A de novo frameshift pathogenic variant in TBR1 identified in autism without intellectual disability

Abstract

Background: In order to be able to provide accurate genetic counseling to patients with Autism Spectrum Disorder (ASD), it is crucial to identify correlations between heterogeneous phenotypes and genetic alterations. Among the hundreds of de novo pathogenic variants reported in ASD, single-nucleotide variations and small insertions/deletions were reported in TBR1. This gene encodes a transcription factor that plays a key role in brain development. Pathogenic variants in TBR1 are often associated with severe forms of ASD, including intellectual disability and language impairment.

Methods: Adults diagnosed with ASD but without intellectual disability (diagnosis of Asperger syndrome, according to the DSM-IV) took part in a genetic consultation encompassing metabolic assessments, a molecular karyotype and the screening of a panel of 268 genes involved in intellectual disability, ASD and epilepsy. In addition, the patient reported here went through a neuropsychological assessment, structural magnetic resonance imaging and magnetic resonance spectroscopy measurements.

Results: Here, we report the case of a young adult male who presents with a typical form of ASD. Importantly, this patient presents with no intellectual disability or language impairment, despite a de novo heterozygous frameshift pathogenic variant in TBR1, leading to an early premature termination codon (c.26del, p.(Pro9Leufs*12)).

Conclusion: Based on this case report, we discuss the role of TBR1 in general brain development, language development, intellectual disability and other symptoms of ASD. Providing a detailed clinical description of the individuals with such pathogenic variants should help to understand the genotype-phenotype relationships in ASD.

Fig. 1

Pathogenic variants associated with ASD identified in the TBR1 protein. Predicted protein consequences of single-nucleotide variants found in TBR1 in ASD, described on https://gene.sfari.org/database/human-gene/TBR1, in the following references [, –34] and in the present study (circled in black). Pathogenic variants found in the T-box domain coding sequence are indicated in dark grey. LD: language delay, VF: verbally fluent, VL: verbally limited (few words or sentences), NV: non-verbal. The TBR1 protein consists of 682 amino acids. References: ① [28], ② [27], ③ [30], ④ [34], ⑤ [31], ⑥ [32], ⑦ [11], ⑧ [33], ⑨ Present study