{'fraction_non_alphanumeric': 0.03268226648617289, 'fraction_numerical': 0.024753432604912008, 'mean_word_length': 5.070422535211268, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
A novel 3017‐bp deletion mutation in the FERMT1 (KIND1) gene in a Chinese family with Kindler syndrome

SIR, Kindler syndrome (KS; OMIM 173650) is a rare autosomal recessive genodermatosis characterized by congenital acral blister formation and a variable degree of photosensitivity, which resolve slowly with age, followed by generalized progressive poikiloderma with extensive cutaneous atrophy. Gingival fragility, progressive periodontitis and gastrointestinal involvement occur in some patients. The KS causative gene, FERMT1 (formerly KIND1), encodes a 677-amino acid protein, kindlin-1, which is implicated in the organization and anchorage of the actin cytoskeleton to integrin-associated platforms. It was reported that loss of kindlin-1 in keratinocytes leads to loss of cell polarity, decreased adhesion, reduced cell proliferation and increased apoptosis. Thus far, 33 different FERMT1 (KIND1) mutations have been identified in more than 100 cases of KS. Most of the reported mutations are point mutations, small insertions or deletions, which could be identified by routinely used strategies based on polymerase chain reaction (PCR) amplification of each coding exon and flanking intronic regions, followed by direct sequencing. In the present study, we identified a novel homozygous 3017-bp deletion mutation spanning exons 7–9 in the FERMT1 gene in a Chinese family with KS. The patient was a 23-year-old Chinese man born of consanguineous parents. During the neonatal period, he developed acral blisters, which appeared spontaneously or after trauma. From the age of 2 years, he developed facial and acral erythema following sun exposure. The blistering and photosensitivity improved with age and were followed by progressive poikiloderma. Subsequently, he developed gingival fragility with bleeding and recurrent angular cheilitis, which restricted mouth opening. He had a circumcision when he was 5 years old. Physical examination showed short stature (height 158 cm, weight 49 kg). Mottled hyperand hypo-pigmentation and telangiectasia were revealed over the face, neck and upper parts of the chest (Fig. 1a). Skin atrophy was seen on the trunk and extremities, with ‘cigarette paper’-like wrinkling on the dorsa of the hands and feet (Fig. 1b). Diffuse hyperkeratosis of the palms and soles, webbing and severe contracture of the fingers, nail dystrophy, gingival swelling, ectropion of the lower lids and alopecia areata were also observed (Fig. 1c–e). Skin biopsies were obtained from involved areas. Histopathological examinations showed hyperkeratosis, atrophy of the epidermis, vacuolization of the basal layer, melanophages in the papillary dermis and dilation of blood vessels (Fig. 1f). Electron microscopy showed reduplication of the lamina densa (Fig. 1g). Blood samples were obtained from the patient and available family members following written informed consent. DNA was extracted from peripheral blood lymphocytes. Exons 1–6 and exons 10–15 of FERMT1 were successfully amplified in the patient with primers designed by the primer design program DNAMAN 4.0 (Lynnon Biosoft Inc., Vandreuil, QC, Canada). No mutation was identified by sequencing these exons and their flanking intronic regions. However, a DNA sample from the patient failed to yield PCR amplification products for exons 7, 8 and 9, while they could be amplified in normal controls. Therefore, we presumed the possibility of the presence of a homozygous large deletion mutation spanning exons 7–9 in the patient’s genomic DNA. To sublocalize the deletion breakpoints, a multiple PCR amplification of nonoverlapping fragments was performed with primer pairs positioned in the middle of intron 6 (n6F and n6R) and in the middle of intron 9 (n9F and n9R). The results of these PCR amplifications enabled us to circumscribe the deleted interval. Subsequently, the junction fragment was PCR-amplified with template DNA from the patient using a pair of primers, br1F in intron 6 (forward) and br1R in intron 9 (reverse), which were designed as close as possible to the deletion breakpoints. A fragment of ~0Æ8 kb of product, instead of ~3Æ8 kb of wild-type PCR product, was obtained from the patient. Sequencing of the 0Æ8-kb fragment revealed the 5¢ and 3¢ breakpoints and a large deletion mutation of 3017 bp in FERMT1 (g.63601_66617del, GenBank AL118505, reverse complemented strand) (Fig. 2a,b). To verify this large deletion mutation in the healthy carriers and normal controls, two PCR reactions were performed. In the first reaction, a pair of primers, br2F (forward) and br2R (reverse) that were close to the breakpoints, were used to amplify a 297-bp fragment in the mutated allele. The second reaction was performed to amplify exon 8, and yielded a 568-bp product in the normal allele. As shown in Figure 2c, the reactions yielded a single band of 297 bp in the patient, two bands of 297 and 568 bp in healthy carriers and a band of 568 bp in the normal controls. Using this assay, the deletion mutation was not detected in any allele of 50 healthy controls. The breakpoint sequence was compared with 100 bp of wild-type sequence on each side. A short homology sequence