Fig. 3

The psoriasis phenotype is caused by a loss-of-function mutation in atp1b1a, which is expressed in multiple epithelia, but not in basal keratinocytes.

(a-d) Exome sequencing links the psoriasis mutation to LG6 and identifies a C to T transition in atp1b1a. (a,b) Heat maps showing the density of variant loci over the whole genome (a) and on chromosome 6 (b). The Y-axis shows the absolute value of the difference in the percentage of DNA harboring the variation between the pool of affected offspring and the pool of their parents. Most of the genome shows a difference close to 0%, indicating that the parental DNA segregated randomly in the affected offspring. Only one peak on chromosome 6 shows low density at a difference of 0%, but high density at between 25% and 50% difference, which is expected at the linked locus under the assumption of a recessive mode of inheritance. (c) Chromatographs of Sanger sequencing of sibling and mutant DNA showing the psoriasis mutation (*). (d) Schematic representation of the atp1b1a locus. Red arrowhead indicates the position of the mutation. (e) Live images of 54 hpf wt siblings, psoriasis mutants, and atp1b1a morphants. MO-based knockdown of atp1b1a in wt embryos phenocopies both the pericardial edema and epidermal aggregates. Scale bars: 500 µm; 250 µm (magnifications). (f-i) WISH detects atp1b1a RNA (blue) in heart and multiple epithelia of 48 hpf wt embryos, including the pronephric duct and the periderm but not in the basal keratinocytes (f-h), as seen at higher magnification after counterstaining of nuclei of basal keratinocytes for p63 protein (i). The atp1b1a RNA signal is not detected around p63 nuclei, but is detected in hexagonal peridermal cells with p63^- nuclei. Abbreviations: h, heart; le, lense; oe, olfactory epithelium; ov, otic vesicle; pd, periderm; pfb, pectoral fin bud; pn, pronephros; pnd, pronephric duct.