FERMT1 promoter mutations in patients with Kindler syndrome

Mutations in the FERMT1 gene, encoding the focal adhesion protein kindlin-1 underlie the Kindler syndrome (KS), an autosomal recessive skin disorder with a phenotype comprising skin blistering, photosensitivity, progressive poikiloderma with extensive skin atrophy, and propensity to skin cancer. The FERMT1 mutational spectrum comprises gross genomic deletions, splice site, nonsense, and frameshift mutations, which are scattered over the coding region spanning exon 2-15. We now report three KS families with mutations affecting the promoter region of FERMT1. Two of these mutations are large deletions (∼38.0 and 1.9 kb in size) and one is a single nucleotide variant (c.-20A>G) within the 5' untranslated region (UTR). Each mutation resulted in loss of gene expression in patient skin or cultured keratinocytes. Reporter assays showed the functional relevance of the genomic regions deleted in our patients for FERMT1 gene transcription and proved the causal role of the c.-20A>G variant in reducing transcriptional activity.

Phenotypic spectrum of epidermolysis bullosa associated with α6β4 integrin mutations

BACKGROUND

Integrin α6β4 is a transmembrane receptor and a key component of the hemidesmosome anchoring complex. It is involved in cell-matrix adhesion and signalling in various tissues. Mutations in the ITGA6 and ITGB4 genes coding for α6β4 integrin compromise dermal-epidermal adhesion and are associated with skin blistering and pyloric atresia (PA), a disorder known as epidermolysis bullosa with PA (EB-PA).

OBJECTIVES

To elucidate the molecular pathology of skin fragility in eight cases, disclose the underlying ITGA6 and ITGB4 mutations and study genotype-phenotype correlations.

METHODS

DNA was isolated from ethylenediaminetetraacetic acid-blood samples, and the coding exons and exon-intron boundaries of ITGA6 and ITGB4 were amplified by polymerase chain reaction (PCR), and directly sequenced. Skin samples were submitted to immunofluorescence mapping with antibodies to adhesion proteins of the dermal-epidermal junction. Primary keratinocytes were isolated, and used for RNA and protein extraction, reverse transcription PCR and immunoblotting. Ultrastructural analysis of the skin was performed in one patient.

RESULTS

We disclose 10 novel mutations, one in ITGA6 and nine in ITGB4. Skin cleavage was either intraepidermal or junctional. Lethal outcome and PA correlated with loss-of-function mutations in two cases. Solely mild skin involvement was associated with deletion of the C-terminus of β4 integrin. Combinations of missense, nonsense or frameshift mutations caused severe urinary tract involvement in addition to skin fragility in five cases.

CONCLUSIONS

The present study reveals novel ITGA6 and ITGB4 gene mutations and supports previous reports showing that the phenotype may lack PA and be limited to skin and nail involvement. In four out of six cases of EB-PA, life expectancy was not impaired. A high frequency of urinary tract involvement was found in this study, and represented the main cause of morbidity. Low levels of β4 integrin expression were compatible with hemidesmosomal integrity and a mild skin phenotype.

Acromelanosis albo-punctata: a distinct inherited dermatosis with acral spotty dyspigmentation without systemic involvement

We describe an otherwise healthy 7-year-old boy who developed confetti-like hypopigmented macules on the dorsal aspects of the hands and feet, spreading to the palms and soles a few months after birth. In 1964 Siemens introduced the term acromelanosis albo-punctata to describe the skin features of a patient who has remained the only reported case in the literature so far and who strongly resembles our patient. By genetic testing we excluded mutations in genes known to be involved in diseases with acral hypo- or hyperpigmentation. We review the differential diagnosis of acral localized spotty dyspigmentation and conclude that acromelanosis albo-punctata may represent a distinct entity.

Poikiloderma with neutropenia: a novel C16orf57 mutation and clinical diagnostic criteria

A new syndrome with poikiloderma was described by Clericuzio et al. in 1991.(1) They reported 14 Navajo native Americans, including eight siblings, developing in the first year of life an erythematous rash, which started on the limbs and spread over the trunk and the face. This rash evolved into poikiloderma. All patients had recurrent bacterial infections. First published as Navajo poikiloderma this syndrome is now known as poikiloderma with neutropenia (PN, OMIM 604173). The inheritance is autosomal recessive, and mutations in a new gene, C16orf57, were recently described in two kindreds.(2) Because of the phenotypic overlap between Rothmund-Thomson syndrome (RTS) and PN, a few patients have been reclassified as mutations in the RECQL4 gene for RTS were absent.(2-5) Until now 27 patients have been described with clinical PN.(1-3,5-8) Here, we report the sixth family with PN outside the Navajo population. We found the previously unreported mutation c.243G>A, p.W81X in the C16orf57 gene, thus confirming the relation of this gene to the disease.(2,6) Because the molecular genetic diagnosis is not always available, we propose clinical and laboratory diagnostic criteria for PN.