Abstract:

Objective To investigate the mutation of typeⅡ human hair basic keratin （hHb） gene in a family with monilethrix. Methods Scanning electron microscopy was used to observe the structure of hair shafts. With informed consent, blood samples were drawn from affected and unaffected members in this family, as well as from 50 healthy controls. Genomic DNA was isolated from these samples. The exon 1 and exon 7 of hHb1, hHb3 and hHb6 were amplified by polymerase chain reaction （PCR）. All the PCR products were sequenced directly using ABI3730 automated sequencer. DNA sequence alignment was carried out with BLAST software. Results A typical beaded appearance was observed in affected hairs by using scanning electron microscopy. There were obvious longitudinal ridges and sulcuses in hair node, and hair cuticles were irregularly shaped. Most cortex and medullary substance were absent in affected hairs of a patient. After sequence alignment, a G1289A point mutation in exon 7 of hHb6 gene, which led to a substitution of arginine for glutamide at codon 430, was detected in affected members of this family, but not in unaffected family members or 50 unrelated human controls. No mutation was observed in exon 1 or exon 7 of hHb1 and hHb3 gene or exon 1 of hHb6 gene. Conclusion The missense mutation of R430Q is a novel mutation, which may be associated with the pathogenesis of monilethrix in this pedigree.

Key words: monilethrix, type II human basic hair keratin, gene mutation