Mutation in the gene for connexin 30.3 in a family with erythrokeratodermia variabilis

Abstract

Erythrokeratodermia variabilis (EKV) is an autosomal dominant keratinization disorder characterized by migratory erythematous lesions and fixed keratotic plaques. All families with EKV show mapping to chromosome 1p34-p35, and mutations in the gene for connexin 31 (Cx31) have been reported in some but not all families. We studied eight affected and three healthy subjects in an Israeli family, of Kurdish origin, with EKV. After having mapped the disorder to chromosome 1p34-p35, we found no mutations in the genes for Cx31, Cx31.1, and Cx37. Further investigation revealed a heterozygous T-->C transition leading to the missense mutation (F137L) in the human gene for Cx30.3 that colocalizes on chromosome 1p34-p35. This nucleotide change cosegregated with the disease and was not found in 200 alleles from normal individuals. This mutation concerns a highly conserved phenylalanine, in the third transmembrane region of the Cx30.3 molecule, known to be implicated in the wall formation of the gap-junction pore. Our results show that mutations in the gene for Cx30.3 can be causally involved in EKV and point to genetic heterogeneity of this disorder. Furthermore, we suggest that our family presents a new type of EKV because of the hitherto unreported association with erythema gyratum repens.

Figure 1

Pedigree and haplotype analysis of the family with EKV. Haplotypes are given (top to bottom) for markers D1S496, D1S472, and D1S186. Haplotype 1-5-4 was found to segregate with the disease. x = meiotic recombination.

Figure 2

Clinical pictures. A, III-6, a 37-year-old man. The nape of the neck has brownish, lichenification-like hyperkeratotic plaque with mostly clear-cut borders. B, IV-1, a 19-year-old man. The periaxillary region has well-demarcated polycyclic plaque composed of diffuse scaling and erythema gyratum repens–like migratory lesions. C, IV-2, a 9.5-year-old girl. The anterior trunk has erythema gyratum repens–like migratory lesions.

Figure 3

Expression analysis of the Cx30.3 transcript. Lanes 1–4, RT-PCR with Cx30.3 primers. Lanes 5–8, PCR with Cx30.3 primers, omitting RT. Lanes 9–12, RT-PCR with actin primers. Total RNA for the reactions was derived from human skin biopsy (lanes 1, 5, and 9), cultured keratinocytes (lanes 2, 6, and 10), cultured skin fibroblasts (lanes 3, 7, and 11), and peripheral leukocytes (lanes 4, 8, and 12).

Figure 4

Molecular analysis of the gene for Cx30.3 (GJB4) in the family with EKV. A and B, Chromatograms of an affected individual with the Cx30.3 mutation, T409C, and a normal individual. C, Inheritance of the T409C mutation by restriction-enzyme digestion with SmlI. Normal alleles produce a 904-bp band that is cleaved into 488- and 416-bp fragments in mutant alleles. Lanes 1–10, Individuals II-1, II-5, III-1, III-2, III-3, III-5, III-6, III-8, III-9, and IV-1, respectively (see pedigree in fig. 1).

Figure 5

Sequence alignment of the M3 and partial E2 domains of human Cx30.3 with other β-class gap-junction proteins. The arrowhead indicates the position of the Cx30.3 mutation, F137L, in the family with EKV. GenBank accession numbers are CAB90270 (for hCx30.3), AAA37428 (for mCx30.3), CAA53762 (for rCx30.3), CAA06165 (for hCx31), AAD18005 (for hCx31.1), NP_003995 (for hCx26), B29005 (for hCx32), and NP_006774 (for hCx30). The sequence of pCx30.3 was obtained from Itahana et al. (1996). h = human, m = mouse, r = rat, and p = porcine.