Obsessive-compulsive symptoms in ACTG1-associated Baraitser-Winter cerebrofrontofacial syndrome

The γ-Actin with pathogenic variants of sites on actin-binding proteins caused earlier onset and more malignant progressive hearing loss

BACKGROUND

The γ-actin protein, encoded by the ACTG1 gene, is a critical cytoskeletal component in non-muscle cells. Mutations in ACTG1 are associated with autosomal dominant, progressive sensorineural hearing loss (HL), but clinical heterogeneity remains poorly understood.

METHODS

We identified a novel missense variant, c.981C>G (p.Ile327Met; I327M), in a Chinese family with hereditary HL through whole exome sequencing. Functional analyses were performed to assess ACTG1 mRNA and protein expression, F-actin organisation and subcellular localisation. Structural modelling and electrostatic analysis were used to predict the impact of the I327M substitution. Additionally, we reviewed 35 published ACTG1-related families involving 82 patients to explore genotype-phenotype correlations.

RESULTS

The I327M variant resulted in significantly reduced ACTG1 transcript and protein levels, accompanied by disrupted F-actin integrity in patient-derived peripheral blood mononuclear cells. Structural modelling suggested that the variant alters the electrostatic environment near the tropomyosin-binding interface, potentially compromising filament stability. Literature review and comparative analysis revealed that variants located within actin-binding protein (ABP) interaction sites were associated with an earlier onset and more severe progression of HL compared with those located outside ABP-binding domains.

CONCLUSION

The c.981C>G (p.Ile327Met) variant contributes to HL pathogenesis through dual mechanisms involving impaired gene expression and filament destabilisation. This study highlights the clinical relevance of variant location relative to ABP binding regions and provides new insights into genotype-phenotype relationships in ACTG1-associated HL.

Hearing Loss in Baraitser-Winter Syndrome: Case Reports and Review of the Literature

Background: Baraitser-Winter Syndrome (BRWS) is a rare autosomal dominant condition associated with hearing loss (HL). In the literature, two types of this condition are reported, Baraitser-Winter type 1 (BRWS1) and type 2 (BRWS2) produced by specific pathogenetic variants of two different genes, ACTB for BRWS1 and ACTG1 for BRWS2. In addition to syndromic BRWS2, some pathogenic variants in ACTG1 are associated also to another pathologic entity, the "Autosomal dominant non-syndromic hearing loss 20/26". In these syndromes, typical craniofacial features, sensory impairment (vision and hearing) and intellectual disabilities are frequently present. Heart anomalies, renal and gastrointestinal involvement and seizure are also common. Wide inter- and intra-familial variety in the phenotypic spectrum is reported. Some phenotypic aspects of these syndromes are not yet fully described, such as the degree and progression of HL, and better knowledge of them could be useful for correct follow-up and treatment. Methods and Results: In this study, we report two cases of children with HL and diagnosis of BRWS and a review of the current literature on HL in these syndromes.

Deep clinical phenotyping of patients with obsessive-compulsive disorder: an approach towards detection of organic causes and first results

In the revised diagnostic classification systems ICD-11 and DSM-5, secondary, organic forms of obsessive-compulsive disorder (OCD) are implemented as specific nosological entities. Therefore, the aim of this study was to clarify whether a comprehensive screening approach, such as the Freiburg-Diagnostic-Protocol for patients with OCD (FDP-OCD), is beneficial for detecting organic OCD forms. The FDP-OCD includes advanced laboratory tests, an expanded magnetic resonance imaging (MRI) protocol, and electroencephalography (EEG) investigations as well as automated MRI and EEG analyses. Cerebrospinal fluid (CSF), [18F]fluorodeoxyglucose positron emission tomography, and genetic analysis were added for patients with suspected organic OCD. The diagnostic findings of the first 61 consecutive OCD inpatients (32 female and 29 male; mean age: 32.7 ± 12.05 years) analyzed using our protocol were investigated. A probable organic cause was assumed in five patients (8%), which included three patients with autoimmune OCD (one patient with neurolupus and two with specific novel neuronal antibodies in CSF) and two patients with newly diagnosed genetic syndromes (both with matching MRI alterations). In another five patients (8%), possible organic OCD was detected (three autoimmune cases and two genetic cases). Immunological serum abnormalities were identified in the entire patient group, particularly with high rates of decreased "neurovitamin" levels (suboptimal vitamin D in 75% and folic acid in 21%) and increased streptococcal (in 46%) and antinuclear antibodies (ANAs; in 36%). In summary, the FDP-OCD screening led to the detection of probable or possible organic OCD forms in 16% of the patients with mostly autoimmune forms of OCD. The frequent presence of systemic autoantibodies such as ANAs further support the possible influence of autoimmune processes in subgroups of patients with OCD. Further research is needed to identify the prevalence of organic OCD forms and its treatment options.