Heterozygous KRT32 variant is responsible for autosomal dominant loose anagen hair syndrome

Abstract

Loose Anagen Hair Syndrome is a form of non-scarring alopecia marked by easily and painlessly pluckable terminal hair during its active growth - anagen - phase. This condition is believed to result from poor hair shaft anchoring within the follicle due to premature keratinization. Our research identified the likely pathogenic c.296C>T (p.T99I) variant in KRT32, which was found to co-segregate with the disorder in a large family with autosomal dominant loose anagen hair syndrome. This study aimed to explore the role of KRT32, previously unassociated with loose anagen hair, in hair anchorage and assess the functional impact of the p.T99I variant. We hypothesized that the p.T99I variant reduces KRT32s binding affinity to KRT82, disrupting the intermediate filament structure in the hair shaft cuticle and leading to weak anagen hair anchorage. To test this hypothesis, we conducted a protein-protein interaction assay using far western blotting and performed in silico intermediate filament network segmentation analysis on high-resolution fluorescent microscopy images. Our results revealed a decreased binding affinity of KRT32T99I for KRT82 compared to KRT32WT, along with significant differences in segment count and filament brightness (thickness) between the two groups.