Genetic and clinical phenotypic analysis of familial stapes sclerosis caused by an NOG mutation

Genotypes and clinical phenotypes of pediatric patients with NOG variants: Middle ear surgical outcomes from a Tertiary Center in South Korea

OBJECTIVE

Although NOG variants are linked to congenital stapes fixation and conductive hearing loss (CHL), little is known about middle ear surgery outcomes and the characteristics of accompanying inner ear anomalies. We explored auditory phenotypes in patients with NOG variants, with a focus on the outcomes of middle ear surgery.

METHODS

This study included 11 patients from five unrelated Korean families harboring NOG variants. Genomic investigations were conducted using whole-exome sequencing and whole-genome sequencing. The clinical phenotypes, including pre- and postoperative audiological profiles, radiological abnormalities, and other comorbidities, were analyzed.

RESULTS

The average age at genetic testing was 8.2 years (range, 0-13 years). Two previously reported NOG variants (c.509C > T:p.Pro170Leu and c.252dup:p.Glu85ArgfsTer97) and three novel NOG variants, including the c.187G > T: p.Glu63Ter and two cryptic large deletion within the 17q22.2 region, were identified. All patients exhibited non-progressive CHL. Inner ear anomalies were documented in two patients, with variations such as cochlea and vestibular dysplasia. In this study, seven ears of four patients underwent stapedotomy, resulting in a significantly reduced air-bone gap of 10.18 ± 1.48 dB (P = 0.016), with sustained improvement. Conversely, patients carrying p.Pro170Leu variant, which is associated with poor outcomes for middle ear surgery, were excluded from surgical consideration.

CONCLUSION

We expanded the spectrum of genotypes and auditory phenotypes associated with NOG variants. Surgical intervention for CHL underlying NOG variants elicits favorable outcomes. However, clinicians should consider the potential for poor prognosis in certain NOG variants. Collectively, identifying NOG variants could guide the treatment strategies to improve CHL.

Timing and Graded BMP Signalling Determines Fate of Neural Crest and Ectodermal Placode Derivatives from Pluripotent Stem Cells

Pluripotent stem cells (PSCs) offer many potential research and clinical benefits due to their ability to differentiate into nearly every cell type in the body. They are often used as model systems to study early stages of ontogenesis to better understand key developmental pathways, as well as for drug screening. However, in order to fully realise the potential of PSCs and their translational applications, a deeper understanding of developmental pathways, especially in humans, is required. Several signalling molecules play important roles during development and are required for proper differentiation of PSCs. The concentration and timing of signal activation are important, with perturbations resulting in improper development and/or pathology. Bone morphogenetic proteins (BMPs) are one such key group of signalling molecules involved in the specification and differentiation of various cell types and tissues in the human body, including those related to tooth and otic development. In this review, we describe the role of BMP signalling and its regulation, the consequences of BMP dysregulation in disease and differentiation, and how PSCs can be used to investigate the effects of BMP modulation during development, mainly focusing on otic development. Finally, we emphasise the unique role of BMP4 in otic specification and how refined understanding of controlling its regulation could lead to the generation of more robust and reproducible human PSC-derived otic organoids for research and translational applications.