Ophthalmologic Manifestations in Autism Spectrum Disorder

Clinical and genetic findings in autism spectrum disorders analyzed using exome sequencing

Autism spectrum disorder (ASD) refers to a group of complex neurodevelopmental disorders and is characterized by impaired reciprocal social interaction and communication, as well as the presence of restricted interests and stereotyped and repetitive behaviors. As a complex neurodevelopmental disorder, the phenotype and severity of autism are extremely heterogeneous, with differences from one patient to another. Chromosome microarray (CMA) and fragile X syndrome analyses has been used as a powerful tool to identify new candidate genes for ASD.

METHODS

In the present study, CMA was first used to scan for genome-wide copy number variants in the patient, and no clinically significant copy number variants were found. Exome sequencing (ES) was used for further genetic testing.

RESULTS

ES was performed on 20 subjects. Eighty percent of our sample presented intellectual disability. Other co-occurring clinical conditions included speech disorders, psychomotor delay, the presence of dysmorphic features and medical co-morbidities. A pathogenic variant was identified in 10 patients (ADNP, FBN1, WAC, ASXL3, NR4A2, ALX4, ANKRD1, POGZ, SHANK3 and BPTF). Patients with a positive finding in ES were more likely to present a dysmorphic trunk, more than three dysmorphic features, hypotonia, psychomotor delay and strabismus.

CONCLUSIONS

ES offers expanded diagnostic options for patients with ASD who are negative on CMA. However, further studies are needed for a better understanding of ASD etiology and also the different phenotypes.

Chromosome 4 Duplication Associated with Strabismus Leads to Gene Expression Changes in iPSC-Derived Cortical Neurons

BACKGROUND/OBJECTIVES

Strabismus is the most common ocular disorder of childhood. Three rare, recurrent genetic duplications have been associated with both esotropia and exotropia, but the mechanisms by which they contribute to strabismus are unknown. This work aims to investigate the mechanisms of the smallest of the three, a 23 kb duplication on chromosome 4 (hg38|4:25,554,985-25,578,843).

METHODS

Using CRISPR and bridging oligos, we introduced the duplication into the Kolf2.1J iPSC line. We differentiated the parent line and the line with the duplication into cortical neurons using a three-dimensional differentiation protocol, and performed bulk RNASeq on neural progenitors (day 14) and differentiated neurons (day 63).

RESULTS

We successfully introduced the duplication into Kolf2.1J iPSCs by nucleofecting a bridging oligo for the newly formed junction along with cas9 ribonucleoparticles. We confirmed that the cells had a tandem duplication without inversion or deletion. The parent line and the line with the duplication both differentiated into neurons reliably. There were a total of 37 differentially expressed genes (DEGs) at day 63, 25 downregulated and 12 upregulated. There were 55 DEGs at day 14, 18 of which were also DEGs at day 63. The DEGs included a number of protocadherins, several genes involved in neuronal development, including SLITRK2, CSMD1, and VGF, and several genes of unknown function.

CONCLUSIONS

A copy number variant (CNV) that confers risk for strabismus affects gene expression of several genes involved in neural development, highlighting that strabismus most likely results from abnormal neural development, and identifying several new genes and pathways for further research into the pathophysiology of strabismus.

Clear lens extraction and refractive lens exchange for the treatment of amblyopia

Treatment of amblyopia typically involves spectacles or penalization of the nonamblyopic eye with occlusive patching or pharmacological penalization. However, these methods can be ineffective or difficult in certain children who may be unable to tolerate or are poorly compliant with such therapies. Untreated high refractive error can result in dense amblyopia, and thus, other treatment methods are necessary in this subset of children. With technological advances in ocular surgery, clear lens extraction (CLE) and refractive lens exchange (RLE) have emerged as popular alternative treatments for amblyopia, as they may avoid some of the challenges surrounding traditional methods. CLE involves lensectomy for refractive purposes in patients without cataracts, while RLE involves lensectomy followed by intraocular lens implantation. The purpose of this review was to summarize the use of CLE and RLE for the treatment of amblyopia in the pediatric population, discussing indications, techniques, treatment outcomes, safety, and potential complications.

Is Visual Prediction Impaired in Adolescents with Autism spectrum Disorder? Event-Related Potentials in a Cued Visual GO/NOGO Task

Aim: Deviant visual processing has been observed in autism spectrum disorder (ASD), manifesting as decreased P1 and P2 components of visual event-related potentials (ERPs). Alterations have been attributed to a failure of Bayesian inference, characterized by hypo-activation of top-down predictive abilities. To test this hypothesis, we measured the visual negativity (vN) as an ERP index of visual preparation hypothesized to mirror predictive brain activity. Method: ERPs in a cued visual GO/NOGO task in 63 adolescents with ASD (IQ > 70, attention-deficit hyperactivity disorder excluded) were compared with ERPs in a sex- and age-matched group of 60 typically developing (TD) controls. Results: The behavioral variables (omissions, commissions, reaction time, and reaction time variability), as well as ERP components reflecting, among other processes, cognitive control (contingent negative variation, P3 GO, P3 NOGO, N2 NOGO) did not differ between the groups. There were group differences in visually based ERPs. Besides P1 and P2 differences, the vN component differentiated the 2 groups with the highest effect size (d  =  0.74).Conclusion: This ERP study lends support to the hypothesis suggesting that a Bayesian hypo-prediction could underlie unique perceptual experiences in individuals with ASD. This could lead to a predisposition to perceive the world with reduced influence and modulation from contextual cues, prior experiences, and pre-existing expectations.

Genetics of strabismus

Strabismus, or misalignment of the eyes, is the most common ocular disorder in the pediatric population, affecting approximately 2%-4% of children. Strabismus leads to the disruption of binocular vision, amblyopia, social and occupational discrimination, and decreased quality of life. Although it has been recognized since ancient times that strabismus runs in families, its inheritance patterns are complex, and its precise genetic mechanisms have not yet been defined. Family, population, and twin studies all support a role of genetics in the development of strabismus. There are multiple forms of strabismus, and it is not known if they have shared genetic mechanisms or are distinct genetic disorders, which complicates studies of strabismus. Studies assuming that strabismus is a Mendelian disorder have found areas of linkage and candidate genes in particular families, but no definitive causal genes. Genome-wide association studies searching for common variation that contributes to strabismus risk have identified two risk loci and three copy number variants in white populations. Causative genes have been identified in congenital cranial dysinnervation disorders, syndromes in which eye movement is limited or paralyzed. The causative genes lead to either improper differentiation of cranial motor neurons or abnormal axon guidance. This article reviews the evidence for a genetic contribution to strabismus and the recent advances that have been made in the genetics of comitant strabismus, the most common form of strabismus.

Discovering the ANK2-related autism phenotype

Interestingly, disease-causing mutations in the ANK2 gene have been identified in patients with autism since 2012, though with no full clinical description. In this Research Letter, for the first time, we describe the detailed characteristics of a patient with autism caused by a new mutation in this gene. Our report is a first step to better understanding ANK2-related autism and will contribute to facilitating its further diagnosis.