Figure 1.
Pedigree of the family segregating AR PHNED and phenotypic features of affected family members.
(A) Pedigree of the consanguineous Pakistani family with PHNED (modified from [2]). Affected individuals are represented by filled symbols. Haplotypes are shown below each individual with microsatellite marker alleles on chromosome 12p11.1-q14.3 used for linkage analysis, as well as the relative position of the KRT74 variant identified. Individuals V:1 and V:3 were selected for exome sequencing. (B) Patients V:2 (panels i, ii), V:3 (panels iii, iv) and V:7 (panels v, vi) show hypotrichosis with brittle hair of the scalp and dystrophic, slightly spoon-shaped nails with distal onycholysis and mild micronychia.
Figure 2.
Protein sequences showing inter-species conservation of Keratin-74 and homologies between 26 human type II keratins.
(A) Clustal Omega alignment of part of Keratin-74 shows complete evolutionary conservation of the Phe274 residue (shaded) in all species with a known keratin-74 ortholog. (B) Alignment of parts of the 26 human type II keratins illustrating the almost identical homology at amino-acid position 274 (shaded). Only Keratin-80 deviates by having a biochemically similar leucine at this position. Position of the first amino acid shown is indicated to the left of each protein sequence. KRT: Keratin.
Figure 3.
Mouse keratin-74 is expressed in the regenerative nail tissue.
(A) H&E staining of a normal mouse nail unit (40x magnification). The continuous line delineates the border of the nail matrix, the dashed line shows the border of the nail bed, and the dotted line illustrates the hyponychium. nb: nail bed, nm: nail matrix, hn: hyponychium. The boxed section is enlarged in (B). (B) Immunofluorescent staining of keratin-74 shows strong expression in the nail matrix, nail bed and hyponychium (100x magnification). Note the single-cell layer immediately adjacent to the nail plate with pronounced staining. The continuous, dashed and dotted lines correspond to the lines presented in (A).
Figure 4.
Keratin-74 is not detected in hair follicles of an individual with AR PHNED.
(A) Sections from a forearm skin biopsy of a healthy control individual show positive staining for Keratin-74 (KRT74; green) in the inner root sheath of the hair follicle. The nuclear envelope marker Lamin B1 (red) is used for co-staining (200x magnification). (B) Skin biopsy from forearm of individual V:3 with AR PHNED shows a hair follicle that stains negative for Keratin-74. Co-staining with Lamin B1 is normal (200x magnification). Dashed lines delineate the outer border of the inner root sheath, and the inner border of the root sheath with the medulla. From left to right: Brightfield (light) microscopy; Keratin-74 staining (KRT74); Lamin B1 staining and merge.