Overlapping Xq13.3 duplications define an X-linked hypotrichosis simplex and implicate TAB3 dosage sensitivity

Area of Science:

• Genetics
• Dermatology
• Molecular Biology

Background:

• Hereditary hypotrichosis is typically autosomal, but X-linked forms are less understood.
• Previous research has primarily linked hair loss disorders to autosomal inheritance patterns.

Purpose of the Study:

• To identify the genetic cause of a novel X-linked hypotrichosis simplex (XLHS) observed in three families.
• To investigate the molecular mechanisms underlying XLHS and explore potential therapeutic targets.

Main Methods:

• Genomic analysis to identify duplications in affected individuals.
• Gene expression and protein abundance analysis in scalp tissue.
• Development of mouse and cell models for functional studies of candidate genes.
• Investigation of signaling pathways, including TAK1-dependent NF-κB signaling.

Main Results:

• Identified partially overlapping duplications at Xq13.3 in affected individuals, encompassing TAB3, FTHL17, and DMD.
• TAB3 showed increased accumulation in scalp tissue of affected individuals, implicating it as the dosage-sensitive candidate gene.
• TAB3 overexpression impaired TAK1-dependent canonical NF-κB signaling and recapitulated hypotrichosis in mice, with associated pathological changes.
• Anti-inflammatory treatment improved hair density in mice, suggesting potential therapeutic avenues.

Conclusions:

• Defined a previously unrecognized X-linked hypotrichosis simplex (XLHS).
• Established increased TAB3 gene dosage as the genetic driver of XLHS.
• Implicated dysregulated TAK1-NF-κB signaling as a pathogenic mechanism and suggested anti-inflammatory therapy as a potential treatment.