated with the 22q11DS.

Otologic and audiologic findings in 22q11.2 deletion syndrome

Hearing loss is frequently present in the 22q11.2 deletion syndrome. Our aim was to describe the audiologic and otologic features of patients with 22q11.2 deletion syndrome. We conducted a retrospective cohort study in a single tertiary referral center. We reviewed medical files of all patients with 22q11.2 deletion syndrome who visited an otolaryngologist, plastic surgeon or speech therapist, for audiologic or otologic features. Hearing loss was defined as a pure tone average (of 0.5, 1, 2, and 4 kHz) of >20 decibel hearing level. Audiograms were available for 102 of 199 included patients, out of which 163 ears were measured in the required frquencies (0.5-4 kHz). Median age at time of most recent audiogram was 7 years (range 3-29 years). In 62 out of 163 ears (38%), hearing loss was present. Most ears had conductive hearing loss (n = 58) and 4 ears had mixed hearing loss. The severity of hearing loss was most frequently mild (pure tone average of ≤40 decibel hearing level). In 22.5% of ears, otitis media with effusion was observed at time of most recent audiogram. Age was not related to mean air conduction hearing thresholds or to otitis media with effusion (p = 0.43 and p = 0.11, respectively). In conclusion, hearing loss and otitis media are frequently present in patients with 22q11.2 deletion syndrome. Moreover, our results suggest that children with 22q11.2 deletion syndrome remain susceptible for otitis media as they age.

Prevalence and Nature of Hearing Loss in 22q11.2 Deletion Syndrome

PURPOSE

The purpose of this study was to clarify the prevalence, type, severity, and age-dependency of hearing loss in 22q11.2 deletion syndrome.

METHOD

Extensive audiological measurements were conducted in 40 persons with proven 22q11.2 deletion (aged 6-36 years). Besides air and bone conduction thresholds in the frequency range between 0.125 and 8.000 kHz, high-frequency thresholds up to 16.000 kHz were determined and tympanometry, acoustic reflex (AR) measurement, and distortion product otoacoustic emission (DPOAE) testing were performed.

RESULTS

Hearing loss was identified in 59% of the tested ears and was mainly conductive in nature. In addition, a high-frequency sensorineural hearing loss with down-sloping curve was found in the majority of patients. Aberrant tympanometric results were recorded in 39% of the ears. In 85% of ears with a Type A or C tympanometric peak, ARs were absent. A DPOAE response in at least 6 frequencies was present in only 23% of the ears with a hearing threshold ≤30 dB HL. In patients above 14 years of age, there was a significantly lower percentage of measurable DPOAEs.

CONCLUSION

Hearing loss in 22q11.2 deletion syndrome is highly prevalent and both conductive and high-frequency sensorineural in nature. The age-dependent absence of DPOAEs in 22q11.2 deletion syndrome suggests cochlear damage underlying the high-frequency hearing loss.

Modeling a model: Mouse genetics, 22q11.2 Deletion Syndrome, and disorders of cortical circuit development

Understanding the developmental etiology of autistic spectrum disorders, attention deficit/hyperactivity disorder and schizophrenia remains a major challenge for establishing new diagnostic and therapeutic approaches to these common, difficult-to-treat diseases that compromise neural circuits in the cerebral cortex. One aspect of this challenge is the breadth and overlap of ASD, ADHD, and SCZ deficits; another is the complexity of mutations associated with each, and a third is the difficulty of analyzing disrupted development in at-risk or affected human fetuses. The identification of distinct genetic syndromes that include behavioral deficits similar to those in ASD, ADHC and SCZ provides a critical starting point for meeting this challenge. We summarize clinical and behavioral impairments in children and adults with one such genetic syndrome, the 22q11.2 Deletion Syndrome, routinely called 22q11DS, caused by micro-deletions of between 1.5 and 3.0 MB on human chromosome 22. Among many syndromic features, including cardiovascular and craniofacial anomalies, 22q11DS patients have a high incidence of brain structural, functional, and behavioral deficits that reflect cerebral cortical dysfunction and fall within the spectrum that defines ASD, ADHD, and SCZ. We show that developmental pathogenesis underlying this apparent genetic "model" syndrome in patients can be defined and analyzed mechanistically using genomically accurate mouse models of the deletion that causes 22q11DS. We conclude that "modeling a model", in this case 22q11DS as a model for idiopathic ASD, ADHD and SCZ, as well as other behavioral disorders like anxiety frequently seen in 22q11DS patients, in genetically engineered mice provides a foundation for understanding the causes and improving diagnosis and therapy for these disorders of cortical circuit development.

A defect in early myogenesis causes Otitis media in two mouse models of 22q11.2 Deletion Syndrome

Otitis media (OM), the inflammation of the middle ear, is the most common disease and cause for surgery in infants worldwide. Chronic Otitis media with effusion (OME) often leads to conductive hearing loss and is a common feature of a number of craniofacial syndromes, such as 22q11.2 Deletion Syndrome (22q11.2DS). OM is more common in children because the more horizontal position of the Eustachian tube (ET) in infants limits or delays clearance of middle ear effusions. Some mouse models with OM have shown alterations in the morphology and angle of the ET. Here, we present a novel mechanism in which OM is caused not by a defect in the ET itself but in the muscles that control its function. Our results show that in two mouse models of 22q11.2DS (Df1/+ and Tbx1(+/-)) presenting with bi- or unilateral OME, the fourth pharyngeal arch-derived levator veli palatini muscles were hypoplastic, which was associated with an earlier altered pattern of MyoD expression. Importantly, in mice with unilateral OME, the side with the inflammation was associated with significantly smaller muscles than the contralateral unaffected ear. Functional tests examining ET patency confirmed a reduced clearing ability in the heterozygous mice. Our findings are also of clinical relevance as targeting hypoplastic muscles might present a novel preventative measure for reducing the high rates of OM in 22q11.2DS patients.